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Proglucagon is the precursor for several peptides: glucagon, glicentin, oxyntomodulin and at least one glucagon-like peptide. Previous reports indicated that proglucagon-derived peptides are important in regulating feeding and energy homeostasis in both mammals and fish. In the present study, a 504 bp cDNA fragment encoding a highly conserved proglucagon in a cyprinid fish ( Schizothorax prenanti ) was amplified by homologous cloning. Tissue expression profiles of proglucagon showed that S. prenanti proglucagon had a broad tissue distribution, but was expressed primarily in the intestine and brain. Proglucagon mRNA levels significantly increased after feeding in the hypothalamus and intestine, while levels were dramatically reduced during a week of food deprivation and increased upon refeeding. Proglucagon mRNA expression changes in the hypothalamus and intestine responded to the altered feeding status and suggest that proglucagon is involved in the regulation of feeding and energy in S. prenanti . Statement of relevance In the present study, we deal with the molecular, distribution expressions and mRNA quantification during periprandial, fasting and refeeding in lower vertebrate Ya-fish ( S. prenanti ). S. prenanti is an endemic cold temperate fish in the southwest of China valuable in both aquaculture and research. However, slow growth rate has been recognized as a major problem in S. prenanti farming, increasing the final production cost. Studies concerning the expression of genes related to feeding and growth regulation have been conducted for this species in our laboratory. Recently, a growing number of homologues of mammalian appetite-regulating peptides and their receptors have been characterized in fish. Proglucagon is the precursor for several peptides: glucagon, glicentin, oxyntomodulin and at least one glucagon-like peptide. These peptides are derived in a tissue-specific manner via post-translational proteolytic processing. Previous reports in mammals indicated that proglucagon-derived peptides are important in regulating feeding and energy homeostasis. However, there is scarce information about their physiological roles in fish. Here, we cloned a 504 bp cDNA fragment of a single proglucagon gene, that is mainly expressed in the intestine and brain and responded to changes of feeding status. These suggest that proglucagon acts as a satiety factor involved in the regulation of food intake in S. prenanti . Our findings of this study provide a basis for future research to better understand the functions and mechanisms of actions of proglucagon and will be helpful in dealing with feeding and growth issues in fishes. We believe that something in this manuscript would be of interest to the journal's readers and hope that this paper is suitable for publication in Aquaculture (Physiology and Endocrinology: Fish).

Five diets were produced with crude protein (CP) from hydrolysed wheat gluten (HWG) replacing graded (0, 12.5, 25, 50, 75%) amounts of CP from LT fish meal. Diets with 0–25% of CP from HWG were extruded with 19–20% water added in the extruder. Water addition was limited to 11% of the extrudate for the 50% HWG diet, and no water was added to the diet with 75% CP from HWG in order to obtain even flow of material in the extruder. Based on the degree of starch gelatinization (DG), estimated by differential scanning calorimetry (DSC), the diets with 19–20% process water were characterized by high gelatinization (HG), medium DG was obtained by limiting water addition to 11% (MG), and low gelatinization (LG) was the result of extruding without water added. Each diet was fed to two groups of rainbow trout in freshwater, and feces were obtained by abdominal stripping. Yttrium oxide (Y 2 O 3 ) was used as inert marker. The average apparent digestibility of starch ranged from 97 to 99% in the HG group, to 76% in the MG group, and 52% in the LG group. The AD of starch increased linearly (R 2 = 0.99) with increasing water addition in the extruder. The AD of lipid was reduced in MG and LG groups, and there was a linear (R 2 = 0.87) relationship between AD of starch and AD of lipid. As a consequence of AD of starch being quantitatively more influenced by water supplementation in the extruder than the AD of lipid, the regression of water supplementation on AD of energy was best explained (R 2 = 0.99) by a 2nd degree polynomial function, in which both the 1st and 2nd degree components were > 0. The findings emphasize the necessity of using sufficient process water during extrusion of salmonid diets both to ensure efficient digestion of starch and lipid. Statement of relevance This paper will increase the awareness in the feed industries of the necessity to secure complete gelatinization in extruded diets, since it is of high importance for digestible energy in the feed.

An increasing number of studies suggest that DHA associated with dietary phospholipid (PL) is better metabolically available for fish larvae. Knowledge on how to increase DHA levels in the major PL classes of the live feed is needed. Brachionus Cayman was cultured in conical fibreglass vessels, enriched with commonly used commercial diet Multigain or DHA Selco (DSelco) in flat bottom vessels at 20 °C. The changes of DHA content in the PL of the rotifers through enrichment and through a starvation phase post-enrichment were investigated in order to define an appropriate enrichment time and to test the stability of DHA post-enrichment. The different dietary non-HUFA (non-highly unsaturated fatty acid) composition of DSelco (25.1% SFA, 32.1% MUFA) and Multigain (40.7% SFA, 2.11% MUFA) allowed an evaluation on how SFA and MUFA might affect the efficiency of DHA enrichment of phospholipid in the rotifers. Rotifer samples were collected at 0 h, 1 h, 2 h, 4 h, 8 h, 12 h and 24 h after initiation of enrichment. Total lipid (TL) and the fatty acid composition in TL, phosphatidylcholine (PC) and phosphatidylethanolamine (PE) of rotifers and enrichment diets were analysed. The highest DHA levels in PC (23.0%) and PE (16.5%) in Cayman were found after 24 h enrichment with Multigain, and levels were far higher than obtained earlier. The enriched DHA was stable at 10 °C for at least 24 h post-enrichment under starving conditions ( p > 0.05), whereas a significant ( p Statement of relevance The paper is bringing information about fatty acid enrichment of rotifers in questions that are so far quite unclear and could have a strong impact on larviculture of marine fish larvae. This study shows methods to obtain high level of DHA in phospholipids of rotifer. The results could potentially have a significant impact to improve current fatty acid enrichment protocols for rotifers.

The adjuvant effects of poly I:C and imiquimod during immunization with a recombinant protein, rVP28 derived from white spot syndrome virus (WSSV) was investigated in kuruma shrimp ( Marsupenaeus japonicus ). Shrimps were injected intramuscularly with different doses of rVP28, poly I:C and imiquimod, and combined rVP28 + poly I:C or imiquimod, and challenged with WSSV. Expression of innate immune-related genes was examined in the heart and lymphoid organ of combined rVP28 + poly I:C or imiquimod immunized shrimps at 1, 3 and 7 days after WSSV challenge. Shrimps which received rVP28 + poly I:C and rVP28 + imiquimod had significantly higher survivals of 52 and 58%, respectively compared to the rVP28 alone or PBS injected control groups ( P Statement of relevance Major contributors to economic losses in shrimp aquaculture are viral diseases, of which white spot syndrome virus (WSSV) is the most important one due to its rapid spread and economic impact. In this paper, we present an immunization method towards prevention of WSSV disease in kuruma shrimp using adjuvants such as poly I:C or imiquimod along with a sub-unit protein (rVP28).

The native tropical seaweed Kappaphycus alvarezii from the Indo-Pacific region has been introduced in many countries because it is the main source of raw material for the carrageenan industry. In Brazil, K. alvarezii aquaculture is allowed in 300 km of the southeastern coast. The aim of this study was to analyze the risk of invasion of this species along the entire Brazilian coast to design public policies and to minimize environmental risks associated with aquaculture. The risk analysis was based on: K. alvarezii suitability models (GARP and MAXENT), coral reef presence, substrate preferences for establishment, and the probability of occurrence of nine species of herbivores that are potential feeders. An invasibility index was created from these parameters and published data of field experiments were used for calibration. The maximum values of suitability corresponded to regions with low temperature ranges, low nitrate availability, high irradiance, and high salinity. Three invasion risk classes were established. The areas of high risk are the eastern and northeastern regions, where the main Atlantic coral reefs are found. This is a priority area for global marine conservation. K. alvarezii introduction is not recommended in this area and the cultivation of native species must be prioritized. The area of medium risk is mainly in the northern region, where local field scale experiments are recommended before widespread introduction. The area of low risk is the southeastern region, where K. alvarezii farming has been established since 2004 with no evidence of invasion. However, considering the high capacity of acclimation of this species, permanent monitoring is recommended, even in areas having a low risk of invasion. Statement of relevance We state the relevance of our paper in commercial aquaculture since we presented a consistent environmental risk analysis for K. alvarezii that according to FAO is the most cultivated seaweed in the world. Our aim is to contribute for development of sustainable seaweed aquaculture, subsiding data to minimize environmental risks associated with K. alvarezii introduction. This kind of analysis also can be adapted to other countries. Our results indicate safe areas to extend K. alvarezii cultivation, areas where the native seaweed should be cultivated and with those conclusions encouraging the expansion of the commercial seaweed aquaculture and highlight for high environmental risks in coral reef areas.

