Utilization of soybean meal as an alternative protein source in the Mediterranean yellowtail, Seriola dumerili

The availability of defatted soybean meal as a substitute for fish meal was evaluated in juvenile (450 g on average) yellowtail fed diets containing several levels of soybean meal (from 20 to 50%). After 153 days, liveweight averages were 980, 925, 795 and 670 g for fish fed diets in which fish meal was partially substituted with 20, 30, 40 and 50% soybean meal, and feed conversion ratios were 2.79, 3.09, 4.57 and 6.52, respectively. Regression analysis showed a negative effect of inclusion of soybean, although fish fed diets containing 20% and 30% of soybean did not present statistical differences and grew significantly more, and had a better feed conversion ratio, than fish fed 40 or 50% diets. Likewise, muscle protein level was lower and lipid content was higher in fish fed 20 or 30% soybean. No differences were obtained for protein digestibility coefficients of experimental diets.     

Effect of fish oil replacement and probiotic addition on growth,body composition and histological parameters of yellowtail (Seriola dumerili)

Fish (175 g of initial weight) were fed in triplicated groups with four diets formulated by 0% (FO 100), 75% (FO 25) and 100% (with and without probiotics, FO 0 and FO 0+) of fish oil replacement consisting of a mixture of linseed, sunflower and palm oils. After 109 days, growth and nutritional parameters were not affected by the treatment; however, fish fed with 0% of fish oil showed the lowest survival rate and without differences between the same diet with probiotics. As for biometric parameters, significant differences in the viscerosomatic index (VSI) were observed between fish fed the FO 0+ diet and the FO 100 and FO 25 diets. Results obtained from histological analysis did not detect inflammation in gut samples, while liver samples showed a remarkable steatosis in all four treatments. Total fish oil replacement produced a significant difference in the width of the lamina propria. The dietary inclusion of probiotics in the FO 0+ diet seems to favour a recovery of intestine histology. In addition, as fish oil substitution increased, the width of the lamina propria also increased. In conclusion, it is possible to affirm that the four diets administrated to Seriola dumerili did not compromise the correct development of the animals.     

Optimum digestible protein and energy levels and ratio for greater amberjack Seriola dumerili (Risso) fingerling

A study was conducted to determine optimum dietary digestible protein (DP) and digestible energy (DE) levels and DP DE⁻¹ ratio for growth of greater amberjack Seriola dumerili fingerlings. A 3 × 3 factorial design with duplication was used in this study. Nine experimental diets were formulated to contain three levels of crude protein (CP; 420, 470 and 530 g kg⁻¹) and three levels of crude lipid (CL; 130, 180 and 230 g kg⁻¹). Nine groups of fingerling (initial weight 51.8 g) were fed each experimental diet for 40 days. Final body weight, feed efficiency, specific growth rate and energy efficiency were significantly affected by dietary protein and lipid level. These parameters tended to improve with increasing dietary protein level. Conversely, an increase of lipid level negatively affected these parameters. High growth rate and feed efficiency were obtained from fish fed the diet containing 393 g kg⁻¹ DP and 14.2 MJ kg⁻¹ DE (27.7 g MJ⁻¹ DP DE⁻¹). The high DP DE⁻¹ (27.7 g MJ⁻¹) indicates that greater amberjack fingerling are highly dependent on dietary protein as an energy source.     

深水网箱高体(鱼师)养殖试验报告

通过对均重1 225 g的大规格高体(鱼师)苗种进行252天的深水网箱养殖,高体(鱼师)的平均体重由1 225 g增至3 350 g, 共收成鱼5 521尾,养殖成活率92.02%,杂鱼饵料系数7.76。     

海水网箱养殖高体鱼师弧菌病致病菌研究

从患病高体鱼师病灶上分离到７株可疑致病菌，人工感染试验证明，菌株９５－５－３和９５－５－５为强毒菌株，这２株菌进行人工感染，死亡率均为１００％，症状与自然发病相似。这２株菌的特征一致，根据形态有主生理生化特征，应归入哈维氏弧菌。药敏实验的结果表明，磺胺类药物和先锋必素对致病菌有较强的抑制作用。     

The influence of dietary phospholipid level on the performances of juvenile amberjack, Seriola dumerili, fed non-fishmeal diets

The objective of the present study was to investigate the effect of dietary phospholipid (PL) level on growth and feed intake of juvenile amberjack ( Seriola dumerili ) fed non-fishmeal (non-FM) diet containing alternative protein sources; soybean protein isolate, tuna muscle by-product powder and krill meal. Three non-FM diets were prepared to contain three levels (14, 37 and 54 g kg⁻¹ dry diet) of PL (soybean lecithin acetone insoluble, 886 g kg⁻¹) and growth performance was monitored in a 30-day growth trial by using 2.6 g of fish. The results indicated that final body weight, weight gain and feed intake significantly increased with increasing dietary PL level. At the highest dietary PL level (54 g kg⁻¹ dry diet), the fish consumed 14.8% and 10.2% as much feed as those fish fed diets containing 14 g kg⁻¹ dry diet and 37 g kg⁻¹ dry diet PL, respectively. An increasing tendency with increasing dietary PL level on feed efficiency was observed. In conclusion, the present study demonstrated that dietary PL supplementation could increase feed intake, and improve the growth of juvenile S. dumerili fed non-FM diets. Therefore, purified PL might be a good candidate to stimulate the growth of fish through enhancing the feed intake when they are fed diets containing alternative protein sources.     

