The effects of tank colours on the growth and survival of cuttlefish (Sepia officinalis,Linnaeus 1758) hatchlings and juveniles

The effects of different tank colours (white, yellow sandy and black) on the growth, mortality and biomass production were studied for hatchling and early juvenile cuttlefish. For hatchlings, the use of different colour tanks did not promote differences in growth due to the higher variability (standard deviation) found in the white‐ and sand‐coloured tanks. Black tanks promoted the lowest and highest values for total mortality and biomass respectively. For juveniles, the use of different tank colours promoted different growth (P<0.05), but not mortality. Black tanks promoted the best results in terms of growth and biomass. The results obtained in the present study advise the use of black (or dark colour) tanks in the hatchling and early juvenile stages to reduce the standard deviations associated with growth, mortality and biomass production. This will contribute to minimize problems associated with slow and fast growers and competition.     

Effects of prey nutritional quality on the growth and survival of juvenile cuttlefish, Sepia officinalis (Linnaeus, 1758)

This investigation examined the effect of prey condition on the growth and survival of juvenile cuttlefish ( Sepia officinalis ). In the first group, cuttlefish were fed with daily captured live Palaeomonetes varians from the wild [daily prey (DP)], the second group was fed 5 days stocked and starved P. varians [starved prey (SP)], while in the third group, cuttlefish were fed 8 days stocked P. varians fed with an artificial diet [fed prey (FP)]. Mean instantaneous growth rate (IGR) was 2.8±1% body weight day⁻¹ (bw day⁻¹), 3.3±1.1% bw day⁻¹ and 4.9±0.5% bw day⁻¹ for SP, DP and FP respectively. At the end of the experiment, final weight gain ( W _g) was 121±21.6%, 153.8±17.3% and 295±29.8% for SP, DP and FP respectively. No significant differences were found ( P >0.05) between growth curves for every group tested, or for the food conversions between those same groups ( P >0.05), but statistical differences ( P <0.05) were found in IGR between DP vs. FP and SP vs. FP. Mortality was 2 and 1 for SP and DP respectively. Results indicate that prey starvation should not be considered when feeding juvenile cuttlefish, as prey can only be stocked if proper artificial diets are provided, to obtain optimal growth.     

Effects of light spectrum and intensity on growth,survival and physiology of leech (Whitmania pigra) larvae under the rearing conditions

Used as a traditional Chinese medicine, the high mortality rate and slow growth of Whitmania pigra larvae are the most serious bottlenecks for the scale development of artificial breeding. Firstly, five light colour treatments (white, blue, green, red and yellow) were tested to determine effects of light spectrum on the growth of larval W. pigra at the same intensity of 70.00 μmol m^?2 s^?1. The experiment lasted for 45 days. Under our experimental conditions, the weight gain (WG) and the specific growth rate (SGR) under blue light condition were significantly higher compared with the other treatments (P ≤ 0.05). It is reasonable to conclude that blue light can promote the leech growth. In addition, reared at five blue light intensity treatments (20.00 ± 3.84, 40.78 ± 4.18, 53.67 ± 5.98, 70.00 ± 7.26 and 87.33 ± 5.77 μmol m^?2 s^?1), the WG and SGR increased with increasing intensity. Meanwhile, they were significantly higher in the 70.00 and 87.33 μmol m^?2 s^?1 treatments (P ≤ 0.05). In the higher intensity light treatments, the digestive enzymes were higher and antioxidant enzymes were lower. These results suggest that the optimal light spectrum for the culture of W. pigra during the early life stage was blue and the optimal light intensity was higher light intensity (70.00–87.33 μmol m^?2 s^?1).     

Growth of young cuttlefish, Sepia officinalis (Linnaeus 1758) at the upper end of the biological distribution temperature range

