Hyperaccumulation of selenium in hybrid striped bass: a functional food for aquaculture?

One method of increasing the value of aquacultured product is to produce fillets that are fortified with minerals that are beneficial to human health – that is enhance the functionality of an already healthy product. A good candidate mineral in this regard is selenium (Se) which is of vital importance to normal metabolism in humans. In order to evaluate the dose response and tissue accumulation of supplemental dietary Se, a study was undertaken with hybrid striped bass (HSB). Animals were fed diets supplemented with either organic (0–3.2 mg kg^?1 as SelPlex^®) or inorganic (0.2 and 0.4 mg kg^?1 as sodium selenite) Se for 6 weeks. Because basal fishmeal‐based diets contained 1.22 mg Se kg^?1, doses of Se delivered equated to 1.22–4.42 mg kg^?1. At trial end, greatest weight gain was observed in fish receiving 0.2 mg Se kg^?1, irrespective of form (organic/inorganic). Se accumulation in HSB liver and fillet revealed a classical dose‐response once a threshold level of 0.2 mg Se kg^?1 was surpassed. Greatest tissue accumulation of Se was observed in fish fed the 3.2 mg Se kg^?1 level (P > 0.0001). A 100 g portion of Se‐enhanced HSB fillet would contain between 33 and 109 μg Se, amounting to a dietary intake of between 25 and 80 μg Se; a level that would satisfy present daily intake recommendations. Comparison of tissue Se levels indicated that the muscle provides a more conspicuous gauge of dietary Se dose‐response than does liver. Dietary treatments of between 0.4 and 1.6 mg organic Se kg^?1 reduced (P < 0.024) plasma glutathione peroxidase (GSH‐Px) activity. No differences were observed in ceruloplasmin, lysozyme or GSH‐Px activities between organic and inorganic Se when delivered at the 0.2 mg Se kg^?1 level. Ceruloplasmin, lysozyme and GSH‐Px levels were elevated (P ≥ 0.025) in fish fed the diet containing 0.4 mg inorganic Se kg^?1.     

Biofouling on Greenshell? mussel (Perna canaliculus) farms: a preliminary assessment and potential implications for sustainable aquaculture practices

Greenshell? mussel (Perna canaliculus) culture is the primary aquaculture industry in New Zealand. However, our knowledge of biofouling on Greenshell? mussel farms, and its contribution to farm ecotrophic effects, is poor. We conducted a preliminary study of biofouling accumulation at two Greenshell? mussel farms during Intermediate and Final seed on-growing stages (each of 6?months duration) with sampling of mussel ropes at 0, 3, 5 and 6?months during each on-growing stage. A diverse range of biofouling organisms (71 distinct taxa) accumulated on mussel ropes, with biofouling biomass dominated by suspension-feeding organisms (~88% of biofouling biomass) such as other bivalves, ascidians and, to a lesser degree, bryozoans. Biofouling biomass increased with culture time, varied between farms and was generally greater at 2?m than at 8?m depth. After 6?months, biofouling organisms on average comprised 54% of the total rope biomass. The reseeding of ropes between Intermediate and Final seed crops reduced the amount of non-Greenshell? mussel biofouling. However, after 6?months, non-Greenshell? mussel biofouling on average still comprised 15% of the total rope biomass. To evaluate potential ecotrophic effects of biofouling on Greenshell? mussel farms, we compare the clearance rates of Greenshell? mussel longlines based on Greenshell? mussels alone and when combined with the two dominant biofouling species observed in our study (the mussel Mytilus galloprovincialis and the ascidian Ciona intestinalis). Our study shows that accumulated biofouling biomass on Greenshell? mussel ropes can be significant and recommends further investigation as to actual ecotrophic effects of biofouling to ensure sustainable mussel farm practices.     

Fishing for health: Do the world’s national policies for fisheries and aquaculture align with those for nutrition?

