Yellowtail Kingfish Seriola Lalandi Research Articles

Coinfection of Caligus lalandei and Benedenia seriolae on the yellowtail kingfish Seriola lalandi farmed in a net cage in northern Chile

The yellowtail kingfish Seriola lalandi is one of the most important fish candidates for the diversification of aquaculture in Chile. Fish farmed experimentally in one floating cage on a site located in Northern Chile, between November 2013 and December 2015, were first detected with the sea lice Caligus lalandei from April 2014. The highest prevalence (100%) was reached in July 2014 and the highest abundance in June 2014 (4.3 lice/fish). The monogenean Benedenia seriolae was also recorded in the same stock of fish from July 2014, reaching the highest abundance of 30.8 parasite/fish and a prevalence of 100% in January 2015. When the abundance of B. seriolae increased, C. lalandei abundance decreased until it disappeared in January 2015, which could be attributed to the increase of the seawater temperature in the period of study. This is the first report of C. lalandei infecting S. lalandi reared in net cage in Chile.

Genetic parameter estimates for growth and non-growth traits and comparison of growth performance in sea cages vs land tanks for yellowtail kingfish Seriola lalandi

The aquaculture of yellowtail kingfish Seriola lalandi, is now expanding worldwide. Production is conducted in two very different types of commercial facilities: predominately in sea cages in Australia, Mexico, Chile and Hawaii; and in indoor facilities in Europe. With expansion, there is concordant commercial interest to develop genetically improved stocks for production. However, there is a great paucity of genetic information about this species. Knowledge gaps include accurate genetic parameter estimates (i.e., from large sample sizes) that are essential to develop accurate and efficient selection indices. Specifically we require accurate information on non-growth traits (such as parasite load and deformities) and their correlations with growth traits (body weight and fork length), and information on any genotype by environment (G×E) interactions between the two major growing systems to determine whether a single or multiple selection programs are required. Here we address all these fundamental genetic knowledge gaps and provide, for the first time: relatively accurate genetic parameter estimates based on approximately 1400 genotyped and phenotyped animals; and preliminary tests for G×E interactions between growth in sea cages vs land tanks. The heritability estimates were moderate and significant (0.42±0.10) for growth traits, whereas heritability estimates for non-growth traits were low (0.01–0.06). The genetic correlation between body weight and fork length was positive and close to one (0.98); in contrast, the correlation between growth traits with occurrence of fluke and deformity were not significant. The genetic correlations for growth traits between two culture environments were high (0.92–0.97); they were however, associated with large standard errors. In summary, the new set of genetic parameters obtained from this study provide accurate information that is essential to develop genetically improved stocks of yellowtail kingfish for commercial production.

Assessment of cathepsin mRNA expression and enzymatic activity during early embryonic development in the yellowtail kingfish Seriola lalandi

In pelagic species such as Seriola lalandi, survival of both the eggs and embryos depends on yolk processing during oocyte maturation and embryo development. The main enzymes involved in these processes are the cathepsins, which are essential for the hydration process, acquiring buoyancy and nutrition of the embryo before hatching. This study aimed to investigate the mRNA expression profiles of cathepsins B, D and L (catb, catd and catl) and the activity of these enzymes during early development in S. lalandi. We included previtellogenic oocytes (PO). All three enzymes were highly expressed in PO, but the expression was reduced throughout development. Between PO and recently spawned eggs (E1) the transcript to catb and catd decreased, unlike catl. Cathepsin B activity, showed stable levels between PO until blastula stage (E4). High activities levels of cathepsins D and L were observed in E1 in comparison with later developmental stages. Cathepsin L activity remained constant until E1, consistent with observations in other pelagic spawners, where its participation in a second protolithic cleavage of the yolk proteins, has been proposed for this enzyme. Their profiles of both mRNA expression and enzymatic activity indicate the importance of these enzymes during early development and suggest different roles in egg yolk processing for the hydration process and nutrition in early embryos in this species.

Potential role of ectoparasites (Zeuxapta seriolae and Caligus lalandei) in the transmission of pathogenic bacteria in yellowtail kingfish Seriola lalandi, inferred from cultivable microbiota and molecular analyses.

Potential role of ectoparasites (Zeuxapta seriolae and Caligus lalandei) in the transmission of pathogenic bacteria in yellowtail kingfish Seriola lalandi, inferred from cultivable microbiota and molecular analyses.