Individual growth rates, feeding rates (%BWd^?1) and food conversions for cuttlefish (S. officinalis) hatchlings and juveniles were determined during this study. A flow‐through system was used. Water temperature reached 30 °C during the hottest part of the day, gradually decreasing to 25 °C during the night; salinity varied between 37 ± 3 ppt and lights were kept on for 14 h day^?1. Hatchlings were placed in separate compartments with a water volume of 1.2 L. Juvenile cuttlefish (from 0.5 to 25 g) were placed in bigger baskets, with a water volume of 5.2 L. Water flow was 120 L h^?1. The biggest cuttlefish used in these experiments (> 25 g) were gathered in groups of five and placed in circular tanks (water volume of 250–300 L). Thus, results obtained in this case are means and not individual data. During the first 10, 20, 30 and 40 days, mean growth rates (of all individuals sampled by age group) decreased consistently (11.8 ± 4.1, 9.8 ± 1.8, 8.1 ± 2.2 and 7.3 ± 0.7%BW^?1 respectively); in similar fashion, mean feeding rates decreased with age group (33.7 ± 13.5, 22.0 ± 7.9, 17.3 ± 3.9 and 16.7%BWd^?1 respectively). Mean food conversions varied between 3.6 and 2.5 between the age groups. When grouping results by weight class, similar patterns occur, as growth and feeding rates decrease consistently as cuttlefish grow bigger. Highest mean growth and feeding rates are obtained by hatchlings (< 0.1 g) with 12.4 ± 4.5 and 35.3 ± 15.1%BWd^?1, respectively, while the lowest growth and feeding rates were recorded for the largest animals, between 15 and 25 g (3.4 ± 1.1 and 10.8 ± 4.1%BWd^?1 respectively). For these weight classes, mean food conversions varied between 2.7 ± 0.9 and 3.8 ± 2.8.     

Effects of live prey availability on growth and survival in the early stages of cuttlefish Sepia officinalis (Linnaeus, 1758) life cycle

This investigation examined the effects of live prey availability on growth and survival of Sepia officinalis. Two independent experiments, comprising two feed rations each, were performed, using adequate prey size. In the first experiment, cuttlefish hatchlings were fed live mysids, Paramysis nouvelli [(feed ratio I (fr I)], at 15% body weight per day (bw day^?1) (fr I₁₅) and 30% bw day^?1 (fr I₃₀). In the second experiment, juvenile cuttlefish were fed live Atlantic ditch shrimp, Paleomonetes varians (fr II), under the same experimental design. In both experiments, the final mean weight, feeding rate and instantaneous growth rate were higher when animals were fed feed ratio fr II₁₅ and fr II₃₀ (30% bw day^?1). The results indicate that prey availability influenced weight gain, irrespective of the prey used, during the first 2 months of cuttlefish life cycle. This effect seems to be more noticeable when a certain limit of prey is achieved. For cuttlefish fed fr II, the optimal prey density is thought to be under 2.5 g prey L^?1 (i.e. 14 shrimp L^?1). Results indicate that cuttlefish can withstand prey densities up to 120 mysids L^?1 for cuttlefish up to 3 weeks old and 19 shrimps L^?1 for cuttlefish up to 6 weeks old.     

Effects of increased tank bottom areas on cuttlefish (Sepia officinalis,L.) reproduction performance

The objective of this research was to determine the effects of using tanks with different bottom areas/volumes on the growth and reproduction of the European cuttlefish, Sepia officinalis. One hundred and eighty‐four juvenile cuttlefish (46.1 ± 20.9 g) were used to test replicates of 9000 L (6.67 m²), 750 L (1.54 m²) and 250 L (0.79 m² – control). Growth and reproduction data were registered. In addition, egg proximate composition differences were assessed by collecting egg samples from each tank. Regarding growth, no statistical differences between tank types were found (P > 0.05), but total absolute mortality was lower in 9000 L tanks. As for reproduction, differences were found (P < 0.05) between individual tanks for mean egg (MEW), male (MW ♂ ) and hatchling (MHW) weights; and egg batch number. One of the 9000 L tanks displayed the highest overall and individual fecundity (16 593 and 1383 eggs respectively) and egg viability (~72%) ever obtained in our facilities. Differences (P < 0.05) regarding egg proximate composition of different tanks were noted. Significant (P < 0.05) correlations were established between the duration of reproduction stage and batch, MEW and MW♀, egg viability and MHW, and MHW and egg ash content. The present results might be related to sex ratios, differences in weight between ♀ and ♂, and/or derived from breeders condition.     