Chinese sturgeon (Acipenser sinensis) is a rare and endangered species, and also an important resource for the sturgeon aquaculture industry in China. Recently, a fatal bacterial disease occurred in farmed Chinese sturgeon. The clinical signs of the diseased fish were systemic blood loss and anemia. The gills were very pale with swollen and hemorrhagic gill filaments. Discrete blood spots were apparent in the oral cavity. Small petechial hemorrhages were present in pale livers and the digestive tract. Hemorrhages were also present in the kidney and gonad. The spleen was red and swollen. Additionally, a small amount of clear ascites fluid was present in the body cavity. A bacterial pathogen was isolated from the internal organs of diseased fish and subsequently identified as Pseudomonas alcaligenes by morphology, biochemical testing and phylogenetic analysis of the 16S rDNA. Experimental infection in healthy hybrid sturgeon confirmed the pathogenicity of the bacterial isolate. The results of this study represent the first isolation and identification of Pseudomonas alcaligenes in cultured Chinese sturgeon in China and provide a foundation for the diagnosis, prevention and treatment of this new disease. Statement of relevance The authors declare that there is no conflict of interests regarding the publication of this paper.

It is widely assumed that pearl oysters, Pinctada margaritifera, producing low quality pearls with concentric grooves or ‘circles’ are unlikely to produce pearls with improved quality if grafted again for pearl production. Such oysters are often discarded. However, if these oysters are capable of improved pearl quality when re-grafted, this would provide opportunities for improved income for pearl farmers. This study aimed to determine whether oysters producing circled pearls are able to produce pearls with improved quality after re-grafting. A total of 100 oysters that produced circled pearls and would have normally been discarded were re-grafted and the quality of successive pearls produced by individual oysters was compared in terms of shape, size, lustre, colour, surface perfection and overall quality. The proportion of pearls with circles decreased from 100% of first graft pearls to 48% after the second graft, and 18% of second graft pearls were classified as ‘semi-round’ and superior in shape to all first graft pearls. There was a significant improvement (p = 0.04) in the overall shape of second graft pearls compared to first graft pearls. The highest proportion of pearls (63%) from the first graft were 10–11 mm in size while the majority of second graft pearls (51%) were 11–12 mm in size, and the differences in pearl size between first and second graft were significant (p = 0.04). Second graft pearls had poorer lustre than first graft pearls with a higher proportion of dull pearls, a lower proportion of medium lustre pearls and no pearls with high lustre. Despite this, the number of pearls in different lustre categories after the first and second graft did not differ significantly (p = 0.07). For overall grading, most first graft pearls (83%) were assessed as ‘C’ grade with 17% categorised as ‘D’ grade. Similarly, most second graft pearls (78%) were assessed as ‘C’ grade and 20% as ‘D’ grade; however, 2% of pearls were assessed as ‘B’ grade which were not present in first graft pearls. Nonetheless, the number of pearls belonging to different grades was not significant (p = 0.08). Our data show for the first time that that production of circled pearls after second graft is not obligatory for P. margaritifera that produced circled pearls after first graft. They further show that marketable pearls can be produced from oysters that are normally discarded after the first pearl harvest and this has potential to generate increased revenue. Statement of relevance This paper presents novel new information on whether P. margaritifera that produced circled pearls after first grafting will produce pearls with improved quality when re-grafted. It clears the confusion among pearl farmers on the decision of whether or not to re-graft P. margaritifera that produced low quality pearls with high number of circles. Overall, the study has a positive impact on pearl aquaculture.

This paper describes a first broad-scale application of quantitative image analysis to the assessment of nutritionally-induced soya bean enteritis in farmed Atlantic salmon. It employs a novel multivariate approach for the histomorphometric analysis of biopsy samples and directly compares the prognostic value of such a quantitative approach against that of a semi-quantitative visual scoring system. This study provides evidence that most of the quantitative indices selected, perform equally well when compared to analogous semi-quantitative descriptive parameters normally used to assess soya bean-induced enteritis seen in Atlantic salmon. The high reproducibility and accuracy of this approach indicate that image analysis can provide a useful and reliable method for the quantification of SB-induced enteritis and by extension, for other facets of gut plasticity/histopathology. Other characteristics of this approach, such as rapidity, simplicity and adaptability similarly favour the use of image analysis, and are particularly useful where less experienced interpreters are performing the analysis. The quantitative assessment system outlined here, clearly identifies soya bean-associated enteropathy in experimental fish, and may thus be recommended for evaluation of related variations in salmon intestinal histomorphology.

Atlantic salmon farmed in seacage facilities are exposed to changing environmental conditions. While growth decline under lower water temperatures are reasonably well understood, the mechanisms behind production decline under high water temperatures are yet to be well elucidated and have been hampered by a lack of data describing pre- and postprandial patterns of endocrine fluctuation. The present research therefore aims to determine whether peak nutrient flux into the blood plasma is the most appropriate time point to investigate the endocrine regulation of growth and appetite under conditions of normal and high temperature, and to investigate the interrelationship between appetite and growth on a pre- and post-prandial time scale. Two experiments are presented which examine ghrelin (GHRL) as an indicator of appetite stimulation, the GH–IGF (growth hormone–insulin-like growth factor) system to describe growth-regulating processes and free amino acids (FAA) to indicate postprandial nutrient influx and link appetite and anabolic processes. Postprandial sampling of plasma and white muscle tissue from short-term adapted postsmolt was conducted at 13 °C and 19 °C at 4, 8, 12, 16, 20 and 24 hours (h). The same samples were taken from long-term adapted big salmon at 12 °C, − 4, − 2, − 1, 0 h pre-prandially and 2, 3, 4 and 6 h post-prandially. While limited relationship between plasma ghrelin concentration and meal times was found for short term adapted postsmolt, clear ghrelin peaks were described for long term adapted salmon prior to the timing of anticipated meals. Possible explanations and consequences to experimental design in this area will be discussed. Postprandial FAA in plasma and white muscle from postsmolt was reduced at 19 °C compared to 13 °C and plasma levels peaked 8 h post-prandially. Muscle Igf1 mRNA expression levels were consistently higher at 13 °C than 19 °C, with no clear postprandial patters. In contrast, plasma IGF-1 concentration was relatively constant over time at 12 °C and 13 °C, but significantly declined from 20 h postprandially at 19 °C. GH receptor (ghr1) mRNA expression in muscle was unaffected by temperature, peaking 4 h post-prandially at both temperatures. This paper describes growth and appetite-regulating processes under conditions of normal and elevated temperature for Atlantic salmon, which is fundamental to our understanding of growth limitations inherent to high water temperature situations.

This paper describes a two-year study of spatial and temporal patterns and processes in the benthos in response to the removal of salmon cages from a sheltered coastal embayment, coupled with the simultaneous reintroduction of cages at an adjacent location. Significant recovery was evident at the fallowed site in the first six months; however, the macrofaunal assemblage remained impacted at the conclusion of the study. By comparison, the reintroduction of a fully operational farm overwhelmed the macrobenthic community within three months, with anoxic and near-azoic conditions developing. Both removal and reintroduction of the farms triggered alternating oscillations of geochemical and biological variables, which were attributed to effects on sediment chemistry from organic loading, ‘boom and bust’ cycles of opportunistic taxa in response to food supply, and the associated variations in metabolic potential. The study also revealed interesting spatial dynamics in the benthos and some useful indicators of different stages of recovery and re-impact. It is concluded that farm reintroductions should aim to gradually increase production; allowing time for the benthos to adapt to the additional organic flux, and be maintained at a level that avoids macrofaunal collapse. The sediment's ability to cope with organic inputs from fish farming, and hence the duration of the recovery period, is contingent on the organic load in each farming cycle and the extent to which the sediment community is allowed to recover. Understanding the influence of each of these on sediment processes is important for sustainable long-term management of farming operations.

Offshore production system is predicted to increase in the near future driven by the lack of coastal space and lower environmental impacts. The aim of this paper has been to evaluate the economic performance of offshore production system respect to inshore one, by comparing net present value (NPV), discounted payback time (DPBT) and internal rate of return (IRR) of two Italian mariculture farms that produce European sea bass. Results showed a better economic profitability of offshore farm, even if sensitivity analysis revealed that financial indicators of both aquaculture production systems have been very sensitive to market condition changes. So, offshore production system could represent an opportunity for fish farmers to increase their profitability, obtaining a more sustainable production and avoiding possible conflicts with other human activities in coastal areas.

