Qualitative analysis of cartilaginous jaw element malformation in cultured yellowtail kingfish (Seriola lalandi) larvae

A central problem facing worldwide culture of yellowtail kingfish (Seriola lalandi) is the presence of skeletal malformations, including jaw deformities. This study presents a morphological characterization of normal and abnormal cartilage jaw structures during early larval development. Samples of 70–150 larvae were collected from three cohorts from 2 to 9 days post hatching, anaesthetized and fixed for cartilage staining. Cartilaginous components were defined clearly at four days post hatch (dph) (4.65 ± 0.05 mm total length), and abnormal jaw structures were detectable at this time. Jaw deformities observed included extension of Meckel's cartilage with or without ventral bending of the anterior tip, displacement of ceratohyal and hypohyal cartilage ventrally and below Meckel's cartilage, and shortening and dorsal flexion of the lower jaw. At 4 dph, between 44% and 47% of all larvae examined had jaw abnormalities. The contribution of each deformity to the total number of deformities was variable among the three cohorts examined. To compare shape difference accurately we performed an exploratory, landmark‐based geometric morphometric analysis using seven homologous landmarks. Larvae were classified into three jaw morphology groups. The geometric morphometric approach provides a useful tool to standardize classification of cartilage jaw abnormalities at early developmental larval stages. Early recognition of developing abnormalities is of importance for fish farmers in both improving fish selection efficiency and for evaluating effects of rearing parameters.     

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。     

Responses of digestive enzymes and body lipids to weaning times in yellowtail kingfish Seriola lalandi (Valenciennes, 1833) larvae

The optimal time to wean fish larvae from live feed to artificial feed was explored in yellowtail kingfish Seriola lalandi (YTK). The same weaning regime started at five different days post hatching (DPH), namely 10 DPH (W10), 13 DPH (W13), 16 DPH (W16), 19 DPH (W19) and 22 DPH (W22). The activities of trypsin, lipase and alkaline phosphatase were detected in fish from 8 DPH throughout the experiment, but pepsin activity was first detected in fish on 15 DPH in the W10 and W13 treatments. The increase in pepsin activity was concomitant with the decrease in trypsin activity. Total fish lipids after weaning reduced by 40% in the W10 and W13 treatments, and increased by 20% in the W19 and W22. Fish survival rate in the W22 treatment was significantly higher than that in the W10 and W13 treatments. The results suggest that 16 DPH is the earliest day to wean and the best weaning window for YTK larvae should be 19–22 DPH. This study provides enzymatic evidence to guide the weaning process for YTK larvae, and offers a useful approach to explore optimal weaning time for fish larvae.     

Karyotype analysis of the yellowtail kingfish Seriola lalandi lalandi (Perciformes: Carangidae) from South Australia

The karyotype and chromosomal characteristics of the yellowtail kingfish Seriola lalandi lalandi were investigated by examining metaphase spreads from kidney cells of 4-month-old fish artificially bred using wild-captured broodstock from the coast of South Australia. A total of 80 mitotic metaphases from 10 individual fish were analysed, with 52 spreads having a mode of 2 n =48 chromosomes, representing 65% of the metaphases observed. The diploid consisted of two metacentric, two submetacentric, six subtelocentric and 38 telocentric chromosomes, with the fundamental number of chromosome arms being 52. The total haploid chromosome length was approximately 44.412 μm. This study shows that the karyotype of S. lalandi lalandi differs from those reported previously for other Seriola species in having one pair of metacentric chromosomes.     

Size heterogeneity, growth potential and aggression in juvenile yellowtail kingfish (Seriola lalandi Valenciennes)

The ontogenetic development of size heterogeneity and aggression was monitored in commercial culture tanks of yellowtail kingfish (Seriola lalandi Valenciennes). Size heterogeneity increased substantially with the introduction of Artemia as a food source at 12 days post‐hatch (DPH), and was correlated with the appearance of aiming behaviour, a precursor to more direct aggressive interactions. Chasing behaviour started at approximately 19 DPH (10–12 mm total length), with the main aggressors being large‐grade individuals comprising 8% of the population. At any one time, only 10–30% of this grade carried out all of the chases, meaning that a very small proportion of the entire population (1%) was responsible for most of the aggressive interactions. The main recipients of aggression were the small grade, comprising 42% of the population, while the medium grade (50% of the population) were generally not aggressive and received only a low to moderate level of aggression. A grading trial showed that large‐grade juveniles only displayed aggressive behaviour in the presence of size heterogeneity, and that medium‐ or small‐grade juveniles did not establish an agonistic hierarchy in the absence of large individuals. A high level of aggression in the ungraded control treatment was associated with mortality of most of the small individuals. Even in the absence of aggression, the small‐grade juveniles failed to gain weight or show an increase in the RNA/DNA ratio after 12 days. The large‐ and medium‐grade larvae showed an isometric increase in RNA/DNA ratio during development, indicating that faster‐growing individuals are likely the result of better food capture or processing traits rather than better protein synthesis rates. Decreasing size heterogeneity and aggression via grading mostly benefits the medium‐grade individuals, as the majority of small individuals within a batch appear to be on a degenerative developmental trajectory irrespective of an aggressive environment.     

