Stock enhancement programme for black sea bream, Acanthopagrus schlegelii (Bleeker), in Hiroshima Bay, Japan: a review

This paper reviews the stock enhancement programme for black sea bream ( Acanthopagrus schlegelii ) in Hiroshima Bay. This bay is one of the biggest production areas for black sea bream in Japan, accounting for about 10% of the total catch of the species in this country in 2004. After intensive fishing pressure caused a drastic decline in the catch of the species in this bay in the 1970s, a stock enhancement programme was conducted in its northern part since 1982 to restore the depleted population. The number of black sea bream juveniles released in 1996 surpassed 9 million, representing the third main species stocked in Japan. Almost 1.4 million of these juveniles were released into Hiroshima Bay. The fast acclimatization of hatchery-reared juveniles released into the bay may have contributed to the recovery of landings in the late 1980s and 1990s. However, this recovery was accompanied by a reduction in the market price of black sea bream. Further studies to assess the effectiveness of the stock enhancement programme as well as the carrying capacity of Hiroshima Bay to maintain the stock of black sea bream at a stable, healthy level are desirable. The necessity of evaluating the secondary effects derived from using a reduced number of breeders as well as finding new markets are suggested.     

Seasonal changes in the distribution of black sea bream Acanthopagrus schlegelii estimated by environmental DNA

Fisheries Science - This study aimed at characterizing the distribution of black sea bream Acanthopagrus schlegelii, a major target fish of commercial and recreational fishing, using environmental...     

Compensatory growth of juvenile black sea bream,Acanthopagrus schlegelii with cyclical feed deprivation and refeeding

An 8‐week feeding trial was conducted to evaluate compensatory growth of juvenile black sea bream, Acanthopagrus schlegelii (initial weight 9.56 ± 0.12 g) in fifteen 300 L indoors flow‐through circular fibreglass tanks. Feeding regimes was designed as follows: the control group (fed continuously), and S1, S2, S3 and S4 groups experienced 1, 2, 3 and 4 days of feed deprivation and then refeeding for the remaining days per week respectively. Changes in body weight, specific growth rate (SGR), feed intake (FI) and feed efficiency ratio (FER) were examined biweekly during the trial. At the end of the cyclical feeding periods, survival was not significantly affected by feeding strategy (P > 0.05). Final body weight of fish in S1 group was significantly higher than the control group (P < 0.05) after an 8 weeks trial, and fish in the S2 group reached the same body weight of the control fish (P > 0.05), however, the growth data in the S3 and S4 groups could not catch‐up with the control treatment (P < 0.05). In the first 4 weeks, SGR values of fish with feed deprivation more than 2 days per week were inferior to those of control group (P < 0.05); however, no significant differences of SGR were observed among the groups for the last 4 weeks (P > 0.05). FI increased significantly with the starvation days increasing during the whole feeding trial (P < 0.05). At the periods 2, 4 and 6 weeks, FER values increased significantly with increasing feed‐deprivation days up to S2 group and then levelled off (P < 0.05); however, FER in S2 group was only higher than that in S0 and S1, but no significant differences were found among the other treatments at the end of week 8. Significant differences were found in apparent digestibility coefficients (ADCs) of dry matter and crude protein among the treatments, while ADCs of crude lipid were unaffected. Protein and lipid contents in whole body and dorsal muscle showed declining tendency with increasing food deprivation days, while moisture contents tended to increase (P < 0.05). Serum parameters were markedly affected by feeding regimes except for total protein concentration and thyroxine level. The present results indicated that starvation for 1 and 2 days per week of juvenile black sea bream could achieve over‐compensation and complete compensation respectively. However, in case of longer term feed restriction regime, fish failed to obtain good growth performance.     

