Effects of stocking density on the growth and flesh quality of rainbow trout (Oncorhynchus mykiss) reared in a low-tech aquaponic system

Metadata

Cite key: biroloEffectsStockingDensity2020
Item type: Journal Article
Authors: Marco Birolo, Francesco Bordignon, Angela Trocino, Luca Fasolato, Antón Pascual, Sergio Godoy, Carlo Nicoletto, Carmelo Maucieri, Gerolamo Xiccato
Affiliation: Department of Agronomy, Food, Natural resources, Animal and Environment (DAFNAE), University of Padova, Legnaro, Italy; Department of Comparative Biomedicine and Food Science (BCA), University of Padova, Legnaro, Italy; Institute of Animal Science and Technology, Group of Aquaculture and Biodiversity, Polytechnic University of Valencia, Valencia, Spain
Journal: Aquaculture 529 (2020) 735653
Date: 12/2020 (Received 8 Apr 2020; Accepted 23 Jun 2020; Available online 2 Jul 2020)
Date added: 2021-02-04
DOI: 10.1016/j.aquaculture.2020.735653
Funding: University of Padova (BIRD 179231; CUP: C52F17000140005); PhD grant of Francesco Bordignon funded by ECCEAQUA project (MIUR; CUP: C26C18000030004)
URL: https://doi.org/10.1016/j.aquaculture.2020.735653
PDF: Birolo et al. - 2020 - Effects of stocking density on the growth and fles.pdf

Opinion

A clean, well-instrumented two-factor design (2 stocking densities x 2 lettuce cycles x fishless hydroponic control, 3 true tank replicates each) that is refreshingly honest about a null result: neither growth, FCR, mortality, slaughter traits, nor flesh quality differed between densities, and the paper says so plainly rather than fishing for significance. The fish-side data (Tables 2-5) is exhaustive and internally consistent — the only wrinkle is a 1-fish accounting gap in the AHD headcount and a rounding difference between the abstract’s “3%” and the discussion’s “3.3%” mortality, neither material. The plant side is weaker for cross-density comparison purposes: marketable lettuce yield is only reported per-density in a bar chart (Fig. 3), with text giving just a 3-group pooled Cycle-1 average and an AP-pooled (ALD+AHD combined) Cycle-2 figure — genuinely useful for the AP-vs-HYP question the paper is asking, but it means this note’s own AP/HYD yield cells are mostly NR to avoid misattributing a pooled number to one density. Would cite for the trout-in-aquaponics growth/flesh-quality benchmark (first of its kind per the authors) and for the practical takeaway that density up to ~17 kg/m3 is safe for both fish and lettuce in this design; would not rely on it for a density-specific yield number without going back to the source figure.

Abstract

In the present study, we evaluated the effects of two stocking densities (low - ALD, 3.81 kg m−3 vs. high - AHD, 7.26 kg m−3) on the growth, health, and flesh quality of rainbow trout (Oncorhynchus mykiss) and the yield and microbiological quality of lettuce (Lactuca sativa) produced in a low-tech aquaponic system compared to hydroponic cultivation (HYP). Nine experimental units (three replications per treatment) were utilised. A total of 123 rainbow trout (initial body weight: 142 ± 35 g) were randomly distributed in six 500-L tanks (3 per stocking density) and monitored during a 117 day trial period. The final weight (331 g on average), specific growth rate (0.73% d−1), feed conversion ratio (1.58), and mortality (3%) of the fish did not differ between stocking densities. The morphometric indices, slaughter results, and flesh quality were not affected. Similarly, the quantity of lettuce produced during two consecutive cycles was similar among treatments (2.4 kg m−2 on average). At harvest, microbial contamination (total viable count, E. coli, Enterobacteriaceae, Pseudomonas, mould, and yeasts) was similar in the fish skin and lettuce produced in aquaponic systems with different stocking densities, as well as in the lettuce produced in aquaponic and hydroponic systems. In conclusion, rainbow trout and lettuce productions were successful in the tested aquaponic system, whereas stocking density did not affect fish growth or flesh quality.

Summary

The authors ran a 117-day winter-season trial at the University of Padova, comparing two rainbow trout stocking densities — low (ALD, initial 3.81 kg/m3) and high (AHD, initial 7.26 kg/m3) — in a low-tech, LECA-media-bed aquaponic system, against a fishless hydroponic control (HYP), with 3 replicate units per treatment (9 total). Two consecutive lettuce cycles (77 and 44 days) were grown across the fish trial. Neither fish growth (final weight, SGR, FCR, mortality) nor slaughter/morphometric traits nor flesh quality (texture, colour, pH, TVB-N) differed between the two stocking densities, even though final biomass density reached ~9 kg/m3 (ALD) and ~17 kg/m3 (AHD) — well above some literature thresholds for stress effects in trout, which the authors attribute to the fish not exceeding a critical ~24 kg/m3 biomass ceiling reported elsewhere. Water quality (ammonium, nitrite, nitrate, EC, redox potential, phosphate) scaled with stocking density as expected (ALD < AHD < HYP for N-species/EC/redox; the reverse for phosphate), and nitrate accumulated well past a commonly cited 400 mg/L guideline in both aquaponic groups by mid-trial. Marketable lettuce yield was statistically indistinguishable across all three groups in Cycle 1, and higher in the pooled aquaponic groups than in hydroponics in Cycle 2. Microbial contamination of fish skin and lettuce (total viable count, Enterobacteriaceae, Pseudomonas) was low and did not differ meaningfully by density or, for lettuce, by aquaponic-vs-hydroponic system; E. coli, moulds and yeasts were not detected anywhere. The paper’s core claim is that a cold-water species (rainbow trout) can be farmed successfully in a simple aquaponic system at densities well above prior recommendations without compromising fish welfare, flesh quality, or co-produced lettuce yield.

Experiment data

Location: Experimental farm of the University of Padova, North-East Italy (45°20’N, 11°57’E, 6 m a.s.l.), inside an unheated plastic greenhouse

Design: 9 identical independent units: 3 hydroponic (HYP, no fish), 3 aquaponic at low stocking density (ALD), 3 aquaponic at high stocking density (AHD); one-way ANOVA (water/yield/microbiology, group as main effect) and separate one-way ANOVA (fish growth/slaughter, density as main effect) and two-way ANOVA (rigor/flesh quality/fish microbiology, density x storage-time)

Replicates / n: 3 tanks per treatment; 123 rainbow trout total (42 ALD, 81 AHD); 18 fish/density sampled at slaughter (9 analysed at 1 d, 9 at 7 d post-slaughter storage)

Duration: 117-day fish trial (winter, Nov-Feb); two lettuce cycles in succession, 77 days (Cycle 1) and 44 days (Cycle 2)

Organisms: Rainbow trout (Oncorhynchus mykiss) / Lettuce (Lactuca sativa)

Statistics: One-way/two-way ANOVA, Bonferroni’s test, PROC GLM (SAS 9.2), p<.05

Stocking density: ALD 3.81 kg m⁻³ → 8.86 kg m⁻³ (d117); AHD 7.26 kg m⁻³ → 16.94 kg m⁻³ (d117) — final biomass did not affect growth or flesh quality

FCR: ALD 1.65, AHD 1.51 (0-117 d), ns (p=.323)

SGR: ALD 0.72, AHD 0.73 %/d (0-117 d), ns (p=.928)

Marketable lettuce yield: Cycle 1, 2.82 ± 0.64 kg m⁻² (3-group pooled average, ns p=.926); Cycle 2, aquaponic-pooled 1.98 vs hydroponic 1.75 kg m⁻² (p<.01)

Fish growth performance and stocking density

This paper: Stocking density (3.81 vs 7.26 kg m⁻³ initial) had no effect on rainbow trout live weight, SGR, or FCR over 117 days (Table 2); mortality was very low (4 fish total, 2 per density) with no symptomatic disease. Final biomass density reached 8.86 (ALD) and 16.94 (AHD) kg m⁻³, both within a range the authors argue is safe because negative stocking-density effects on trout growth in the literature only appear once biomass surpasses ~24 kg m⁻³.

Compared with:

todo Zahedi et al. 2019 — rainbow trout stocking-density effects on growth only detectable above 24 kg m⁻³ (677 g final weight); not reached in this trial. (p.6)
todo North et al. 2006 — no significant final-weight differences in female rainbow trout stocked at 10, 40, and 80 kg m⁻³ (180 g initial, ~400 g final); cited as a precedent for density-insensitivity in trout under some conditions. (p.6)
todo Suárez et al. 2014 — decreased final weight, length, fillet weight and viscerosomatic index when density rose from 15 to 40 kg m⁻³ in one-year-old trout; contrasts with this paper’s null result, attributed to this trial’s lower absolute densities. (p.6-7)
todo Hussain et al. 2014 — Koi carp mortality increased with stocking density (2.1→2.8 kg m⁻³) in aquaponics. (p.6)
todo Rayhan et al. 2018 — Nile tilapia mortality increased with stocking density (0.5→1.6 kg m⁻³) in aquaponics. (p.6)
todo Maucieri et al. 2019 — same aquaponic system/site, European carp at similar densities (2.5-4.6→6.9-11.5 kg m⁻³), comparably low mortality; also found similar lettuce yield in hydroponics vs aquaponics at low fish density. (p.6, p.8)

Flesh quality and shelf life

This paper: Stocking density did not affect morphometric indices, slaughter yields (carcass 89.0%, fillet 49.1% on average), or any flesh-quality trait (texture, colour, pH, TVB-N) at either 1 or 7 days post-slaughter storage in ice. Storage time itself drove significant changes (decreasing rigor index, muscle pH, hardness, chewiness; increasing skin/fillet lightness), consistent with normal post-mortem/cold-storage autolysis. TVB-N remained below the 25-27 mg/100 g acceptability threshold throughout.

Compared with:

todo Suárez et al. 2014 — high rainbow trout stocking density (40 kg m⁻³) reduced muscle pH and water-holding capacity, increased rigor strength and firmness; not replicated here, attributed to this trial’s lower peak density (~17 kg m⁻³) not being stressful. (p.6)
todo Erikson and Misimi 2008 — lighter Atlantic salmon skin after a week of ice storage, consistent with this paper’s own lightness increase. (p.7)
todo Ninan et al. 2011 — shelf life for iced rainbow trout ~8-11 days; TVB-N acceptability threshold 25-27 mg/100 g, used as this paper’s own benchmark. (p.7-8)

Lettuce yield and aquaponic vs hydroponic comparison

This paper: Marketable lettuce yield did not differ among ALD/AHD/HYP in Cycle 1 (2.82 ± 0.64 kg m⁻², 3-group pooled average, p=.926) and was higher in the pooled aquaponic groups than hydroponics in Cycle 2 (1.98 vs 1.75 kg m⁻², p<.01) — i.e. aquaponics matched or exceeded hydroponic yield despite receiving no synthetic N fertilizer, relying solely on fish waste. Neither stocking density’s own Cycle-specific yield number is given anywhere except as an unlabelled bar in Fig. 3 (see Extraction notes).

Compared with:

todo Pantanella et al. 2012 — lettuce yield DECREASED in aquaponics vs hydroponics when fish density dropped from 8 to 5 kg m⁻³; this paper found no such density effect, interpreted as evidence that nutrient supply was adequate even at the low (3.81 kg m⁻³) density tested here. (p.8)
todo Lennard and Ward 2019 — NFT hydroponic vs NFT aquaponic plant growth rate comparison; cited alongside this paper’s own comparable-or-better aquaponic yield finding. (p.1, p.8)
todo Suhl et al. 2016 — aquaponics equalling/exceeding hydroponic yield for tomato; general precedent cited for the same pattern seen here with lettuce. (p.8)

Water quality and stocking density

This paper: EC, redox potential, and ammonium/nitrite/nitrate all increased with stocking density (ALD < AHD < HYP, p<.001), while phosphate was highest in AHD and lowest in HYP (p<.001) — see Table 1. Water nitrate exceeded a 400 mg/L guideline cited for cold-water species for roughly a third (ALD) to half (AHD) of the trial (Fig. 2f), yet did not translate into any fish growth or welfare effect, which the authors attribute to trout tolerance and moderate absolute concentrations relative to unionised-ammonia and nitrite toxicity thresholds.