Phylogeography of the pelagic fish Seriola lalandi at different scales: confirmation of inter-ocean population structure and evaluation of southern African genetic diversity

The study investigated the global and regional phylogeography of the yellowtail kingfish Seriola lalandi by examining genetic diversity and population genetic structure of this species at inter-and intra-ocean level and on a regional scale. DNA fragments of two mitochondrial genes, cytochrome b (Cytb) and cytochrome c oxidase subunit I (COI) and one nuclear gene, recombination activating gene 1 (RAG1), were sequenced to investigate the global-scale phylogeography of this species. The population genetic structure within the South Pacific, as well as along the South African coastline, was examined further using six microsatellite markers. Three distinct clades were identified for S. lalandi, which correspond with previously described subspecies of the North-East Pacific, North-West Pacific and the Southern Hemisphere. Within the latter, additional divergence was observed between the South Pacific and the South-East Atlantic regions. Divergence estimates were indicative of a Pacific origin for S. lalandi populations, because of Pleistocene vicariant events. Microsatellite analyses revealed overall significant genetic differentiation between South African and South Pacific samples. This corroborates recent findings on the global phylogeography of the species. No population differentiation was observed within South Africa, indicating high levels of gene flow.

Praziquantel delivery via moist pellets to treat monogenean parasites of yellowtail kingfish Seriola lalandi: efficacy and feed acceptance.

Praziquantel (PZQ) is registered for oral use against Benedenia seriolae infecting Seriola spp. in Japan, but its bitter taste causes poor palatability. Incorporating PZQ in a moist pellet may help mask the flavor to improve intake. Altering delivery, however, may influence efficacy. We assessed the minimum effective concentrations of PZQ in moist pellets delivered by intubation for the monogeneans Zeuxapta seriolae and B. seriolae infecting yellowtail kingfish Seriola lalandi in flow-through tanks. The optimised dose was then evaluated in a sea-cage of S. lalandi to assess feed acceptance and efficacy. During intubation trials, efficacy was assessed as a percent reduction compared to control groups; in the field trial, efficacy was assessed by a percent reduction after treatment. PZQ delivered by intubation at 70 mg kg-1 body weight (BW) for 3 d was 99.7 and 81.7% effective against Z. seriolae and B. seriolae, respectively. Increasing the dose to 120 mg kg-1 BW for 3 d had a similar efficacy against Z. seriolae (98.4%) and increased efficacy against B. seriolae to 89.2%, but partial emesis of the medicated feed was sometimes noted. S. lalandi in a sea-cage at 17°C readily consumed PZQ administered daily in moist pellets at 70 mg kg-1 BW for 3 d (inclusion rate: 5.15 g kg-1), which significantly reduced Z. seriolae and B. seriolae abundance with 99.4 and 81.6% efficacy, respectively. Juvenile B. seriolae were common on the eyes of fish post-treatment which indicates a strategically timed repeat treatment is necessary.

The effects of gonadotropin-releasing hormone analog on yellowtail kingfish Seriola lalandi (Valenciennes, 1833) spawning and egg quality

Communal spawning behaviour in marine aquaculture species often results in a few individuals contributing disproportionate amounts of gametes. This can lead to a reduction in genetic variability and increases the risk of inbreeding among successive generations. Therefore, long term sustainability of captive breeding programmes for such species partly depends upon maintaining a sufficiently high proportion of parents contributing high quality gametes during spawning. The current study was conducted to evaluate if the use of slow-release gonadotropin-releasing hormone analog (GnRHa) implants could increase the number of females spawning high quality gametes, and thus increase genetic variation in a captive population of yellowtail kingfish Seriola lalandi (Valenciennes, 1833). Broodstock fish received implants with or without 500μg of GnRHa during the spawning season. GnRHa treatment was associated with a higher proportion of females contributing to spawning. However, compared to eggs from non-GnRHa-treated broodstock, GnRHa significantly decreased the floating rate, fertilisation rate, number of viable eggs and egg oil globule diameter. Overall, the use of slow-release GnRHa implants is a useful tool to increase parental contribution to spawning, but this benefit must be carefully balanced against lower egg quality.