Tuna bioenergetics can be described by the following relationship: the energy available for growth is equal to the food energy minus all metabolic costs. These costs include routine metabolic rate, specific dynamic action, increased activity level, eliminated waste, and gonadal development. Captive populations of Pacific bluefin tuna (Thunnus orientalis) were held at ~ 20 °C in fiberglass tanks and fed on a regular schedule with a diet formulated to achieve an energetic content of 176 ± 36 kJ · kg− 1 of biomass · day− 1 (mean ± s.d.). To conduct a bioenergetic study, growth rates during the captive period and tissue energy values post-mortem were empirically determined. Daily growth rates were obtained from a von Bertalanffy growth function based on curved fork length (CFL) measurements of live fish and post-mortem morphometrics. The parameters obtained for the captive bluefin growth function were 225.13 cm straight fork length (SFL), 0.173, and − 0.497 years for L∞, k, and to, respectively. The growth equation, SFL = 225.13 · (1 −e (− 0.173(t-(− 0.497)))) in conjunction with the length-mass regression (where body mass M = 4.98 × 10− 6 × SFL 3.3186) gave a daily growth increase of 32.60 ± 2.40 g · day− 1 for Pacific bluefin tuna of 2.2 years of age and 11.4 ± 1.0 kg (the average age and mass of a fish in the study). The average tissue energy value from four sampled tuna was 7.66 ± 0.40 kJ · g− 1, and applying the daily growth increase estimate provides a daily energy gain of 249.7 kJ, which is 12.4% of an ingested meal's total energy content. A food conversion ratio of 17.8:1 is estimated for a meal consisting solely of sardines and 22.6:1 for a mixed diet consisting of sardines, squid, and a gelatin-vitamin mixture at the stated feeding regimen. This paper presents the first data on actual food conversion ratios and bioenergetic utilization for Pacific bluefin tuna.

Previous reports have described bioenergetic models for juvenile salmonid growth that were validated using data from laboratory and production-scale feeding studies. Time variable functions and power correlations with body weight based on measurement of proximate composition were used to delineate the fish energy density in these models. Although model simulations for growth corresponded closely with measured data using either characterization of energy density, there is significant laboratory burden associated with the measurement of proximate composition throughout the simulation period, and this approach may therefore be impractical for many hatchery applications. Here measurements of fish water fraction are used to estimate the mass of protein and ash using correlations developed in a companion paper. Lipid is subsequently determined by difference, and energy content is calculated using the proximate composition. Model simulations of juvenile coho (Oncorhynchus kisutch) growth and proximate composition using this approach closely matched measured data when provided steady satiation and maintenance rations. The model was less successful predicting detailed protein and lipid dynamics following large abrupt decreases in the food supply rate. However, model simulation errors associated with fish growth were small because of the off-setting nature of the proximate composition model errors. It is concluded that coho water fraction measurements and correlations for protein and ash offer a practical and convenient alternative to direct measurement of fish energy density for many bioenergetic model hatchery applications.

Pure cultures of Vibrio parahaemolyticus were obtained from the haemolymph of moribund shrimp following disease outbreak and mass mortality in the east coast of India during October to November 2013. The organism could not be found in haemolymph of healthy animals from farms in east and west coasts of India. All the isolates were negative for virulence genes associated with human pathogenic strains of V. parahaemolyticus. All the isolates were negative by PCR for genomic region considered specific for V. parahaemolyticus strains associated with acute hepatopancreatic necrosis disease (AHPND) but were positive for T3SS1. The isolates showed genetic diversity as indicated by random amplification of polymorphic DNA (RAPD). Challenge studies with representative isolates by immersion did not cause mortalities or histopathological changes in the experimental shrimps. The present study has demonstrated the association of V. parahaemolyticus with outbreaks of mortalities among cultured Pacific white shrimp Litopenaeus vannamei in the grow-out ponds. Further, the V. parahaemolyticus isolates did not match the characteristics of strains associated with EMS/AHPND and results demonstrate that these strains are probably opportunistic pathogens of immunocompromised cultured L. vannamei under unfavourable environmental conditions and the evidence presented in this paper strongly suggests that the outbreak was due to vibriosis rather than AHPND in India.

This paper explores the interaction between food standards and vertical coordination in the Vietnamese pangasius sector. For farmers and processors alike, the adoption of standards is motivated by a desire to improve market access by ensuring high quality supply. Instead of encouraging the application of standards and contract farming, processing companies prefer to vertically integrate primary production largely due to concerns over the stable supply of pangasius with satisfactory quality and safety attributes. These tendencies increase the market dominance of industrial farming and worsen the position of small household farms.

The production of high quality juveniles at hatchery stages is important to ensure high growth potential during the on-growing phase. In the present paper, molecular growth markers of muscle development and growth in gilthead sea bream were validated in developmental stages/sizes that exhibit high accelerated growth rate, and rearing practices that are characterized by considerable size disparity. In gilthead sea bream the skeletal myosin light chain 2 (MLC2) is a structural molecule of the muscle that exists in two isoforms, A and B, which are known to mark hyperplasia and hypertrophy, respectively. The expression levels of the two isoforms and the robustness of its correlation with length growth were validated in a) larvae and juveniles of gilthead sea bream originating from the same broodstock and raised under intensive vs semi-intensive conditions, and b) in juvenile gilthead sea bream reared under commercial aquaculture practices and subjected to size grading with sorters of increasing diameter. A replacement of MLC2A by MLC2B was observed at metamorphosis in agreement with previous results. Larvae reared at the semi-intensive system outperformed in length growth and MLC2 expression those reared intensively and an earlier and faster replacement of MLC2A by MLC2B was observed at metamorphosis. Similarly, the ratio of MLC2A/MLC2B expression exhibited a tight, significantly negative correlation to total length of juveniles, independent of age. Overall, comparison of groups of gilthead sea bream of different origin rose under different conditions and of different developmental stages (larvae vs juveniles) provided significant evidence for the robustness of MLC2 expression as a growth marker.

This paper assesses factors influencing adoption of new shrimp aquaculture technologies within aquatic-agricultural farming systems in southwestern Bangladesh. The impacts of three new technologies were assessed: two Modified Traditional Technologies (MTT 1 and MTT 2) and a Closed System Technology (CST). A total of 789 farmers from 10 sub-districts in Khulna Division were surveyed randomly, including a control group of 350 farmers using traditional technologies. Farmers gained significantly higher (P 0.05) financial benefit was derived from adoption of MTT1 and MTT2 technologies. Feed use, stocking density, gher size and white spot syndrome virus incidence were key factors associated with the economic returns of CST farms, while various supplementary feed inputs made a significant positive contribution towards increased return for the MTT farms. Lime was an important input for increased return both for MTTs and traditional farms. Farmer age and access to training influenced adoption of both technologies, and gher size and access to financing were significant for the more intensive Closed System Technology (CST).

The main aim of this paper was to report genetic parameters and selection response from a synthetic population of Nile tilapia selected for improved growth performance in brackish water systems in Vietnam. The synthetic base population was formed in 2007 from the best performing individuals for growth produced from a complete diallel cross involving three strains of Nile tilapia, namely GIFT (Genetically Improved Farmed Tilapia), Taiwan and NOVIT4 (GIFT-derived) strains. Selection was practised for increased harvest weight in brackish water (15–20 ppt) over four generations from 2008 to 2011. A total of 12,006 individuals had performance data records. They were offspring of 341 sires and 450 dams (averaging 3000 offspring and 70 sires and 90 dams in each generation). Mixed models fitted to the data included the fixed effects of generation, sex, their two way interaction and a linear covariate of age within sex and generation. The random terms in the model were sire within generation and dam within sire and generation. The estimates of heritability for body traits and survival were moderate to high (0.27 to 0.53). Genetic correlations between harvest weight and body length were high and positive (0.97), whereas those between body traits and survival were low and not significantly different from zero. Genetic gain per generation was measured as estimated breeding values and expressed in actual units (original scale of measurement) and genetic standard deviation unit (σG). The improvement achieved for harvest weight ranged from 1.1 to 1.6 σG after four generations of selection (one year per generation). Selection for increased harvest weight was however accompanied by a non-significant decrease in survival by − 0.24%-units or − 0.16σG. The large genetic variation in both harvest weight and survival, however, suggests that there is a scope for simultaneous improvement of both traits in this population of Nile tilapia. It is concluded that our selective breeding programme has succeeded in developing a productive strain of Nile tilapia under brackish water systems, but the future work should include survival rate in the recording system, selection index and breeding objective.