Seasonal changes in proteolytic enzymes of yellowtail Seriola quinqueradiata (Temminck & Schlegel; Carangidae) fed extruded diets containing different protein and energy levels

Seasonal variations in pepsin, trypsin and chymotrypsin activities and protein digestibility were studied in yellowtails (Seriola quinqueradiata) reared for 1 year with extruded diets containing different levels of protein. Trypsin and chymotrypsin storage levels in the digestive tissues of starved fish were affected by seasonal changes in water temperature. Actual digestion activities of trypsin and chymotrypsin were low at lower water temperatures, but pepsin activity in the stomach tissue was not affected by low temperatures. On the other hand, trypsin and chymotrypsin activities in the intestinal contents were higher during lower water temperature months, while pepsin activity in the stomach contents was low at lower water temperatures. Apparent protein digestibility (APD) did not differ among the dietary treatments in the higher water temperature months, while in colder months it was higher in fish fed diet 1 than in fish fed diets 2 and 3. The APD values reflected pepsin activity in the stomach contents in all sampling months. Therefore, lower APD in colder months seems to be attributed to lower protease activity in the gastric digesta, implying that enhanced pepsin secretion from the stomach tissue might improve protein digestibility and growth performance in yellowtails during winter.     

Effect of different rearing conditions on body lipid composition of greater amberjack broodstock (Seriola dumerili)

The aim of this study was to assess the effect of two rearing conditions: outdoor environment with great volume tanks (500 m³) and low stocking density (~0.4 kg m^?3); and indoor environment with smaller volume tanks (10 m³) and higher stocking density (~5 kg m^?3), on muscle, liver and ovary lipid composition of Seriola dumerili broodstock born in captivity. The rearing conditions tested seem to affect the pattern of lipid body deposition in broodstock fish of S. dumerili, increasing the muscle and liver triacylglycerides (TG) accumulation of fish kept under indoor conditions, probably due to reduced energy expenditure in swimming, with some variations in the fatty acid profile that may respond to the differences in the culture conditions tested. No significant differences were found for Gonadosomatic Index (GSI) or ovary lipid deposition between groups in this study, which may suggest that the conditions tested do not have a major effect on ovary development. However, one season later the females kept under outdoor conditions released eggs spontaneously, whereas those kept under indoor conditions did not spawn, suggesting that the conditions tested actually have an effect on the broodstock's reproductive fitness. More studies are needed in order to evaluate whether the conditions tested have or not any influence on ovary development.     

Effects of dietary supplementation with feeding stimulants on yellowtail Seriola quinqueradiata (Temminck & Schlegel; Carangidae) protein digestion at low water temperatures

Feeding trials were carried out to examine substances that could be used as supplements in low‐protein/high‐lipid diets to improve protein digestion of yellowtails (Seriola quinqueradiata) during winter. Dietary supplementation with synthetic or natural (krill and squid extracts) feeding stimulants (FS) improved feed intake and growth performance of yellowtails. Moreover, the apparent protein digestibility (APD) and pepsin, trypsin and chymotrypsin secretions in fish fed diets supplemented with the different FS were superior to those in fish fed the control diet. These findings suggest that the dietary inclusion of either synthetic or natural FS is a potential tool for improving protein digestion at low water temperatures, and may provide a promising solution for the winter growth retardation experienced in yellowtail culture.     

Effect of reward level on the number of food demands in yellowtail Seriola quinqueradiata

ABSTRACT: The effect of reward level (amount of food received in response to one trigger actuation) on the self-feeding activity of juvenile yellowtails was examined. Three groups of 10 juvenile yellowtails (mean bodyweight, 65.6 g) were allocated randomly to three 200 L cylindrical tanks set in the experiment room. Each tank was illuminated by overhead fluorescent lamps with a light : dark photoperiod regimen of 12 h : 12 h (light 06.00–18.00 hours). A rod-type tactile switch was used to activate the self-feeding device. Three levels of reward were set up by installing a different number of identical feeders for each group: one feeder for the low-reward group, three feeders for the medium-reward group and five feeders for the high-reward group. Each feeder delivered 3–7 pellets per actuation. Yellowtails in all groups showed a clearly diurnal feeding pattern that was synchronized to the given photoperiod. Average number of feeder actuations per day was highest (219/day) in the low-reward group. Second highest was the medium-reward group (116/day), and last was the high-reward group (67/day). The resultant average feed intake per day was 27.1 g/day in the low-reward group, 31.5 g/day in the medium-reward group and 28.4 g/day in the high-reward group. Thus, yellowtails appear to have the ability to regulate the amount of feed delivered daily by increasing the number of food demands when the reward is low and decreasing the number of food demands when the reward is high.     