A comparison of the palatability of racemic praziquantel and its two enantioseparated isomers in yellowtail kingfish Seriola lalandi (Valenciennes, 1833)

The bitterness of racemic praziquantel (Rac-PZQ) constrains its use as an in-feed treatment against monogenean flukes in finfish aquaculture. Evidence exists in mammals that the R-(-) enantiomer of PZQ is less bitter than the S-(+) enantiomer. If fish exhibit this same response, then the recently described techniques for the large-scale resolution of R-(-)-PZQ from Rac-PZQ could facilitate the wide-spread application of this effective anthelmintic compound via feed. The hypothesis that yellowtail kingfish Seriola lalandi would find R-(-)-PZQ more palatable than Rac-PZQ and S-(+)-PZQ was tested in four trials. During the first three trials, the palatability of diets top-coated with 10 g kg-1 of Rac-PZQ or its two enantioseparated isomers were compared in small (85-160 g) and large (1.2 kg) yellowtail kingfish. A fourth trial compared the palatability of R-(-)-PZQ and Rac-PZQ at dietary inclusion levels of 2.5, 5.0 and 10.0 g kg-1 in small yellowtail kingfish (170 g). Ingestion data showed that R-(-)-PZQ to be no more palatable than either Rac-PZQ or S-(+)-PZQ to yellowtail kingfish, regardless of size. Indeed, evidence suggested that the S-(+)-PZQ to be slightly more palatable than both R-(-)-PZQ and Rac-PZQ. From these data, we hypothesize that the strong smell of R-(-)-PZQ (which was not present in S-(+)-PZQ) is an equally important determinant to palatability as taste in yellowtail kingfish. Results demonstrate that dietary inclusion level is a more important determinant to palatability than PZQ chirality; however, administration of R-(-)-PZQ may still be advantageous if it is demonstrated to be the only enantiomer efficacious against monogeneans.

The performance of larvalSeriola lalandi(Valenciennes, 1833) is affected by the taurine content of theArtemiaon which they are fed

This study describes the effects of feeding taurine-supplemented Artemia on the growth, survival, whole body taurine content and jaw malformation rate of larval yellowtail kingfish Seriola lalandi. Larvae were fed rotifers containing no supplemental taurine from 3 to 15 day post hatch (dph) and Artemia co-enriched with taurine from 12 to 22 dph. Artemia were supplemented at concentrations of either 0, 0.8, 1.6, 2.4, 3.2 or 4.0 g of taurine L−1 during the 18 h HUFA enrichment process. Taurine content in the Artemia increased from 0.76 ± 0.04% DW in those without supplementation to 3.95 ± 0.17% DW in those supplemented at 4.0 g L−1. Survival rates of larval yellowtail kingfish were significantly lower in all taurine-supplemented treatments compared to the unsupplemented control. Growth was significantly improved in those larvae fed taurine-supplemented Artemia; however, we cannot attribute this improvement solely to taurine, as improved growth may have been a function of the reduced survival, and therefore increased prey availability, in these treatments. The whole body taurine content of larvae fed unsupplemented Artemia was significantly lower (1.85 ± 0.03% DW) than those fed supplemented Artemia, which did not differ from each other (pooled average 2.48 ± 0.03% DW), suggesting either a functional excretion mechanism is in place or that this represents the saturation value for larvae of this age. Jaw malformation rates were not affected by Artemia taurine content. The results of this research suggest yellowtail kingfish larvae may have a lower requirement and/or a reduced tolerance to excess dietary taurine than juveniles.

Common pathogens found in yellowtail kingfish Seriola lalandi during aquaculture in Australia

Yellowtail kingfish aquaculture in sea-cages is an emerging industry in Australia. Monogenean, myxozoan and bacterial pathogens sometimes cause health issues that require diagnosis or monitoring.

Use of Organic Selenium Supplements in Soybean Meal- Based Diets for Juvenile Yellowtail Kingfish (Seriolalalandi)

Sustainable aquaculture, from both ecological and economic perspectives, demands a substantial reduction of the amount of fishmeal used in aqua feed. Instead, plant-derived protein feed stuff, which provide a nutritious diet offer a promising alternative for inclusion in aqua feed. In this study, the effects of organic selenium supplementation in low and high soybean meal-based practical diets for yellowtail kingfish (Seriola lalandi) were evaluated over a 60-day feeding experiment. The juvenile yellowtail kingfish (initial weight 5.02 ± 0.04 g fish −1 ) were fed five iso-nitrogenous and iso-caloric diets containing 49% crude protein and 22 MJ kg −1 gross energy. The control diet(C) includes 46% fishmeal, whereas the other diets used soybean meal to replace 25% and 75% of the fishmeal protein, both without and with organic selenium supplementation (SBM 25 , SBM 25+Se , SBM 75 , and SBM 75+Se ). Fish were fed ad libitum two times a day at 09:00 and 15:00 hours. No differences were observed in feed intake among dietary treatment groups (P > 0.05). Organic selenium-supplemented diets improved final weight; however, final weight was significantly reduced when fish were fed high soybean meal diets (P < 0.05). Organic selenium supplementation had a significant effect on specific growth rate at low soybean meal diets, but did not affect specific growth rate when fish were fed high soybean meal diets. Selenium accumulation in fish fillet was strongly correlated with selenium concentration in the diets. While fish fed the SBM 25+Se diets had significantly higher glutathione peroxidase activity than those fed other diets, the lowest glutathione peroxidase activity was found in fish fed SBM 75 diets. Histologically, selenium-deficient diets induced myopathy and alterations in tissue structure were most prevalent in fish fed the SBM 75 diet. The findings of this study indicate that, with Se supplementation, soybean meal could supply 25% of the protein in yellowtail kingfish diets.