The effects of water temperature at 23, 27, 31, 33 and 35 °C on growth and bioenergetics of cobia Rachycentron canadum with initial body weights about 10, 30, 70 and 200 g were investigated in this paper. Food consumption, fecal production, nitrogenous excretion, growth rate and metabolic rate of cobia were affected significantly by both water temperature and fish size. However, the relationships between food energy and feces, excretion, growth and metabolism energy exhibited linear curves and seemed independent of water temperature and fish size in the present study. For each fish size growth increased with temperature up to 33 °C and then declined at 35 °C. The optimal temperature for growth (Topt.G) of 10–200 g cobia was 33 °C. For each water temperature growth was negatively correlated to fish size and the model, SGR = a + blnW or SGR = aWb, provided a good fit to the data obtained for 10–200 g cobia. Food conversion efficiency (FCE) was highest at 31 °C and lowest at 35 °C for each size cobia. The optimal temperature for FCE (Topt.FCE) of 10–200 g cobia was 31 °C. An increasing trend of FCE with fish size was seen at each temperature and indicated that larger cobia had a superior capacity of food utilization. Energy budgets of cobia were also influenced significantly by water temperature and fish size. However, energy budgets were relatively constant over the 27-33 °C temperature and 70-200 g size ranges for cobia. Over the whole temperature and size ranges the proportion of food energy lost in feces and excretion for cobia was small (

The purpose of this paper was to determine aspects of the reproductive biology of captively bred Fenneropenaeus merguiensis under commercial broodstock production conditions that relate to the design and implementation of genetic improvement programmes for this species. First, we tested whether there is evidence for polygamy vs monogamy by genotyping females, the material found in their thelycums, and material that leaches out of the thelycum using DNA microsatellite loci. All genotypes in all animals and tissues tested could be accounted for using a monogamy model. Second we compared the accuracy of pedigrees formed under assumptions of monogamy vs polygamy. Pedigrees were formed using microsatellite genotypes from 73 dams and 400 offspring. Sibship groups and dam–offspring groups from pedigrees developed assuming monogamy almost always had the same mtDNA haplotypes, suggesting a high accuracy of the pedigrees, but those formed under the assumption of polygamy were less accurate, and together these results also support the monogamy model. Third, we assessed the between family variance in offspring family numbers from two sets of mass spawnings of about 40 inseminated females per spawn. About half of the offspring originated from just 20 percent of the dams, i.e. many dams contributed few offspring. These data can help predict optimal sample sizes required for accurate future estimates of genetic parameters.

This paper describes a study in which environmental manipulation of salmon swimming depth was tested in an attempt to reduce farm infection of Atlantic salmon, Salmo salar by the salmon louse, Lepeophtheirus salmonis. The effects of submerged artificial lighting (positioned at 10 m depth) in combination with submerged feeding (delivered at 5 m depth) were tested with respect to salmon swimming depth and sea lice infection, following the hypothesis that L. salmonis infection in a commercial salmon population is reduced when exposed to deep lighting and feeding. This is based on two assumptions, firstly that planktonic L. salmonis larvae principally remain in surface waters (top 4 m) and secondly, that deep lighting and feeding attract salmon to deeper water depths. Results from commercial scale trials confirmed that salmon swimming behaviour is altered under submerged feeding conditions with fish attracted to the feeding corridor during the feeding process. When the fish reached satiation or feeding ceased, they returned to the surface waters during the day. Submerged lighting attracted the fish to the illuminated water depths during the night. During the day, natural light overruled these effects to some extent. The number of L. salmonis on fish exposed to deep submerged lighting was significantly lower than the number of lice found on salmon in cages with surface lighting during the summer months. Submerged feeding showed no advantage over surface feeding with respect to the number of L. salmonis found in these trials. The results of the study suggest that swimming depth manipulation can be used at a commercial scale to reduce salmon lice burdens on Atlantic salmon stocks.

This paper evaluates the feed cost differences in salmon farming based on two energy dense feed strategies: one resembles the industrial preference of using high-fat diets (LP: low protein-to-lipid ratio) whereas in the other strategy the dietary energy is to a greater degree derived from protein (HP: high protein-to-lipid ratio). Two different economical models are presented based on three different feeding experiments: one commercial large-scale and two small-scale trials. All trials were conducted with year old smolt (S1). Production costs have increased from 2009 to 2016, and the presented data depict a general increase in price of feed proteins and oils. Dietary proteins are more expensive than lipids and in isoenergetic diets, protein denser feeds are higher priced than the lipid dense alternative. HP diets lead to a higher feed deposition in carcass which results in a significantly lower feed conversion rate compared to the preferred isoenergetic LP commercial diets. Because of the improved feed-to-carcass conversion, the HP feed strategy yields a lower feed cost. In addition, the HP feed strategy induces faster growth that enables farmers to reduce the production cycle. A reduced production cycle represents an opportunity of reducing overall production costs. If improved growth is induced by dietary strategy, the reduction of overall costs should be assigned to the feed costs, i.e. a reduction of feed cost. Finally, dietary induced improvements in carcass weight yields more tradeable product which increases income. Thus, the present model system revealed that the traditional high-fat diets preferred in the salmon industry, although they are cheaper than the isoenergetic protein rich diets, are necessarily not precursors for overall lower feed costs.

An outbreak of skin ulcers with morbidity and mortality rate of 80% and 20% respectively, among Genetically Improved Farmed Tilapia (GIFT) sub-adults reared in a brackish water floating cage farm of Kochi, Kerala, India was reported. Bacterial isolation attempts from various internal organs (blood, kidney, liver, spleen and brain) of different diseased fish indicated a common bacterial etiology. Organisms were identified as Vibrio vulnificus based on conventional microbiological methods followed by molecular confirmation. Additionally, V. vulnificus marker specific for fish virulence was present in the isolates. Fish pathogenicity was confirmed by challenge tests. LD50 was calculated as 2.1 × 105.13 CFU/fish and 2.1 × 106.12 CFU/mL in injection and immersion route respectively. pilF polymorphism-based PCR and vvhA gene sequence indicated potential danger for humans. The strain was positive for siderophore, hemolysin, capsule, polar and lateral flagella. The strain could multiply rapidly in healthy fish serum. All these results indicated that the isolate could act as a primary pathogen for tilapia fish. Interestingly, serum survival ratio of the pathogen was significantly larger at higher temperatures (p ≤ .05); which may explain the increase in infective capacity of V. vulnificus at higher temperature. Multiple antibiotic resistance index of the strain was ≤0.2. In conclusion, the paper provides detailed descriptions of clinical signs, microscopic and macroscopic lesions of a natural disease outbreak among tilapia raised in brackish water cage farms of India. The concurrent attempts to identify and characterize the etiology fetches the basis for future development of effective control and preventive measures against V. vulnificus, the most infectious and lethal of all zoonotic vibrios.

The Auburn University Aquaculture Genetics Program has an 80-year history with focused efforts on genetics and breeding, transgenic technology and genomics being initiated 43, 27 and 18 years ago. This resulted in the first successful selection experiments for channel catfish, Ictalurus punctatus, the basis of the monosex tilapia industry, the first production of transgenic fish in the US, major advances in catfish genomics and the first production of a xenogenic catfish. The most significant impact has been the establishment of the technology to allow a hybrid catfish industry, which produced 150 million hybrid catfish fry in 2012. Paper presented at the International Symposium on Genetics in Aquaculture XI, Auburn, AL, June 24–30, 2012.

Plant protein sources have been identified to have the greatest potential to replace fish meal protein in aquafeeds. However, plant ingredients contain significant quantities of carbohydrates, and the ability of fish to utilize dietary carbohydrates as energy sources for growth is limited. Included in the carbohydrate group, cellulose is not tolerated by most fish. In the present study, the grass carp, a typical herbivorous fish, fed with duckweed was selected to study the effect of exogenous cellulase on the growth. The results of 2-month feeding experiment showed that the cellulase promoted the growth of grass carp. In addition, the cellulase increased various digestive enzyme activities, such as cellulase, amylase and protease but not the lipase activity. Meanwhile, the polymerase chain reaction denaturing gradient gel electrophoresis (PCR-DGGE) analysis indicated that the intestinal microbiota of fish fed with the supplemental cellulase changed in bacteria species and density. Band patterns derived from control and cellulase samples showed a low degree of similarity when analyzed by cluster analysis. Some bands were unique to control samples, whereas other bands were obtained only with samples of the cellulase group. The 16S rRNA gene sequencing identified that Proteobacteria and Firmicutes were the two dominant groups, and the emergence of certain bacterial strains including Bacilli and Sphingomonas may contribute to the digestion of cellulose. The former researches and this paper results suggest that the endogenous cellulase is far from sufficient to fully digest the ingested fiber, so cellulase should be developed as a kind of aquatic additive.

