Mercury comparisons between farmed and wild Atlantic salmon (Salmo salar L.) and Atlantic cod (Gadus morhua L.)

Wild and farmed Atlantic salmon ( Salmo salar L.) and Atlantic cod ( Gadus morhua L.) were collected to assess changes in mercury with size in wild vs. farmed fish. Mercury concentrations were compared with Health Canada and United States Environmental Protection Agency consumption guidelines. Lipid dilution of mercury was examined by comparing lipid-extracted (LE) and non-lipid-extracted (NLE) flesh samples in both farmed and wild fish. Mercury concentrations in the flesh and liver of farmed salmon were significantly lower than concentrations in wild salmon of similar fork length ( P <0.001), possibly due to growth dilution in rapidly growing farmed fish. Mercury concentrations were higher in LE tissue compared with NLE ( P <0.05), suggesting lipid dilution of mercury in farmed fish with a high lipid content. Farmed cod, which do not grow more rapidly than wild cod, did not have significantly different flesh and liver concentrations compared with wild cod of similar fork length ( P >0.05). Between species of farmed fish, cod had significantly higher mercury concentrations than salmon ( P <0.05), but neither farmed nor wild salmon mercury concentrations exceeded federal consumption guidelines. These results suggest that rapid growth rates and a high lipid content may play important roles in regulating concentrations of contaminants such as mercury.     

大西洋大眼金枪鱼资源开发研究

统计分析了1995-2004年间大西洋大眼金枪鱼总渔获量及各渔区、各主要生产国的渔获量变化情况,结果表明：整个大西洋大眼金枪鱼渔获量呈下降趋势,其开发类型主要有延绳钓、饵钓和围网,其中以延绳钓的渔获量最大,1995-2004年期间以西北大西洋（21区）产量最高,为9.53×10^7t,东北大西洋与中西大西洋相对渔获量较少,各为2.47×10^4t,我国对大西洋大眼金枪鱼开发程度不高,占总渔获量的比例较小,针对我国的情况提出开发大西洋大眼金枪鱼相关建议。     

陆封型大西洋鲑的全人工繁殖

本文报道了陆封型大西洋鲑全人工繁殖的实验结果。 2 0 0 0年 1月从美国缅因州格兰特湖增殖站引进的陆封型大西鲑发眼卵 ,在北京房山中国水产科学研究院鲟鱼繁育技术工程中心进行了发眼卵孵化、苗种培育 ,亲鱼养成实验研究。结果表明 :引进的发眼卵经 930d ( 1 1 783度日 )培育成产卵亲鱼 ,雌、雄亲鱼成熟系数分别为 42 7%、 4 2 3% ;怀卵量为 1 0 98～ 362 1粒 /尾 (叉长 36～ 5 5cm) ,平均卵径 5 4mm (吸水膨胀前 )、 6 2mm(吸水后 ) ;平均卵重 8 5粒 /g (吸水后 )、 7 5粒 /g (吸水前 ) ;精液浓度 2 0 0亿个 /ml,精子寿命 70～ 90s,精子快速运动时间为 2 0～ 40s;个体繁殖率E (粒 )与叉长 (L)的相关公式为E =1 32 5L - 3671 8,相关系数r=0 89。受精卵在水温 6～ 1 1℃进行孵化 ,达到发眼所需积温为 2 64 5℃·d ;达到破膜所需 483℃·d ;仔鱼上浮所需 880℃·d。试验亲鱼雌、雄按 2比 1配组 ,1 0 75尾雌鱼共采卵 90 47万粒 ,受精率为 89 88%、发眼率为77 83%。产卵后 ( 3个月后 )存活率分别为雌鱼 30 % ,雄鱼 1 0 %。     

Evidence for atmosphere–ocean forcing of yellowtail flounder (Limanda ferruginea) recruitment in the Middle Atlantic Bight