Compared with:

todo Somerville et al. 2014 — small-scale aquaponics design guidelines (10-20 kg m⁻³ stocking density range; 400 mg/L NO3 ceiling for cold species) used directly to justify this paper’s density choices and to flag the nitrate overshoot. (p.2, p.5)
todo Wortman 2015 — reduced nutrient uptake by plants at higher pH, offered as a partial explanation for progressive nitrate accumulation in this trial. (p.5)
todo Wang et al. 2020 — highlights foodborne-pathogen (E. coli STEC) risk in aquaponic/hydroponic systems generally; offered as a counterpoint to this paper’s own clean E. coli result. (p.8)

Linked claims

Citations to chase

Extraction notes

Trial structure: this paper has two orthogonal, independently-analysed design axes — fish stocking density (ALD/AHD, each n=3 tanks) and lettuce cultivation cycle (Cycle 1 = 77 days, Cycle 2 = 44 days, each with its own ANOVA and p-value in Fig. 3a/b). Both axes are evidenced by labelled, separately-analysed arms (not just repeated conflicting statements), so trials.csv gets 4 rows: T1=ALD/Cycle1, T2=ALD/Cycle2, T3=AHD/Cycle1, T4=AHD/Cycle2. Fish-side columns (growth, water quality) are identical between the two cycle-rows of a density (T1=T2; T3=T4), since fish were sampled once continuously over the full 117-day trial, not per lettuce cycle. Paired control for all 4 rows is HYP (hydroponic, no fish; a single undivided group, not split by density).

Severity-tagged contradictions (0 BLOCK, 0 MATERIAL, 1 MINOR, 1 CHECK — quality: ok per SCHEMA.md’s 0 BLOCK/≤2 MATERIAL rule):

⚠️MINOR — Fish count/mortality rounding. Materials 2.2 (p.2): “the three ALD units received 14 fish per tank” and “the three AHD units received 27 fish per tank” → 42 and 81 initial fish (42+81=123, matching the abstract’s “123 rainbow trout”). Results 3.2 (p.4): “only four fish died (2 from ALD and 2 from AHD treatments).” Expected survivors: ALD 42−2=40 (matches Table 2’s “Total fish per treatment (n)” = 40 exactly); AHD 81−2=79, but Table 2 states AHD n=78 (off by one, ~1.2%). Separately, the abstract states mortality “3%” while Discussion 4.1 states “very low (3.3% on average)” — both are compatible roundings of the same ~3.25% overall figure (4/123), not a real conflict. Recorded/why: neither discrepancy touches any extracted cell — “Fish survival rate” is left NR for both densities because the paper never states a per-treatment survival percentage (only raw death counts), and computing one from counts would be derivation. Affects: nothing downstream; noted for anyone later trying to recompute survival % by hand.
⚠️CHECK — Water NH4+/NO2-/NO3- vs schema’s “-N” column naming. Table 1 and Fig. 2 (p.4-5) report these as ion species (NH4+, NO2-, NO3-, measured by ion chromatography per Maucieri et al. 2019, p.3) — this schema’s columns are named TAN / NH4-N, NO2-N, NO3-N, implying nitrogen-only mass, a factor of ~1.29x (NH4+ vs NH4-N), ~3.29x (NO2- vs NO2-N), and 4.43x (NO3- vs NO3-N) apart from the ion mass. The paper itself is internally consistent — it always reports the ion (axis labels “mg L⁻¹” beside the chemical formula in Fig. 2; Discussion 4.1 compares its own NO3- figure directly against Somerville et al. (2014)‘s 400 mg/L guideline using, apparently, the same ion-based convention) — so there is no ambiguity about what the paper measured, only a mismatch with this schema’s column name. Recorded as printed (ion mass, the paper’s own stated method and units are the clearest basis); no N-only conversion applied since the paper gives no N-only figure to check against, and applying the 4.43/3.29/1.29 factor would be derivation. Added to REVIEW.md per SCHEMA.md’s instruction that every CHECK gets a row there.
RECOVERED (not BLOCK, not derivation) — EC unit. Table 1 prints the EC unit as “ds cm⁻¹” (deciSiemens per cm). Taken literally this is physically implausible for aquaculture/hydroponic water (1.63-2.81 dS/cm = 1630-2810 mS/cm, several orders of magnitude too high for any real freshwater or nutrient solution). The same values are entirely typical hydroponic-nutrient-solution EC if read as dS/m (=mS/cm), which is also this schema’s own EC unit. Read as dS/m (the printed “cm⁻¹” almost certainly a typesetting substitution for “m⁻¹”), per the general principle that BLOCK is for values that cannot be determined, not values written oddly (cf. SCHEMA.md’s DMS-coordinate example). Value recorded unchanged (1.63 ALD / 1.89 AHD); not tallied as a severity flag since only one physically sensible reading exists.

[not reported] fields (grouped by field name): Fish Category (species/lifestage never categorised beyond “rainbow trout”); N, K (feed nitrogen/potassium content — only crude protein 40% and phosphorus 0.8% given; converting protein→N via a 6.25 factor would be derivation); % of body weight (feed ration is a 3-segment step schedule — 1.5%/1.0%/1.5% — not one constant number; kept in Feed regime instead); Total Feed (kg) (only %-of-biomass daily rates given, never a cycle-total mass); Fish biomass created (kg) (paper gives biomass growth only in kg/m³, converting via tank volume would be derivation); Fish survival rate (only raw death counts given, no stated %); Fish weight gain (only sequential mean weights given, no stated “gain” figure); Water volume in the system (component tank volumes are given — 500 L main + 2×275 L veg + 50 L storage — but the paper’s own daily-water-loss statistic, 2.45 L/d = 0.41% of “the total water contained in each unit”, implies ≈598 L, not the ≈1100 L nominal tank-capacity sum, most likely because LECA media displaces volume in the veg tanks; the paper never states one authoritative total, so left NR rather than guessing which reading is right); Water classification; pHOptimal, FUE AP, FUE HYD, WUE (no target/efficiency figures computed by the authors); Average room Temperature (only water temperature is tracked; greenhouse air temperature is never given a number); Plant Category (see judgement call below); SPAD, Plant height, Leaf count, Plant dry matter (none of these were measured — only area-based fresh yield and microbiology were); Plant fresh weight g/plant (only area-based kg/m² yield is reported, never a per-plant weight); Tissue nitrate AP/HYD (the paper measures lettuce microbial contamination, never tissue nitrate); AP/HYD marketable yield (see below — NR for all 4 rows, for different reasons per cycle, both explained in each row’s own remarks and summarised again here for visibility).

[unclear] fields: none — every ambiguity in this paper was either resolved (EC unit), left cleanly NR with a stated reason, or escalated to a named ⚠️CHECK/⚠️MINOR above; no cell was UNCLEAR.

Plant Category judgement call: the Introduction (p.1) lists “herbs, fruiting species, and leafy vegetables” as crop categories grown in aquaponics generally, then separately says “Lettuce (Lactuca sativa) is one of the main plant species used in aquaponic systems” — it is a reasonable inference that lettuce is “a leafy vegetable,” but the paper never explicitly applies that category label to lettuce itself (unlike, e.g., a table column naming the category directly). Left NR per the prime directive rather than inferring the label myself.

AP/HYD marketable-yield cells (all 4 rows NR): Cycle 1 (T1, T3) — only a 3-group pooled average exists in text (2.82 ± 0.64 kg m⁻², “average of the three groups,” p=.926, Fig. 3a), pooling ALD+AHD+HYP together; there is no way to recover an AP-only or HYP-only number from that without derivation, and the only density-specific numbers are unlabelled Fig. 3a bar heights (not used, per the “never read a value off a figure” rule). Cycle 2 (T2, T4) — text gives “1.98 vs. 1.75 kg m⁻² (p<.01)” where 1.75 is HYP’s own unambiguous value (recorded as HYD for both T2 and T4) but 1.98 is explicitly the ALD+AHD pooled aquaponic average, not either density’s own figure; recording it in a density-specific AP cell risked misattributing one density’s yield contribution to the other, so it is left NR in the cell and quoted, clearly labelled as pooled, in that row’s remarks instead.

NO COLUMN items (fish flesh-quality/slaughter/skin-microbiology data with no dedicated schema column, full numbers repeated in each trials.csv row’s Experimental Remarks): Table 3 morphometric/slaughter indices (total/standard/head length, max height, condition factor, relative profile, cranial index, carcass/fillet weight and yield) by density; Table 4 rigor index, muscle pH, texture (hardness/cohesiveness/springiness/chewiness), TVB-N, and skin/fillet Lab* colour at 1 d and 7 d post-slaughter storage, by density; Table 5 skin microbial counts (TVC, Enterobacteriaceae, Pseudomonas, H2S-producing bacteria) at 0 d and 7 d, by density. Lettuce microbiology (Table 6: TVC, Enterobacteriaceae, Pseudomonas, plus explicit non-detection of E. coli/mould/yeast) does fit plant_measurements.csv’s microbiology category and was recorded there instead (System=AP for the relevant density, HYD for the shared hydroponic control; only for T2/T4 since Methods 2.6 states this sampling happened “at the time of fish slaughter” using “leaves from all plants (i.e. those of the second cycle),” i.e. Cycle 2 only).

Water panel: Table 1’s chlorophyll (μg/L) and redox potential (mV) columns have no home in trials.csv or plant_measurements.csv (chlorophyll is a water-column measurement here, not a plant tissue analyte, and there is no ORP column) — not extracted anywhere, values are: Chlorophyll ALD 55.3, AHD 80.2, HYP 14.1 μg/L (p<.001); Redox potential ALD 75.2, AHD 83.1, HYP 90.6 mV (p<.001). Flagging per SCHEMA.md’s instruction to say so explicitly if a water panel seems too valuable to discard, rather than silently dropping it or misrouting it into plant_measurements.csv.

Scanned PDF check: clean text layer, not a scan; no OCR issue, not added to NEEDS_OCR.md.

New tags introduced: Meta/Fish/Trout (new — no existing Trout facet in the vault; checked against Meta/Fish/Tilapia, Meta/Fish/Koi, Meta/Fish/Koi-Carp, Meta/Fish/Yellow-Perch, Meta/Fish/Goldfish). Meta/Type/Experiment, Meta/Region/Europe, Meta/Plant/Lettuce all reused from existing vault entries (aslanidouNutrientsUseEfficiency2023 for Europe; singhAquaponicProductionOrnamental2024/tadesseComprehensiveComparisonLettuce2023/andersonGrowthTissueElemental2017 for Lettuce).

New wikilink targets introduced: Marco Birolo, Francesco Bordignon, Angela Trocino, Luca Fasolato, Antón Pascual, Sergio Godoy, Carlo Nicoletto, Carmelo Maucieri, Gerolamo Xiccato, Rainbow trout (Oncorhynchus mykiss), Lettuce (Lactuca sativa), Rainbow trout can be farmed in low-tech aquaponic systems at densities above prior small-scale recommendations without growth or flesh-quality penalties, Aquaponic lettuce yield can match or exceed hydroponic yield without synthetic nitrogen fertilizer, Water nitrate can exceed cold-water aquaponic guideline thresholds without a detectable fish welfare effect in a low-tech system.

Source: Birolo et al. - 2020 - Effects of stocking density on the growth and fles.pdf

Data Tables

Structured data extracted from this paper into the vault's trials.csv / plant_measurements.csv datasets. Fields the paper didn't report are omitted. Download the full datasets (measurements).