Morphological development and allometric growth of yellowtail kingfish Seriola lalandi V. larvae under culture conditions

Morphological development and allometric growth patterns of Seriola lalandi larvae were assessed to characterize normal growth patterns under culture conditions. Early ontogenetic stages of yellowtail kingfish exhibited an exponential growth in terms of standard length as a function of age. Five development stages were characterized from hatching to the juvenile stage: larval stage I (0–2 days post hatch, dph) with endogenous feeding, characterized by a small yolk sac, unpigmented eyes, primordial finfold surrounding the body and a closed mouth; larval stage II (2–15 dph) characterized by mouth opening, complete pigmentation of eyes and the beginning of the exogenous feeding; subsequently, in the larval stage III (15–25 dph) the posterior tip of notochord of the larvae bended upward and the first rays appeared in fins, concomitant with a change in swimming behaviour; thereafter, larval stage IV (post‐flexion stage; 25–30 dph) began when larvae resembled in morphology to a juvenile organism; however, caudal and dorsal fins were not completely development. Lastly, the juvenile stage was reached 30 dph characterized by a morphology and fin structures similar to those of the adults. Growth and development of structures and organs associated with vital functions such as feeding, sensorial and breathing systems seemed to be more critical previous to 23 dph, which was reflected with a positive allometric growth of head and eyes during this period. The results from this study can be used as a tool‐guide to assess normal development in larval research with S. lalandi to improve existing rearing protocols in hatchery production.     

Modelling of nitrogen loads from the farming of yellowtail kingfish Seriola lalandi (Valenciennes, 1833)

Farming of yellowtail kingfish ( Seriola lalandi , Valenciennes, 1833) in the coastal waters of Australia is a relatively new aquaculture industry, and little is known about the magnitude of nutrient discharges from individual pens. In this work, we modelled the flow of nitrogen for each of two commercial pens in Fitzgerald Bay, upper Spencer Gulf, South Australia. The fish were fed commercial pellets with feed conversion ratios (FCRs) between 3.0 and 3.2 (dry weight feed/wet weight growth). These high values of FCR were reflected in the high nitrogen loads to the environment (176–195 kg N tonne⁻¹ growth) and a small retention of nitrogen in fish growth (14–16% of feed inputs). Considering an annual production of 2000 tonnes, total loads to the environment can reach 391 tonnes N year⁻¹. Eighty-two per cent of these loads are expected to be lost to the water column as dissolved wastes. The high nutrient loads and the importance of dissolved wastes compared with other aquaculture species, such as salmon and trout, reflect the distinctly higher metabolic rates of this pelagic predatory species. The nature of the wastes suggests low localized impacts at current production levels, but regional effects remain unknown.     

The effect of different rotifer feeding regimes on the growth and survival of yellowtail kingfish Seriola lalandi (Valenciennes, 1833) larvae

First feeding success is critical to larval marine finfish and optimization of live feed densities is important for larval performance and the economics of commercial hatchery production. This study investigated various rotifer feeding regimes on the prey consumption, growth and survival of yellowtail kingfish Seriola lalandi larvae over the first 12 days post hatch (dph). The common practice of maintaining high densities of rotifers (10–30 ind. mL^?1) in the rearing tank was compared to a low density feeding technique, where 5–8 ind. mL^?1 of rotifers were offered. A ‘hybrid’ feeding regime offered rotifers at the high density treatment until 5 dph and the lower feeding densities thereafter. There was no significant difference in larval survival (hybrid: 28.9 ± 7%, low density: 17.3 ± 5% and high density: 17.2 ± 9%) or growth (hybrid: 6.12 ± 0.18 mm, low density: 6.03 ± 0.10 mm and high density: 6.11 ± 0.23 mm) between treatments. Rotifer ingestion was independent of rotifer density throughout the trial and increased with larval age, with larvae at 4 dph ingesting 22 ± 1.5 rotifers larvae^?1 h^?1 and by 11 dph ingesting 59 ± 1.6 rotifers larvae^?1 h^?1. These data demonstrate that from first feeding, yellowtail kingfish larvae are efficient at capturing prey at the densities presented here and consequently significant savings in rotifer production costs as well as other potential benefits such as facilitation of early weaning and improved rotifer nutritional value may be obtained by utilizing lower density rotifer feeding regimes.     