We investigated the relationship between large-scale climate variability (the North Atlantic Oscillation, NAO), continental shelf hydrography, and year-class strength of yellowtail flounder (Limanda ferruginea) in the Middle Atlantic Bight. Using long-term environmental time series (1963–98), dominant winter NAO phase in the northeast region of the United States was correlated with local air temperature records from Block Island, Rhode Island (December–March). Air temperature also influenced the characteristics of a pool of remnant winter cold water on the continental shelf, such that negative NAO winters produced a colder-than-average summer cold pool, and vice versa. Smoothed data sets of L. ferruginea recruitment over the 36-yr period (using Southern New England VPA and hindcast data) were highly correlated with the NAO and air temperature, highlighting the influence of multi-year variability. Although less robust, the relationship with the NAO remained significant after removing equal-but-opposite long-term linear trends from the series. Surprisingly, recruitment and cold pool bottom temperature were only marginally correlated. Data from independent 2-m beam trawl and submersible sampling in the region (1994, 1996–2000) indicated a strong relationship between the abundance of recent settlers and cold pool temperature; however, this pattern was often modified by subsequent changes in cold pool stratification (fall overturn). These results underscore the dynamic role thermal habitats play in the lives of early stage benthic fishes. For yellowtail flounder, the generation of recruitment variability represents one endpoint of a complex interaction between large-scale phenomena (climate) and more localized, event-scale features (cold pool).     

Growth, feed conversion and chemical composition of Atlantic salmon (Salmo salar L.) and Atlantic halibut (Hippoglossus hippoglossus L.) fed diets supplemented with krill or amphipods

The effects of partial replacement of fish meal (FM) with meal made from northern krill (Thysanoessa inermis), Antarctic krill (Euphausia superba) or Arctic amphipod (Themsto libellula) as protein source in the diets for Atlantic salmon (Salmo salar L.) and Atlantic halibut (Hippoglossus hippoglossus L.) on growth, feed conversion, macro‐nutrient utilization, muscle chemical composition and fish welfare were studied. Six experimental diets were prepared using a low‐temperature FM diet as control. The other diets included northern krill where 20, 40 or 60% of the dietary FM protein was replaced with protein from northern krill, and two diets where the FM protein was replaced with protein from Antarctic krill or Arctic amphipod at 40% protein replacement level. All diets were iso‐nitrogenous and iso‐caloric. Atlantic salmon grew from 410 g to approximately 1500 g during the 160 day experiment, and Atlantic halibut grew from 345 g to 500–600 g during the 150 day experiment. Inclusion of krill in the diets enhanced specific growth rate in salmon, especially during the first 100 days (P < 0.01), and in a dose–response manner in halibut for over the 150 day feeding period (P < 0.05). Feed conversion ratio did not differ between dietary treatments, and no difference was found in dry matter digestibility, protein digestibility and fish muscle composition. Good growth rates, blood parameters within normal ranges and low mortalities in all experimental treatments indicted that fish health was not affected either Atlantic salmon or Atlantic halibut fed the various zooplankton diets.     

Francisella infections in fish and shellfish

A series of recent reports have implicated bacteria from the family Francisellaceae as the cause of disease in farmed and wild fish and shellfish species such as Atlantic cod, Gadus morhua L., tilapia, Oreochromis spp., Atlantic salmon, Salmo salar L., three‐line grunt, Parapristipoma trilineatum (Thunberg), ornamental cichlid species, hybrid striped bass Morone chrysops x M. saxatilis and, recently, a shellfish species, the giant abalone, Haliotisgigantea Gmelin. The range of taxa affected will very probably rise as it is likely that there has been considerable under‐reporting to date of these disease agents. In common with other Francisella species, their isolation and culture require specialized solid and liquid media containing cysteine and a source of iron. This likely restricted earlier efforts to identify them correctly as the cause of disease in aquatic animals. The most information to date relates to disease in cod, caused by F. noatunensis and tilapia, caused by F. noatunensis subsp. orientalis (also termed F. asiatica), both causing granulomatous inflammatory reactions. Mortalities in both species can be high and, as the disease can likely be transferred via live fish movements, they pose a significant threat to tilapia and cod aquaculture operations. Although the fish‐pathogenic Francisella species are classified in the same genus as the human pathogens F. tularensis, causative agent of tularemia, and F. philomiragia, the risk to humans from the fish and shellfish pathogenic Francisella species is considered very low.     