Aquatic foods are rich in micronutrients essential to human health, and fisheries and aquaculture are increasingly recognized for their capacity to contribute to reducing global micronutrient deficiencies and diet-based health risks. Whether fisheries and aquaculture sector and public health nutrition policies align to meet this goal, however, is unclear. Do fisheries and aquaculture policies have explicit nutrition and public health objectives? Do public health nutrition policies recognize the contribution of aquatic foods? Using content analysis, we assessed the alignment of objectives in national fisheries and public health nutrition policies. We further determined conditions associated with varying levels of cohesion among policies in these sectors or domains. We found that 77 of 158 national fisheries policies identified nutrition as a key objective in the sector, and 68 of 165 public health nutrition policies identified the importance of fish and shellfish consumption as key objectives. More recent policies were associated with improved coherence among sectors. International organization presence in policy development was also associated with greater coherence. Countries with higher overweight prevalence had fisheries and public health nutrition policies that were not aligned. There has been a promising recent trend for improved alignment of objectives between fisheries and public health nutrition policies, but more targeted and systematic policy approaches are needed to realize the potential contribution of nutrient-rich fish and shellfish to healthier food systems.     

Start-up of a “zero-discharge” recirculating aquaculture system using woodchip denitrification,constructed wetland,and sand infiltration

Recirculating aquaculture systems (RAS) discharge management limits the development of the aquaculture sector, because RAS do not automatically result in low nutrient emissions. Research has helped develop discharge management systems such as wetlands and woodchip bioreactors that have been adopted by Danish commercial model trout farms. To further develop the Danish concept, we have modelled and built a novel “zero-discharge” recirculating aquaculture system with an annual capacity of approximately 14 tonnes. The aim of this paper is to describe the entire concept and present the results from the start-up phase of the whole system. The concept includes the treatment of RAS effluent (overflow and sludge supernatant) using a hybrid solution of a woodchip bioreactor, constructed vertical wetland, and sand infiltration. Using this three-step process, the nitrate, phosphorus, and organic matter effluent are decreased to acceptable levels to reuse the water in the RAS process reducing the need for new raw water. In the first nine months of operation, a water treatment field was used as an end-of-pipe treatment to ensure the water was safe to recirculate for fish. During the winter, the water temperature dropped to 2.7 degrees in the sand filter, but the frost did not reach the water levels in any of the treatment processes. It therefore appears that a hybrid solution can operate sufficiently even in winter conditions. In the first year of operation, a woodchip bioreactor can remove 97 % of the nitrate, although the slow start-up of the RAS caused the bioreactor to be N-limited. On average, 79 % and 92 % of the inflow phosphate concentration was removed in the woodchip bioreactor and the entire hybrid treatment field respectively. The wetland and sand filter removed organic matter sufficiently (35 %), but because of the longer than designed actual water residence, it leached from the bioreactor more than was expected. Further experimentation is needed to identify the financial applicability and performance during higher feeding rates.     

Feeding Ration,Genetics, and Reproductive Traits in Female Coho Salmon: Is Bigger Better?

We assessed the effects of different feeding regimes on reproductive traits in coho salmon, Oncorhynchus kisutch. Ration treatments subjected fish to different energy levels during oocyte proliferation (Year 1) and oocyte maturation (Year 2). Fish from 10 full‐sibling families were fed at either the recommended feeding rate or double the recommended ration during the first year. At the beginning of the second year, each ration group was split again into recommended and double ration tanks for a total of four dietary treatments. At the end of the second year, 365 females from the four treatment groups were spawned and body weight, egg weight, and egg number were measured. Overall, the fish fed the double ration during both years grew the fastest (50.1% larger than controls), had the highest egg number (46.3% larger), and had the largest eggs (9.6% larger), although similar increases were observed feeding at the double ration level during the second year alone. Ration modification produced significant changes in some reproductive traits, especially egg number, while family effects had a greater influence on relative fecundity (eggs/g female body weight) and egg weight. In fact, family effects were significant for all of the traits. Results indicate that reproductive traits can be manipulated through changes in ration and/or via genetic selection, either directly or indirectly.     

Can patch size and patch distance improve the recolonization of mussel‐seed beds exploited for aquaculture?

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New species in aquaculture: are the striped venus clam Chamelea gallina (Linnaeus, 1758) and the surf clam Spisula solida (Linnaeus 1758) potential candidates for diversification in shellfish aquaculture?