中性植酸酶替代磷酸二氢钙对黑鲷生长和磷利用的影响

以鱼粉、豆粕、菜粕等为蛋白原料设计配方, 磷酸二氢钙的添加量分别为1.5%、1.0%、0.5%和0(对应的饲料组为P1.5、PP1.0、PP0.5和PP0组), 其中PP1.0、PP0.5和PP0组中均添加200 mg/kg的中性植酸酶, 开展为期8周的黑鲷(Acanthopagrus schlegelii)养殖实验, 以探讨中性植酸酶替代磷酸二氢钙对黑鲷生长和磷利用的影响。结果显示, 黑鲷摄食实验饲料8周后, 各组间成活率无显著差异(P>0.05); 摄食饲料PP1.0、PP0.5和对照组(P1.5组)实验鱼的增重率无显著差异(P>0.05), 但均显著高于PP0处理组, 饲料系数则显著低于PP0处理组(P<0.05)。摄食不同饲料的黑鲷全鱼中蛋白质、脂肪、灰分及钙磷含量在不同组间均无显著差异(P>0.05)。添加植酸酶的各组鱼磷的表观消化率均显著高于对照组(P<0.05)。随着磷酸二氢钙添加量的降低, 黑鲷对干物质和蛋白质的表观消化率呈升高的趋势, 当饲料中磷酸二氢钙的添加量降到0时, 黑鲷对干物质和蛋白质的表观消化率显著高于对照组(P<0.05)。以上结果说明, 在本研究配方下, 黑鲷正常生长对饲料有效磷的需求量≥0.51%; 磷酸二氢钙可部分被植酸酶替代, 当黑鲷饲料中含有20%鱼粉、32%豆粕和12%菜粕, 且植酸酶添加量为200 mg/kg时, 与饲料中添加1%的磷酸二氢钙相当; 在不影响黑鲷生长的前提下, 植酸酶部分替代磷酸二氢钙不仅可降低无机磷的添加, 同时可提高饲料中磷的利用率, 降低磷排放。

     

Spatial movement of black sea bream <Emphasis Type="Italic">Acanthopagrus schlegelii</Emphasis> around the oyster farming area in Hiroshima Bay,Japan

In order to obtain information for preventing oyster spats predation, we investigated the horizontal and vertical movement patterns of black sea bream Acanthopagrus schlegelii inhabiting an oyster farming area in Hiroshima Bay by active tracking. Seven adult fish equipped with depth transmitters were tracked for 65 days around the oyster farming area. Six of the seven fish were found in the oyster rafts for a cumulative duration of 55 days. The daily movement distance and minimum convex polygon home range of these fish were 0.13–0.78 km/day and 0.11–1.14 km², respectively. The swimming depth of these fish were mainly between 1 and 15 m, which coincided with the depths of the submerged oyster wires. Our observations suggest that black sea bream inhabiting the oyster farming area in Hiroshima Bay are highly dependent on the spatial arrangement of the oyster rafts.     

Evaluation of pea proteins and poultry protein as fish meal alternatives in the diets for juvenile black sea bream,Acanthopagrus schlegelii

The potential of three different protein resources (pea protein isolate, PPI; pea protein concentrate, PPC; enzyme treated poultry protein, ETPP) as fish meal (FM) alternative protein in diets for juvenile black sea bream, Acanthopagrus schlegelii. (initial average weight 7.90 ± 0.13 g) was evaluated. Seven isonitrogenous and isoenergetic diets were formulated to replace FM at 0% (T0, control diet), 8% (designated as T1‐T3) and 16% (designated as T4‐T6) using PPI, PPC and ETPP respectively. Each diet was randomly assigned to triplicate groups of 25 juvenile fish for 8 weeks. At the end of the feeding period, survival rate was not significantly affected by dietary treatments. Growth performance in T6 (16% ETPP) group was significantly inferior to T0 group, however, weight gain and specific growth rate in other treatments showed no significant differences (P > 0.05). Mean feed intake, feed efficiency ratio and protein efficiency ratio were also poorer in fish fed in T6 than those of fish fed with the control diet respectively. Apparent digestibility coefficients (ADCs) of dry matter and crude protein for fish fed ETPP diets were significant lower than those of fish fed with the control diet, whereas ADCs of lipid were unaffected by dietary treatments. ADC's of dietary Leu, Ile, His and Lys was also significantly influenced. There were no marked variations in proximate compositions of dorsal muscle. With regard to plasma characteristics, significant difference was observed in triacylglycerol content. Ammonia concentration in plasma tended to increase in alternative protein diets as substitution level increased. There were significant differences in aspartate aminotransferase activities among groups, but alanine aminotransferase levels were unaffected by treatments. In conclusion, the present study demonstrated that PPI and PPC were potential protein sources for using in juvenile black sea bream diet. However, the substitution level of FM by ETPP should be limited within 16%.     