Swimbladder inflation,growth and survival of yellowtail kingfish Seriola lalandi (Valenciennes, 1833) larvae under different temperature,light and oxygen conditions

Poor swimbladder inflation leads to low fish survival due to resulting spinal deformities and the inability to feed and develop normally. Failure of swimbladder inflation may be attributed to the inappropriate range of abiotic conditions. This study investigated the effects of temperature, light source and intensity, and oxygen conditions on initial swimbladder inflation, growth and survival of yellowtail kingfish Seriola lalandi larvae. The study consisted of four separate trials including low (21.5°C) and high (24.5°C) temperatures, natural and artificial light sources, low (1000 lux) and high (32 000 lux) light intensities, and ambient and supersaturated dissolved oxygen. Initial swimbladder inflation was only significantly affected by light source, with the highest inflation rate (97.5 ± 3.5%) under artificial light. Fish growth was improved at the higher temperature and at the higher light intensity. Survival was only significantly influenced by light intensity, with the highest survival (11.0 ± 2.3%) at the high intensity (32 000 lux). This study indicates that light source affects swimbladder inflation timing and high artificial light intensity improves larval fish growth and survival.     

Food ingestion,prey selectivity,feeding incidence,and performance of yellowtail kingfish Seriola lalandi larvae under constant and varying temperatures

This study tested the effects of constant and varying temperatures on newly hatched yellowtail kingfish Seriola lalandi larvae in two experiments. In Experiment I, four constant temperatures (21, 23, 25, and 27 °C) were tested under fed or unfed conditions with the fish age from the day of hatch to 24 days post hatch (DPH). Temperatures at 25 and 27 °C reduced the time of fish to reach irreversible starvation, but did not affect the percentage of fish that were able to ingest food. Fish survivals at 21 and 23 °C were significantly higher than those at 25 °C by 24 DPH, but all fish died at 27 °C by 24 DPH in the treatment with food. In Experiment II, three constant temperatures (21, 23, and 25 °C) and two varying temperatures (21–23 and 21–25 °C) were compared using fish from hatch to 28 DPH. On 4 DPH, fish ingested more rotifers, but from 6 to 9 DPH, fish ingested fewer rotifers at 25 °C than at other temperatures. On 19 and 23 DPH, fish ingested more Artemia at 25 °C than at other temperatures. At 25 °C, fish selected for Artemia nauplii earlier than at other temperatures. Fish length and survival between constant temperatures (21 and 23 °C) were not significantly different, but fish survival at the constant 21 °C or at the 21–25 °C varying temperature was significantly higher than that at the constant 23 °C or at the 21–23 °C varying temperature. This study indicates that within the range of temperature tested, the optimal temperature for the first feeding larvae is 21–23 °C after hatch and mortality is likely to occur at ≥25 °C in the first 10 DPH, but fish grew faster at 25 °C after they adapted to the increasing temperature.     

Temperature and dissolved oxygen influence growth and digestive enzyme activities of yellowtail kingfish Seriola lalandi (Valenciennes, 1833)

A 5 week experiment was carried out with juvenile yellowtail kingfish Seriola lalandi to investigate the interactive effects of water temperature (21, 24, or 27°C) and dissolved oxygen regime (normoxic vs. hypoxic) on the growth rate, feed intake and digestive enzyme activity of this species. Specific growth rate (SGR) was highest at 24°C, regardless of oxygen regime, but the SGRs of the fish exposed to hypoxia at 21, 24 and 27°C were 13%, 20% and 17% lower, respectively, than the SGRs recorded for the fish reared under normoxic conditions. The digestive enzyme activities (i.e. trypsin, lipase and α‐amylase) were influenced by temperature but did not appear to be affected by dissolved oxygen concentration. Information about the effects of water temperature and dissolved oxygen on feeding, growth and digestive capacity of juvenile yellowtail kingfish could contribute to improving feed management decisions for production of this fish species under different environmental conditions.     