The surf Spisula solida and the striped venus Chamelea gallina clams support important fisheries in Europe. These fisheries have been affected by inter‐annual fluctuations in stock abundance and recruitment failures. Aquaculture could contribute to address these problems through the production of larvae or juveniles for stock‐enhancement programmes. In the present study, the prerequisites to produce these species in hatchery were established. Of the different methods used to obtain gametes (thermal stimulation, scarification and flow through), C. gallina spawned in the flow through only. By its turn, the best method for obtaining gametes for S. solida was stripping. Higher survivals of D‐larvae were found at 15 and 17°C. The greatest larval survival and growth rates were obtained from larvae fed Isochrysis aff. galbana (T‐iso). First C. gallina and S. solida pediveliger larvae were found at day 8 and day 26 respectively. The presence of metamorphosed larvae found even in the unfed treatment for C. gallina and for S. solida is an advantage for aquaculture production. After metamorphosis, the S. solida juveniles' survival was quite low, whereas there was no mortality for C. gallina juveniles reared without substrate regardless the diet provided. Juveniles fed the binary diet (Chaetoceros calcitrans ‐ C. cal + T.iso) and the monodiet T‐iso showed relatively higher growth in shell length and weight than C. cal. The hatchery production of these two species was possible, however the results of this study showed that C. gallina can be more attractive for aquaculture than S. solida.     

Can Different Body Tissues of Two Sea Cucumbers Supply a Fair Amount of Omega 3 for Health Benefit?

The lipid content and fatty acids profile of different tissues of Holothuria tubulosa and H. polii were analyzed to assess the suitability of the central Mediterranean species as a potential marine resource for fatty acids, in particular omega-3 polyunsaturated fatty acids (n-3 PUFAs). Simultaneously, their important indices for human health were evaluated. Gonad and respiratory tree had the highest lipid content, while the body had the lowest values. The results showed significant differences between species and among the different portions analyzed. Internal tunic and longitudinal muscle of H. tubulosa exhibited the highest PUFA proportion (55.3 and 46.4%, respectively). Eicosapentaenoic acid (EPA, C20:5n-3) and arachidonic acid (ARA, C20:4n-6) were the most abundant PUFAs in both species, with a favorable n-3/n-6 ratio in all tissues. The atherogenic and thrombogenicity indices and hypocholesterolaemic/hypercholesterolaemic fatty acid ratio suggested the high-quality of this food, similar to the nutritional values of most popular fish.     

Is current floodplain management a cause for concern for fish and bird conservation in Bangladesh's largest wetland?

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Breeding,economic traits evaluation,and commercial cultivation of a new Saccharina variety “Huangguan No. 1”

New variety breeding is very significant for Saccharina japonica cultivation industry. In this paper, we reported the breeding process, evaluation of economic traits, and commercial cultivation of a new Saccharina variety “Huangguan No. 1” (variety approval number: GS-01-006-2011). The sporophytes with best performance were screened out from varieties cultivated throughout Fujian Province, China, and mixed together as the parent population. The “Huangguan No. 1” variety was bred successfully from 5 years of targeted selection of objective traits and continuous progeny selfing/inbreeding. This new variety has a much longer, wider, and thicker blade; faster growth rate; heavier individual weight; and stronger resistance to high temperatures compared to the control variety (p < 0.05). Cultivation tests showed that the economically important traits remained steady in different years and sea areas, implying that “Huangguan No. 1” has the stable genetic basis for its excellent performance. Compared to the control variety, the yield and final product rate of “Huangguan No. 1” increased 30 and 25 %, respectively. Nutritional constituent analysis indicated that “Huangguan No. 1” could be used as a healthy food because of its higher protein (6.85 %) but lower fat content (0.2 %). Heavy metal (As, Cd, Pb) content was lower than the standard content for food safety. The suitability of “Huangguan No. 1” as a food source rather than a raw material for the chemical industry was increased due to the low algin (10.2 %) and iodine content (0.32 %). “Huangguan No. 1” variety was welcomed by farmers and has been commercially cultivated about 13,293 ha.     

Liquid fat,a potential abiotic vector for horizontal transmission of salmonid alphavirus?