Aspects of the growth of cultured cuttlefish Sepia officinalis (Linnaeus 1758)

Feeding rates, growth rates and feed efficiency ratios were studied in experimentally reared juvenile cuttlefish Sepia officinalis which had been hatched from eggs collected from three different locations, Plymouth, North Wales and Southampton. Groups of newly hatched cuttlefish were either maintained at 19°C and well fed (experiment 1) or were maintained at ambient seawater temperature (7–16°C) with little food for 6 months so that their development was delayed and then transferred to optimum conditions (experiment 2). In the first investigation (expt 1), no significant differences in growth rates (3.72±0.08%, 3.75±0.04% and 3.55±0.04% body weight (BW) day^?1 respectively), feeding rates (9.53±0.36%, 9.28±0.36% and 8.95±0.37% BW day^?1 respectively) and feed efficiency ratios (38.11±1.67%, 40.52±1.78% and 39.96±1.78% respectively) were observed between cuttlefish from the 3 locations. During the second investigation (expt 2), cuttlefish, whose development was initially delayed after hatching and then were stimulated to grow under optimum conditions (19°C and fed), showed growth rates (3.46±0.08% BW day^?1) similar to those held under optimum conditions of seawater temperature (19°C) and food supply shortly after hatching. Feeding rates and feed efficiency ratios were however significantly higher in cuttlefish maintained at 19°C compared to 11°C (8.27±0.14% BW day^?1, 41.25±0.52% and 2.75±0.09% BW day^?1, 24.87±1.87% respectively).     

Early weaning of cuttlefish (Sepia officinalis,L.) with frozen grass shrimp (Palaemonetes varians) from the first day after hatching

The suitability of early weaning cuttlefish using frozen grass shrimp, and its effects on growth and mortality was determined in a 50‐day experiment. Three food groups were used. One group (C) was fed with live prey until 25th DAH and weaned with frozen prey until the end of the experiment. In the other two groups, weaning started at the fifth DAH (W5) and first DAH (W1), also with frozen diet. Significant differences were found between C and the remaining treatments (P < 0.05) for mean wet weight (MWW), instantaneous growth rate (IGR), biomass (B) and mortality at the 25th and the 50th DAH. Despite the lower growth (~1/3 of the achieved with live food) and higher mortality (3% obtained by C versus 23% in the W1 and W5 groups), C cuttlefish presented a similar weight gain tendency to W1 and W5 groups after weaning. This is the first record of early acceptance (at the first DAH) of frozen food by cuttlefish hatchlings. These differences could be related with digestive enzymes of cuttlefish and prey, changes in nutritional composition and amount of captured prey, etc. Future research should also address the effects of this early weaning on cuttlefish life cycle.     

Effects of light quality and intensity on the growth,survival and metamorphosis of Haliotis discus hannai Ino larvae

Light is a key environmental factor that influences the growth, culture and survival of aquatic organisms. This study examined the effects of different light qualities (red, orange, white, blue and green light) and intensities (5 μmol m^?2 s^?1, 15 μmol m^?2 s^?1 and 40 μmol m^?2 s^?1) on the hatching and metamorphosis of larva of Haliotis discus hannai Ino and the growth and survival of juveniles. It was found that under blue and green light, the hatching success rate and metamorphosis of larva were significantly higher than those for any other light quality (P < 0.05), and there was a decreasing trend with an increase in light intensity. Under red and orange light, the abnormality rate of trochophores in each light intensity treatment and the time required for the metamorphosis of larva were significantly higher than those for any other light group (P < 0.05). Both the abnormality and metamorphosis rates significantly increased with light intensity. Under white light, at an intensity of 40 μmol m^?2 s^?1, the settlement and size of larva at metamorphosis were significantly smaller than those for any other light intensity (P < 0.05). Under red and orange light, the SGR of juvenile abalone in each light intensity treatment was significantly lower than that in any other light group (P < 0.05), but no significant difference was identified (P > 0.05). Therefore, selecting blue and green light and controlling the light intensity to 5–15 μmol m^?2 s^?1 during fingerling reproduction of abalone should increase the hatching success rate of larva and the yield per water body.     

The use of alternative diets to culture juvenile cuttlefish,Sepia officinalis: effects on growth and lipid composition