大西洋金枪鱼延绳钓主要渔获种类及其分布

根据收集的有关文献和海上调查资料，分析了大西洋金枪鱼延绳钓生产的主要渔获品种的生物学特性、捕捞生产情况及管理措施等。此外，还根据FAO建立的金枪鱼生产数据库，采用GIS软件制作了大西洋金枪鱼延绳钓主要渔获种类捕捞产量的地理空间分布图。并分析了其资源的空间分布特征。     

A comparative study of susceptibility and induced pathology of cod, Gadus morhua (L.), and halibut, Hippoglossus hippoglossus (L.), following experimental infection with Moritella viscosa

In this study experimental challenges with Moritella viscosa, the causative agent of winter ulcers in salmonids, were performed on juvenile Atlantic cod and Atlantic halibut. The challenges involved both intramuscular (i.m.) and intraperitoneal (i.p.) injections and bath with a strain originally isolated from Atlantic salmon. Cod was found to be significantly more sensitive than halibut to the infection. Both fish species were found to be more sensitive to i.m. than i.p. challenges. Both challenges induced a systemic disease in cod and halibut, but only cod was infected with an experimental bath challenge. Pathognomonic signs were found to be comparable with those described in M. viscosa-infected salmon and turbot. The main distinguishing pathological sign was that the cod showed host response to M. viscosa infection resulting in granuloma formation in infected tissues, which is a known response of cod to a infection with another Gram-negative bacterium, Aeromonas salmonicida. Re-isolation of M. viscosa from kidneys of cod and halibut with clear disease signs was problematic and optimization of isolation measures is needed. The results of this study indicate that M. viscosa infection may be a risk factor in cod farming, but that halibut is more resistant.     

Effects of protein hydrolysate in weaning diets for Atlantic cod (Gadus morhua L.) and Atlantic halibut (Hippoglossus hippoglossus L.)

The study aims to test whether predigested dietary protein enhances the utilization of formulated diets at weaning, and also whether it stimulates intestinal maturation. In this study, Atlantic cod [ Gadus morhua L.; 41 days posthatch (dph)] and Atlantic halibut [ Hippoglossus hippoglossus L.; 63 days postfirst feeding (dpff)] were weaned onto diets with graded levels of protein hydrolysate. By increasing the inclusion of dietary protein as hydrolysate from 0 to 400 g kg⁻¹, cod increased the rate of survival from 7 ± 1% to 18 ± 2% (82 dph; regression, P =  4*10⁻⁷). In halibut, the survival rate decreased from 57 ± 9% to 22 ± 7% as the inclusion of protein in the form of hydrolysate increased from 0 to 450 g kg⁻¹ (119 dpff; regression, P =  8*10⁻⁵). Growth was not affected in any of the species. Results in specific activities of the intestinal enzymes leucine aminopeptidase (LAP) and alkaline phospatase (AP) supported the results in survival in halibut and partly also in cod, by showing increased activities in groups with increased survival ( anova , P <  0.05). The lower optimal level of hydrolysed protein in halibut than in cod is suggested mainly because of a slower feeding practice in halibut, which allows more extensive nutrient leaching before ingestion.     

Some behavioural and ecological factors affecting distribution,biomass and production of juvenile Atlantic salmon

Observations were made in an experimental stream tank (total area 14.7 m²) on juvenile Atlantic salmon, Salmo salar L (parr), relating experimental observations to field observations, including the reported diurnal fasting behaviour of juvenile salmon at water temperatures <10 °C. Densities in the tank ranged from five to twenty parr, at water temperatures ranging from 4.6 °C to 15.8 °C. The wide channel of the stream tank, with mean water velocity of 18.8 cm·s^?1, was the preferred section, where territorial behaviour was observed. Biomass was regulated in the wide channel by territorial mosaics or by dominance hierarchies. Dominance hierarchies were reflected in coloration of the fish. Dominant salmon were generally in the wide channel. Densities of salmon parr (of mean fork length 10.2 cm) in the channel ranged from 0.84 m^?2 to 1.73 m^?2, with an average biomass of 14.2 g·m^?2. Growth was least at the 5.9 °C temperature treatment. In experiments at temperatures below 10 °C, feeding, dominance hierarchy and territorial behaviour were observed in daylight hours, contrary to the published literature. Interactions with other species may affect behaviour. Some observations were made on a closely related species, brown trout (Salmo trutta L.), a commonly cohabiting species in many systems. Trout displaced salmon from their preferred locations in the tank and were more aggressive than the salmon, reducing agonistic behaviour by the salmon. The commonest agonistic act shown by salmon was ‘charge’ and that by the trout was ‘approach’. Some field observations affecting behaviour and production are discussed.     

