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The objective of this study was to optimize nursery diets for post‐metamorphic stage black sea bass by evaluating growth performance, whole‐body proximate and fatty acid composition, and utilization of University of North Carolina Wilmington (UNCW)‐formulated and commercial diets under laboratory conditions. A feeding trial was conducted to compare two UNCW‐formulated diets (D1 and D2) for black sea bass (54% crude protein = CP and 14% crude lipid = CL) and two premium, commercial marine finfish fry diets, Otohime (Reed Mariculture Inc., Campbell, CA, CP = 48% and CL = 14%, CD3) and Gemma Diamond (Skretting, Nutreco, Canada, CP = 57%, CL = 15%, CD4). The UNCW‐formulated diet 1 (D1) contained high fish meal (FM, 40% of diet), whereas UNCW‐formulated diet 2 (D2) replaced 50% FM protein by high‐quality poultry by‐product meal (PBM) protein. Post‐metamorphic stage black sea bass (~0.60 g, d40ph) were stocked in each of sixteen 75‐L tanks at a density of 1 fish per L (75 per tank), with four replicate aquaria per treatment. Fish were fed four times per day (0800, 1100, 1400, and 1600 h) to apparent satiation for 30 days. Final body weight (5.70–5.74), specific growth rate (7.40–7.45%/d), and percent body weight gain (834–848%) of fish fed the UNCW‐formulated D1 (FM‐based) and D2 (FM + PBM‐based) were higher (p <.05) than in fish fed the commercial diets CD3 and CD4 (4.66–5.21 g, 6.80–7.15%/d, and 668–756%, respectively). Feed intake (% body weight/d was significantly lower for fish fed commercial diet (CD4) (3.94) compared with fish fed CD3 (4.20), but feed intake for CD3 was not significantly different compared with the UNCW‐formulated diets D1 and D2 (4.10–4.12). Feed conversion ratios (0.76–0.82) were significantly higher for fish fed CD3 (0.82) than for fish fed D1 and CD4 (0.76). Survival was high (99–100%) in all diet treatments. Final whole‐body crude protein content (15.2 to 15.9% wet basis), moisture (68.9–69.6%), and ash (4.31–4.77%) showed no significant differences; however, whole‐body crude lipid was lower in fish fed CD3 (9.67%) than in fish fed the other diets (9.96–10.22%). Final whole‐body fatty acid composition reflected the diet composition. Higher feed consumption and growth of fish fed the UNCW‐formulated diets were attributed to a more optimal combination of marine (fish, squid, and krill meals), terrestrial plant (soybean meal) protein sources, and the addition of chemo‐attractants, which provided both higher nutritional quality and palatability. The study suggests that the species‐specific starter diets may improve growth performance and fingerling quality and may therefore lower production costs under intensive nursery conditions. [ABSTRACT FROM AUTHOR]

Black sea bass (BSB), Centropristis striata, inhabit continental shelf waters of the eastern United States and are a member of the family Serranidae comprising true sea basses and groupers. Highly sought by fishermen, BSB are sustainably managed with 2018 commercial and recreational catch quotas of 1,600 and 1,664 m.t. (3.52 and 3.66 million lb), respectively. Wild broodstock are easily caught and adapted to recirculating aquaculture systems (RASs). The initiation and duration of the spawning period are controlled by photothermal conditioning, and eggs and larvae have been produced from December through August. GnRHa (5–10 μg/g bw) implants are effective at inducing ovulation in post‐vitellogenic females (>500 μm mean oocyte diameter = MOD). Fertilized eggs (0.94 mm diameter) are obtainable by strip spawning, but volitional spawning may yield higher egg quality. Most BSB develop as females and then switch to male (protogynous hermaphrodites) after several years. Yolksac larvae (YSL, 0 day post‐hatching = 0 dph, 3.0 mm total length = TL) are reared to the post‐metamorphic stage in RASs using greenwater Nannochloropsis oculata and enriched rotifers (2–22 dph), Artemia nauplii (16–22 dph) and enriched metanauplii (23–36 dph), and co‐feeding microparticulate diets (55.5–59% crude protein (CP), 10–15% crude lipid (CL)) from 15 dph, with complete weaning by 36 dph. Environmental optima for larvae are temperature (19–22°C), salinity (28–36 g/L), light intensity (1,500 lx), and photoperiod (16 L: 8 D). Survival of YSL to 50 dph (1 g) averages 12–15%. Advanced fingerlings (mean wt. = 27 g) were stocked in 16 m3 RAS tanks (103 fish/m3) at 33 g/L and 21°C and fed a commercial diet (55% CP, 15% CL) reached mean marketable sizes of 454 g (1 lb), 568 g (1.25 lb), and 682 g (1.5 lb) in 17, 20.2, and 22.9 months post‐hatching, respectively, with high growth variation. Harvest biomass density was 55 kg/m3 and feed conversion ratio was 1.1–1.2. Pasteurellosis Photobacterium damsela infections during growout were controlled by lowering water temperature. Wholesale prices for whole‐on‐ice BSB (0.75 lb to >2.0 lb) are size‐tiered, with higher per pound prices for larger fish. BSB growers target niche markets for ultra‐fresh product, which garner premium prices for fish of assorted sizes. Availability of BSB fingerlings from the University of North Carolina Wilmington's hatchery has enabled startup RAS farmers to grow and to market BSB, but commercial expansion will require investment in research to lower production costs. Research is needed to lower feed and fingerling costs, increase growth and minimize size variation through grading and selective breeding, maximize biomass densities in RAS, and biomitigate RAS nutrients by multitrophic aquaculture. In‐depth economic modeling of BSB production in RAS incorporating the latest and untapped advances in culture technologies will be important to understand opportunities for improving profitability. [ABSTRACT FROM AUTHOR]