Viral diseases represent serious challenge in marine farming of Atlantic salmon (Salmo salar L). Pancreas disease (PD) caused by a salmonid alphavirus (SAV) is by far the most serious in northern Europe. To control PD, it is necessary to identify virus transmission routes. One aspect to consider is whether the virus is transported as free particles or associated with potential vectors. Farmed salmonids have high lipid content in their tissue which may be released into the environment from decomposing dead fish. At the seawater surface, the effects of wind and ocean currents are most prominent. The aim of this study was primarily to identify whether the lipid fraction leaking from dead infected salmon contains SAV. Adipose tissue from dead SAV‐infected fish from three farming sites was submerged in beakers with sea water in the laboratory and stored at different temperature and time conditions. SAV was identified by real‐time RT‐PCR in the lipid fractions accumulating at the water surface in the beakers. SAV‐RNA was also present in the sea water. Lipid fractions were transferred to cell culture, and viable SAV was identified. Due to its hydrophobic nature, fat with infective pathogenic virus at the surface may contribute to long‐distance transmission of SAV.     

Tub gurnard Chelidonichthys lucerna L.: a new fish species suitable for farming? First answers evaluating the growth of juveniles reared at different stocking densities,welfare and fillet quality

A trial was conducted to evaluate the growth performance and survival of Chelidonichthys lucerna. A total of 13 352 180‐days old juveniles (5.5 ± 2 g; 5 ± 1 cm) were reared at two different densities (A‐EXP = 68 fish m^?3; B‐FFA = 15 fish m^?3) in eight tanks (four tanks per group) for 360 days. The welfare status and meat quality of fish were evaluated for the A‐EXP and B‐FFA groups in comparison with wild‐caught fishery gurnard (C‐WID). The survival rate was high for both A‐EXP (79%) and B‐FFA (93.5%). B‐FFA fish had the highest specific growth rate (1.16 vs. 1.07; P < 0.05), and were heavier than A‐EXP fish (321 ± 40 g vs .239 ± 44 g; P < 0.01). Rearing conditions did not affect blood metabolites, except for glucose concentrations, which were higher in C‐WID (P < 0.05). The meat quality traits showed that reared groups were fatter (2.8–3.2%) than C‐WID (0.94%); total n‐3 fatty acids (19.02–19.26%) were lower in reared groups than C‐WID (29.99%); and EPA + DHA were similar in all groups (15.1–16.61% vs. 27.99%). Despite the good growth and survival, the final mean weight was below that requested by the market (400–500 g). Future research efforts should focus on reducing the feed conversion rate (3:1).     

Biomass removal by dolphins and fisheries in a Mediterranean Sea coastal area: do dolphins have an ecological impact on fisheries?

• 1. Dolphins are often claimed to compete with fisheries, including through removal of substantial biomass. To calculate the biomass removed by fisheries and the degree of resource overlap with dolphins in a coastal area of Greece, estimates of dolphin abundance based on photographic capture–recapture were combined with an assessment of fishing effort and catch.
• 2. The estimated total biomass consumed annually by local dolphin populations – 15 short‐beaked common dolphins and 42 common bottlenose dolphins – was 15.5 and 89.8 tonnes, respectively. The total biomass removed by the local fishing fleet (307 fishing boats) was 3469.2 tonnes, i.e. about 33 times greater than that removed by dolphins.
• 3. Dolphins removed 2.9% of the total biomass, fisheries 97.1%. Nine purse seiners (representing only 3% of the active fishing fleet) were responsible for 31.9% of biomass removal. Similarity of biomass composition between dolphins and fisheries was expressed by a Pianka index of 0.46 for common dolphins and 0.66 for bottlenose dolphins.
• 4. Overlap differed according to fishing gear. Common dolphin overlap was higher with purse seiners (0.82), and lower with beach seiners (0.31), bottom trawlers (0.11) and trammel boats (0.06). There was virtually no overlap with longliners (0.02). Bottlenose dolphin overlap was higher with trammel boats (0.89) and bottom trawlers (0.75), and lower with longliners (0.38), purse seiners (0.24) and beach seiners (0.18). There was minimal overlap (0.12) between the two dolphin species.
• 5. This study suggests that ecological interactions between dolphins and fisheries in this coastal area have minor effects on fisheries. Conversely, prey depletion resulting from overfishing can negatively affect dolphins. Fisheries management measures consistent with national and EU legislation are proposed to ensure sustainability and to protect marine biodiversity. Copyright © 2010 John Wiley & Sons, Ltd.