The influence of hydrology and hydraulics on salmonids between spawning and emergence: implications for the management of flows in regulated rivers

Abstract Flow regulation is a major constraint on fish populations in many river systems. Current scientific understanding of the direct and indirect influence of hydrology on salmonids between spawning and emergence is reviewed and used to identify key knowledge gaps. The review emphasises difficulties in linking ecological response to physical process understanding and, conversely, the difficulties in applying detailed process understanding to large‐scale management. It is suggested that the lack of process understanding in the development of current environmental standards reflects differences in perspective, language and scale consideration between researchers and river managers. This presents considerable difficulties for the development of new and more defensible environmental standards. Although upscaling of process understanding should remain a focus for researchers, it is also necessary to acknowledge the ‘uniqueness of place’ and consequently that local data collection may frequently be required.     

Effect of marine Eubothrium sp. (Cestoda: Pseudophyllidea) on the growth of Atlantic salmon, Salmo salar L.

Atlantic Salmon, Salmo salar L., experimentally infected with marine Eubothrium sp. were kept together with uninfected salmon in the laboratory for 11 months in two tanks, 80 infected and 80 uninfected in each tank. The infected fish had a reduced growth rate compared with the uninfected fish. Significant differences in growth between infected and uninfected fish were not observed until several months post-infection. There was no correlation between the number of Eubothrium sp. and fish weight, indicating that even low intensity alters the growth rate of the salmon. The cestode had the same effect on both sexes of salmon. Haematocrit level was found to be significantly lower in infected compared with uninfected salmon in one of the samples during the experiment.     

Design, loading, and water quality in recirculating systems for Atlantic Salmon (Salmo salar) at the USDA ARS National Cold Water Marine Aquaculture Center (Franklin, Maine)

The Northeastern U.S. has the ideal location and unique opportunity to be a leader in cold water marine finfish aquaculture. However, problems and regulations on environmental issues, mandatory stocking of 100% native North American salmon, and disease have impacted economic viability of the U.S. salmon industry. In response to these problems, the USDA ARS developed the National Cold Water Marine Aquaculture Center (NCWMAC) in Franklin, Maine. The NCWMAC is adjacent to the University of Maine Center for Cooperative Aquaculture Research on the shore of Taunton Bay and shares essential infrastructure to maximize efficiency. Facilities are used to conduct research on Atlantic salmon and other cold water marine finfish species. The initial research focus for the Franklin location is to develop a comprehensive Atlantic salmon breeding program from native North American fish stocks leading to the development and release of genetically improved salmon to commercial producers. The Franklin location has unique ground water resources to supply freshwater, brackish water, salt water or filtered seawater to fish culture tanks. Research facilities include office space, primary and secondary hygiene rooms, and research tank bays for culturing 200+ Atlantic salmon families with incubation, parr, smolt, on-grow, and broodstock tanks. Tank sizes are 0.14 m³ for parr, 9 m³ for smolts, and 36, 46 and 90 m³ for subadults and broodfish. Culture tanks are equipped with recirculating systems utilizing biological (fluidized sand) filtration, carbon dioxide stripping, supplemental oxygenation and ozonation, and ultraviolet sterilization. Water from the research facility discharges into a wastewater treatment building and passes through micro-screen drum filtration, an inclined traveling belt screen to exclude all eggs or fish from the discharge, and UV irradiation to disinfect the water. The facility was completed in June 2007, and all water used in the facility has been from groundwater sources. Mean facility discharge has been approximately 0.50 m³/min (130 gpm). The facility was designed for stocking densities of 20–47 kg/m³ and a maximum biomass of 26,000 kg. The maximum system density obtained from June 2007 through January 2008 has approached 40 kg/m³, maximum facility biomass was 11,021 kg, water exchange rates have typically been 2–3% of the recirculating system flow rate, and tank temperatures have ranged from a high of 15.4 °C in July to a low of 6.6 °C in January 2008 without supplemental heating or cooling.     