Dietary branched‐chain amino acid supplementation affects growth and hepatic insulin‐like growth factor gene expression in yellowtail,Seriola quinqueradiata

We investigated the effect of dietary supplementation with a branched‐chain amino acid (BCAA) mixture (valine, leucine and isoleucine) on juvenile yellowtail (Seriola quinqueradiata) growth and hepatic insulin‐like growth factor (IGF) gene expression. Total dietary BCAA content was 8.1, 8.5, 9.0 and 9.8 g   kg^?1 for the control, 0.4%, 1.0% and 2.0% BCAA experimental groups, respectively. Body weight was measured on day 77, after which fish were fasted for 3 days and refed; the livers were then removed 3 or 9 h later for analysis of hepatic gene expression. Body weight significantly increased in the BCAA‐supplemented groups. Hepatic expression of IGF1 and IGF2 significantly increased in the 2% BCAA group at 3 and 9 h after refeeding. In the 1% BCAA group, hepatic IGF1 expression tended to be higher at 9 h than in the control group after refeeding. Also, hepatic IGF2 significantly increased at only 9 h after refeeding in the 1% BCAA group. In conclusion, dietary supplementation with crystalline BCAAs increased growth and hepatic expression of IGF1 and IGF2. These results suggest that dietary crystalline BCAA supplementation would be a valuable addition to yellowtail aquaculture practices.     

Further clarification of winter energy and protein requirements at the optimum feeding frequency for yellowtail

SUMMARY: This is another report from a series of studies aimed at determining the energy and protein requirements based on the optimum feeding frequency of yellowtail during the winter season. Experiments were conducted at Mie and Oita Prefectures, Japan, employing extruded pellets of known digestible energy (DE) and digestible protein (DP) values. Four groups of fish were fed at frequencies of five, three, two, and one time(s) per week. The most efficient feed performance was obtained for the feeding frequenecy of three times per week. The DE and DP requirements calculated based on the feeding rate at this frequency were 38.7 kcal and 2.8 g/kgBW per day (14.3–17.3°C) in Mie and 30.4 kcal and 2.2 g/kgBW per day (13.8–17.5°C) in Oita, respectively. The present results and the observations on the changes of the contents in digestive tracts tallied with our previous work, confirming that the optimum feeding frequency was three times per week.     

Response changes with growth in the gustatory receptors of young yellowtails (Seriola quinqueradiata)

SUMMARY: Laboratory-hatched juvenile yellowtails (mean fork length, 9.3 cm) were reared for 2 months in two groups on different kinds of food, mysid and squid in one group and fish in the other, and the gustatory neural responses to seven chemicals (adenosine-5'-monophosphate, alanine, arginine, betaine, proline, tryptophan, and valine) were recorded in fish before and after the 2-month rearing period. Large variances in the responses to some chemicals were noticed in the juveniles before the rearing experiment. Mann–Whitney U -tests on the neural responses indicated significant changes in the magnitude of the responses to valine and some other chemicals relative to that for proline or tryptophan between the pre- and the two post-rearing groups. No significant differences in the response magnitude for the seven chemicals were observed for the two post-rearing groups suggesting that the response changes during the 2-month rearing might have been intrinsic and not due to specific food items in the diet. The dose–response relationship for some chemicals was also examined in the juveniles before and after the 2-month rearing. A slight lowering of threshold was noticed for alanine and valine after the rearing. Data on the responses of wild yellowtails were in support of the changing responsiveness of gustatory receptors during development of juvenile yellowtails.     

Effect of Continuous Food Supply on the Oxygen Consumption of Young Mediterranean Yellowtail (Seriola dumerili Risso, 1810)

The aim of this work was to investigate the effect of a continuous food supply on the oxygen consumption of young Mediterranean yellowtails (Seriola dumerili Risso, 1810) during the photophase period (14LL:10DD). Four groups with six fish each, weighing individually approx. 600 g, were distributed into open 2 m³ quadrangular fibreglass tanks, and fed with commercial pellets for 60 days. Two of the tanks received a continuous feed supply by means of automatic band feeders (ABF), whilst fish in the other two tanks were fed by hand, twice a day. To improve accuracy in calculating oxygen consumption, the effect of oxygen diffusion between the air and the water was determined by the use of a control tank of similar characteristics, containing no fish. Oxygen consumption instantaneous rate was calculated by the difference between dissolved oxygen concentrations in tanks with and without fish, multiplied by the water flow and divided by the estimated total fish biomass in each tank. In both feeding regimes, an increase in the oxygen consumption levels after feeding commencement was observed. The amplitude, however, was lower and the duration of feeding effect was higher in the group fed by ABF.     