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.

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.

Hyper-Saline Conditions Affect Growth, Osmoregulation and Survival of Fingerling and Juvenile Yellowtail Kingfish, Seriola Lalandi

Hyper Saline Conditions Affect Growth Osmoregulation and Survival of Fingerling and Juvenile Yellowtail Kingfish Seriola Lalandi

Growth differentiation factor 9 and bone morphogenetic protein 15 expression in previtellogenic oocytes and during early embryonic development of Yellow-tail Kingfish Seriola lalandi.

BackgroundDuring fish oocyte maturation, specific molecules are expressed and accumulated within oocyte until fertilization and embryo development. Special attention have been paid in members of the transforming growth factor (TGF-β) superfamily; growth differentiation factor 9 (GDF9/gdf9) and bone morphogenetic protein 15 (BMP15/bmp15), which exert regulatory functions during oocyte maturation and follicle development. However, little attention has been paid to the involvement of these molecules during embryogenesis considering its importance for the formation of a good quality egg and subsequent embryo survival. The purpose of this study was to analyze the expression of gdf9 and bmp15 in previtellogenic oocytes and during early embryonic development in Seriola lalandi, a pelagic fish with increasing prospect for its aquaculture development, which however, show high mortality at embryo and larval stages.ResultsThrough RT-qPCR it was found that gdf9 expression was higher in previtellogenic oocytes decreasing after ovulation. This expression profile agrees with its participation in early stages of the follicular development. The transcripts for bmp15 also showed the highest levels in previtellogenic oocytes, however this expression was lower than obtained with gdf9. Conversely, in recently spawned oocytes mRNA bmp15 levels were highest than observed to gdf9. This, is consequent with the main role proposed for this growth factor at the final fish oocyte maturation: avoid the ovulation of an immature oocyte. During embryo development, low levels of mRNA were detected to gdf9, with an increase in 48 H post-fertilization embryos. The bmp15 expression did not change throughout development and was higher than gdf9 at 16 cells, blastula and appearance embryos stages.ConclusionsBoth (gdf9 and bmp15) expression profiles in previtellogenic oocytes and newly spawned eggs are consistent with the described functions for these growth factors in vertebrate ovarian physiology in early and late stages of the follicular development. So, these genes could be considered as quality biomarkers at these stages. However, further studies of these proteins throughout folliculogenesis, are necessaries to fully understand their functions during the oocyte formation. In addition, the persistent expression of these growth factors during development, allows us to speculate possible roles in embryonic processes, which must also be addressed.

First record of Unicapsula seriolae (Myxozoa: Multivalvulida) from the muscle of Malabar grouper Epinephelus malabaricus in Japan

Unicapsula seriolae (Myxozoa; Multivalvulida) was found in the trunk muscle of Malabar grouper Epinephelus malabaricus caught off Wakayama Prefecture, Japan. Numerous filamentous or sesamoid brown to black lesions were observed in the skeletal muscle. Histopathological observation indicated that the lesions were myxosporean plasmodia encapsulated by a fibrous layer, accompanied by melanin deposition. Spores having one large and two rudimentary polar capsules were subspherical in shape and 6.6×6.9μm in size. Scanning electron microscopy revealed that spores were composed of three spore valves. Morphological characteristics were consistent with U. seriolae, which is reported to cause myoliquefaction in yellowtail kingfish Seriola lalandi in Australia. Molecular analysis of the SSU and LSU rDNA supported identification of the species as U. seriolae. This is the first report of Unicapsula in Japan.