陆封型大西洋鲑生物学特性与移植驯化技术

本文报道了陆封型大西洋鲑移植驯化技术及养殖生物学跟踪观察结果。通过引进陆封型大西洋鲑发眼卵，在水温3～11℃的条件下进行孵化，积温达到140～22l度日孵出仔鱼，孵化率达到85％；历经3周年流水低温育种，培育出苗种10万尾。采用强化培育，人工调控环境生态因子诱导亲鱼性成熟的方法，育出后备亲鱼5万尾，成熟亲鱼0．4万尾，成功地实现了大西洋鲑在我国全人工繁殖的研究工作。     

Dietary phosphorus requirement of juvenile Atlantic salmon, Salmo salar L.

The objective of this study was to determine the dietary phosphorus (P) requirement of juvenile Atlantic salmon, Salmon salar L. Triplicate groups of fish (mean initial weight 1.4 g) were fed semipurified, casein-gelatine-based diets containing one of five levels of P (4, 8, 10, 15 and 25 g kg⁻¹) from Ca(H₂PO₄)₂·H₂O, or a commercial feed (17 g kg⁻¹ P) for 9 weeks. Weight gains did not differ significantly among treatment groups fed the experimental diets but were slightly less than gains in fish fed the commercial feed. Feed efficiency (wet weight gain/dry feed consumed) was similar in all groups, averaging 1.45. Availability of dietary P, estimated from apparent retention and apparent digestibility, was 86%. Whole-body P concentrations declined in fish fed diets containing less than 10 g kg⁻¹ P. Fitting a logistic curve to dietary P vs. whole-body P concentrations indicated that a minimum of 11 g kg⁻¹ dietary P (9 g kg⁻¹ digestible P) was required by juvenile Atlantic salmon to maintain whole-body P concentrations at initial levels. Calculation of a dietary requirement using a simple factorial model which incorporated measurements of P availability, feed efficiency and normal whole-body P concentration indicated that the dietary requirement was approximately 10 g kg⁻¹. The dietary requirement established in this study (10–11 g kg⁻¹) is higher than previously reported for Atlantic salmon or other fishes. Possible reasons for the wide range of reported dietary P requirements in fishes are discussed.     

Astaxanthin deposition in the flesh of Atlantic Salmon, Salmo salar L., in relation to dietary astaxanthin concentration and feeding period

Atlantic salmon, Salmo salar L., were fed nine experimental diets containing from 0 to 200 mg astaxanthin per kg^?1 for six time periods, ranging from 3 to 21 months, in sea cages at Matre Aquaculture Research Station, Matredal, Norway. The sampled fish had an initial mean weight of 115 g and reached a weight of 3.2 kg at the termination of the experiment. Every third month, 10 fish from each dose and time group were sampled and the astaxanthin concentration in the flesh determined. The amount of astaxanthin in the flesh ranged from 0.7 to 8.9 mg kg^?1 at the termination of the experiment. This paper discusses deposition of astaxanthin in the flesh of Atlantic salmon in relation to dietary carotenoid levels in the 0–200 mg kg^?1 range and feeding times of 3–21 months. Under the conditions of this experiment, no significant effect on astaxanthin deposition rate could be achieved by increasing the astaxanthin level above 60 mg kg dry feed^?1. Atlantic salmon should be fed astaxanthin-supplemented diets during the whole seawater stage in order to obtain maximal astaxanthin level in the flesh.     

陆封型大西洋鲑的池塘养殖及生物学研究

对从美国缅因州格兰特湖引进陆封型大西洋鲑发眼卵,经过人工孵化、培育的3龄鱼种的生长发育、摄食、形态、生物学以及养殖环境等因素进行了观察和研究。