Spawning season,spawning grounds,and egg production of red sea bream in Hiuchi-nada,Seto Inland Sea

The spawning season and grounds of red sea bream in Hiuchi-nada, the central part of the Seto Inland Sea, were described using a new method based on monoclonal antibodies for identifying Pagrus major eggs, and the daily egg production (standardized by the incubation time and survival rate) was estimated. At the peak of spawning (May), the ranges of sea temperature, salinity, and chlorophyll a where red sea bream eggs occurred were 14.8–17.4°C, 32.0–33.0, 0.5–4.4 μg/L, respectively. The main spawning grounds of the red sea bream were confirmed as being the areas near the Geiyo Islands, Misaki Peninsula, Saijyo, Niihama. The spatial spread of red sea bream eggs increased with the egg developmental stage. The ranges of daily egg production in 2005 and 2006 were 0.3–19.3 and 0.2–6.7 × 10⁹ eggs/day, respectively. In Hiuchi-nada, aquaculture farms are located close to the spawning grounds, and the potential spawning population from the aquaculture farms equaled or exceeded that of the estimated spawning population obtained by the egg production method. Red sea bream eggs in Hiuchi-nada might be produced by both wild and aquaculture-based spawning populations.     

Partial replacement of fishmeal with Clostridium autoethanogenum single‐cell protein in the diet for juvenile black sea bream (Acanthopagrus schlegelii)

Clostridium autoethanogenum protein (CAP) is a single‐cell protein derived from ethanol production and may have potential to become a substitute for fishmeal in aquafeeds. A 70‐day feeding trial was conducted with black sea bream (Acanthopagrus schlegelii) (mean initial weight 6.03 ± 0.09 g) to evaluate partial replacement of fishmeal with CAP in diets. Seven isonitrogenous and isoenergetic diets were formulated with graded levels of CAP (0, 4.85, 9.70, 14.55, 19.40, 38.80 and 58.20%) to replace fishmeal. The inclusion of CAP at all dietary levels tested did not significantly affect the growth performance (p > .05). Fish fed the CAP58.20% diet showed a significantly lower feeding rate, with significantly higher protein efficiency ratio and feed efficiency ratio compared with fish fed the other diets (p < .05). No statistical differences were found in dorsal muscle and whole‐body compositions. Total superoxide dismutase in serum of fish fed CAP58.20% diet was significantly lower compared with that of the control. Malondialdehyde, catalase, total antioxidant capacity and digestive enzyme activities revealed no significant differences among dietary treatments. Phosphorus retention efficiency significantly increased, and phosphorus discharge showed a downward trend with increasing CAP inclusion levels. In conclusion, the results indicated that CAP is a safe and effective alternative protein source, which can replace fishmeal in the diet of black sea bream up to 58.20%, without adverse effects on growth performance, antioxidation and digestive enzyme activity. This study has shown the potential of converting industrial waste into a high protein feed ingredient for aquafeeds.     