Trial Parameters

biroloEffectsStockingDensity2020-T1

Fish

Field	Value
Fish	Rainbow trout (Oncorhynchus mykiss)
Initial Stock density	3.81
FCR	1.65
SGR	0.72
Protein	40
P	0.8
Fish size initial	143
Fish size final	333
Feed routine	Fed manually once daily until apparent satiation, in two rounds separated by 20-30 min (p.2, Section 2.2).
Feed regime	1.5% of biomass from day 0-20; 1.0% from day 23-53; 1.5% from day 56-117 (recalculated at each monthly weighing) (p.2).
Fish trial duration (days)	117

Water

Field	Value
Water recycle	5
Water type	Municipal (tap) water, no pre-treatment (p.2)
Daily Water exchange rate	0.41
Aq pH	7.43
Dissolved Oxigen	9.58
EC	1.63
Water temperature	10.8
TAN / NH4-N	0.55
NO2-N	0.07
NO3-N	314

Plant

Field	Value
Plant	Lettuce (Lactuca sativa L.)
Details	first cultivation cycle (77 days); 20 plants/unit (10 plants/tank) transplanted at third true leaf stage; harvest = all plants divided into aboveground/belowground parts, fresh weight of leaves recorded immediately per Maucieri et al. (2019) procedure (p.3). Cycle 1 began 3 days before fish addition; Cycle 2 harvested the day after fish harvest (p.2).
Days Plant after transplant	77
Plants/m2	13

System & Setup

Field	Value
Media Details	Each unit: 1 main tank (500 L, 0.80 m height, 0.90 m diameter) for fish (aquaponic) or nutrient solution (hydroponic); 2 vegetable tanks (275 L each, 0.35 m height, 1.00 m diameter; total crop area 1.6 m2) filled with 225 L of light expanded clay aggregates (LECA; specific area 250 m2/m3, packing density 300 kg/m3, total porosity 0.55 m3/m3; LECA Laterlite, Solignano, Italy), acting as both biofilter media and hydroponic growing substrate; 1 storage tank (50 L, 0.45 m height) collecting water from the vegetable tanks before pumping back to the main tank; flow driven by gravity/overflow between the 3 parts, powered by a single submersible pump (300 L/h) returning water from storage to main tank (p.2, Fig. 1).
Biological system already in use	Y (System previously used for one full cycle with European carp (Cyprinus carpio) prior to this trial, which ‘guaranteed about the regular functioning of the biofilter’ (Maucieri et al., 2019) (p.2). Municipal water used without pre-treatment to fill the systems at the start of that prior carp cycle.)
Air supplement	Y (Porous stone diffuser (4.0x4.0x15.0 cm, 14 L/min; Sweetwater AS15S) per main (fish) tank, connected to a shared aerator (Scubla D100); tanks covered with a net to prevent fish jumping (p.2).)
Iron supplemented	Y (10 g/unit of Fe-EDTA added to ALL 9 units (aquaponic and hydroponic) before the trial began (p.2), alongside other base minerals (see Remineralization).)
Remineralization	Y (Before trial start, all 9 units (both ALD/AHD aquaponic units and HYP hydroponic units) received a baseline mineral charge: 132 g/unit KH2PO4, 197 g/unit K2SO4, 273 g/unit MgSO4.7H2O, 10 g/unit Fe-EDTA, and 5 g/unit micronutrients (p.2).)
pH Buffers	N (Explicit absence stated: ‘No correction for alkalinity was performed’ (p.2).)
Climate control	N (Explicit absence stated: ‘No energy to regulate water temperature… were used’ (p.2). Grown in an unheated plastic greenhouse under natural photoperiod during the winter season (November-February); water temperature tracked ambient conditions, ranging 7.0-15.9 degC (mean 10.7 degC, Fig. 2a; Discussion 4.1).)
Artificial Lighting	N (Trial run ‘under a natural photoperiod’ (p.2, Section 2.2) with no mention of supplemental/artificial lighting equipment anywhere in Methods; read as an explicit statement that the light regime was unmodified natural daylight, not merely silence on the topic.)
Nutrient supplemented	Y (All 9 units (AP and HYP) received the same baseline mineral charge before start (see Remineralization). HYP units ADDITIONALLY received a nitrogen fertilizer charge: 333 g/unit Ca(NO3)2 and 480 g/unit NH4NO3, calculated via the free software HydroBuddy for optimal lettuce hydroponic nutrition (p.2). The ALD/AHD aquaponic units received NO additional N fertilizer beyond the baseline charge — their nitrogen supply came solely from fish feed/waste inputs over the trial.)
Equipment	Submersible pump (Newa Jet 1700, NEWA TecnoIndustria Srl, Loreggia, Italy; 300 L/h flow rate); porous stone air diffuser (4.0x4.0x15.0 cm, 14 L/min; Sweetwater AS15S, Pentair) connected to an aerator (Scubla D100, Scubla Srl); portable multi-parameter apparatus (HQ40d, Hach Lange GmbH) for temperature/DO/pH/ORP/EC; fluorescence chlorophyll detector (HHLD, Turner Designs); ion chromatography for NO2-, NO3-, PO4(3-) and NH4+ (per Maucieri et al., 2019); precision scale (1 g; Wunder Sa.Bi. srl); Minolta CM-508C spectrophotometer (skin/fillet colour Lab*); TA.XT.plus Texture Analyser (Stable Micro Systems, 20 mm cylindrical probe) for texture profile analysis; pH meter (Basic 20; Crison Instruments Sa) with specific electrode for muscle pH.
Control Parameters	Outflow water of fish tanks monitored 2x/week for temperature, dissolved oxygen, pH, redox potential (ORP) and electrical conductivity via portable multi-probe; NO2-, NO3-, PO4(3-) and NH4+ measured by ion chromatography; chlorophyll by fluorescence detector (p.2-3). Explicitly NO energy used to regulate water temperature, NO continuous water-quality probe or remote management, NO water sanitation device, and NO correction for alkalinity (p.2).
Combination	Rainbow trout (Oncorhynchus mykiss) and lettuce (Lactuca sativa L.); low-tech media-bed (expanded clay aggregate) aquaponic system at two fish stocking densities (low=ALD, high=AHD) compared against a fishless hydroponic control (HYP); winter-season trial (Nov-Feb) in an unheated plastic greenhouse, North-East Italy.

Site

Field	Value
Region	Europe
Country	Italy
Lat	45.3333
Long	11.95

Results & Statistics

Field	Value
Measured Unit	kg/m2 (marketable fresh yield: aboveground+belowground leaf fresh weight per experimental unit, per Maucieri et al. 2019 procedure)
Statistic Details	One-way ANOVA (water quality, vegetable yields, microbiological quality) with experimental group (ALD/AHD/HYP) as main effect; separate one-way ANOVA (fish growth performance and slaughter data) with stocking density (ALD/AHD) as main effect; two-way ANOVA (rigor mortis, physicochemical traits, microbiological quality of fish) with stocking density x storage time (1/7d) and their interaction as main effects; Bonferroni’s test used to compare means; PROC GLM, SAS 9.2 (Statistical Analysis System, 2013); significance at p<.05 (Section 2.8, p.4).
Statistically analysed	Y
Replicates (n)	3

Experimental Remarks: TRIAL DEFINITION: T1 = aquaponic ALD stocking density (low, initial 3.81 kg/m3), first cultivation cycle of lettuce cultivation (77 days). This paper has two orthogonal, independently-analysed design axes: fish stocking density (ALD vs AHD, 3 tanks/replicates each) and lettuce cultivation cycle (Cycle 1 vs Cycle 2, each with its own ANOVA/p-value in Fig. 3a/b and different plant duration, 77 vs 44 days). Both are evidenced by labelled, separately-analysed treatment arms, so this paper contributes 4 trial rows (2 densities x 2 cycles), not 2 or 1. Paired control for ALL 4 rows = HYP (hydroponic, no fish; single group, not split by density). Fish-side data (growth, water quality) is identical between the two cycle-rows of the same density (T1=T2 for ALD; T3=T4 for AHD), since fish were measured once continuously over the full 117-day trial, not per lettuce cycle. | Fish growth (Table 2, ALD, n=3 tanks, 0-117d): weight 143g(d0)->170(d22)->217(d55)->264(d84)->333g(d117,final); SGR 0-117d=0.72%/d (period SGRs: 0-22d=0.79, 22-55d=0.74, 55-84d=0.69, 84-117d=0.70); FCR 0-117d=1.65 (period FCRs: 0-22d=1.52, 22-55d=1.28, 55-84d=1.84, 84-117d=1.73); biomass density 3.81(d0)->4.53->5.78->7.04->8.86 kg/m3(d117); biomass growth 0-117d=5.05 kg/m3 (period growths: 0.72,1.25,1.26,1.82 kg/m3). None of the growth/FCR/SGR traits differed significantly from AHD (all p>=.255); biomass and biomass growth differed significantly (p<.001) purely because they track the designed stocking density itself. NOT DERIVED, left NR: Fish biomass created (kg) — paper gives biomass GROWTH only in kg/m3 (5.05 for ALD, Table 2), not an absolute kg mass; converting via tank volume would be derivation per SCHEMA.md’s explicit warning against computing ‘biomass gain’ even when inputs look present. Fish survival rate (%) — only raw death counts given (2 ALD fish died, p.4), no stated percentage; computing one = derivation. Fish weight gain (g/fish) — only sequential mean weights given per interval, no stated ‘gain’ figure; would be derivation. Total Feed (kg) — only %-of-biomass daily rates given (1.0-1.5%), never a cycle-total feed mass. % of body weight — left NR in that column because it is a 3-segment step schedule (1.5%/1.0%/1.5%), not one constant daily ration; full schedule recorded in Feed regime instead to avoid collapsing 3 distinct values into one misleading number. | NO COLUMN: Table 3 morphometric/slaughter results (n=18 fish/density, at day117): ALD — total length 289 mm, standard length 250 mm, head length 61 mm, max height 71 mm, condition factor 1.37, relative profile 0.25, cranial index 0.21, carcass weight 287 g, carcass yield 89.0%, fillet weight 165 g, fillet yield 49.9%. AHD — total length 290 mm, standard length 248 mm, head length 61 mm, max height 73 mm, condition factor 1.35, relative profile 0.25, cranial index 0.21, carcass weight 289 g, carcass yield 89.0%, fillet weight 160 g, fillet yield 48.3%. All ns (p>0.05; closest was fillet yield p=.095). | NO COLUMN: Table 4 flesh quality/rigor across ice storage (1d vs 7d post-slaughter); stocking-density main effect ns for every trait (p>=.105). ALD (1d/7d) vs AHD (1d/7d): Rigor index % 92.4/18.7 vs 89.2/11.6; muscle pH 6.55/6.45 vs 6.54/6.45; hardness N 25.0/6.9 vs 20.2/6.7; cohesiveness 0.82/0.77 vs 0.83/0.71; springiness mm 0.39/0.34 vs 0.32/0.45; chewiness N.mm 7.74/1.88 vs 5.59/1.28; TVB-N mg/100g 16.3/16.5 vs 16.9/16.7; skin L* 41.0/48.6 vs 37.1/54.8; skin a* 4.06/0.02 vs 3.34/0.11; skin b* 6.94/11.00 vs 7.40/9.03; fillet L* 38.3/43.8 vs 39.1/45.0; fillet a* -1.71/-1.32 vs -1.65/-1.06; fillet b* 9.72/7.58 vs 9.78/8.33. Storage-Time effect significant (p<=.014 to p<.001) for rigor index, muscle pH, hardness, chewiness and all colour indices except fillet a* (p=.088, ns); Density x Time interaction ns throughout (Table 4). | NO COLUMN: Table 5 skin microbial counts (log10 CFU/20cm2) at 0d/7d post-slaughter: ALD — TVC 2.06/2.41, Enterobacteriaceae 0.63/1.00, Pseudomonas 0.39/0.33, H2S-producing bacteria 0.41/0.41. AHD — TVC 2.59/2.44, Enterobacteriaceae 0.92/0.93, Pseudomonas 0.87/0.74, H2S-producing bacteria 0.89/0.82. Density effect significant only for Pseudomonas (p=.024, higher in AHD) and near-significant for H2S bacteria (p=.072); TVC/Enterobacteriaceae ns for D, T, D x T. E. coli, moulds and yeasts were NOT DETECTED in skin or lettuce and are not given numeric values anywhere in the paper (p.4, Results 3.5) — recorded as ‘not detected’ in plant_measurements.csv for the lettuce side, not fabricated as 0 or NR. | Plant yield (Cycle 1, 77 days): only a 3-GROUP POOLED average is given in text — ‘2.82 +/- 0.64 kg m-2 at the end of the first cycle… average of the three groups’ (Results 3.4, p.4), and this pools ALD+AHD+HYP together (p=.926, ns; Fig. 3a) — there is no way to disaggregate an AP-only or HYP-only Cycle-1 number from that pooled 3-way mean without derivation. The only density-specific Cycle-1 numbers exist solely as unlabelled bar heights in Fig. 3a, not reproduced in text or a table — NOT used, per the ‘never read a value off a figure’ rule. AP and HYD recorded NR for this row. | WARN-CHECK Water NH4+/NO2-/NO3-: Table 1 and Fig. 2 report these as the ion species (NH4+, NO2-, NO3-, measured by ion chromatography, p.3), matching the schema columns’ intent (TAN/NH4-N, NO2-N, NO3-N) only if those columns are read as ion mass rather than N-only mass — a factor of ~1.29x (NH4+ vs NH4-N), ~3.29x (NO2- vs NO2-N) and 4.43x (NO3- vs NO3-N) apart. The paper itself is internally consistent (always reports the ion, e.g. axis labels ‘mg.L-1’ next to the chemical formula NH4+/NO2-/NO3- in Fig. 2, and Discussion 4.1 compares its own NO3- figure directly against Somerville et al. (2014)‘s 400 mg/L guideline using the same, apparently ion-based, convention) — there is no internal ambiguity about WHAT was measured, only a mismatch with this schema’s own ‘-N’ column naming. Recorded as printed (ion mass, clearest basis: the paper’s own stated analytical method and units); no N-only conversion applied since the paper gives no N-only figure to cross-check against (applying the 4.43/3.29/1.29 factor would be derivation). Same value shared between both cycle-rows of a density (T1=T2 for ALD; T3=T4 for AHD), since water was measured once over the full 117-day fish trial. | RECOVERED (not BLOCK, not derivation): Table 1 prints the EC unit as ‘ds cm-1’ (deciSiemens per cm). Taken literally this would be a physically implausible reading for aquaculture/hydroponic water (1.63-2.81 dS/cm = 1630-2810 mS/cm, several orders of magnitude above any real freshwater or nutrient-solution EC). The values 1.63-2.81 are entirely typical for hydroponic nutrient-solution EC if read in dS/m (=mS/cm), which is also this schema’s own EC unit. Read as dS/m (the ‘c’ in ‘cm-1’ almost certainly a typesetting/OCR substitution for ‘m-1’), per the general principle that BLOCK is for values that cannot be determined, not values written oddly (cf. SCHEMA.md’s DMS-coordinate example). Recorded value unchanged (1.63 ALD / 1.89 AHD), unit understood as dS/m. | WARN-MINOR Fish count/mortality rounding: Materials 2.2 (p.2) states 14 fish/tank x 3 tanks = 42 initial ALD fish, and 27 fish/tank x 3 tanks = 81 initial AHD fish (42+81=123, matching the abstract’s ‘123 rainbow trout’). Results 3.2 (p.4) states ‘only four fish died (2 from ALD and 2 from AHD)’. Expected survivors: ALD 42-2=40 (MATCHES Table 2’s ‘Total fish per treatment (n)’ = 40 exactly); AHD 81-2=79, but Table 2 states AHD n=78 (off by one, ~1.2%). Separately, the abstract states mortality ‘3%’ while Discussion 4.1 states ‘very low (3.3% on average)’ — both are compatible roundings of a ~3.25% overall figure (4/123), not a real conflict. Neither discrepancy affects any extracted cell: ‘Fish survival rate’ is left NR for both densities since the paper never states a per-treatment survival PERCENTAGE (only raw death counts), and computing one from counts would be derivation. | Overall (all-cycle) marketable yield context: paper’s headline yield figures span both cycles and, for Cycle 1, all three groups pooled — see AP/HYD note above for why this row’s own AP/HYD cells are NR.

