养殖花羔红点鲑营养价值分析

本文对人工养殖的花羔红点鲑的肌肉组成进行了分析。花羔红点鲑的水分、粗脂肪、粗蛋白、粗灰分含量十分丰富。不同年龄花羔红点鲑肌肉氨基酸含量有一定差异。花羔红点鲑肌肉脂肪酸含量高,并随年龄增长成升高趋势。花羔红点鲑有较高的营养价值,是一种可大力推广的优良品种。     

Assessing the food web impacts of an anadromous Arctic charr introduction to a sub‐Arctic watershed using stable isotopes

Anadromous Arctic charr, Salvelinus alpinus (L.), was introduced to a sub‐Arctic river–lake system near the village of Kujjuuaq, Nunavik, and the stable isotope values and diets of key resident fish species were used to assess changes in feeding patterns. Stable isotope values for most species did not differ significantly between the pre‐ and post‐introduction periods, with observed shifts being within the bounds of expected natural variation. Lake chub, Couesius plumbeus (Agassiz), were the single species to show a difference between study periods, with a small but significant increase in δ¹⁵N. No significant post‐introduction changes were seen in lake trout, Salvelinus namaycush (Walbaum), omnivory or in any of the assessed quantitative food web metrics. Gut contents of major fish species similarly showed significant temporal overlap between the pre‐ and post‐introduction periods, and there was no significant change in species' weight–length relationships. The minor ecological impact was interpreted in relation to the availability of open niches exploitable by ecological generalists such as Arctic charr. The explanation accords with the known habitat and feeding flexibility of Arctic charr and the ecological immaturity of sub‐Arctic lakes known to have driven adaptive variation among Arctic charr. Findings suggest that anadromous Arctic charr may be introduced at moderate densities to other sub‐Arctic watersheds without major negative food web consequences for other resident fish species.     

Baseline demographics of a non‐native lake trout population and inferences for suppression from sensitivity‐elasticity analyses

Management agencies in several western states of the United States are implementing suppression programmes to control non‐native lake trout, Salvelinus namaycush (Walbaum), for the conservation of native species. This study was implemented to ascertain the population demographics of an expanding lake trout population and use those data to construct an age‐structured model to inform suppression efforts. Population projection matrices were used to model population growth and identify age or stage classes with the greatest influence on population growth. The size and age structure of lake trout sampled was skewed towards juveniles, indicating strong recruitment and a growing population. Matrix‐model simulations corroborated the observed size and age structure, as the lake trout population was predicted to grow exponentially (λ = 1.35, 95% CL: 1.25–1.43) with no suppression efforts. Elasticity analysis of matrix models indicated the relative contribution of survival rates to population growth among immature age classes was equal from age 0 to age at first maturity, but immature survival rates contributed more than adult survival and fertility rates. These results emphasise the importance of targeting juvenile lake trout for suppression efforts during exponential growth in recently established populations.     

花糕红点鲑多态性微卫星筛选及鸭绿江种群遗传多样性分析

利用强壮红点鲑（Salvelinus confluentus）的微卫星筛选出适用于我国的珍稀濒危冷水性鱼类——花糕红点鲑（Salvelinus malma）的多态性引物,并分析其鸭绿江种群的遗传多样性。结果显示,在强壮红点鲑的10个微卫星引物中有5个在花糕红点鲑群体中具有多态性,鸭绿江种群的等位基因数（N）a为6~22（平均15）,杂合度（H）为0.4063~0.9333（平均0.7851）,多态信息含量（PIC）为0.7164~0.9198（平均0.8536）。强壮红点鲑微卫星引物在花糕红点鲑中具有很好的通用性,花糕红点鲑的鸭绿江种群具有较高的遗传多样性水平。本研究结果为我国花糕红点鲑种质资源保护和管理提供遗传学理论依据。     

Developing bioelectrical impedance analysis methods for age‐0 brook trout

Year class strength of many fishes often is determined by survival through the first winter. Increased fat reserves improve survival and overall cohort success. Bioelectrical impedance analysis (BIA) methods are established for estimating proximate composition of adult brook trout, Salvelinus fontinalis (Mitchill), but none have been developed for early life stages. Small‐fish BIA would provide information about age‐0 percent dry weight, a proxy for fat reserves, allowing for better prediction of cohort success. The objective of this study was to develop BIA methods that provide reliable estimates of percent dry weight for age‐0 brook trout. BIA measurements were taken at seven anatomical locations from 48 to 115 mm fish. A model developed using BIA measures taken by subdermal needle electrodes precisely predicted percent dry weight (best model, RMSE = 1.03, R² = 0.86). Although lacking support, as determined by information theoretical analysis, BIA measured with non‐invasive external rod electrodes also precisely predicted percent dry weight (RMSE = 1.09, R² = 0.85). Models developed using two electrode locations performed better than models developed with only one location. For small brook trout, a dorsal to ventral pre‐dorsal fin electrode location should be used in conjunction with a dorsal total length location when measuring BIA to predict percent dry weight.     