The effects of feeding three natural frozen diets, grass shrimp (Palaemonetes sp.), crayfish (Procambarus clarkii) and fish (Sardina pilchardus) and two semi‐humid artificial diets (based on fish or shrimp powder) to the cuttlefish, Sepia officinalis, were analysed. Growth rate and feeding rate [FR; % body weight (BW) day^?1] and food conversions (FC, %) were determined. Cuttlefish fed shrimp grew larger (3.8% BW day^?1) and had the highest FC, followed by those fed crayfish, and sardine. The highest FR was obtained for cuttlefish fed crayfish (10.5% BW day^?1). Although both artificial diets were accepted, none produced growth. Digestive gland‐to‐body weight ratio (DG/BW ratio) was calculated for animals fed each diet. A positive correlation (r = 0.94) between cuttlefish ingestion FR and DG weight was obtained. Mortality occurred mainly during the last week, and some cannibalism occurred among cuttlefish fed artificial diets. Finally, lipid composition of diets, DG and mantle of each group were analysed. Sardine diet was characterized by high levels of triacylglycerol (TG), whereas the main difference between shrimp and crayfish was the higher n‐3/n‐6 ratio found in shrimp. Changes in the lipid composition of DG were related to diet, but did not correlate with growth data. A strong loss of TG in the DG of artificial diets groups was notable. No differences in mantle lipid composition among the natural diets were found, but artificial diet groups showed higher contents of neutral lipids in their mantle respect to natural diets. According to results obtained, crayfish (P. clarkii) could be used as an alternative prey for rearing S. officinalis compared with shrimp. Artificial diets showed the worst effects in growth and mortality as well as the stronger influence on DG and mantle lipid composition of cuttlefish.     

Effects of probiotic doses on the survival and growth of hatchlings,fry, and advanced fry of Rohu (Labeo rohita Hamilton)

ABSTRACT

Rohu (Labeo rohita) is the most popular fish in South Asia. Its farming is often constrained by shortages of seed due to low survival (20%–30%) during nursing. Hypothesizing that probiotics might help, varying doses of two multistrain commercial probiotics were tested at hatchling (days 8–38), fry (days 38–68), and advanced fry (days 68–98) stages. The first probiotics (P1) consisted of Bacillus subtilis, Pediococcus acidilactici, and yeast (Saccharomyces cerevisiae) and the second probiotics (P2) of Bifidobacterium and Lactobacilli plus yeast (Saccharomyces cerevisiae), microalgae (Spirulina sp.), and phytase. Low, medium, and high doses of P1 (1.0, 2.0, and 3.0 g/kg) and P2 (0.5, 1.0, and 2.0 g/kg) were tested, supplementing the control diet, which consisted of mustard oil cake (40%), rice bran (30%), wheat flour (20%), and fish powder (10%). At the hatchling stage results showed that medium and high doses of P1 increased survival by 14.4% and 16.2% respectively over the control. Similarly, medium and high doses of P2 increased survival by 22.1% and 22.3% respectively compared to the control. Survival of hatchlings and fry increased linearly (P < 0.01) with the increase in the doses of P1. The dose of P2 had a quadratic relationship with the survival based on which dose of 1.5 g and 1.7 g/kg feed was found to maximize the survival of hatchlings (72%) and fry (99%) respectively. Regression analysis also showed that maximum specific growth rate (SGR%/day) of fry could be obtained with the estimated dose of 3.3 g/kg diet for P1 and for 1.5 g/kg diet for P2. Therefore, tested probiotics are beneficial during the nursing of Rohu hatchlings and fry or before the age of 68 days but not for nursing afterwards.     

The effect of light intensity on the growth of Brachymystax lenok (Pallas, 1773)

A 35‐day experiment was carried out to investigate the effect of light intensity on growth of Brachymystax lenok under different light intensities: 10, 70, 240 and 1000 lx. Fish(5.5 ± 0.24 g)used in the experiment were fed to satiation twice a day (08:00 hours, 14:00 hours).The photoperiod was 12L:12D (08:00–20:00 hours). The specific growth rate(SGR) of B. lenok under lower intensities(10 lx,70 lx)was significantly higher than the other groups(P < 0.05).No significant difference in feed intake was observed at different light intensities, but feed efficiency (FE) in wet weight at lower intensities (1070 lx) was higher than that at higher intensities(240,1000 lx) (P < 0.05).The final survival rate of juveniles varied from 86.33% to 93.66%,and there was no significant difference between experimental groups. The tested fish under higher light intensities (240 and 1000 lx) spent much more energy in respiration and excretion while depositing less energy for growth than those fish under lower light intensities. It is concluded that light intensity significantly affected growth and optimal light intensity for B. lenok juveniles was about 10–70 lx.     