biroloEffectsStockingDensity2020-T2

Fish

Field	Value
Fish	Rainbow trout (Oncorhynchus mykiss)
Initial Stock density	3.81
FCR	1.65
SGR	0.72
Protein	40
P	0.8
Fish size initial	143
Fish size final	333
Feed routine	Fed manually once daily until apparent satiation, in two rounds separated by 20-30 min (p.2, Section 2.2).
Feed regime	1.5% of biomass from day 0-20; 1.0% from day 23-53; 1.5% from day 56-117 (recalculated at each monthly weighing) (p.2).
Fish trial duration (days)	117

Water

Field	Value
Water recycle	5
Water type	Municipal (tap) water, no pre-treatment (p.2)
Daily Water exchange rate	0.41
Aq pH	7.43
Dissolved Oxigen	9.58
EC	1.63
Water temperature	10.8
TAN / NH4-N	0.55
NO2-N	0.07
NO3-N	314

Plant

Field	Value
Plant	Lettuce (Lactuca sativa L.)
Details	second cultivation cycle (44 days); 20 plants/unit (10 plants/tank) transplanted at third true leaf stage; harvest = all plants divided into aboveground/belowground parts, fresh weight of leaves recorded immediately per Maucieri et al. (2019) procedure (p.3). Cycle 1 began 3 days before fish addition; Cycle 2 harvested the day after fish harvest (p.2).
Days Plant after transplant	44
Plants/m2	13

System & Setup

Field	Value
Media Details	Each unit: 1 main tank (500 L, 0.80 m height, 0.90 m diameter) for fish (aquaponic) or nutrient solution (hydroponic); 2 vegetable tanks (275 L each, 0.35 m height, 1.00 m diameter; total crop area 1.6 m2) filled with 225 L of light expanded clay aggregates (LECA; specific area 250 m2/m3, packing density 300 kg/m3, total porosity 0.55 m3/m3; LECA Laterlite, Solignano, Italy), acting as both biofilter media and hydroponic growing substrate; 1 storage tank (50 L, 0.45 m height) collecting water from the vegetable tanks before pumping back to the main tank; flow driven by gravity/overflow between the 3 parts, powered by a single submersible pump (300 L/h) returning water from storage to main tank (p.2, Fig. 1).
Biological system already in use	Y (System previously used for one full cycle with European carp (Cyprinus carpio) prior to this trial, which ‘guaranteed about the regular functioning of the biofilter’ (Maucieri et al., 2019) (p.2). Municipal water used without pre-treatment to fill the systems at the start of that prior carp cycle.)
Air supplement	Y (Porous stone diffuser (4.0x4.0x15.0 cm, 14 L/min; Sweetwater AS15S) per main (fish) tank, connected to a shared aerator (Scubla D100); tanks covered with a net to prevent fish jumping (p.2).)
Iron supplemented	Y (10 g/unit of Fe-EDTA added to ALL 9 units (aquaponic and hydroponic) before the trial began (p.2), alongside other base minerals (see Remineralization).)
Remineralization	Y (Before trial start, all 9 units (both ALD/AHD aquaponic units and HYP hydroponic units) received a baseline mineral charge: 132 g/unit KH2PO4, 197 g/unit K2SO4, 273 g/unit MgSO4.7H2O, 10 g/unit Fe-EDTA, and 5 g/unit micronutrients (p.2).)
pH Buffers	N (Explicit absence stated: ‘No correction for alkalinity was performed’ (p.2).)
Climate control	N (Explicit absence stated: ‘No energy to regulate water temperature… were used’ (p.2). Grown in an unheated plastic greenhouse under natural photoperiod during the winter season (November-February); water temperature tracked ambient conditions, ranging 7.0-15.9 degC (mean 10.7 degC, Fig. 2a; Discussion 4.1).)
Artificial Lighting	N (Trial run ‘under a natural photoperiod’ (p.2, Section 2.2) with no mention of supplemental/artificial lighting equipment anywhere in Methods; read as an explicit statement that the light regime was unmodified natural daylight, not merely silence on the topic.)
Nutrient supplemented	Y (All 9 units (AP and HYP) received the same baseline mineral charge before start (see Remineralization). HYP units ADDITIONALLY received a nitrogen fertilizer charge: 333 g/unit Ca(NO3)2 and 480 g/unit NH4NO3, calculated via the free software HydroBuddy for optimal lettuce hydroponic nutrition (p.2). The ALD/AHD aquaponic units received NO additional N fertilizer beyond the baseline charge — their nitrogen supply came solely from fish feed/waste inputs over the trial.)
Equipment	Submersible pump (Newa Jet 1700, NEWA TecnoIndustria Srl, Loreggia, Italy; 300 L/h flow rate); porous stone air diffuser (4.0x4.0x15.0 cm, 14 L/min; Sweetwater AS15S, Pentair) connected to an aerator (Scubla D100, Scubla Srl); portable multi-parameter apparatus (HQ40d, Hach Lange GmbH) for temperature/DO/pH/ORP/EC; fluorescence chlorophyll detector (HHLD, Turner Designs); ion chromatography for NO2-, NO3-, PO4(3-) and NH4+ (per Maucieri et al., 2019); precision scale (1 g; Wunder Sa.Bi. srl); Minolta CM-508C spectrophotometer (skin/fillet colour Lab*); TA.XT.plus Texture Analyser (Stable Micro Systems, 20 mm cylindrical probe) for texture profile analysis; pH meter (Basic 20; Crison Instruments Sa) with specific electrode for muscle pH.
Control Parameters	Outflow water of fish tanks monitored 2x/week for temperature, dissolved oxygen, pH, redox potential (ORP) and electrical conductivity via portable multi-probe; NO2-, NO3-, PO4(3-) and NH4+ measured by ion chromatography; chlorophyll by fluorescence detector (p.2-3). Explicitly NO energy used to regulate water temperature, NO continuous water-quality probe or remote management, NO water sanitation device, and NO correction for alkalinity (p.2).
Combination	Rainbow trout (Oncorhynchus mykiss) and lettuce (Lactuca sativa L.); low-tech media-bed (expanded clay aggregate) aquaponic system at two fish stocking densities (low=ALD, high=AHD) compared against a fishless hydroponic control (HYP); winter-season trial (Nov-Feb) in an unheated plastic greenhouse, North-East Italy.