Antipredator behaviour of naïve Arctic charr young in the presence of predator odours and conspecific alarm cues

Abstract –  We investigated how Arctic charr young respond behaviourally to olfactory cues from skin-damaged conspecifics, charr-fed pikeperch, and the combination of food-deprived pikeperch and skin-damaged conspecific cues in a two-channel Y-maze fluviarium test arena. Significant antipredator responses were found to skin-damaged conspecifics in three behavioural traits, to charr-fed pikeperch in two traits and to the combination of pikeperch and skin-damaged conspecific cues in all six behaviours investigated. The combination of predator and conspecific cues significantly increased spatial avoidance and cautiousness to approach the source of scent compared with odours from charr-fed predators. The results suggest that damage-released alarm cues exist in charr, and they strengthen the antipredator responses in conspecifics. As the charr used different behaviours and levels of response in the presence of different cues, they seem to have sophisticated skills to distinguish between different odour combinations and be able to adjust their behaviour according to the current predation risk level.     

The effect of lake morphometry on thermal habitat use and growth in Arctic charr populations: implications for understanding climate‐change impacts

Oxygen stable isotope temperature reconstruction methods were used to estimate mean experienced summer temperatures from growth zones within individual Arctic charr otoliths sampled from lakes with contrasting morphologies but proximate locations. For either lake, otolith‐estimated temperatures were not significantly related to back‐calculated growth. Fish in the smaller lake evidenced an increase in growth with age related to increasing use of cooler thermal habitats, with the use of thermal habitat possibly governed by predation risks. No relationships between age, growth or temperature were observed in the larger lake. Significant negative effects on back‐calculated growth were observed due to increasing air temperatures in the smaller and shallower lake, possibly owing to warmer surface and littoral waters and a limited amount of preferred cool‐water habitat. A similar relationship was not observed in the larger and deeper lake and indicated that resident Arctic charr were not as vulnerable to the impacts of temperature warming, possibly because of better behavioural thermoregulation opportunities in the cooler, deeper lake. Results provide evidence for differing climate‐influenced growth outcomes among proximately located populations, with outcomes likely to depend on the differences among habitats, including lake size and morphometry which may act to influence fish densities in available preferred thermal habitats.     

Summer habitat use and feeding of juvenile Arctic charr,Salvelinus alpinus,in the Canadian High Arctic

Abstract – Owing to limited knowledge of the habitat use and diet of juvenile Arctic charr from the High Arctic, particularly young‐of‐the‐year (YOY), we assembled data obtained from samples taken in and around Lake Hazen, Nunavut, Canada, to assess juvenile habitat use and feeding. Juvenile charr demonstrated a preference for stream environments, particularly those fed by warm upstream ponds. Charr occupying both stream and nearshore lake habitats were found to feed similarly, with chironomids occurring most frequently in diets. Some older stream‐dwelling charr preyed on smaller, younger Arctic charr. Preferred stream occupancy is likely mediated by physical barriers created mainly by water velocity, and by distance from the lake, lake‐ice dynamics, low water depth, and turbidity. Water velocities resulted in stream habitat segregation by size, with YOY mainly found in low‐velocity pools and back eddies adjacent to stream banks, but not in water velocities >0.1 m·s^?1. Greatest charr densities in streams were found in small, shallow, slow‐flowing side channels, which are highly susceptible to drought. Under predicted climate change scenarios, streams fed by small ponds will be susceptible to intermittent flow conditions, which could result in increased competition among juvenile charr for the remaining stream habitats. In addition, glacier‐fed streams are likely to experience increased flow conditions that will exacerbate physical barriers created by water velocity and further reduce the availability of preferred stream habitat.     

Otolith size differences during early life of dwarf and cannibal Arctic char (Salvelinus alpinus)

In Arctic and alpine lakes, Arctic char [Salvelinus alpinus (L.)] often form two distinct morphs: invertebrate feeders (‘dwarfs’) and piscivores (‘giant or cannibals’). Here, we test for early life history growth variation in dimorphic Arctic char as a proximate explanation for the observed life history variation between the two forms. Char were sampled in 11 alpine and Arctic Norwegian lakes. Dwarfs (defined as sexually mature char less than 15 cm long; N = 304) had a mean total length of 105 mm, whereas the typical cannibal (body length above 20 cm; N = 153) was 388 mm long. A positive correlation between egg size and otolith hatching ring were ascertained in a separate hatching experiment with brown trout (Salmo trutta) and it is assumed that this relationship also is valid for Arctic char, and otolith size was used as a proxy for length. Otolith hatching ring from Arctic char cannibals was larger (mean ± SD; 187 ± 24 μm) than those from dwarfs (mean ± SD; 164 ± 23 μm). There were only minor size differences between dwarfs and cannibals during the next three years, after which dwarfs usually matured. Two mutually nonexclusive, proximate explanations for the differentiation into separate morphs (dwarfs and cannibals) are therefore maternal effects and/or genetic based differentiation. The high catchability of large piscivorous char and low production in alpine and Arctic lake ecosystems may make these stocks particularly vulnerable to overexploitation.