Effect of Degree of Hydrolysis and Protease Type on the Antioxidant Activity of Protein Hydrolysates From Cuttlefish (Sepia officinalis) By-Products

We have investigated the antioxidant activities of eight hydrolysates from cuttlefish by-products obtained by treatment with various gastrointestinal proteases (chymotrypsin, trypsin, and crude alkaline enzyme extracts from cuttlefish and sardinelle) and bacterial proteases (Alcalase and crude enzymes from Bacillus pumilus A1, Bacillus mojavensis A21, and Bacillus cereus BG1). The antioxidant activities of the cuttlefish by-products protein hydrolysates (CPHs) were evaluated using various in vitro antioxidant assays, such as 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical-scavenging activity, reducing power, and total antioxidant capacity. All hydrolysates showed different degrees of hydrolysis (DH) and varying degrees of antioxidant activity. Among the different hydrolysates, cuttlefish crude enzyme hydrolysate exhibited the highest antioxidant activity, followed by sardinelle crude enzyme and Alcalase hydrolysates. Further, CPHs with different degrees of hydrolysis were prepared by treatment with proteolytic enzymes from cuttlefish, sardinelle, and B. mojavensis A21. All hydrolysates showed a greater antioxidative activity as indicated by all the methods considered. In addition, antioxidant activity in hydrolysates was positively correlated with the increase of DH. The results of this study indicated that CPHs might be a good candidate for further investigation in developing new antioxidants.     

西非沿岸乌贼角质颚形态及生长特征

乌贼(Sepia officinalis)是生活在大西洋西岸的重要头足类之一,研究乌贼角质颚形态及生长特征有利于对其的开发利用。本研究根据2015年在毛里塔尼亚附近海域生产期间所获得的乌贼渔获样本,对乌贼角质颚的各项形态参数进行描述,探究不同胴长和不同性腺成熟阶段角质颚生长情况的差异,并估算乌贼个体的大小。通过对乌贼上、下颚各长度指标的比值比较发现,乌贼角质颚下颚的长度比值波动较大,较不稳定。t检验表明,将各项形态参数除以胴长消除样本规格影响差异后,乌贼雌性个体在角质颚的各项形态参数上均极显著大于雄性(P0.01);方差分析及多重比较(LSD法)表明,随着胴长的增加,乌贼的各个角质颚的形态参数也极显著增加(P0.01)。在性腺成熟期Ⅱ~Ⅳ中,乌贼角质颚的形态参数随着性腺成熟度的增加而显著增加(P0.05),但性腺成熟度为Ⅴ期的个体的角质颚形态参数却显著小于前面几期(P0.05)。主成分分析显示,第一主成分的负载绝对值最高的指标为上头盖长(Upper hood length,UHL)和下脊突长(Lower crest length,LCL);第二主成分下喙长(Lower rostrum length,LRL)和下喙宽(Lower rostrum width,LRW),利用主成分分析得到的前2个主成分可以对乌贼的胴长进行估算。研究表明,同一种类不同性别的乌贼个体角质颚形态参数及其比值存在特异性,研究结果为西非沿岸乌贼类分类及生态研究提供基础资料。     

Effects of including shrimp protein hydrolysate in practical diets on the growth and survival of redclaw crayfish hatchlings Cherax quadricarinatus (Von Martens, 1868)

An experiment was carried out to analyse the effects of substituting fish‐meal (FM) with soya bean meal and shrimp protein hydrolysate (SPH) on the percent survival, growth rate, feed efficiency and molt frequency of redclaw crayfish hatchlings, Cherax quadricarinatus. The experiment was performed in a closed recirculating‐water system over a 56‐day period. Five diets were tested: a control diet (SPH₀) comprising 100% FM without SPH, and four diets with 2.5%, 5.0%, 10.0% and 15.0% SPH substitution (diets SPH_2.5, SPH₅, SPH₁₀ and SPH₁₅ respectively). Analysis of water quality indicated that it was adequate to maintain a good growth and survival of hatchlings. The results showed that 100% survival was obtained for hatchlings fed with SPH₅, SPH₁₀ and SPH₁₅ diets. Higher mean values of final weight were obtained for the SPH₅ diet. The highest weight gain was observed in SPH_2.5 and SPH₅ diets. Hatchlings showed similar specific growth rates for all diets. The efficiency rate of the SPH₁₅ diet was lower compared to the other diets. Overall, individual feed consumption was higher in hatchlings fed diets of SPH₅ and SPH₁₅. It is recommended that 5.0% of SPH could be included in diets of hatchling redclaw crayfish to improve their growth efficiency.     