Site

Field	Value
Region	Europe
Country	Italy
Lat	45.3333
Long	11.95

Results & Statistics

Field	Value
Measured Unit	kg/m2 (marketable fresh yield: aboveground+belowground leaf fresh weight per experimental unit, per Maucieri et al. 2019 procedure)
Statistic Details	One-way ANOVA (water quality, vegetable yields, microbiological quality) with experimental group (ALD/AHD/HYP) as main effect; separate one-way ANOVA (fish growth performance and slaughter data) with stocking density (ALD/AHD) as main effect; two-way ANOVA (rigor mortis, physicochemical traits, microbiological quality of fish) with stocking density x storage time (1/7d) and their interaction as main effects; Bonferroni’s test used to compare means; PROC GLM, SAS 9.2 (Statistical Analysis System, 2013); significance at p<.05 (Section 2.8, p.4).
Statistically analysed	Y
Replicates (n)	3
HYD	1.75

Experimental Remarks: TRIAL DEFINITION: T2 = aquaponic ALD stocking density (low, initial 3.81 kg/m3), second cultivation cycle of lettuce cultivation (44 days). This paper has two orthogonal, independently-analysed design axes: fish stocking density (ALD vs AHD, 3 tanks/replicates each) and lettuce cultivation cycle (Cycle 1 vs Cycle 2, each with its own ANOVA/p-value in Fig. 3a/b and different plant duration, 77 vs 44 days). Both are evidenced by labelled, separately-analysed treatment arms, so this paper contributes 4 trial rows (2 densities x 2 cycles), not 2 or 1. Paired control for ALL 4 rows = HYP (hydroponic, no fish; single group, not split by density). Fish-side data (growth, water quality) is identical between the two cycle-rows of the same density (T1=T2 for ALD; T3=T4 for AHD), since fish were measured once continuously over the full 117-day trial, not per lettuce cycle. | Fish growth (Table 2, ALD, n=3 tanks, 0-117d): weight 143g(d0)->170(d22)->217(d55)->264(d84)->333g(d117,final); SGR 0-117d=0.72%/d (period SGRs: 0-22d=0.79, 22-55d=0.74, 55-84d=0.69, 84-117d=0.70); FCR 0-117d=1.65 (period FCRs: 0-22d=1.52, 22-55d=1.28, 55-84d=1.84, 84-117d=1.73); biomass density 3.81(d0)->4.53->5.78->7.04->8.86 kg/m3(d117); biomass growth 0-117d=5.05 kg/m3 (period growths: 0.72,1.25,1.26,1.82 kg/m3). None of the growth/FCR/SGR traits differed significantly from AHD (all p>=.255); biomass and biomass growth differed significantly (p<.001) purely because they track the designed stocking density itself. NOT DERIVED, left NR: Fish biomass created (kg) — paper gives biomass GROWTH only in kg/m3 (5.05 for ALD, Table 2), not an absolute kg mass; converting via tank volume would be derivation per SCHEMA.md’s explicit warning against computing ‘biomass gain’ even when inputs look present. Fish survival rate (%) — only raw death counts given (2 ALD fish died, p.4), no stated percentage; computing one = derivation. Fish weight gain (g/fish) — only sequential mean weights given per interval, no stated ‘gain’ figure; would be derivation. Total Feed (kg) — only %-of-biomass daily rates given (1.0-1.5%), never a cycle-total feed mass. % of body weight — left NR in that column because it is a 3-segment step schedule (1.5%/1.0%/1.5%), not one constant daily ration; full schedule recorded in Feed regime instead to avoid collapsing 3 distinct values into one misleading number. | NO COLUMN: Table 3 morphometric/slaughter results (n=18 fish/density, at day117): ALD — total length 289 mm, standard length 250 mm, head length 61 mm, max height 71 mm, condition factor 1.37, relative profile 0.25, cranial index 0.21, carcass weight 287 g, carcass yield 89.0%, fillet weight 165 g, fillet yield 49.9%. AHD — total length 290 mm, standard length 248 mm, head length 61 mm, max height 73 mm, condition factor 1.35, relative profile 0.25, cranial index 0.21, carcass weight 289 g, carcass yield 89.0%, fillet weight 160 g, fillet yield 48.3%. All ns (p>0.05; closest was fillet yield p=.095). | NO COLUMN: Table 4 flesh quality/rigor across ice storage (1d vs 7d post-slaughter); stocking-density main effect ns for every trait (p>=.105). ALD (1d/7d) vs AHD (1d/7d): Rigor index % 92.4/18.7 vs 89.2/11.6; muscle pH 6.55/6.45 vs 6.54/6.45; hardness N 25.0/6.9 vs 20.2/6.7; cohesiveness 0.82/0.77 vs 0.83/0.71; springiness mm 0.39/0.34 vs 0.32/0.45; chewiness N.mm 7.74/1.88 vs 5.59/1.28; TVB-N mg/100g 16.3/16.5 vs 16.9/16.7; skin L* 41.0/48.6 vs 37.1/54.8; skin a* 4.06/0.02 vs 3.34/0.11; skin b* 6.94/11.00 vs 7.40/9.03; fillet L* 38.3/43.8 vs 39.1/45.0; fillet a* -1.71/-1.32 vs -1.65/-1.06; fillet b* 9.72/7.58 vs 9.78/8.33. Storage-Time effect significant (p<=.014 to p<.001) for rigor index, muscle pH, hardness, chewiness and all colour indices except fillet a* (p=.088, ns); Density x Time interaction ns throughout (Table 4). | NO COLUMN: Table 5 skin microbial counts (log10 CFU/20cm2) at 0d/7d post-slaughter: ALD — TVC 2.06/2.41, Enterobacteriaceae 0.63/1.00, Pseudomonas 0.39/0.33, H2S-producing bacteria 0.41/0.41. AHD — TVC 2.59/2.44, Enterobacteriaceae 0.92/0.93, Pseudomonas 0.87/0.74, H2S-producing bacteria 0.89/0.82. Density effect significant only for Pseudomonas (p=.024, higher in AHD) and near-significant for H2S bacteria (p=.072); TVC/Enterobacteriaceae ns for D, T, D x T. E. coli, moulds and yeasts were NOT DETECTED in skin or lettuce and are not given numeric values anywhere in the paper (p.4, Results 3.5) — recorded as ‘not detected’ in plant_measurements.csv for the lettuce side, not fabricated as 0 or NR. | Plant yield (Cycle 2, 44 days): Results 3.4 (p.4) states explicitly ‘a higher production was recorded in aquaponic units compared to hydroponic ones in the second cycle (on average 1.98 vs. 1.75 kg m-2, p<.01; Fig. 3)’. HYD=1.75 kg/m2 is unambiguous (HYP is a single, undivided group) and is recorded here. AP=1.98 kg/m2 is explicitly a POOLED average across BOTH ALD and AHD densities together, not this row’s density alone — using it in this density-specific row would risk misattributing AHD’s contribution to an ALD row (or vice versa). No ALD-only or AHD-only Cycle-2 number exists in text or a table; the only per-density breakdown is again unlabelled Fig. 3b bar heights (not used, per the figure-reading rule). To avoid misattribution, AP is recorded NR here and the pooled 1.98 kg/m2 figure is kept only in this remark, clearly labelled as the ALD+AHD combined value, not this trial’s own. | WARN-CHECK Water NH4+/NO2-/NO3-: Table 1 and Fig. 2 report these as the ion species (NH4+, NO2-, NO3-, measured by ion chromatography, p.3), matching the schema columns’ intent (TAN/NH4-N, NO2-N, NO3-N) only if those columns are read as ion mass rather than N-only mass — a factor of ~1.29x (NH4+ vs NH4-N), ~3.29x (NO2- vs NO2-N) and 4.43x (NO3- vs NO3-N) apart. The paper itself is internally consistent (always reports the ion, e.g. axis labels ‘mg.L-1’ next to the chemical formula NH4+/NO2-/NO3- in Fig. 2, and Discussion 4.1 compares its own NO3- figure directly against Somerville et al. (2014)‘s 400 mg/L guideline using the same, apparently ion-based, convention) — there is no internal ambiguity about WHAT was measured, only a mismatch with this schema’s own ‘-N’ column naming. Recorded as printed (ion mass, clearest basis: the paper’s own stated analytical method and units); no N-only conversion applied since the paper gives no N-only figure to cross-check against (applying the 4.43/3.29/1.29 factor would be derivation). Same value shared between both cycle-rows of a density (T1=T2 for ALD; T3=T4 for AHD), since water was measured once over the full 117-day fish trial. | RECOVERED (not BLOCK, not derivation): Table 1 prints the EC unit as ‘ds cm-1’ (deciSiemens per cm). Taken literally this would be a physically implausible reading for aquaculture/hydroponic water (1.63-2.81 dS/cm = 1630-2810 mS/cm, several orders of magnitude above any real freshwater or nutrient-solution EC). The values 1.63-2.81 are entirely typical for hydroponic nutrient-solution EC if read in dS/m (=mS/cm), which is also this schema’s own EC unit. Read as dS/m (the ‘c’ in ‘cm-1’ almost certainly a typesetting/OCR substitution for ‘m-1’), per the general principle that BLOCK is for values that cannot be determined, not values written oddly (cf. SCHEMA.md’s DMS-coordinate example). Recorded value unchanged (1.63 ALD / 1.89 AHD), unit understood as dS/m. | WARN-MINOR Fish count/mortality rounding: Materials 2.2 (p.2) states 14 fish/tank x 3 tanks = 42 initial ALD fish, and 27 fish/tank x 3 tanks = 81 initial AHD fish (42+81=123, matching the abstract’s ‘123 rainbow trout’). Results 3.2 (p.4) states ‘only four fish died (2 from ALD and 2 from AHD)’. Expected survivors: ALD 42-2=40 (MATCHES Table 2’s ‘Total fish per treatment (n)’ = 40 exactly); AHD 81-2=79, but Table 2 states AHD n=78 (off by one, ~1.2%). Separately, the abstract states mortality ‘3%’ while Discussion 4.1 states ‘very low (3.3% on average)’ — both are compatible roundings of a ~3.25% overall figure (4/123), not a real conflict. Neither discrepancy affects any extracted cell: ‘Fish survival rate’ is left NR for both densities since the paper never states a per-treatment survival PERCENTAGE (only raw death counts), and computing one from counts would be derivation. | Lettuce microbiology (Table 6, log10 CFU/mL rinsate, measured ONLY at Cycle-2 harvest per Methods 2.6 ‘leaves from all plants (i.e. those of the second cycle) were collected and pooled’, p.3): recorded separately in plant_measurements.csv (TVC, Enterobacteriaceae, Pseudomonas for ALD/AHD/HYD, plus explicit non-detection of E. coli/mould/yeast). Not duplicated here.

biroloEffectsStockingDensity2020-T3

Fish

Field	Value
Fish	Rainbow trout (Oncorhynchus mykiss)
Initial Stock density	7.26
FCR	1.51
SGR	0.73
Protein	40
P	0.8
Fish size initial	140
Fish size final	329
Feed routine	Fed manually once daily until apparent satiation, in two rounds separated by 20-30 min (p.2, Section 2.2).
Feed regime	1.5% of biomass from day 0-20; 1.0% from day 23-53; 1.5% from day 56-117 (recalculated at each monthly weighing) (p.2).
Fish trial duration (days)	117

Water

Field	Value
Water recycle	5
Water type	Municipal (tap) water, no pre-treatment (p.2)
Daily Water exchange rate	0.41
Aq pH	7.24
Dissolved Oxigen	8.69
EC	1.89
Water temperature	10.8
TAN / NH4-N	0.80
NO2-N	0.18
NO3-N	417

Plant

Field	Value
Plant	Lettuce (Lactuca sativa L.)
Details	first cultivation cycle (77 days); 20 plants/unit (10 plants/tank) transplanted at third true leaf stage; harvest = all plants divided into aboveground/belowground parts, fresh weight of leaves recorded immediately per Maucieri et al. (2019) procedure (p.3). Cycle 1 began 3 days before fish addition; Cycle 2 harvested the day after fish harvest (p.2).
Days Plant after transplant	77
Plants/m2	13