This paper used value chain analysis to determine economically viable opportunities for increased female participation in the aquaculture value chains in Kenya. The main opportunities for women are as fish marketers and as fish farmers, especially in the Western Province of Kenya. Fish marketing is economically more viable than fish farming with an overall benefit–cost ratio of over 1.00 while the benefit–cost ratios for fish farmers were less than 0.5. The western region had the strongest fish production sector compared to the Central Province and the Rift Valley and provides relatively better opportunities for women participation in fish production. In the Rift Valley Province, women could work as paid laborers on fish farms as this region showed the largest employment impact on the community from a growth in fish farming activities.

Marteilia “type C” was recently identified, by molecular characterization, in the cockle Cerastoderma edule from the Ebro Delta in southern Catalonia (Spain) where it caused high mortalities during the summer of 2008. The present paper provides a transmission electron microscopic morphological description and additional molecular analyses. Specific ultrastructural diagnosis is based in TEM observations of mature stages of the parasite characterized by four secondary cells which subdivide into three “proteic masses”. Each proteic mass contained two spores and thus six spores per secondary cell were suspected. The number of secondary cells and number and nature of spores define the morphological taxobasis to distinguish different members of the Phylum Paramyxea. New sequences included in the phylogenetic analysis place Marteilia “type C” in a well-defined cluster proximal to Marteilia refringens . The new data thus corroborate previous results and lead us to formally describe Marteilia “type C” as a new species, Marteilia cochillia n. sp. affecting bivalves in Europe.

Massive mortality outbreaks, mostly affecting spat Crassostrea gigas , have been reported in France since 2008. Disease investigations revealed that most of the mortality events are related to the detection of the Ostreid herpesvirus 1 (OsHV-1 μVar). Meanwhile, selection to improve the survival in juvenile C. gigas has been successfully implemented in this context and selected oysters were found disease-resistant to OsHV-1 infection. This paper reports the first investigation of the horizontal transmission of the disease throughout cohabitation trials within batch and between batches using unselected and selected oysters for their higher survival. Two batches, unselected (AC) and selected (AR), were produced in February 2009 and deployed in the field in August 2009. Mortality associated with OsHV-1 detection occurred within the first two weeks of the deployment to reach 19% and 56% for the AR and AC batches, respectively. The remaining alive oysters were then brought into the laboratory in March 2010 for the cohabitation trials to assess the potential horizontal transmission of OsHV-1 within batch or between one of the batches and a third. The third batch (J) was produced using unselected oysters in August 2009 and it was always kept in the hatchery and the nursery to isolate it from the mortality risk factors. At the end of the cohabitation trials in July 2010, no mortality was found for the cohabitation trials between AR and J oysters as well as for the AR oysters and also for the J oysters grown alone in a tank. Conversely, high mortality was reported for the cohabitation trials using the J and AC batches as well as for the AC oysters alone. For the later, mortality occurred 3 days post-spawning while the AR oysters, which also spawned the same day, did not suffer of any abnormal mortality. Disease screening revealed that OsHV-1 was not detected for the J batch in March 2010, while 4 and 46% of the AR and AC oysters were found positive seven months post-mortality, indicating a difference in potential reservoir role within the C. gigas species. Our study clearly revealed the horizontal transmission of the disease from unselected asymptomatic adult to juvenile C. gigas , inducing mortality, and that OsHV-1 resistant oysters may offer one way to limit the spread of the disease and the potential reservoir role. Mortality due to OsHV-1 and its kinetic depended of the seawater temperature, which appeared as a strong risk factor that can reactivate the virus from latent-like or sub-clinical infection in asymptomatic adults. The lower threshold of 14 °C to observe mortality due to OsHV-1 was evidenced even if its replication was activated during the two previous weeks when seawater temperature was 16 °C. Finally, a sub-clinical level of virus was observed in AC asymptomatic oysters, it can be reactivated and cause viral replication, suggesting latency-like infection can exist in OsHV-1.

In this paper, we report the first successful attempt to grow Maja squinado in captivity from larvae to sexual maturity. Eggs were obtained from wild-caught crabs in the laboratory. The larvae-juveniles were reared together to an age of 150-210days. Subsequently, up to seven consecutive molts were individually monitored to an age of 490days maximum. Based on these individually monitored crabs, a growth model was developed to predict the molting probability and molting increment as a function of sex, temperature, and pre-molt size. The predictions of the model show that the females (25-75% percentiles of the 7th monitored molt: 106 to 139mm and 456 to 654days) appear to have a lower but less variable growth rate than the males (98 to 152mm and 378 to 518days). The size at first maturity for females was estimated to be 103.6mm. Although the model was parameterized using individuals raised in aquaculture, data and models of this type are very scarce for crustaceans and will be useful for managing the ongoing stocking program for M. squinado in the Balearic Islands. In addition, the full life cycle of the Mediterranean spider crab was completed in captivity. The mating of laboratory-reared crabs was repeatedly observed, and viable eggs and larvae were obtained from laboratory-reared adults. © 2013 Elsevier B.V., Financial support was provided by JACUMAR (“Cultivo de la centolla” and “Propuestas y mejoras para el diseño de los planes de repoblación y evaluación del impacto de los escapes” projects) and by the Government of the Balearic Islands

Agglutination plays a crucial role in eliminating potential pathogens in marine invertebrates. In this paper, cell-free haemolymph (CFH) and crude extracts from the haemocytes, gills, mantle, hepatopancreas, gonad, kidney and adductor muscle of scallop (Chlamys farreri) were obtained, and the agglutination activities of these extracts were tested separately against mouse blood cells (MBC) and fluorescein isothiocyanate-labelled microbes. Agglutination inhibition assays were carried out with EDTA and saccharides. Finally, a mannan-binding lectin (MBL, one of the main lectins in haemolymph) was purified from CFH by affinity chromatography using a mannan-sepharose column and analysed using native- and denaturing-PAGE. The results showed the CFH could aggregate Vibrio anguillarum, Staphylococcus aureus, Bacillus subtilis, Pichia pastoris and MBC, and the agglutination could be inhibited by DEAE dextran, EDTA, D-mannose-6-phosphate, N-acetyl glucosamine, mannan, zymosan A, chondroitin sulphate, peptidoglycan (PGN) and lipopolysaccharides (LPS); Gill extracts aggregated S. aureus, B. subtilis and P. pastoris, and the agglutination activity could be inhibited by EDTA, N-acetyl galactosamine, mannan, zymosan A, chondroitin sulphate, PGN and LPS; Mantle, hepatopancreas, gonad and kidney extracts could only aggregate B. subtilis, and this could be inhibited by mannan, zymosan A and PGN; however, no agglutination activity was detected using haemocyte or adductor muscle extracts. The results indicate that multiple types of lectins exist in C. farreri, and CFH has the highest agglutination activity. Purified MBL exhibited a molecular mass of 645 kDa using native-PAGE and 73 kDa using SDS-PAGE.

In this paper, we analyze total factor productivity change in the Norwegian salmon aquaculture sector from 1996 to 2008. During this period, the production has on average been growing with 8% per year. At the same time, the price of salmon has stabilized indicating that an increase in demand is driving the production growth rather than increasing productivity in the sector. A Malmquist index approach is used to calculate total factor productivity change applying data envelopment analysis to construct the underlying production frontier. Furthermore, the bootstrap approach has been applied to construct confidence intervals for the Malmquist change indices. The results show a total factor productivity change of 1–2% a year, where the contribution from technical efficiency change is between 0.2 and 1.2% and technological change is between 0.6 and 0.8%. The results show that productivity growth has slowed down over the years indicating that demand growth is the main driver of production growth. Furthermore, as productivity growth is slowing down production growth can only happen when the production area is increased. The scarcity of suitable production sites can potentially be the most limiting factor to future production growth in the salmon aquaculture industry.