Effect of dietary replacement of fish meal by soybean protein concentrate on growth performance and phosphorus discharging of juvenile black sea bream,Acanthopagrus schlegelii

The 8‐week experiment was conducted to evaluate the effects of partial replacement of fish meal (FM) with soybean protein concentrate (SPC) on juvenile black sea bream, Acanthopagrus schlegelii (10.70 ± 0.04 g). Diets were formulated to replace FM protein by SPC at 0, 8, 16, 24, 32 or 40% (designated as T1, T2, T3, T4, T5 and T6, respectively). Diets except T1 were supplemented with phytase at 2000 phytase activity U kg^?1. The results showed that survival rate, growth performance and feed utilization were not significantly affected by increasing dietary SPC. Fish fed diet T3 had higher feed intake compared to those fed T1, T2 and T5 diets. Whole body compositions of black sea bream were significantly influenced by SPC replacing FM except for protein, ash and phosphorus content. Condition factor of fish was significantly lower in T2 than that of fish in T3 group. Apparent digestibility coefficients (ADCs) of dry matter was higher in fish fed T6 diet than those of fish fed T1 and T2 diets, ADCs of phosphorus increased with dietary SPC level up to T3 and then decreased. The results obtained in this study indicate that FM protein could be effectively replaced by SPC protein with phytase in diet of black sea bream.     

Effects of butyrate glycerides supplementation in high soybean meal diet on growth performance,intestinal morphology and antioxidative status of juvenile black sea bream,Acanthopagrus schlegelii

This study aimed to investigate the effects of graded butyrate glyceride (BG) supplementation levels in high soybean meal diet on juvenile black sea bream. Three hundred and sixty fish were fed diets containing 199 g/kg fishmeal and 450 g/kg soybean meal, with increasing levels of BG at 0, 2, 4, 6, 8 or 16 g/kg for eight weeks. The growth performance of the fish increased with increasing dietary BG supplementation up to 6 g BG/kg, beyond which growth rate reduced significantly (p < .05). Dietary BG supplementation increased the intestinal protease activity, but had no significant (p > .05) effect on lipase and amylase activities. Fish fed the basal diet exhibited villus shortening with a decrease in the number of goblet cells and a reduction in absorptive and digestive epithelial surface, while fish fed ≥4 g BG/kg diets showed a well‐integrated gut, with large absorptive and digestive epithelial surface. Dietary BG supplementation also improved antioxidative capacity by increasing superoxide dismutase and glutathione peroxidase activities while decreasing malondialdehyde content. The inclusion of BG in high soybean meal diets can improve growth performance, maintain healthy gut morphology and enhance antioxidative capacity of black sea bream.     

大亚湾黑鲷标志放流及回捕率调查

为评价大亚湾海域黑鲷(Acanthopagrusschlegelii)增殖放流效果,使用塑料椭圆标志牌(plasticovaltags,POTs),开展了黑鲷幼鱼标志保持率与生长实验。结果显示,背鳍鳍棘基部第4～6鳍棘下方5mm左右的背部肌肉为最适标志位置, 90 d后标志保持率为81.76%。POTs标志黑鲷幼鱼45 d内生长与对照组无显著性差异(P>0.05),而90 d后标志组生长显著缓于对照组(P<0.05)。并于2014—2016年每年1次在大亚湾开展黑鲷幼鱼标志放流试验。采用有奖回收方式进行标志鱼回捕,测量体长、体重,收集回捕日期、回捕地点、回捕方式等信息,整理分析相关数据。3年共放流标志黑鲷幼鱼60115尾,共2758尾回捕标志鱼被定置网、流刺网及垂钓捕获(总回捕率4.59%);大规格放流苗种回捕率高于小规格放流苗种;垂钓回捕鱼数量占总回捕数量的比例为62.08%。通过对反馈信息的分析,认为放流后的标志鱼最初主要沿湾内和湾外两个方向呈近岸辐射状扩散,最远扩散距离约70 km。放流后1～2个月标志黑鲷生长较慢,随后相对加快,放流5～7个月后,黑鲷幼鱼体长、体重分别增长59.51%～127.20%和322.75%～989.83%。结论认为,POT是黑鲷幼鱼体外标志的适宜选择;在研究海域,放流后的标志黑鲷更易于被垂钓方式捕获;丰富的食物和可供躲避敌害的空间是影响其扩散、生长的因素。     