System & Setup

Field	Value
Media Details	Each unit: 1 main tank (500 L, 0.80 m height, 0.90 m diameter) for fish (aquaponic) or nutrient solution (hydroponic); 2 vegetable tanks (275 L each, 0.35 m height, 1.00 m diameter; total crop area 1.6 m2) filled with 225 L of light expanded clay aggregates (LECA; specific area 250 m2/m3, packing density 300 kg/m3, total porosity 0.55 m3/m3; LECA Laterlite, Solignano, Italy), acting as both biofilter media and hydroponic growing substrate; 1 storage tank (50 L, 0.45 m height) collecting water from the vegetable tanks before pumping back to the main tank; flow driven by gravity/overflow between the 3 parts, powered by a single submersible pump (300 L/h) returning water from storage to main tank (p.2, Fig. 1).
Biological system already in use	Y (System previously used for one full cycle with European carp (Cyprinus carpio) prior to this trial, which ‘guaranteed about the regular functioning of the biofilter’ (Maucieri et al., 2019) (p.2). Municipal water used without pre-treatment to fill the systems at the start of that prior carp cycle.)
Air supplement	Y (Porous stone diffuser (4.0x4.0x15.0 cm, 14 L/min; Sweetwater AS15S) per main (fish) tank, connected to a shared aerator (Scubla D100); tanks covered with a net to prevent fish jumping (p.2).)
Iron supplemented	Y (10 g/unit of Fe-EDTA added to ALL 9 units (aquaponic and hydroponic) before the trial began (p.2), alongside other base minerals (see Remineralization).)
Remineralization	Y (Before trial start, all 9 units (both ALD/AHD aquaponic units and HYP hydroponic units) received a baseline mineral charge: 132 g/unit KH2PO4, 197 g/unit K2SO4, 273 g/unit MgSO4.7H2O, 10 g/unit Fe-EDTA, and 5 g/unit micronutrients (p.2).)
pH Buffers	N (Explicit absence stated: ‘No correction for alkalinity was performed’ (p.2).)
Climate control	N (Explicit absence stated: ‘No energy to regulate water temperature… were used’ (p.2). Grown in an unheated plastic greenhouse under natural photoperiod during the winter season (November-February); water temperature tracked ambient conditions, ranging 7.0-15.9 degC (mean 10.7 degC, Fig. 2a; Discussion 4.1).)
Artificial Lighting	N (Trial run ‘under a natural photoperiod’ (p.2, Section 2.2) with no mention of supplemental/artificial lighting equipment anywhere in Methods; read as an explicit statement that the light regime was unmodified natural daylight, not merely silence on the topic.)
Nutrient supplemented	Y (All 9 units (AP and HYP) received the same baseline mineral charge before start (see Remineralization). HYP units ADDITIONALLY received a nitrogen fertilizer charge: 333 g/unit Ca(NO3)2 and 480 g/unit NH4NO3, calculated via the free software HydroBuddy for optimal lettuce hydroponic nutrition (p.2). The ALD/AHD aquaponic units received NO additional N fertilizer beyond the baseline charge — their nitrogen supply came solely from fish feed/waste inputs over the trial.)
Equipment	Submersible pump (Newa Jet 1700, NEWA TecnoIndustria Srl, Loreggia, Italy; 300 L/h flow rate); porous stone air diffuser (4.0x4.0x15.0 cm, 14 L/min; Sweetwater AS15S, Pentair) connected to an aerator (Scubla D100, Scubla Srl); portable multi-parameter apparatus (HQ40d, Hach Lange GmbH) for temperature/DO/pH/ORP/EC; fluorescence chlorophyll detector (HHLD, Turner Designs); ion chromatography for NO2-, NO3-, PO4(3-) and NH4+ (per Maucieri et al., 2019); precision scale (1 g; Wunder Sa.Bi. srl); Minolta CM-508C spectrophotometer (skin/fillet colour Lab*); TA.XT.plus Texture Analyser (Stable Micro Systems, 20 mm cylindrical probe) for texture profile analysis; pH meter (Basic 20; Crison Instruments Sa) with specific electrode for muscle pH.
Control Parameters	Outflow water of fish tanks monitored 2x/week for temperature, dissolved oxygen, pH, redox potential (ORP) and electrical conductivity via portable multi-probe; NO2-, NO3-, PO4(3-) and NH4+ measured by ion chromatography; chlorophyll by fluorescence detector (p.2-3). Explicitly NO energy used to regulate water temperature, NO continuous water-quality probe or remote management, NO water sanitation device, and NO correction for alkalinity (p.2).
Combination	Rainbow trout (Oncorhynchus mykiss) and lettuce (Lactuca sativa L.); low-tech media-bed (expanded clay aggregate) aquaponic system at two fish stocking densities (low=ALD, high=AHD) compared against a fishless hydroponic control (HYP); winter-season trial (Nov-Feb) in an unheated plastic greenhouse, North-East Italy.

Site

Field	Value
Region	Europe
Country	Italy
Lat	45.3333
Long	11.95

Results & Statistics

Field	Value
Measured Unit	kg/m2 (marketable fresh yield: aboveground+belowground leaf fresh weight per experimental unit, per Maucieri et al. 2019 procedure)
Statistic Details	One-way ANOVA (water quality, vegetable yields, microbiological quality) with experimental group (ALD/AHD/HYP) as main effect; separate one-way ANOVA (fish growth performance and slaughter data) with stocking density (ALD/AHD) as main effect; two-way ANOVA (rigor mortis, physicochemical traits, microbiological quality of fish) with stocking density x storage time (1/7d) and their interaction as main effects; Bonferroni’s test used to compare means; PROC GLM, SAS 9.2 (Statistical Analysis System, 2013); significance at p<.05 (Section 2.8, p.4).
Statistically analysed	Y
Replicates (n)	3

Experimental Remarks: TRIAL DEFINITION: T3 = aquaponic AHD stocking density (high, initial 7.26 kg/m3), first cultivation cycle of lettuce cultivation (77 days). This paper has two orthogonal, independently-analysed design axes: fish stocking density (ALD vs AHD, 3 tanks/replicates each) and lettuce cultivation cycle (Cycle 1 vs Cycle 2, each with its own ANOVA/p-value in Fig. 3a/b and different plant duration, 77 vs 44 days). Both are evidenced by labelled, separately-analysed treatment arms, so this paper contributes 4 trial rows (2 densities x 2 cycles), not 2 or 1. Paired control for ALL 4 rows = HYP (hydroponic, no fish; single group, not split by density). Fish-side data (growth, water quality) is identical between the two cycle-rows of the same density (T1=T2 for ALD; T3=T4 for AHD), since fish were measured once continuously over the full 117-day trial, not per lettuce cycle. | Fish growth (Table 2, AHD, n=3 tanks, 0-117d): weight 140g(d0)->166(d22)->215(d55)->256(d84)->329g(d117,final); SGR 0-117d=0.73%/d (period SGRs: 0-22d=0.76, 22-55d=0.77, 55-84d=0.62, 84-117d=0.76); FCR 0-117d=1.51 (period FCRs: 0-22d=1.58, 22-55d=1.14, 55-84d=1.87, 84-117d=1.44); biomass density 7.26(d0)->8.57->11.04->13.20->16.94 kg/m3(d117, matches Conclusion’s rounded ‘approximately 17 kg m-3’); biomass growth 0-117d=9.68 kg/m3 (period growths: 1.31,2.47,2.16,3.74 kg/m3). None of the growth/FCR/SGR traits differed significantly from ALD (all p>=.255); biomass and biomass growth differed significantly (p<.001) purely because they track the designed stocking density itself. NOT DERIVED, left NR: Fish biomass created (kg) — paper gives biomass GROWTH only in kg/m3 (9.68 for AHD, Table 2), not an absolute kg mass; converting via tank volume would be derivation per SCHEMA.md’s explicit warning against computing ‘biomass gain’ even when inputs look present. Fish survival rate (%) — only raw death counts given (2 AHD fish died, p.4), no stated percentage; computing one = derivation. Fish weight gain (g/fish) — only sequential mean weights given per interval, no stated ‘gain’ figure; would be derivation. Total Feed (kg) — only %-of-biomass daily rates given, never a cycle-total feed mass. % of body weight — left NR in that column because it is a 3-segment step schedule (1.5%/1.0%/1.5%), not one constant daily ration; full schedule recorded in Feed regime instead. | NO COLUMN: Table 3 morphometric/slaughter results (n=18 fish/density, at day117): ALD — total length 289 mm, standard length 250 mm, head length 61 mm, max height 71 mm, condition factor 1.37, relative profile 0.25, cranial index 0.21, carcass weight 287 g, carcass yield 89.0%, fillet weight 165 g, fillet yield 49.9%. AHD — total length 290 mm, standard length 248 mm, head length 61 mm, max height 73 mm, condition factor 1.35, relative profile 0.25, cranial index 0.21, carcass weight 289 g, carcass yield 89.0%, fillet weight 160 g, fillet yield 48.3%. All ns (p>0.05; closest was fillet yield p=.095). | NO COLUMN: Table 4 flesh quality/rigor across ice storage (1d vs 7d post-slaughter); stocking-density main effect ns for every trait (p>=.105). ALD (1d/7d) vs AHD (1d/7d): Rigor index % 92.4/18.7 vs 89.2/11.6; muscle pH 6.55/6.45 vs 6.54/6.45; hardness N 25.0/6.9 vs 20.2/6.7; cohesiveness 0.82/0.77 vs 0.83/0.71; springiness mm 0.39/0.34 vs 0.32/0.45; chewiness N.mm 7.74/1.88 vs 5.59/1.28; TVB-N mg/100g 16.3/16.5 vs 16.9/16.7; skin L* 41.0/48.6 vs 37.1/54.8; skin a* 4.06/0.02 vs 3.34/0.11; skin b* 6.94/11.00 vs 7.40/9.03; fillet L* 38.3/43.8 vs 39.1/45.0; fillet a* -1.71/-1.32 vs -1.65/-1.06; fillet b* 9.72/7.58 vs 9.78/8.33. Storage-Time effect significant (p<=.014 to p<.001) for rigor index, muscle pH, hardness, chewiness and all colour indices except fillet a* (p=.088, ns); Density x Time interaction ns throughout (Table 4). | NO COLUMN: Table 5 skin microbial counts (log10 CFU/20cm2) at 0d/7d post-slaughter: ALD — TVC 2.06/2.41, Enterobacteriaceae 0.63/1.00, Pseudomonas 0.39/0.33, H2S-producing bacteria 0.41/0.41. AHD — TVC 2.59/2.44, Enterobacteriaceae 0.92/0.93, Pseudomonas 0.87/0.74, H2S-producing bacteria 0.89/0.82. Density effect significant only for Pseudomonas (p=.024, higher in AHD) and near-significant for H2S bacteria (p=.072); TVC/Enterobacteriaceae ns for D, T, D x T. E. coli, moulds and yeasts were NOT DETECTED in skin or lettuce and are not given numeric values anywhere in the paper (p.4, Results 3.5) — recorded as ‘not detected’ in plant_measurements.csv for the lettuce side, not fabricated as 0 or NR. | Plant yield (Cycle 1, 77 days): only a 3-GROUP POOLED average is given in text — ‘2.82 +/- 0.64 kg m-2 at the end of the first cycle… average of the three groups’ (Results 3.4, p.4), and this pools ALD+AHD+HYP together (p=.926, ns; Fig. 3a) — there is no way to disaggregate an AP-only or HYP-only Cycle-1 number from that pooled 3-way mean without derivation. The only density-specific Cycle-1 numbers exist solely as unlabelled bar heights in Fig. 3a, not reproduced in text or a table — NOT used, per the ‘never read a value off a figure’ rule. AP and HYD recorded NR for this row. | WARN-CHECK Water NH4+/NO2-/NO3-: Table 1 and Fig. 2 report these as the ion species (NH4+, NO2-, NO3-, measured by ion chromatography, p.3), matching the schema columns’ intent (TAN/NH4-N, NO2-N, NO3-N) only if those columns are read as ion mass rather than N-only mass — a factor of ~1.29x (NH4+ vs NH4-N), ~3.29x (NO2- vs NO2-N) and 4.43x (NO3- vs NO3-N) apart. The paper itself is internally consistent (always reports the ion, e.g. axis labels ‘mg.L-1’ next to the chemical formula NH4+/NO2-/NO3- in Fig. 2, and Discussion 4.1 compares its own NO3- figure directly against Somerville et al. (2014)‘s 400 mg/L guideline using the same, apparently ion-based, convention) — there is no internal ambiguity about WHAT was measured, only a mismatch with this schema’s own ‘-N’ column naming. Recorded as printed (ion mass, clearest basis: the paper’s own stated analytical method and units); no N-only conversion applied since the paper gives no N-only figure to cross-check against (applying the 4.43/3.29/1.29 factor would be derivation). Same value shared between both cycle-rows of a density (T1=T2 for ALD; T3=T4 for AHD), since water was measured once over the full 117-day fish trial. | RECOVERED (not BLOCK, not derivation): Table 1 prints the EC unit as ‘ds cm-1’ (deciSiemens per cm). Taken literally this would be a physically implausible reading for aquaculture/hydroponic water (1.63-2.81 dS/cm = 1630-2810 mS/cm, several orders of magnitude above any real freshwater or nutrient-solution EC). The values 1.63-2.81 are entirely typical for hydroponic nutrient-solution EC if read in dS/m (=mS/cm), which is also this schema’s own EC unit. Read as dS/m (the ‘c’ in ‘cm-1’ almost certainly a typesetting/OCR substitution for ‘m-1’), per the general principle that BLOCK is for values that cannot be determined, not values written oddly (cf. SCHEMA.md’s DMS-coordinate example). Recorded value unchanged (1.63 ALD / 1.89 AHD), unit understood as dS/m. | WARN-MINOR Fish count/mortality rounding: Materials 2.2 (p.2) states 14 fish/tank x 3 tanks = 42 initial ALD fish, and 27 fish/tank x 3 tanks = 81 initial AHD fish (42+81=123, matching the abstract’s ‘123 rainbow trout’). Results 3.2 (p.4) states ‘only four fish died (2 from ALD and 2 from AHD)’. Expected survivors: ALD 42-2=40 (MATCHES Table 2’s ‘Total fish per treatment (n)’ = 40 exactly); AHD 81-2=79, but Table 2 states AHD n=78 (off by one, ~1.2%). Separately, the abstract states mortality ‘3%’ while Discussion 4.1 states ‘very low (3.3% on average)’ — both are compatible roundings of a ~3.25% overall figure (4/123), not a real conflict. Neither discrepancy affects any extracted cell: ‘Fish survival rate’ is left NR for both densities since the paper never states a per-treatment survival PERCENTAGE (only raw death counts), and computing one from counts would be derivation. | Overall (all-cycle) marketable yield context: paper’s headline yield figures span both cycles and, for Cycle 1, all three groups pooled — see AP/HYD note above for why this row’s own AP/HYD cells are NR.