The striped catfish, Pangasianodon hypophthalmus, farming sector in the Mekong Delta, Vietnam (8°33′–10°55′ N; 104°30′–106°50′ E), has been one of the major global aquaculture successes. The sector currently produces over a million tons, of export value of 1.4 billion US$, in an area of about 7000 ha and provides employment to over 180,000. Catfish farming is pond based, along two main branches of the Lower Mekong and associated waterways. The sector has integrated independent sub-sectors viz. hatchery production, fry to fingerling rearing and grow-out and product processing for export. These are linked through coordinated transportation by water using especially designed boats with the ability to navigate narrow channels along the production chain. This paper deals with the aspects of transportation of 2,264,448 fry/fingerlings, weighing approximately 48,330 kg, to grow-out operations involving 20 producers. All transportation is by boat, of two size classes, 20 and 30 t capacities, with easy access to farms. In general, a fry/fingerling farmer enters into a contract for the transportation to a grow-out farmer and a number of trips are required to complete an operation, depending on the size of the fish and the densities at transportation. Transportation mortalities were relatively low but on delivery to the grow-out farms mortalities increased in the first two days post-stocking and decreased gradually. A cost analysis of the transportation sector is provided and it was seen that the return of the capital cost per year on a boat was relatively high.

Identifying the sex of captive fish is crucial to aquaculture broodstock management. Hapuku (Polyprion oxygeneios) are sexually monomorphic fish that are reared in New Zealand as a potential aquaculture species. In order to identify the sex of 23 F1 captive hapuku, three methods, namely ultrasound imaging, plasma vitellogenin (Vtg) enzyme-linked immunosorbent assay (ELISA) and plasma sex steroid (17β-estradiol (E2) and 11-ketotestosterone (11-KT)) radioimmunoassay (RIA), were compared. Results suggest that all three methods may be used two months prior to- and during the -spawning season of adult captive broodstock (which occurs between August and December) when used on sexually developing fish. Furthermore, ultrasound and RIA showed the potential to identify the sex of sexually undeveloped fish. Only repeated ultrasound scans allowed for very high sex identification accuracy (95%). Vtg analysis yielded a 92% positive identification of samples but there was a narrow cut-off margin between males and females (relative absorbance values: 0.0043–0.022). However, compared to RIA, this method allowed a larger number of samples to be tested. The sex steroid ratio method using RIA was more accurate (100%) and robust than the Vtg analysis as the cut-off margin between males and females was more distinct (11-KT/E2 ratios of between 0.17 and 0.83). Overall, a combination of the methods provides validation and increases the accuracy of identification. This paper also provides the first evidence of the sexual development of captive reared hapuku.

In this paper, an approach based on geometric features to count overlapping fry fish is presented. Back propagation neural network (BPNN) and least squares support vector machine (LS-SVM) were used to construct classification models. 19 video clips with fish numbers varying from 10 to 100 were captured by a computer vision system. A total of 600 sub-images with overlapping fish were randomly selected, 300 images were used as a training set to create a calibration model, and remaining images were used to verify the model. 7 geometric features (area, perimeter, convex area, bounding box width, bounding box height, skeleton length, endpoint number) were obtained from the overlapping fish images. Results indicate that the best performance with about 98.73% of the average counting accuracy rate is achieved by LS-SVM model, which is better than the performance of BPNN model. The combined multiple geometric features coupled with an LS-SVM classifier is a highly accurate way for fry fish counting. (C) 2012 Published by Elsevier B.V.

Shellfish aquaculture forms a small but expanding section of Scotland's seafood production. This production benefits from a good health status with the absence of notifiable diseases, except for localised cases of Bonamia ostreae . In this paper we review factors that could lead to the introduction and/or spread of key diseases in order that associated risk can be minimised. We selected B. ostreae and Bonamia exitiosa , Marteilia refringens and oyster herpesvirus as key pathogens; all of which have been found in and are notifiable within the United Kingdom. Vulnerabilities of molluscs farmed in Scotland to these pathogens are reviewed, as are sources of infection in neighbouring areas from which the pathogens might be introduced. We then examine: key pathways of introduction, whether conditions are suitable for the pathogens to persist in Scotland, potential for spread within Scotland and likelihood, and consequence of disease outbreaks. The major pathway for potential introduction is with the import of Pacific oysters from hatcheries. B. ostreae is the pathogen that has the highest probability of causing disease, however B. ostreae is restricted to native oysters whose production in Scotland is very small. Oyster herpesvirus could cause far larger economic consequences due to the size of the Pacific oyster industry but is less likely to invade. Therefore risks for B. ostreae and oyster herpesvirus are similar. Risks could change if imports are sourced from higher risk areas or pathogens spread in areas where currently used hatcheries are located. Water temperature in Scotland is marginal for oyster herpesvirus and M. refringens so continuation of warming trends could increase risks from these pathogens.

We studied the growth of O. vulgaris and the digestibility of two semi-moist diets (50% water) based exclusively on dry and freeze-dried ingredients (Diet S: 20% gelatin, 10% egg yolk powder, 5% Sardinella aurita and 15% Todarodes sagittatus ; and Diet P: the same as the previous diet but substituting T. sagittatus by pea). Both diets had a similar macronutrient composition (70–73% protein DW, 12–13% lipids DW), a firm texture when introduced into the water and good acceptability. Survival was 100% with both diets. The specific feeding rates were also similar for both diets (1.0% body weight/day; P > 0.05), although the best results were obtained with diet S, which was responsible for an absolute growth rate of 9.6 g/day and a feed conversion rate of 1.0, compared with the 2.2 g/day and 3.9 obtained with diet P; P O. vulgaris can be fed with dry or freeze-dried ingredients that have undergone mild heat treatments since they lead to good growth, feed efficiency and digestibility. Future studies on octopus on-growing could use a similar base to that proposed in this paper to obtain diets with better acceptability, stability or nutritional composition for commercial purposes.

White spot syndrome virus (WSSV) has caused significant economic losses in shrimp farming industry. In this paper, WSSV was injected into Penaeus vannamei and the survivors were used for breeding of WSSV-resistant broodstock. During year 2002 to 2007, 120 full-sib WSSV-resistant families were established. Experimental WSSV challenging tests showed that the survival rates of generation 2 (G 2 ), G 3 , G 4 and G 5 were 5.57 ± 9.83%, 7.78 ± 10.89%, 9.52 ± 8.84% and 13.79 ± 11.52%, respectively. Furthermore, the time-until-death prolonged gradually from G 2 to G 5 . Shrimps with the highest WSSV resistance from G 4 families were selected and assayed for commercial performance in outdoor ponds. In commercial outdoor ponds, the survival rate, production and harvest body weight of these shrimps were 25.33%, 82.14% and 34.51% higher than those of unselected shrimps, respectively, and the feed coefficient was 13.86% lower. Thus, the WSSV resistance and commercial performance of these shrimps have been apparently improved.

Genetic selection is being developed as a management tool for the control of amoebic gill disease (AGD) in Atlantic salmon. AGD is caused by an external gill parasite and is an animal health issue that results in significant economic loss to the Tasmanian salmon industry. This paper presents genetic parameters for AGD resistance, describes patterns of genetic variation over multiple infection cycles, and discusses the development of a selective breeding program to exploit this variation. Measurements of visible gill signs were made on over 12,000 individuals representing 326 sires and 297 dams from four genetically linked year classes. Between three and six sequential infections were measured on each year class. All measures of gill signs in all year classes had significant genetic variation with heritabilities ranging from 0.09 ± 0.03 to 0.56 ± 0.07. Genetic correlations between infections indicate two distinct traits which are only weakly correlated (average r g = 0.24). One is measured at first infection on naive fish and the other can be measured at all subsequent infections. This pattern is suggestive of an adaptive immune response for reinfections, and conforms with patterns seen for resistance to other parasitic diseases in terrestrial livestock. In an analysis combining all year classes, the heritability for first infection was 0.14 ± 0.02 and heritabilities for reinfections ranged from 0.23 ± 0.08 to 0.40 ± 0.03. Reinfections appeared to be mostly under common genetic control, although there appear to be additional genetic traits that cause lower correlations for a small proportion (about 10%) of the population. Consistent and stable patterns of inheritance are indicated by the medium to high genetic correlations between year classes and by the high genetic correlations between infection cycles with a seasonal shift. Estimation of genetic correlations between AGD resistance and growth rate are problematic due to confounding effects but it is likely that this correlation is near zero. Selection for AGD resistance can assist with disease management and is part of the breeding objective of the Tasmanian salmon breeding program. Adaptive AGD resistance is one of the primary selection traits and a field challenge based on assessment of gill signs is an effective way of selecting for resistance. The current selective breeding strategy is predicted to increase the interval between treatments by 3% per year.