Quantitative genetic properties of four measures of deformity in yellowtail kingfish Seriola lalandi Valenciennes, 1833

The main aim of this study was to estimate the heritability for four measures of deformity and their genetic associations with growth (body weight and length), carcass (fillet weight and yield) and flesh‐quality (fillet fat content) traits in yellowtail kingfish Seriola lalandi. The observed major deformities included lower jaw, nasal erosion, deformed operculum and skinny fish on 480 individuals from 22 families at Clean Seas Tuna Ltd. They were typically recorded as binary traits (presence or absence) and were analysed separately by both threshold generalized models and standard animal mixed models. Consistency of the models was evaluated by calculating simple Pearson correlation of breeding values of full‐sib families for jaw deformity. Genetic and phenotypic correlations among traits were estimated using a multitrait linear mixed model in ASReml. Both threshold and linear mixed model analysis showed that there is additive genetic variation in the four measures of deformity, with the estimates of heritability obtained from the former (threshold) models on liability scale ranging from 0.14 to 0.66 (SE 0.32–0.56) and from the latter (linear animal and sire) models on original (observed) scale, 0.01–0.23 (SE 0.03–0.16). When the estimates on the underlying liability were transformed to the observed scale (0, 1), they were generally consistent between threshold and linear mixed models. Phenotypic correlations among deformity traits were weak (close to zero). The genetic correlations among deformity traits were not significantly different from zero. Body weight and fillet carcass showed significant positive genetic correlations with jaw deformity (0.75 and 0.95, respectively). Genetic correlation between body weight and operculum was negative (?0.51, P < 0.05). The genetic correlations' estimates of body and carcass traits with other deformity were not significant due to their relatively high standard errors. Our results showed that there are prospects for genetic selection to improve deformity in yellowtail kingfish and that measures of deformity should be included in the recording scheme, breeding objectives and selection index in practical selective breeding programmes due to the antagonistic genetic correlations of deformed jaws with body and carcass performance.     

Environmental drivers of yellowtail kingfish,Seriola lalandi,activity inferred through a continental acoustic tracking network

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Selenium and vitamin E interaction in the nutrition of yellowtail kingfish (Seriola lalandi): physiological and immune responses

Six dietary treatments were prepared in a 3 × 2 factorial design (unsupplemented or supplemented with Se at 1 or 2 mg kg^?1 × supplemented with vitamin E at 40 or 180 mg kg^?1) and fed to yellowtail kingfish (Seriola lalandi) for 6 weeks to evaluate the effects of dietary Se and vitamin E on growth performance, immune and antioxidant responses and to investigate the potential interaction between these two micronutrients in this species. The results have revealed significantly interactive effects with positive physiological responses. Se significantly increased weight gain of fish fed diets low in vitamin E, but not high in vitamin E, whereas serum lysozyme activity was significantly improved by Se in diets high in vitamin E, but not low in vitamin E. Moreover, there was evidence of myopathy in fish deficient in both Se and vitamin E, but not single deficiency. There was no significant effect of dietary Se, vitamin E or their interaction on survival, antibody titre, feed intake, feed conversion ratio and fillet proximate composition; however, fillet Se and vitamin E were significantly responsive to dietary Se and vitamin E, respectively, and higher dietary Se intakes produced significantly higher red blood cell glutathione peroxidase activity.     

Nutritional parameters of dorsal and ventral fillets in summer and winter from farmed yellowtail kingfish Seriola lalandi (Valenciennes, 1833)

The nutritional profile of dorsal and ventral portions of fillets from farmed yellowtail kingfish (YTK) (Seriola lalandi, Valenciennes, 1833) was assessed in winter and summer months to evaluate if there were differential distributions of proximate constituents, fatty acid composition and mineral content seasonally and through the dorso‐ventral axis. The proximate composition of YTK fillets varied between the two anatomical locations examined. In particular, a relatively large variation was observed in crude fat content, which decreased significantly from ventral to dorsal portions of the fillet and was inversely proportional to moisture and protein content. Higher crude fat content was also observed in the fish sampled in summer, compared to those sampled in winter. The omega 3/6 ratio remained constant between fillet portions but was significantly different between seasons (summer > winter). The index of nutritional quality for EPA and DHA was markedly different regarding to fillet portion and season (summer > winter, ventral > dorsal), and significant differences in the levels of potassium, phosphorus, magnesium and iron were also evident between the seasons examined. This study clearly shows differences in nutritional profiles of fillets from farmed YTK in South Australia relative to anatomical location and season. The increase in knowledge gained from this study may lead to improved farm management practices of YTK, which may extend to other commercially relevant species to enhance the production of premium farmed products.     