biroloEffectsStockingDensity2020-T4

Fish

Field	Value
Fish	Rainbow trout (Oncorhynchus mykiss)
Initial Stock density	7.26
FCR	1.51
SGR	0.73
Protein	40
P	0.8
Fish size initial	140
Fish size final	329
Feed routine	Fed manually once daily until apparent satiation, in two rounds separated by 20-30 min (p.2, Section 2.2).
Feed regime	1.5% of biomass from day 0-20; 1.0% from day 23-53; 1.5% from day 56-117 (recalculated at each monthly weighing) (p.2).
Fish trial duration (days)	117

Water

Field	Value
Water recycle	5
Water type	Municipal (tap) water, no pre-treatment (p.2)
Daily Water exchange rate	0.41
Aq pH	7.24
Dissolved Oxigen	8.69
EC	1.89
Water temperature	10.8
TAN / NH4-N	0.80
NO2-N	0.18
NO3-N	417

Plant

Field	Value
Plant	Lettuce (Lactuca sativa L.)
Details	second cultivation cycle (44 days); 20 plants/unit (10 plants/tank) transplanted at third true leaf stage; harvest = all plants divided into aboveground/belowground parts, fresh weight of leaves recorded immediately per Maucieri et al. (2019) procedure (p.3). Cycle 1 began 3 days before fish addition; Cycle 2 harvested the day after fish harvest (p.2).
Days Plant after transplant	44
Plants/m2	13

System & Setup

Field	Value
Media Details	Each unit: 1 main tank (500 L, 0.80 m height, 0.90 m diameter) for fish (aquaponic) or nutrient solution (hydroponic); 2 vegetable tanks (275 L each, 0.35 m height, 1.00 m diameter; total crop area 1.6 m2) filled with 225 L of light expanded clay aggregates (LECA; specific area 250 m2/m3, packing density 300 kg/m3, total porosity 0.55 m3/m3; LECA Laterlite, Solignano, Italy), acting as both biofilter media and hydroponic growing substrate; 1 storage tank (50 L, 0.45 m height) collecting water from the vegetable tanks before pumping back to the main tank; flow driven by gravity/overflow between the 3 parts, powered by a single submersible pump (300 L/h) returning water from storage to main tank (p.2, Fig. 1).
Biological system already in use	Y (System previously used for one full cycle with European carp (Cyprinus carpio) prior to this trial, which ‘guaranteed about the regular functioning of the biofilter’ (Maucieri et al., 2019) (p.2). Municipal water used without pre-treatment to fill the systems at the start of that prior carp cycle.)
Air supplement	Y (Porous stone diffuser (4.0x4.0x15.0 cm, 14 L/min; Sweetwater AS15S) per main (fish) tank, connected to a shared aerator (Scubla D100); tanks covered with a net to prevent fish jumping (p.2).)
Iron supplemented	Y (10 g/unit of Fe-EDTA added to ALL 9 units (aquaponic and hydroponic) before the trial began (p.2), alongside other base minerals (see Remineralization).)
Remineralization	Y (Before trial start, all 9 units (both ALD/AHD aquaponic units and HYP hydroponic units) received a baseline mineral charge: 132 g/unit KH2PO4, 197 g/unit K2SO4, 273 g/unit MgSO4.7H2O, 10 g/unit Fe-EDTA, and 5 g/unit micronutrients (p.2).)
pH Buffers	N (Explicit absence stated: ‘No correction for alkalinity was performed’ (p.2).)
Climate control	N (Explicit absence stated: ‘No energy to regulate water temperature… were used’ (p.2). Grown in an unheated plastic greenhouse under natural photoperiod during the winter season (November-February); water temperature tracked ambient conditions, ranging 7.0-15.9 degC (mean 10.7 degC, Fig. 2a; Discussion 4.1).)
Artificial Lighting	N (Trial run ‘under a natural photoperiod’ (p.2, Section 2.2) with no mention of supplemental/artificial lighting equipment anywhere in Methods; read as an explicit statement that the light regime was unmodified natural daylight, not merely silence on the topic.)
Nutrient supplemented	Y (All 9 units (AP and HYP) received the same baseline mineral charge before start (see Remineralization). HYP units ADDITIONALLY received a nitrogen fertilizer charge: 333 g/unit Ca(NO3)2 and 480 g/unit NH4NO3, calculated via the free software HydroBuddy for optimal lettuce hydroponic nutrition (p.2). The ALD/AHD aquaponic units received NO additional N fertilizer beyond the baseline charge — their nitrogen supply came solely from fish feed/waste inputs over the trial.)
Equipment	Submersible pump (Newa Jet 1700, NEWA TecnoIndustria Srl, Loreggia, Italy; 300 L/h flow rate); porous stone air diffuser (4.0x4.0x15.0 cm, 14 L/min; Sweetwater AS15S, Pentair) connected to an aerator (Scubla D100, Scubla Srl); portable multi-parameter apparatus (HQ40d, Hach Lange GmbH) for temperature/DO/pH/ORP/EC; fluorescence chlorophyll detector (HHLD, Turner Designs); ion chromatography for NO2-, NO3-, PO4(3-) and NH4+ (per Maucieri et al., 2019); precision scale (1 g; Wunder Sa.Bi. srl); Minolta CM-508C spectrophotometer (skin/fillet colour Lab*); TA.XT.plus Texture Analyser (Stable Micro Systems, 20 mm cylindrical probe) for texture profile analysis; pH meter (Basic 20; Crison Instruments Sa) with specific electrode for muscle pH.
Control Parameters	Outflow water of fish tanks monitored 2x/week for temperature, dissolved oxygen, pH, redox potential (ORP) and electrical conductivity via portable multi-probe; NO2-, NO3-, PO4(3-) and NH4+ measured by ion chromatography; chlorophyll by fluorescence detector (p.2-3). Explicitly NO energy used to regulate water temperature, NO continuous water-quality probe or remote management, NO water sanitation device, and NO correction for alkalinity (p.2).
Combination	Rainbow trout (Oncorhynchus mykiss) and lettuce (Lactuca sativa L.); low-tech media-bed (expanded clay aggregate) aquaponic system at two fish stocking densities (low=ALD, high=AHD) compared against a fishless hydroponic control (HYP); winter-season trial (Nov-Feb) in an unheated plastic greenhouse, North-East Italy.

Site

Field	Value
Region	Europe
Country	Italy
Lat	45.3333
Long	11.95

Results & Statistics

Field	Value
Measured Unit	kg/m2 (marketable fresh yield: aboveground+belowground leaf fresh weight per experimental unit, per Maucieri et al. 2019 procedure)
Statistic Details	One-way ANOVA (water quality, vegetable yields, microbiological quality) with experimental group (ALD/AHD/HYP) as main effect; separate one-way ANOVA (fish growth performance and slaughter data) with stocking density (ALD/AHD) as main effect; two-way ANOVA (rigor mortis, physicochemical traits, microbiological quality of fish) with stocking density x storage time (1/7d) and their interaction as main effects; Bonferroni’s test used to compare means; PROC GLM, SAS 9.2 (Statistical Analysis System, 2013); significance at p<.05 (Section 2.8, p.4).
Statistically analysed	Y
Replicates (n)	3
HYD	1.75

