Growth and diet of anadromous Arctic charr after their return to freshwater

Abstract – The post smolt of anadromous Arctic charr ( Salvelinus alpinus ) from Lake Storvatn, northern Norway (70°39'48"), continued to feed and grow after their return to freshwater in late summer, but in late autumn (October) both their growth rate and feeding intensity ceased along with the drop in water temperature. In contrast, adult, sexually mature anadromous charr did not appear to feed during their freshwater residency. The stomach fullness of post smolts were similar to that of resident Arctic charr during early autumn, and their diets were similar, being dominated by pelagic prey such as surface insects, Holopedium sp., Bosmina sp. and chironomid pupae. Later in the autumn, the resident charr also included some more benthic prey, in particular gastropods, whereas the post smolts continued to feed predominantly on zooplankton and surface insects, but with a lower stomach fullness than the resident fish. This suggests that after arrival in freshwater, the post smolts continue their pelagic feeding behaviour displayed during the sea-migration.     

Patterns of phenotypic and genetic variability show hidden diversity in Scottish Arctic charr

Abstract –  This study examined the degree and pattern of variability in trophic morphology in Arctic charr ( Salvelinus alpinus L. ) at three spatial scales: across 22 populations from Scotland and between and within two adjacent catchments (Laxford and Shin) in northern Scotland. In addition, the variability at six microsatellite loci between and within the Laxford and Shin systems was determined. Habitat use by charr differed significantly between populations. The pattern of variability in trophic morphology, known to influence foraging ability in charr, showed a very high degree of between-population variation with at least 52% of population pairs showing significant differences in head shape. Trophic morphology and genetic variation was also high over small geographical scales; variation being as high between charr from lakes within the same catchment, as between adjacent catchments. The pattern of both phenotypic and genotypic variation suggests a mosaic of variation across populations with geographically close populations often as distinct from each other as populations with much greater separation. Very low levels of effective migrants between populations, even within the same catchment, suggest that this variation is being maintained by very low straying rates between phenotypically and genetically distinct populations, even when there is no apparent barrier to movement. We conclude that the genetic and phenotypic integrity of charr populations across Scotland is high and that this adaptive radiation constitutes a 'hidden' element of diversity in northern freshwater systems. Two consequences of this are that the population (rather than the species) makes a more rational unit for the consideration of conservation strategies and that the habitat requirements and therefore management needs may differ significantly between populations.     

Tissue concentrations of RNA and protein for juvenile brook trout (Salvelinus fontinalis): lagged responses to fluctuations in food availability

To be useful as short-term indices of nutritional status when food availability varies, wet weight-at-length and tissue concentrations of nucleic acids and protein must covary closely with a fish's recent feeding history. We measured changes in these indices for young brook trout (Salvelinus fontinalis) (fork length: 20–34 mm) reared under alternating, 4 to 5 d periods of food provisioning and food deprivation. Weight-at-length corresponded closely with current feeding conditions, being higher when the trout were fed than when they were deprived. Concentrations of RNA and protein, however, did not correspond closely with current feeding conditions. Instead, there were significant carry-over effects whereby responses to feeding conditions experienced in one treatment period were not exhibited until the following treatment period. Food provisioning had positive carry-over effects on concentrations of RNA and protein while food deprivation had negative carry-over effects. Consequently, food-deprived trout sometimes had higher concentrations of RNA and protein than well fed trout. Since wild fish may experience short-term fluctuations in food availability, lagged responses in concentrations of nucleic acids or protein like those reported here could hamper attempts to use these biochemical measures to assess the nutritional status of juvenile fish in the field.Author to whom all correspondence should be addressed.     

花羔红点鲑cDNA文库的构建

以花羔红点鲑为研究对象,从肝、肾和肌肉中提取总RNA,进一步纯化出mRNA,反转录成cD-NA,构建其cDNA文库,为进行遗传基因的研究奠定基础,同时挽救和保存濒危冷水性鱼类资源花羔红点鲑的遗传信息。     

Putative virulence factors of atypical Aeromonas salmonicida isolated from Arctic charr,Salvelinus alpinus (L.), and European grayling,Thymallus thymallus (L.)