黄尾鰤的生物学特性与养殖

介绍了黄尾鰤的分布、形态特征、生活习性、繁殖与生长特性等生物学知识;对黄尾鰤亲鱼的促熟培养、产卵孵化和仔鱼培育技术进行了综述;概述了目前国外两种主要养殖方式即网箱养殖和陆基(工厂化)养殖的技术要求。     

Captive spawning and larval rearing of California yellowtail (Seriola lalandi)

A captive population of California yellowtail (Seriola lalandi) was used to document spawning patterns, including measures of egg production, population fecundity and egg and larval quality from 2007 to 2010. Spawned eggs were also used to document larval development and to develop rearing techniques for aquaculture in the region. Broodstock growth and condition factor were best when feeding rations were maintained at 10–15% body weight week^?1 during the warm summer months. A winter ration based on satiation feeding was typically 4% body weight week^?1. During the 4‐year study period, the only broodstock health issue was an infestation by the parasitic gill fluke Zeuxapta seriolae, which was readily treated. Spawning occurred naturally in the 140 m³ tank when the ambient water temperature reached 16°C and ended when the temperature exceeded 22°C. Egg production reached a maximum in 2010 when 43 spawn events were recorded from a pool of nine females yielding 36.8 million eggs in total. The average female size at this time was 20 kg, which equated to a total annual population fecundity of approximately 226 000 eggs kg^?1 female year^?1. Larval rearing trials yielded survival rates as high as 5.8% from egg to 50 days post‐hatch (dph). Successful larval culture methods included the addition of algae paste for green water culture, rotifers (20 rotifers mL^?1) at 2 dph and Artemia (5 Artemia mL^?1) at 6 dph. Larvae were transferred from the incubation tank at 10 dph to a shallower tank with 33% greater surface area to accommodate the larvae's strong orientation to surface waters. This research represents the first documentation of successful spawning and larval rearing for S. lalandi in the eastern Pacific.     

Replacement of fresh algae with commercial formulas to enrich rotifers in larval rearing of yellowtail kingfish Seriola lalandi (Valenciennes, 1833)

This study compared the efficacy of four products that are commonly used in hatchery for nutritional enhancement of rotifer Brachionus plicatilis as the starter food for yellowtail kingfish Seriola lalandi larvae. This experiment consisted of one fresh algae and three enrichment products: (1) Fresh algae were a mixture of Nannochloropsis and Isochrysis at 2:1 on a cell concentration basis; (2) S.presso, (Selco S.presso ^®, INVE Aquaculture); (3) Algamac 3050^® (Aquafauna, USA); (4) Nutrokol ^® (Nutra‐Kol, Australia). Survival rates of the fish fed rotifers enriched with fresh microalgae (40.69%) and S.presso (31.21%) were higher than those fed Algamac 3050 (10.31%). On 3 day post hatch (DPH), fish feeding incidence in the fresh algae treatment was significantly higher than that in other treatments. On 6 DPH, fish showed the lowest feeding incidence in the Algamac 3050 treatment. The methods of enrichment did not affect total lipid levels in either rotifer or fish larvae, but Algamac 3050 enrichment achieved the highest DHA/EPA ratio and lowest EPA/ARA ratio in both rotifers and fish larvae. This study indicates that fresh algae can be replaced by S.presso, but Algamac 3050 is not as good as other formula for rotifer enrichment in rearing yellowtail kingfish larvae in this system.     

棉酚对鲤鱼急性中毒的研究

鲤鱼（体重约16克）腹腔注射乙酸棉酚0，7．3，54，100，200，400mg/kg体重，经四天（96小时）后，死亡率分别是0，0，20％，70％，90％，100％。96小时半数致死剂量是63．6mg/kg体重。注射剂量高于54mg/kg体重时，发生腹腔红肿、体壁溃烂，甚至死亡。实验结果说明虽然棉籽水平的棉酚不引起鲤鱼的任何可见的中毒症状，但是腹腔注射大剂量棉酚可引起与哺乳类相似的中毒症状。