Experimental Remarks: TRIAL DEFINITION: T4 = aquaponic AHD stocking density (high, initial 7.26 kg/m3), second cultivation cycle of lettuce cultivation (44 days). This paper has two orthogonal, independently-analysed design axes: fish stocking density (ALD vs AHD, 3 tanks/replicates each) and lettuce cultivation cycle (Cycle 1 vs Cycle 2, each with its own ANOVA/p-value in Fig. 3a/b and different plant duration, 77 vs 44 days). Both are evidenced by labelled, separately-analysed treatment arms, so this paper contributes 4 trial rows (2 densities x 2 cycles), not 2 or 1. Paired control for ALL 4 rows = HYP (hydroponic, no fish; single group, not split by density). Fish-side data (growth, water quality) is identical between the two cycle-rows of the same density (T1=T2 for ALD; T3=T4 for AHD), since fish were measured once continuously over the full 117-day trial, not per lettuce cycle. | Fish growth (Table 2, AHD, n=3 tanks, 0-117d): weight 140g(d0)->166(d22)->215(d55)->256(d84)->329g(d117,final); SGR 0-117d=0.73%/d (period SGRs: 0-22d=0.76, 22-55d=0.77, 55-84d=0.62, 84-117d=0.76); FCR 0-117d=1.51 (period FCRs: 0-22d=1.58, 22-55d=1.14, 55-84d=1.87, 84-117d=1.44); biomass density 7.26(d0)->8.57->11.04->13.20->16.94 kg/m3(d117, matches Conclusion’s rounded ‘approximately 17 kg m-3’); biomass growth 0-117d=9.68 kg/m3 (period growths: 1.31,2.47,2.16,3.74 kg/m3). None of the growth/FCR/SGR traits differed significantly from ALD (all p>=.255); biomass and biomass growth differed significantly (p<.001) purely because they track the designed stocking density itself. NOT DERIVED, left NR: Fish biomass created (kg) — paper gives biomass GROWTH only in kg/m3 (9.68 for AHD, Table 2), not an absolute kg mass; converting via tank volume would be derivation per SCHEMA.md’s explicit warning against computing ‘biomass gain’ even when inputs look present. Fish survival rate (%) — only raw death counts given (2 AHD fish died, p.4), no stated percentage; computing one = derivation. Fish weight gain (g/fish) — only sequential mean weights given per interval, no stated ‘gain’ figure; would be derivation. Total Feed (kg) — only %-of-biomass daily rates given, never a cycle-total feed mass. % of body weight — left NR in that column because it is a 3-segment step schedule (1.5%/1.0%/1.5%), not one constant daily ration; full schedule recorded in Feed regime instead. | NO COLUMN: Table 3 morphometric/slaughter results (n=18 fish/density, at day117): ALD — total length 289 mm, standard length 250 mm, head length 61 mm, max height 71 mm, condition factor 1.37, relative profile 0.25, cranial index 0.21, carcass weight 287 g, carcass yield 89.0%, fillet weight 165 g, fillet yield 49.9%. AHD — total length 290 mm, standard length 248 mm, head length 61 mm, max height 73 mm, condition factor 1.35, relative profile 0.25, cranial index 0.21, carcass weight 289 g, carcass yield 89.0%, fillet weight 160 g, fillet yield 48.3%. All ns (p>0.05; closest was fillet yield p=.095). | NO COLUMN: Table 4 flesh quality/rigor across ice storage (1d vs 7d post-slaughter); stocking-density main effect ns for every trait (p>=.105). ALD (1d/7d) vs AHD (1d/7d): Rigor index % 92.4/18.7 vs 89.2/11.6; muscle pH 6.55/6.45 vs 6.54/6.45; hardness N 25.0/6.9 vs 20.2/6.7; cohesiveness 0.82/0.77 vs 0.83/0.71; springiness mm 0.39/0.34 vs 0.32/0.45; chewiness N.mm 7.74/1.88 vs 5.59/1.28; TVB-N mg/100g 16.3/16.5 vs 16.9/16.7; skin L* 41.0/48.6 vs 37.1/54.8; skin a* 4.06/0.02 vs 3.34/0.11; skin b* 6.94/11.00 vs 7.40/9.03; fillet L* 38.3/43.8 vs 39.1/45.0; fillet a* -1.71/-1.32 vs -1.65/-1.06; fillet b* 9.72/7.58 vs 9.78/8.33. Storage-Time effect significant (p<=.014 to p<.001) for rigor index, muscle pH, hardness, chewiness and all colour indices except fillet a* (p=.088, ns); Density x Time interaction ns throughout (Table 4). | NO COLUMN: Table 5 skin microbial counts (log10 CFU/20cm2) at 0d/7d post-slaughter: ALD — TVC 2.06/2.41, Enterobacteriaceae 0.63/1.00, Pseudomonas 0.39/0.33, H2S-producing bacteria 0.41/0.41. AHD — TVC 2.59/2.44, Enterobacteriaceae 0.92/0.93, Pseudomonas 0.87/0.74, H2S-producing bacteria 0.89/0.82. Density effect significant only for Pseudomonas (p=.024, higher in AHD) and near-significant for H2S bacteria (p=.072); TVC/Enterobacteriaceae ns for D, T, D x T. E. coli, moulds and yeasts were NOT DETECTED in skin or lettuce and are not given numeric values anywhere in the paper (p.4, Results 3.5) — recorded as ‘not detected’ in plant_measurements.csv for the lettuce side, not fabricated as 0 or NR. | Plant yield (Cycle 2, 44 days): Results 3.4 (p.4) states explicitly ‘a higher production was recorded in aquaponic units compared to hydroponic ones in the second cycle (on average 1.98 vs. 1.75 kg m-2, p<.01; Fig. 3)’. HYD=1.75 kg/m2 is unambiguous (HYP is a single, undivided group) and is recorded here. AP=1.98 kg/m2 is explicitly a POOLED average across BOTH ALD and AHD densities together, not this row’s density alone — using it in this density-specific row would risk misattributing AHD’s contribution to an ALD row (or vice versa). No ALD-only or AHD-only Cycle-2 number exists in text or a table; the only per-density breakdown is again unlabelled Fig. 3b bar heights (not used, per the figure-reading rule). To avoid misattribution, AP is recorded NR here and the pooled 1.98 kg/m2 figure is kept only in this remark, clearly labelled as the ALD+AHD combined value, not this trial’s own. | WARN-CHECK Water NH4+/NO2-/NO3-: Table 1 and Fig. 2 report these as the ion species (NH4+, NO2-, NO3-, measured by ion chromatography, p.3), matching the schema columns’ intent (TAN/NH4-N, NO2-N, NO3-N) only if those columns are read as ion mass rather than N-only mass — a factor of ~1.29x (NH4+ vs NH4-N), ~3.29x (NO2- vs NO2-N) and 4.43x (NO3- vs NO3-N) apart. The paper itself is internally consistent (always reports the ion, e.g. axis labels ‘mg.L-1’ next to the chemical formula NH4+/NO2-/NO3- in Fig. 2, and Discussion 4.1 compares its own NO3- figure directly against Somerville et al. (2014)‘s 400 mg/L guideline using the same, apparently ion-based, convention) — there is no internal ambiguity about WHAT was measured, only a mismatch with this schema’s own ‘-N’ column naming. Recorded as printed (ion mass, clearest basis: the paper’s own stated analytical method and units); no N-only conversion applied since the paper gives no N-only figure to cross-check against (applying the 4.43/3.29/1.29 factor would be derivation). Same value shared between both cycle-rows of a density (T1=T2 for ALD; T3=T4 for AHD), since water was measured once over the full 117-day fish trial. | RECOVERED (not BLOCK, not derivation): Table 1 prints the EC unit as ‘ds cm-1’ (deciSiemens per cm). Taken literally this would be a physically implausible reading for aquaculture/hydroponic water (1.63-2.81 dS/cm = 1630-2810 mS/cm, several orders of magnitude above any real freshwater or nutrient-solution EC). The values 1.63-2.81 are entirely typical for hydroponic nutrient-solution EC if read in dS/m (=mS/cm), which is also this schema’s own EC unit. Read as dS/m (the ‘c’ in ‘cm-1’ almost certainly a typesetting/OCR substitution for ‘m-1’), per the general principle that BLOCK is for values that cannot be determined, not values written oddly (cf. SCHEMA.md’s DMS-coordinate example). Recorded value unchanged (1.63 ALD / 1.89 AHD), unit understood as dS/m. | WARN-MINOR Fish count/mortality rounding: Materials 2.2 (p.2) states 14 fish/tank x 3 tanks = 42 initial ALD fish, and 27 fish/tank x 3 tanks = 81 initial AHD fish (42+81=123, matching the abstract’s ‘123 rainbow trout’). Results 3.2 (p.4) states ‘only four fish died (2 from ALD and 2 from AHD)’. Expected survivors: ALD 42-2=40 (MATCHES Table 2’s ‘Total fish per treatment (n)’ = 40 exactly); AHD 81-2=79, but Table 2 states AHD n=78 (off by one, ~1.2%). Separately, the abstract states mortality ‘3%’ while Discussion 4.1 states ‘very low (3.3% on average)’ — both are compatible roundings of a ~3.25% overall figure (4/123), not a real conflict. Neither discrepancy affects any extracted cell: ‘Fish survival rate’ is left NR for both densities since the paper never states a per-treatment survival PERCENTAGE (only raw death counts), and computing one from counts would be derivation. | Lettuce microbiology (Table 6, log10 CFU/mL rinsate, measured ONLY at Cycle-2 harvest per Methods 2.6 ‘leaves from all plants (i.e. those of the second cycle) were collected and pooled’, p.3): recorded separately in plant_measurements.csv (TVC, Enterobacteriaceae, Pseudomonas for ALD/AHD/HYD, plus explicit non-detection of E. coli/mould/yeast). Not duplicated here.

Plant Measurements

Trial	System	Category	Analyte	Value	Unit	Sig.	Location
biroloEffectsStockingDensity2020-T2	AP	microbiology	Total viable count	5.41	log10 CFU/mL (rinsate)	ns (p=.536)	Table 6
biroloEffectsStockingDensity2020-T2	HYD	microbiology	Total viable count	5.64	log10 CFU/mL (rinsate)	ns (p=.536)	Table 6
biroloEffectsStockingDensity2020-T4	AP	microbiology	Total viable count	5.89	log10 CFU/mL (rinsate)	ns (p=.536)	Table 6
biroloEffectsStockingDensity2020-T4	HYD	microbiology	Total viable count	5.64	log10 CFU/mL (rinsate)	ns (p=.536)	Table 6
biroloEffectsStockingDensity2020-T2	AP	microbiology	Enterobacteriaceae	3.43	log10 CFU/mL (rinsate)	ns (p=.274)	Table 6
biroloEffectsStockingDensity2020-T2	HYD	microbiology	Enterobacteriaceae	1.98	log10 CFU/mL (rinsate)	ns (p=.274)	Table 6
biroloEffectsStockingDensity2020-T4	AP	microbiology	Enterobacteriaceae	2.44	log10 CFU/mL (rinsate)	ns (p=.274)	Table 6
biroloEffectsStockingDensity2020-T4	HYD	microbiology	Enterobacteriaceae	1.98	log10 CFU/mL (rinsate)	ns (p=.274)	Table 6
biroloEffectsStockingDensity2020-T2	AP	microbiology	Pseudomonas	6.04	log10 CFU/mL (rinsate)	ns (p=.492)	Table 6
biroloEffectsStockingDensity2020-T2	HYD	microbiology	Pseudomonas	6.03	log10 CFU/mL (rinsate)	ns (p=.492)	Table 6
biroloEffectsStockingDensity2020-T4	AP	microbiology	Pseudomonas	5.70	log10 CFU/mL (rinsate)	ns (p=.492)	Table 6
biroloEffectsStockingDensity2020-T4	HYD	microbiology	Pseudomonas	6.03	log10 CFU/mL (rinsate)	ns (p=.492)	Table 6
biroloEffectsStockingDensity2020-T2	AP	microbiology	Escherichia coli	not detected	log10 CFU/mL (rinsate)	NR	Results 3.5, p.4
biroloEffectsStockingDensity2020-T2	AP	microbiology	Moulds	not detected	log10 CFU/mL (rinsate)	NR	Results 3.5, p.4
biroloEffectsStockingDensity2020-T2	AP	microbiology	Yeasts	not detected	log10 CFU/mL (rinsate)	NR	Results 3.5, p.4
biroloEffectsStockingDensity2020-T2	HYD	microbiology	Escherichia coli	not detected	log10 CFU/mL (rinsate)	NR	Results 3.5, p.4
biroloEffectsStockingDensity2020-T2	HYD	microbiology	Moulds	not detected	log10 CFU/mL (rinsate)	NR	Results 3.5, p.4
biroloEffectsStockingDensity2020-T2	HYD	microbiology	Yeasts	not detected	log10 CFU/mL (rinsate)	NR	Results 3.5, p.4
biroloEffectsStockingDensity2020-T4	AP	microbiology	Escherichia coli	not detected	log10 CFU/mL (rinsate)	NR	Results 3.5, p.4
biroloEffectsStockingDensity2020-T4	AP	microbiology	Moulds	not detected	log10 CFU/mL (rinsate)	NR	Results 3.5, p.4
biroloEffectsStockingDensity2020-T4	AP	microbiology	Yeasts	not detected	log10 CFU/mL (rinsate)	NR	Results 3.5, p.4
biroloEffectsStockingDensity2020-T4	HYD	microbiology	Escherichia coli	not detected	log10 CFU/mL (rinsate)	NR	Results 3.5, p.4
biroloEffectsStockingDensity2020-T4	HYD	microbiology	Moulds	not detected	log10 CFU/mL (rinsate)	NR	Results 3.5, p.4
biroloEffectsStockingDensity2020-T4	HYD	microbiology	Yeasts	not detected	log10 CFU/mL (rinsate)	NR	Results 3.5, p.4

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Effects of stocking density on the growth and flesh quality of rainbow trout (Oncorhynchus mykiss) reared in a low-tech aquaponic system

Effects of stocking density on the growth and flesh quality of rainbow trout (Oncorhynchus mykiss) reared in a low-tech aquaponic system

Metadata

Abstract

Summary

Fish growth performance and stocking density

Flesh quality and shelf life

Lettuce yield and aquaponic vs hydroponic comparison

Water quality and stocking density

Linked claims

Citations to chase

Extraction notes

Data Tables

Trial Parameters

biroloEffectsStockingDensity2020-T1

biroloEffectsStockingDensity2020-T2

biroloEffectsStockingDensity2020-T3

biroloEffectsStockingDensity2020-T4

Plant Measurements

Graph View

Table of Contents

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