Very rapid developments are widely believed to have occurred within Bangladesh's aquaculture sector in recent years, but have yet to be adequately documented. This paper addresses the information gap based on a comprehensive review of literature and data. The current status of pond based aquaculture in Bangladesh is summarized in terms of the quantities and species of fish produced and the technical and social characteristics of the production systems from which they originate. The main systems of pond aquaculture practiced in Bangladesh are analyzed, paying particular attention to the technical, social and economic characteristics of two dominant forms of production. These are categorized here as homestead pond culture (carp dominated low intensity production conducted on a semi-subsistence basis, requiring limited management, labor and capital investment) and entrepreneurial pond culture (semi-intensive or intensive culture entered into as a productive investment with moderate or high capital costs and frequently employing labor). An estimate of national fish production and consumption disaggregated by culture system is presented. The discussion section synthesizes these results and considers their present and future implications.

Electric field exposure is used to stun or immobilize fish prior to slaughter in the aquaculture industry and for field sampling purposes (i.e. electrofishing), but the physiological response of fish to this exposure is incompletely understood. In this paper we report on changes in blood pressure, heart and ventilation rates, and hematological variables in chronically cannulated Arctic char (Salvelinus alpinus) in response to exposure to an electric field of 4 V/cm (125 Hz) for 5 and 30 s. Both durations of exposure resulted in a brief (total duration: 5.2 to 6.0 s, respectively) four-fold blood pressure increase above resting levels. The 5 s exposure was followed by a period of cardiac and ventilatory arrest (for 35 and 176 s on average, respectively), but cardioventilatory activity recovered in ten out of eleven fish. Nevertheless, signs of systemic stress responses were evident after the exposure. These included moderate hypertension, increased ventilation amplitude, increased plasma cortisol levels and altered hydromineral balance. After the 30 s exposure, cardiac activity initially appeared to recover, but subsequently declined. Ventilation did not recover. It is suggested that circulatory failure due to cardiac ischemia resulting from ventilatory failure; rather than instantaneous and irrecoverable cardiac arrest from the electric field exposure per se, is the ultimate cause of death in fish that fail to recover from exposure to an electric field in water. The brief dramatic hypertension observed in char may partly explain the haemorrhages that are frequently observed in electrically stunned fish of some species.

Mortality is a major concern in larval fish rearing during exogenous feeding. An important cause of mortality of larval yellowtail kingfish (Seriola lalandi) during the rotifer - Artemia weaning period was hypothesised as being due to larval sinking response after satiated feeding prior to dusk. This paper documents the effect of larval body density change under different Artemia feeding regimes and adds to the understanding of the cause of mortality of yellowtail kingfish larvae. The change in body density was used as a tool to determine the time of last feed in a day to ensure larvae were neutrally buoyant at dusk. An adaptive Artemia feeding regime was implemented, in which the amount of feed applied to the larvae was modified based on the body density. Larvae were denser than the seawater in which they were reared when fully satiated with Artemia. The time required to return to pre-feeding density significantly decreased with larval age. At 12days post hatch (dph), the peak in body density of larvae fed Artemia to satiation was 1.0320gcm -3 and they did not return to a pre-feeding body density (1.0260gcm -3), for approximately 10h. By 19dph, larval body density only increased to 1.0275gcm -3 when larvae were fully satiated and they were neutrally buoyant again by 4h. The decrease in larval body density when fully satiated at 16dph demonstrated that overfeeding larvae with Artemia should be avoided prior to dusk before this age to maintain neutral buoyancy. The use of the adaptive regime reduced mortality by 20% compared with the control, from 13 to 17dph, without sacrificing larval growth. Transition to Artemia feeding is a critical stage for yellowtail kingfish larvae and mortalities can be significantly reduced during this period by managing the timing of Artemia feeds throughout the day. The strategy of an adaptive feeding method may be considered a novel management tool to prevent larval sinking and associated mortality during the period of weaning from rotifers to Artemia during larval rearing.

The aquaculture of the sea cucumber Apostichopus japonicus has grown rapidly over recent years in China and become an important sector of the marine industry. However, with rapid growth and the use of non-standard practices and culture techniques, epidemic diseases of A. japonicus now pose increasing problems to the industry. Prevention and control of diseases seriously affecting aquaculture of A. japonicus , a major marine industry in China, are essential for its development. We have previously isolated two pathogenic bacteria Pseudoalteromonas sp and Pseudoalteromonas tetraodonis associated with ulceration and peristome tumescence of A. japonicus . In this study, we isolated 266 bacteria from A. japonicus and its cultural environment, and identified 5 bacteria Vibrio ordalii, Bacillus safensis, P. tetraodonis, Pseudoalteromonas elyakovii and Pseudomonas segetis with strong antimicrobial activity to P. sp and P. tetraodonis using point inoculation, filter paper and Oxford cylinder methods. Further investigation on their growth and antagonistic characteristics indicated that 1) V. ordalii has the strongest antimicrobial ability even at low temperature and its extracellular products precipitated with ammonium sulfate at different growth stages also have antimicrobial activity; 2) P. tetraodonis and P. elyakovii only have antimicrobial activity at 28 °C and their extracellular products at different growth stages also have strong antagonistic effects; 3) the extracellular products of B. safensis at different growth stages have no antibacterial activity. Injection of extracellular products of P. elyakovii and V. ordalii into A. japonicus can enhance its non-specific immune-related enzyme activities and disease resistance. The study provides a theoretical basis and products for A. japonicus disease prevention and healthy aquaculture.

A sustainable semi-intensive pond aquaculture technology including major carp species as ‘cash-crop’ and small indigenous fish species (SIS) as food for the farmers' families is being optimized in Bangladesh. This is done through manipulations of the fish species combinations stocked, considering the ecological effects produced by bottom feeders on the pond bottom and filter feeders in the water column. The present paper presents results of experiments performed simultaneously in 64 farmers' fish ponds, located in 4 distant agro-ecological regions of Bangladesh. In each region each experiment involved 4 treatments, 4 replicates per treatment. The control polyculture was the traditional stocking of 33 rohu ( Labeo rohita) , 33 catla ( Catla catla ), and 34 common carp ( Cyprinus carpio ) per 100 m 2 , with the addition of 250 SIS and 3 silver carp ( Hypophthalmichthys molitrix ) per 100 m 2 . In previous experiments this silver carp addition was found to have no effects on the other fish and on the environment, compared to the traditional stocking without silver carp. Interferences on the water column (Water treatment) were achieved changing the density of the herbivorous fish (reducing catla density to 24/100 m 2 and increasing silver carp to 12/100 m 2 ), and on the bottom (Bottom treatment) doing so on the benthophagous fish (replacing 10/100 m 2 common carp by mrigal). Both interferences were simultaneously carried out in the Water and Bottom treatment. Harvesting weight and biomass, growth rate, survival and yield of each species and total yield, food conversion ratio and income obtained in the different treatments and regions are presented and their interactions through the food web are discussed. Performing the same experiment in four distant regions of the country allowed observing if the effects of the Water column and/or Bottom interventions differ among regions, and accelerating the dissemination of the “cash-SIS” technology throughout the country. The manipulations performed did not affect the small fish mola, which reproduced and yielded equally well in all the polycultures. This allowed a continuous mola supply for consumption by the farmers' families throughout the culture season, and opened the option to consume or sell the larger amounts of mola gathered at final harvest. Manipulation of species composition proved to be a useful tool to affect the pond ecosystem towards improving fish yield and corresponding income. Just by substituting almost a third of the catla by silver carp increased total yield by 16%. When also almost a third of the common carp was substituted by mrigal, total yield increased a further 3%. In both cases selling the whole production increased income by 27%, which gives the farmer the option to keep part of the fish for family consumption.