The abundance of juvenile yellowtail (Seriola quinqueradiata) near the Kuroshio: the roles of drifting seaweed and regional hydrography

We assess the effect of drifting seaweed (Sargassum sp.) biomass, geography and hydrography on juvenile yellowtail (Seriola quinqueradiata) abundance variation off the southeast coast of Japan, near the Kuroshio Current. The amount of drifting seaweed mats progressively increased northeastward into the cooler, coastal waters. Frontal structure indexed using a station‐to‐station ΔSST did not explain spatial variation in the seaweed mat distribution, although the western extent of the Kuroshio Current appeared to act as a boundary. Juvenile yellowtail constituted 51–62% of the fish collected in association with drifting seaweed mats in April 1996 and 1997 and 29% in June 1996. The abundance of juvenile yellowtail was positively correlated with seaweed biomass. The geographic distribution of juvenile yellowtail associated with drifting mats varied among sampling periods, being more southwesterly in April and more northeasterly in June. Simple multiple regression models based on seaweed biomass and geographic distribution (latitude) explained between 35% and 43% of the variation in juvenile yellowtail abundance in spring. Associations with spatial and temporal variations in hydrographic conditions did not contribute to explained variation in a meaningful manner. The results presented here indicate that, off the southeast coast of Japan during April, yellowtail juveniles are likely to be most abundant when seaweed biomass is high, occur offshore, and are bounded by the western extent of the Kuroshio Current near the 19–20°C SST isotherm.     

黄条鰤生长性状全基因组关联分析

利用2b-RAD技术对119尾黄条鰤(Seriola lalandi)个体进行测序,共获得黄条鰤SNP分子标记26665个,对黄条鰤个体的体质量和全长这2个重要生长性状进行全基因组关联分析,筛选与体质量和全长性状相关的SNP位点和候选基因。结果显示,黄条鰤体质量性状中共筛选到17个体质量显著关联的SNP位点,找到17个可能的候选基因,全长性状共筛选到12个潜在显著关联位点,找到12个可能的候选基因。利用KEGG数据库对可能的候选基因进行Pathway分析,得知候选基因主要参与了细胞或组织生长发育相关的代谢通路调控过程,可能是影响黄条鰤生长性状密切相关的重要候选SNP位点和功能基因,结果可为今后黄条鰤种质资源可持续利用和育种提供遗传信息资料积累。     

Some Protozoan and Metazoan Parasites of the Amberjack From the Balearic Sea (Western Mediterranean)

A survey of protozoan and metazoan parasites of wild amberjack (Seriola dumerili) from the Balearic Sea revealed one myxozoan (Myxobolus sp.), one monogenean (Heteraxine heterocerca), 10 trematodes (Bucephalus polymorphus, Prosorhynchus crucibulum, Bucephalopsis sp., Hemiurus communis, Aponurus sp., Acanthocolpus Iiodorus, Stephanozostomum pristis, Nematobothrium scombri, Wedlia bipartita, Paradeontacylix sp.), one nematode (Philometra globiceps), one copepod (Caligus curtus) and one isopod (Gnathia vorax larva) species to be present. The prevalence and intensity of infection and the distribution of each species is described. Their possible interactions with farmed amberjack are discussed.     

Ambient salinity and osmoregulation,energy metabolism and growth in juvenile yellowtail kingfish (Seriola lalandi Valenciennes 1833) in a recirculating aquaculture system

The effects of salinity on plasma osmolality, branchial chloride cell density, feed consumption and conversion and growth performance of yellowtail kingfish (Seriola lalandi) were evaluated. Fish (11.6 ± 0.6 g) were kept for 29 days at 14, 18, 22, 26 (experimental) and 30 g L^?1 (control) salinity in independent, pilot‐scale recirculation aquaculture systems. No differences in plasma osmolality or chloride cell numbers in gills were observed, pointing to a strong osmoregulatory capacity in the juveniles. Fish at 14, 18 and 22 g L^?1 (7.61 ± 0.19, 7.61 ± 0.01 and 7.61 ± 0.13% day^?1, respectively) had higher growth rates than fish at 26 and 30 g L^?1 (7.10 ± 0.05 and 6.97 ± 0.06% day^?1 respectively). The higher growth rate at lower salinity resulted from increased feed intake; feed conversion was not different. An evaluation of the impact of salinity on growth rate of on‐growing stages (till market size) seems warranted to assess whether the profitable effects of low salinity persist in later stages of this important aquaculture species.