Parentage assignment of stocked black sea bream <Emphasis Type="Italic">Acanthopagrus schlegelii</Emphasis> in Hiroshima Bay using microsatellite DNA markers

The genetic contribution of 51 broodstock, comprising 29 females and 22 males, reared at Hiroshima City Marine Products Promotion Center for the production of stocked black sea bream was monitored during two consecutive years using seven microsatellite DNA loci. The high discrimination ability of these markers was reflected in the polymorphic identification content (PIC=0.831), the exclusion probability (Q≈1), and the low probability of identity index (I=3.635⁻¹⁰). The total number of breeders contributing to the mating process was estimated at 32 (62.7%) in 2000 and 30 (58.8%) in 2001. On pedigree reconstruction, 69.3% of the offspring were successfully assigned to a single broodstock pair. Loss of alleles accounted for 16.9% during seed production; nevertheless, 90.9% of males and 69.0% of females participated in the mating process. Based on microsatellite genetic tagging, 58.9% of the fish sampled during the two months after release were identified as hatchery stock, presenting no significant differences from wild conspecifics in either fork length or body weight.     

Ontogeny of tolerance to and avoidance of ultraviolet radiation in red sea bream Pagrus major and black sea bream Acanthopagrus schlegeli

ABSTRACT:   Ontogenetic changes of tolerance to, and avoidance of, ultraviolet-B radiation (UV-B) were examined in red sea bream Pagrus major and black sea bream Acanthopagrus schlegeli . In the tolerance experiment, larvae and juveniles (age 13–46 days) were put in beakers, and were exposed to one of five different levels of UV-B radiation (1.8, 1.1, 0.2, 0.1, and 0 W/m²) for one hour. Their survival rates were calculated either 12 or 24 h later. In the avoidance experiment, fish (age 3–49 days) were put in a long experimental tank, half of which was covered with UV-blocking film and placed under two levels of UV-B radiation (1.1 and 0.2 W/m²), and their avoidance indices were calculated. Black sea bream had significantly better survival compared to red sea bream for most ages. Only black sea bream of ages 37 and 49 days showed significant avoidance of UV radiation under the higher level of UV-B, whereas both species did not show avoidance on any days at the lower level. The present results suggest that black sea bream are significantly better adapted to habitats with high UV-B radiation, than red sea bream, reflecting that back sea bream live in shallower waters through their early life stages.     

Daily change of genetic variability in hatchery offspring of red sea bream during spawning season

ABSTRACT:   In order to assess a daily change of genetic variability during spawning season, hatched larvae of red sea bream sampled on different dates were assayed by polymorphic markers such as microsatellite DNA (msDNA) and mitochondria DNA (mtDNA) control region. Based on the microsatellite loci, the average number of alleles per locus ranged between 13.7 and 18.3. The expected heterozygosities ranged between 0.843 and 0.919. A total of 23 mtDNA haplotypes were detected via digestion of mtDNA D-loop sequences with five endonucleases: Taq  I, Alu  I, Mbo  I, Rsa  I and Hinf  I. Significant fluctuation of genetic variability during spawning season was detected by both types of DNA markers. It was suggested that the genetic variability was maintained by pooling the seed fish collected on different spawning dates in a hatchery.     