     

Is Guam a regional source,destination, or stepping‐stone for larvae of three fisheries species?

The pelagic larval duration (PLD) period of fish can influence dispersal, recruitment, and population connectivity, thereby potentially informing best strategies for fisheries management. Computer models were used to simulate the dispersal of larvae of three species, representing a range of PLDs, from the Pacific island of Guam and neighboring islands for a 9‐year period (2004–2012) to gain insight into the best management strategies for these species. The species included two springtime spawners with shorter and longer PLDs, scribbled rabbitfish (Siganus spinus; 33 days) and yellowfin goatfish (Mulloidichthys flavolineatus; ~90 days maximum), and a fall spawner with a similarly long PLD, bluespine unicornfish (Naso unicornis; ~94 days maximum). An ocean circulation model coupled with a particle dispersal model provided simulated numbers of larvae settling at each island in relation to the island where they were spawned. Graph analysis was used to examine generational connections between islands. For S. spinus, self‐seeding was the dominant means of replenishment at Guam. Local management actions to maintain adequate spawning stock may be a primary control on long‐term sustainability for that fishery. In contrast, N. unicornis and M. flavolineatus populations at Guam were reliant on outside sources for 92%–98% of larval supply. For them, identifying and negotiating the preservation of upstream spawning potential in the Marshall Islands and Federated States of Micronesia will be needed. Guam played a relatively minor role in generational connectivity across the region. Shortest paths spanning the region often did not pass through Guam, or there were equally short paths through other islands.     

Adverse consequences of stock recovery: European hake,a new “choke” species under a discard ban?

Many commercial fish stocks are beginning to recover under more sustainable exploitation regimes. In this study, we document the temporal and spatial changes in one remarkable example of stock recovery: northern European hake (Merluccius merluccius). Analysing data from several scientific surveys, we document a dramatic increase in estimates of biomass between 2004 and 2011 throughout the larger area now occupied by the stock. The largest increase occurred in the North Sea, where hake have been largely absent for over 50 years. Spatio‐temporally resolved commercial landings show that high densities occur in the North Sea only between April and September, suggesting a density‐dependent seasonal habitat expansion to suitable temperature and depth conditions. These changes have implications for the management of the stock which are discussed. Notably, if discards are banned as part of management revisions, the relatively low quota for hake in the North Sea will be a limiting factor (the so‐called ‘choke’ species) which may result in a premature closure of the entire demersal mixed fishery in the North Sea, jeopardizing many commercial fisheries in the region. This example of the unforeseen consequences of improved stewardship highlight the need for a more holistic, regional and responsive approach to managing our marine ecosystems.     

Habitat overlap of juvenile and adult lake trout of Great Bear Lake: Evidence for lack of a predation gradient?

A range of organisms, from plankton to fish, commonly shift their habitat distributions horizontally or vertically due to predation risk. Juvenile lake trout, Salvelinus namaycush, are generally viewed as occupying deep areas of lakes to decrease predation pressure from adults. In contrast, we found that juvenile lake trout from Great Bear Lake, NT, Canada, occupied a variety of habitats and from shallow to deep depths (0–150 m), overlapping with adult lake trout. No evidence occurred for a length depth‐based segregation (e.g., ontogenetic shift). Genetic variation was also similar among juveniles in the different depth zones. However, isotopic niches and C:N ratios among juveniles showed some variability in niche widths and positions for individuals caught from the 51–150 m zone compared to juvenile individuals caught from 0–20 m and 21–50 m zones. The uniformly distributed adult lake trout in Great Bear Lake may evenly distribute predation pressure (including cannibalism) across shallow‐ and deep‐water habitats more than in other lakes. As a result, juveniles may respond to differences in foraging opportunities rather than predation risks. Juvenile lake trout did not appear to conform to the general pattern of juveniles seeking a deep‐water refuge to reduce predation risks. In contrast, juvenile lake trout of Great Bear Lake displayed broad resource use across all depths and habitats.