This paper gives an account of the pathogens found in the cultivated Japanese oyster Crassostrea gigas and in the mangrove oyster Crassostrea rhizophorae from natural populations of two sites, Sambaqui (27° 29′18″S, 48° 32′1″W) and Ribeirao da Ilha (27° 42′51″S, 48° 34′6″W), Santa Catarina Island, Brazil. Oysters were collected in March 2008 and April 2009, 150 per site, year and condition (rocky shore and culture). For pathological study, the techniques used were: macroscopic examination, histology and tissue culture in fluid thioglycollate medium specific for Perkinsus . The results showed the presence of the polychaete Polydora sp. with high prevalence (up to 100%) in C. gigas ; gametic hypertrophy in C. rhizophorae from Ribeirao da Ilha and in C . gigas from Sambaqui and Ribeirao da Ilha with low prevalence (3.3%); rickettsia-type bacteria, with greater prevalence in C. gigas (30%) than in C. rhizophorae , causing alteration in the epithelium of the stomach. It was not detected the presence of Perkinsus in any oyster sample analyzed of any site. Ciliates of genus Trichodina were observed among gill lamellae, digestive tubules, and adhered to the gills of oysters from Ribeirao da Ilha, with higher prevalence in C. rhizophorae (50%) and without causing injury. Protozoa Sphenophrya -type was found in the gills of C. gigas and C. rhizophorae , with higher prevalence in C. gigas from Sambaqui (70%), not causing changes in the gills. Protozoa of the genus Ancistrocoma were detected in the digestive tubules of C. gigas (36.7%) and C. rhizophorae (40%) from Sambaqui at low intensity and without causing apparent damage. Steinhausia -type microsporidians were observed in the cytoplasm of oocytes of C. rhizophorae and C. gigas with prevalences up to 33.3%. The intensity of infection in the animals was low, with only one oyster presenting more than 50 oocytes infected. The sporocysts of the pathogen caused alteration in the normal structure of the oocytes cytoplasm. Protozoa of genus Nematopsis were observed in the connective tissue of the gills and mantle with high prevalence (100%) in C. rhizophorae from Sambaqui, without host defense response. The observed metazoan were: turbellarians Urastoma -type, metacestode of genus Tylocephalum and copepods possibly of genus Pseudomiycola , all in low prevalence. None of the pathological occurrences found seems to cause significant damage in oysters, once they were found at low intensities. However, due to the great socioeconomic importance that the shellfish represent to the State of Santa Catarina, it's necessary to keep monitoring the health status of these populations.

With a growing global human population and an increasing demand for food protein, aquatic animal protein has become an increasingly important resource. In several geographic areas, wild stocks have been severely overfished, increasing the demands on aquaculture. In response, aquaculture production has dramatically risen over the last 30 years. Movement of live aquatic animals, within and between countries, for aquaculture and the ornamental trade, is an important route of disease spread. Over the last decades, many aquatic animal diseases have emerged to have a substantial economic impact on aquaculture, sometimes with ecological consequences. Effective biosecurity strategies provide protection to both farmed and wild aquatic animal populations by minimising the risk of introducing pathogens and minimising the consequences if the pathogen was introduced. We provide an overview of international, supranational and national biosecurity strategies for aquatic animal health. The role of the World Organisation for Animal Health (OIE) as the reference organisation for the development of standards relating to international trade in animals and animal products is described and an overview of the OIE standards provided; Europe and England and Wales are used as examples to illustrate how the international standards are implemented at supranational and national level other important elements of biosecurity not defined by international standards are described. At the national level, the paper describes and discusses the role of the competent authority, instruments to prevent the introduction of exotic diseases and limit the impact of endemic diseases; it highlights the relevance of import risk assessments and the importance for awareness of international developments. At farm level, it summarises available standards and the role of farm biosecurity plans. Challenges to biosecurity strategies at the various levels are discussed.

This work describes a new polymerase chain reaction (PCR) assay for the accurate and fast identification of the fish pathogen Tenacibaculum soleae. The selected primers amplified a 248 bp fragment of the T. soleae 16S rRNA gene. The PCR system was specific and very sensitive with a detection limit of approximately 1 to 10 bacterial cells per reaction when pure cultures of T. soleae are used. The PCR approach described in this paper allowed detection of the pathogen in mixed plate cultures obtained from diseased fish affected by tenacibaculosis, in which growth of this bacterium cannot always be visualized. Our results indicated that the specific primers and PCR method designed provide sensitive and fast diagnosis of the tenacibaculosis caused by the fish pathogen T. soleae.

Cultivation of Palmaria palmata was performed by a technique introduced in this paper of tetraspore release and attachment to culture string. Optimal conditions for laboratory growth were investigated with respect to irradiance and nutrient media. The length of laboratory culture required for the growth and development of attached sporelings was also investigated, prior to deployment of seeded strings on a longline structure in Strangford Lough, Northern Ireland. Of sporelings grown in 5, 10, 25 and 50 μmol m − 2 s − 1 , those at the lower irradiances (5 and 10 μmol m − 2 s − 1 ) were significantly longer than those at higher irradiances after 12 weeks. Sporeling length was also significantly greater at lower irradiances when in F/2 nutrient media with additional vitamin solution, compared with F/2 medium without the vitamin solution. Seeded string was held in the laboratory for 2, 4, 6, or 8 weeks. After 3 months at sea, the 2-week strings had fewer visible plants and had shorter plants than the 4, 6 and 8-week strings, but plants on all strings were similar in length after 7 months at sea. The demand for P. palmata as a snack food in Northern Ireland regularly outstrips the supply obtainable from natural populations. The technique of seeding string with tetraspores is proposed as one method of commercially cultivating P. palmata on a large scale.

Recently, several groups of researchers reported that besides serine proteinases, other classes of proteinases may be involved in crustacean's food protein digestion, including cysteine and aspartic proteinases. In this paper, a comparative study of the class and type of digestive proteinases of whiteleg shrimp Penaeus vannamei, blue shrimp Penaeus stylirostris, and yellowleg shrimp Penaeus californiensis is addressed, along with some operational characteristics. The substrate-SDS-PAGE zymogram of the three species showed varieties of different proteinases that were species-specific and proteinase composition that may be used for species identification or population studies. In the three species, trypsin and chymotrypsin were present as isoenzymes. Some active bands were active at acid pH and were partially inhibited by pepstatin A and based on bibliography information they are digestive enzymes. The involvement of these enzymes in food protein digestion is discussed and compared with digestive enzymes present in other decapod species. This and additional information expand the knowledge about enzyme food protein digestion in crustaceans, making clear that digestion process is more complex than previously alleged and if common patrons exist, there are some individualities. This information opens a line of research trying to fully understand the mechanism of protein digestion.

During the MOREST project (2001–2006), oyster summer mortality was extensively investigated in Crassostrea gigas in France. However, significant increases in magnitude and geographic distribution of summer mortality episodes have been reported since 2008. This paper investigates the response to selection for survival, which was successfully performed between 2001 and 2003, in this new context. It also examines the relationship between the mortality and the three pathogens Vibrio aestuarianus , V. splendidus and the Ostreid herpesvirus 1 (OsHV-1). Three batches of juvenile (6-month-old) Crassostrea gigas were produced in February 2009 and tested in the field in the Marennes-Oleron Bay during summer (August and September) 2009: one control batch, one batch descended from one family selected to be resistant (R) to the summer mortality phenomenon and one descended from one family selected to be susceptible (S). For each batch, mortality was monitored and oysters were diagnosed for the presence and intensity of the three pathogens. A mortality episode started 11 days post deployment and had finished by day 17. A significant difference in mortality was found among the batches, with 5, 53 and 94% for the R, control and S batches, respectively. This finding indicates that the selection previously made for resistance to summer mortality still confers an advantage for the survival of juvenile C. gigas to descendant batches in the context of the recent massive oyster mortality that has occurred in France since 2008. Disease diagnoses revealed V. splendidus at all sampling dates but never V. aestuarianus , showing that only the first of these bacteria could have been involved in this mortality event. However correlations between the mortality and the presence or the bacterial load of V. splendidus were weak, negative and not significant. In contrast, high and significant correlations were found between the mortality and the prevalence of OsHV-1, as well as between the mortality and OsHV-1 viral load. This study clearly revealed the suddenness of the infection in juvenile C. gigas in field conditions, as no OsHV-1 was detected in seed at deployment, while all juvenile oysters tested 7 days post-deployment were infected and the peak of the viral load was observed 11 days post-deployment. Finally, this study is the first report of herpesvirus resistance in the R oysters. Even if all R oysters had been infected by the OsHV-1, they were able, first, to limit the amount of the viral load in their tissues, and, second, either to eliminate the virus from their tissue or to decrease the quantity of viral DNA to a level below the threshold of the real-time PCR technique, as OsHV-1 prevalence decreased from 100% to 33% for the R oysters screened at 7 and 17 days post-deployment, respectively.

The paper presents a review of the recent developments in research and production of cobia in Vietnam in hatching and cage farming, which have made Vietnam the 3rd largest producer of farmed cobia in the world. Conservative estimations for the 2007 production for the Asian-Pacific region exceed 35,000 t, with remaining global production adding an additional 2000 t, while official farm production registered by FAO is considerably lower. Estimated 2008 production in Vietnam was 1500 t, following the major production of PR China and Taiwan Province of China. This review reports on the various aspects of hatchery technology such as broodstock management, intensive and semi-intensive larval rearing, fry transportation as well as small-scale grow-out in wooden raft cages and large-scale in Norwegian style circular HDPE cages. Some of the prospects for accelerating future development of this species in aquaculture and challenges to be solved are also identified.