Effect of Ulva meal supplementation on lipid metabolism of black sea bream,Acanthopagrus schlegeli (Bleeker)

Black sea bream (Acanthopagrus schlegeli) were fed on a diet supplemented with 10% Ulva pertusa meal for 143 days in indoor tanks. Ulva meal supplementation resulted in an increase in total body lipid and influenced the composition of triglycerides (TG). The similarity of the pattern of fatty acid composition between dietary lipid and the reserve lipids was relatively great in the Ulva-fed group.Wintering for 138 days without feeding caused some differences in the mode of lipid mobilization between two dietary groups. In the fish fed Ulva meal, the muscle TG were primarily exhaused prior to the visceral lipid. While specific fatty acids were selectively consumed from the lipid reserves in the control group, all fatty acids were equally mobilized in the Ulva-fed group.It was concluded that the Ulva meal supplement was associated with activation of lipid metabolism such as accumulation and mobilization. The availability of dietary algae was discussed in regard to improvement of physiological condition.     

Tributyrin‐supplemented high‐soya bean meal diets of juvenile black sea bream,Acanthopagrus schlegelii: Study on growth performance and intestinal morphology and structure

An 8‐week growth trial was conducted to evaluate the effects of different levels of tributyrin supplementation in a high‐soya bean meal diet on juvenile black sea bream (11.30 ± 0.16 g). The positive control (PC) diet contained 45% fishmeal and 20% soya bean meal, while the negative control (NC) contained 12% fishmeal and 45% soya bean meal. Graded levels of tributyrin were added to the NC diet at 0.05% (TB 0.05), 0.1% (TB 0.1), 0.2% (TB 0.2), 0.4% (TB 0.4) and 0.8% (TB 0.8). Ultimately, the fish fed the PC diet had a higher weight gain and specific growth rate than the fish fed other diets. The fish fed the NC diet had the lowest growth, and TB 0.05–TB 0.2 diets increased growth performance while TB 0.4–TB 0.8 diets caused reduction in growth. Dietary tributyrin supplementation improved protease activity and enhanced antioxidant capacity. Compared with the fish fed the NC diet, the fish fed the tributyrin‐supplemented diets had improved gut morphology and structure, and the results were similar to those of the fish fed the PC diet. Furthermore, the analysis of the dose response with second‐order polynomial regression indicated that the optimum tributyrin supplementation for juvenile black sea bream is 2.24 g/kg in the 45% soya bean meal diet.     

Additive genetic and other sources of variation in growth traits of juvenile black bream Acanthopagrus butcheri

We used a factorial mating design to estimate the contribution of additive genetic, non‐additive genetic and maternal effects to variation in growth traits of black bream Acanthopagrus butcheri (Munro) at 75, 130 and 180 days of age in the hatchery. Maternal genetic and environmental effects were greatest at 75 days of age, accounting for 9.1% of total phenotypic variance in wet weight, 11.4% of variance in standard length and 8.8% of variance in total length. At later ages maternal effects were much reduced, explaining 0.8–3.7% of phenotypic variance in growth traits. Additive genetic effects were greatest at 130 days of age, when they accounted for 17.4% of total phenotypic variance in wet weight, 21.4% of variance in standard length and 18.7% of variance in total length. Additive genetic effects were negligible (<1%) at 75 days of age and 4.8–5.5% of total phenotypic variance in growth traits at 180 days of age. Non‐additive genetic effects (which also included common environmental effects because of families being raised in the same tank) explained 5.8–7.3% of total phenotypic variance in growth traits at 75 days of age, but were much smaller at later ages. Variable stocking densities among tanks up to 75 days significantly affected all growth trait measurements below 180 days of age.     

日本鹿儿岛湾真鲷的资源评估和增殖策略

通过世代分析对1990年至2002年鹿儿岛湾真鲷（Pagrus major）自然种群和放流种群的种群大小进行了评估,评估模型考虑了渔业资源管理和增殖放流措施。结果表明放流种群的规模有所减少,而自然种群的规模维持不变。真鲷自然种群的捕获量日趋减少,而放流种群的捕获量已超过50吨。研究结果表明增殖700000—800000尾真鲷种苗与其50吨的捕捞量相协调。在各种捕获量和放流量情况下,采用种群动力学模型预测了2017年真鲷的捕获量,其结果表明提高放流真鲷的数量能增加其捕获量。