Effects of Pro-Tex on zebrafish (Danio rerio) larvae, adult common carp (Cyprinus carpio) and adult yellowtail kingfish (Seriola lalandi)

Aquaculture practices bring several stressful events to fish. Stressors not only activate the hypothalamus-pituitary-interrenal-axis, but also evoke cellular stress responses. Up-regulation of heatshock proteins (HSPs) is among the best studied mechanisms of the cellular stress response. An extract of the prickly pear cactus (Opuntia ficus indica), Pro-Tex, a soluble variant of TEX-OE(®), may induce expression of HSPs and reduce negative effects of cellular stress. Pro-Tex therefore is used to ameliorate conditions during stressful aquaculture-related practices. We tested Pro-Tex in zebrafish (Danio rerio), common carp (Cyprinus carpio L.) and yellowtail kingfish (Seriola lalandi) exposed to aquaculture-relevant stressors (thermal stress, net confinement, transport) and assessed its effects on stress physiology. Heat shock produced a mild increase in hsp70 mRNA expression in 5-day-old zebrafish larvae. Pro-Tex increased basal hsp70 mRNA expression, but decreased heat-shock-induced expression of hsp70 mRNA. In carp, Pro-Tex increased plasma cortisol and glucose levels, while it did not affect the mild stress response (increased plasma cortisol and glucose) to net confinement. In gills, and proximal and distal intestine, stress increased hsp70 mRNA expression; in the distal intestine, an additive enhancement of hsp70 mRNA expression by Pro-Tex was seen under stress. In yellowtail kingfish, Pro-Tex reduced the negative physiological effects of transport more efficiently than when fish were sedated with AQUI-S(®). Overall, our data indicate that Pro-Tex has protective effects under high levels of stress only. As Pro-Tex has potential for use in aquaculture, its functioning and impact on health and welfare of fish should be further studied.

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.

Assessing the risk of climate change to aquaculture: a case study from south-east Australia

A qualitative screening-level risk assessment was developed to evaluate relative lev- els of risk from climate change to aquaculture industries. The assessment was applied to 7 major industries in the temperate south-east region of Australia and involved a simple, transparent and repeatable methodology that was appropriate for a range of different aquaculture systems and taxa. Two key stages were involved: the development of comprehensive expertise-based litera- ture reviews or 'species profiles' and a scoring assessment, with the latter providing a defined framework within which industries could be ranked (from high to low risk). In addition to inform- ing the second stage of the risk assessment process, the species' profiles also highlighted impor- tant climate change drivers and key information uncertainties and knowledge gaps. There was good resolution among the scoring assessments, with only 2 industries receiving the same risk score. The results indicated that oysters farmed from wild spat (Sydney rock oysters Saccostrea glomerata) were at most risk to climate change, with warm temperate hatchery-based finfish spe- cies (yellowtail kingfish Seriola lalandi) being the least at risk. This study provides critical guid- ance for scientists, resource managers and stakeholders for future research, both in addressing key knowledge gaps and focussing the development of more detailed risk analyses for high risk aquaculture industries in south-east Australia.

Genetic parameters for economically important traits in yellowtail kingfish Seriola lalandi

The aim of the present study was to estimate genetic parameters for body and carcass traits, visual condition score, and deformity in yellowtail kingfish Seriola lalandi, an emerging aquaculture species in Australia. These novel data and genetic parameters are required to solve the problem of how to conduct efficient selection in this and related species. Analyses were performed on a total of 400 data records collected from a yellowtail kingfish breeding population at Cleanseas Tuna Ltd. farm. They were progeny of 22 full- and half-sib families (eight sires and six dams). Six newly developed and four published microsatellite markers were used to construct the pedigree. Genetic parameters were estimated using average information algorithm in ASReml with a multiple trait model. Fixed effects included sex, seal bite and deformity status. Random effects were the additive genetics of individual animal, and maternal and common environmental effects (i.e., dam-tank effect arising from a short period of separate rearing of offspring that came from two different broodstock tanks). The estimates of heritability for body and carcass traits were moderate (h2=0.15 to 0.30, s.e. ranging from 0.09 to 0.19). Fillet fat content showed an unusually high heritability (0.94±0.21) with a standard animal model, but was only moderate (0.41±0.26) when tank and dam were included as random effects. The estimate for condition score was 0.15±0.11, whereas the heritability for deformity was close to zero (h2=0.02). The genetic correlations between body and carcass (fillet weight and fillet yield) traits were high and positive (0.57 to 0.94, s.e. 0.05 to 0.46). Genetic correlations between body traits and condition score were moderate to high and positive (i.e. favourable). These results suggest that selection for high growth would result in concomitant increase in fillet weight, a carcass trait of paramount importance. It is concluded that there is substantial potential for genetic improvement of economically important traits especially growth performance and fillet weight in the current population of yellowtail kingfish.