Atypical Aeromonas salmonicida (AAS) causes generalized lethal infections in farmed Arctic charr, Salvelinus alpinus (L.), and European grayling, Thymallus thymallus (L.), and is thus a serious threat for culture of these fish species. Virulence factors were studied among isolates of AAS from Arctic charr (n = 20), European grayling (n = 19) and other fish species (n = 20), of which 48 were of Finnish and 11 of Swedish origin. All isolates produced an A-layer. Extracellular products (ECP) of the AAS isolates did not produce detectable gelatinase and caseinase activity in test assays. Analysis of the same ECP preparations with substrate sodium dodecyl sulphate-polyacrylamide gel electrophoresis showed weak proteolytic activity, indicating the different sensitivity of the detection methods used. The ECP from AAS isolates showed low cytotoxic activity against cultured cells. However, the ECP did not induce mortality in challenged Arctic charr. The results suggest that toxic components, like ECP, secreted by the bacterium may not be the major virulence factor in AAS-infection in Arctic charr and European grayling, and hence the pathogenesis also differs from the pathogenesis of AAS-infection in Atlantic salmon, Salmo salar L.     

MS-222对细鳞鲑和美洲红点鲑的麻醉效果研究

通过测定不同质量浓度MS-222对细鳞鲑和美洲红点鲑的麻醉效果,检测麻醉时鱼的呼吸频率以及空气暴露时长对鱼体复苏的影响,探究两种鱼类在渔业生产和科研实验中的最适麻醉剂浓度。结果显示：当MS-222质量浓度为80、100 mg/L时,细鳞鲑麻醉所需的时间显著少于40、60 mg/L浓度组,而显著多于其余浓度组(P<0.05)。当MS-222质量浓度为100 mg/L时,细鳞鲑的复苏时长最短(P<0.05)。当MS-222质量浓度为80 mg/L时,美洲红点鲑麻醉所需的时间显著少于40、60 mg/L浓度组,而显著多于其余浓度组(P<0.05)。当MS-222质量浓度为100 mg/L时,美洲红点鲑的复苏时长显著大于40、60和80 mg/L浓度组,而显著小于其余浓度组(P<0.05)。比较MS-222对两种鱼的麻醉效果,美洲红点鲑对MS-222更为敏感。两种鱼的呼吸频率总体上都随着麻醉程度的加深而下降,当空气暴露时长少于5 min时,细鳞鲑的复苏时长先减少后增加,美洲红点鲑的复苏时长则呈逐渐减少趋势。     

红点鲑属鱼类资源现状及保护利用

本文综述了国内外红点鲑属鱼类的种类,资源及其发展利用现状,并对我国保护和发展利用红点鲑资源提出措施和建议。     

鸭绿江上游花羔红点鲑(Salvelinus malma)的食性分析及生态位

对鸭绿江上游花羔红点鲑（Ｓａｌｖｅｌｉｎｕｓ ｍａｌａｍ）的食性进行了分析,比较不了同年龄组和季节的食物组成及摄食强度的变化,探讨了鸭绿江上游花羔红点鲑的三维生态位及其分化。     

An experimental comparison of cannibalistic response in different Arctic charr (Salvelinus alpinus (L.)) stocks

Abstract– The cannibalistic response of four domesticated Arctic charr stocks were compared experimentally using a radiographic technique. Charr from Arctic Spitsbergen (80°N) consistently exhibited a much higher frequency of cannibalistic response than fish from three charr strains from mainland Norway (70°N). The results indicate that the extent of cannibalistic feeding in Arctic charr is population specific and support the hypothesis that charr from Arctic populations have stronger cannibalistic tendencies than do fish from more temperate regions.     

REVIEW Cultivation of Arctic charr: an update

There has been interest in farming Arctic charr, Salvelinus alpinus, since the 1970s, but expansion of the industry has not been as rapid as originally predicted due to problems experienced with obtaining supplies of viable eggs and juveniles, variable growth and flesh pigmentation during grow-out, problems with year-round culture in sea water, early maturation, and problems related to the marketing of portion-size fish. Several of these problems are probably a manifestation of a mismatch between the environmental requirements of the fish and the rearing environment. For example, variable rates of broodstock maturation and poor survival of eggs are probably the result of holding broodstock charr at temperatures that are unsuitable for optimal reproduction. Poor and heterogeneous rates of growth during grow-out may be the result of rearing the fish at sub-optimal stocking densities. Further, variable fillet pigmentation may be a manifestation of variable growth rates, rather than being a true reflection of the ability of charr to deposit carotenoids in their flesh. Provided that the fish are held under conditions that promote good rates of growth, charr appear to be able to deposit adequate amounts of pigment in their flesh when fed diets that contain 50–70 mg pigment per kg diet. © Rapid Science Ltd. 1998