The use of Artemia sp. or mysids as food source for hatchlings of the cuttlefish (Sepia officinalis L.); effects on growth and survival throughout the life cycle

Twoexperiments were conducted to determine the effects ofArtemia sp. or mysids on growth and survival ofS. officinalis hatchlings, and their effect throughout thelife cycle. For experiment I, for the first 20 days, one group was fed adultArtemia sp. and the other was fed mysid shrimp(Paramysis nouvelli). Eggs laid by females in both groupswere counted and weighed, and hatchlings were weighed, to determine differencesin both groups. For experiment II, during the first 10 days, one group was fedArtemia sp. and the other was fed mysids (P.nouveli). After the period of differentiated feeding, the 2 groupsinexperiment I were fed grass shrimp (Paleomonetes varians)to 70 days old, and dead crabs (Carcinus maenas)afterwards. Cuttlefish in experiment II were fed grass shrimp from day 10 untilthe end of the experiment. For both experiments, hatchlings fed mysids grewsignificantly bigger (p < 0.01) and survival was higher. For experiment I,eggs laid by females fed mysids and the hatchlings born from these eggs werebigger (p < 0.001) compared to the group fed Artemiasp.initially. Individual fecundity was slightly higher for females in the groupfedArtemia sp. (163 eggs female^–1) than forthe group fed mysids (144 eggs female^–1). Egg laying startedatthe age of 125 days and lasted 45 days in both groups. Time between first egglaying day and first hatchlings to be born was 21 days. The last female to die(after spawning) in both groups was 167 days (less than 6 months old).     

Effects of light intensity on larval development and juvenile growth of sea cucumber Apostichopus japonicus

The growth rate, survival rate, development and setting rate of larval sea cucumber Apostichopus japonicus were measured under four light intensities (0, 50, 500 and 2,000 lx), and the growth rate and metabolism of the juvenile sea cucumbers were investigated under four light intensity treatments (0, 100, 1,000 and 2,500 lx). The light requirements (i.e. intensity) of the sea cucumber changed as they grew. Better growth performance, development and survival rate were observed in embryos and larvae under 500 lx treatment. However, reduced light intensity (50 lx) increased the settlement rate of the larvae. The highest specific growth rate occurred in juvenile sea cucumbers under 1,000 lx. The sea cucumbers in this group also had the lowest oxygen consumption rate and ammonia excretion rate, but the highest O:N ratio, indicating that the optimal light intensity for the juvenile sea cucumber culture was 1,000 lx. Therefore, appropriate light intensities were suggested to provide larval and juvenile sea cucumbers with better growth and development conditions.     

The impact of light intensity and algal-induced turbidity on first-feeding Seriola lalandi larvae

Feeding performance (intensity and incidence) of first‐feeding yellowtail kingfish larvae was evaluated under a range of light intensities and algal‐induced turbidities. Larvae were fed with varying degrees of success under all light intensities tested (0–17 μmol s^?1 m^?2), in both clearwater and greenwater (8 × 10⁴ cells mL^?1). There was a consistent trend for feeding performance to increase with larval age and light intensity in both clearwater and greenwater conditions, demonstrating that visual proficiency increases with larval age. Feeding intensity remained low over the first 3 days of first feeding across all light intensities tested. Days 6 and 7 post‐hatch larvae showed considerably higher feeding intensities particularly at 8 and 17 μmol s^?1 m^?2. This improvement indicates an ontogenetic shift in sensory or locomotor competence. First‐feeding larvae performed equally well in both clearwater and greenwater (8 × 10⁴ cells mL^?1) conditions, although at the lowest light intensity tested (0.1 μmol s^?1 m^?2) feeding performance was noticeably reduced. Feeding performance was severely diminished across all larval ages at an algal cell density of 32 × 10⁴ cells mL^?1, demonstrating that for this species algal‐induced turbidities >16 × 10⁴ cells mL^?1 adversely affect the ability to capture free‐swimming prey during the first‐feeding window.     

Effect of light intensity and feed density on feeding behaviour,growth and survival of larval sablefish Anoplopoma fimbria

We studied the effects of light intensity on larval activity, feeding behaviour, growth and survival of a candidate species for aquaculture – sablefish (Anoplopoma fimbria). Of six light intensities ranging from 2 to 750 lux at the water surface, the greatest surviving biomass in small tanks was observed at 12–42 lux. In another experiment in larger tanks, behavioural observations showed that larvae fed poorly under light brighter than 800 lux but fed better at lower light intensities, depending on tank type. In a separate experiment, where live feed densities were varied between 2.5 and 17.5 rotifers per mL of tank water, surviving biomass and dry weight increased with higher feed densities. These experiments help refine methods for rearing larval sablefish by demonstrating effects of light intensity and feed density on larval performance.