2023年三峡水库生态调度对四大家鱼生境面积影响研究

2023年5月27日至6月3日，三峡水库开展了针对葛洲坝下游四大家鱼自然繁殖的生态调度试验，为量化此次生态调度对四大家鱼生境面积影响，以葛洲坝至枝江江段为研究区域，选择水位变幅、水深、流速、水温4个主要生境因子，建立了耦合平面二维水动力学模型和产卵栖息地适宜度曲线的四大家鱼产卵生境质量评估模型，实现了产卵综合适宜度指数的时空分布的精细化模拟。结果表明：生态调度期间，研究区域四大家鱼产卵综合适宜度指数呈现稳定增加趋势，四大家鱼产卵加权可利用面积占研究区域总面积比例由30.45%增加至约55%；适宜四大家鱼产卵区域（产卵综合适宜度指数在0.6～1.0范围）明显增加，占研究区域总面积比例由4.67%增加至约60%。2023年三峡水库生态调度显著改善了葛洲坝至枝江江段四大家鱼产卵生境质量。     

Gonadal recrudescence and induced spawning in Barbus altianalis

Gonadal recrudescence in Barbus altianalis from River Nile, Jinja (33°05E; 0°45N) Uganda was studied prior to induced spawning. Oocytes in B. altianalis were found to develop in cohorts suggesting batch spawning throughout the year with pronounced spawning activities coinciding with rainfall peaks of April and September. There was a strong positive correlation between rainfall and gonadosomatic index (r_S = 0.75, P = 0.008). B. altianalis had low fecundity (6.0 ± 2.0 per gram) and large‐sized eggs (2.97 ± 0.1 mm). Induced spawning was successful with exogenous hormones and water current. Results from this study suggested that total striping may not be appropriate, but larger eggs would confer high survival of offsprings under optimal conditions. The success registered in induced spawning of B. altianalis provides a breakthrough in seed production for multiplication and culture of this economically important fish species.     

东、黄渤海带鱼的洄游路线

为了研究带鱼的洄游路线,根据我国10余个主要渔业公司1971、1972、1981和1982年带鱼捕捞统计资料,先绘制带鱼鱼群移动影像图,据此进一步研究东、黄渤海近海带鱼的洄游路线图。结果显示,带鱼越冬场、产卵场和索饵场范围广阔,在空间上具有一定的重叠性。带鱼还有分批越冬、产卵和索饵洄游的特性,不同群体越冬、产卵和索饵洄游在时间上也有一定的重叠性。北方带鱼群体的越冬场主要在32°00'～36°00'N,124°00'～126°00'E黄海暖流水域。3—7月北上进入海州湾、乳山湾、海洋岛和渤海各湾产卵场;8—9月在产卵场外围宽阔水域索饵;9—11月游出渤海,绕过成山头南下,沿禁渔线外侧,沿途分别汇合海州湾、乳山湾及海洋岛的越冬鱼群,到了34°00'N后折向东南,分批于12月到达越冬场。南方带鱼群体越冬场主要位于浙江中南部禁渔线外侧,其次是济州岛西南海域。每年3—4月起,南部越冬的带鱼鱼群大致以每2个月1个纬度的速度向东北方向移动;5—7月,产卵洄游的鱼群到达舟山渔场和长江口渔场产卵;7—8月,产卵后的索饵群体北上黄海南部大沙渔场索饵;9月,索饵群体前锋到达35°00'N禁渔线外侧。10月以后,随着冷空气南下,南部群体带鱼向南越冬洄游,并且在10月回到长江口海域。其中小部分群体游向外海越冬场,大部分群体继续南下回到东海中南部近海的越冬场。台湾暖流和黄海暖流的进退和消长是影响带鱼越冬洄游路线空间和时间变化的主要环境因素。     

Influence of hormonal induction and broodstock feeding on longfin yellowtail Seriola rivoliana maturation,spawning quality and egg biochemical composition

To optimize broodstock management for Seriola rivoliana, a survey over 5 years was performed to evaluate the effects of successive hormonal inductions with GnRHa or dietary regime on spawning quality. Running males and females with an oocyte diameter > 500 μm were injected with GnRHa. The spawning quality was compared among consecutive years and different moments along the spawning season. Besides, three different feeding regimes were tested. Spawning quality parameters were not significantly affected by time along the spawning season, whereas they were clearly influenced by diet. Particularly, broodfish fed the mackerel regime (M) showed a significantly higher number of eggs than other treatments. Besides, dietary protein content significantly improved broodstock fecundity of S. rivoliana. Moreover, hatching rates were also higher in broodfish fed mackerel and the dietary docosahexaenoic acid (DHA) levels significantly increased this parameter. Despite polar lipids were not significantly affected, neutral lipids fatty acid composition of S. rivoliana eggs showed higher 18:2n‐6 in eggs, whereas ARA content was not affected. The results of this study denoted the high fecundity and good spawning quality of S. rivoliana broodfish and suggested the importance of high protein, energy and DHA levels in broodstock diets.     

Incidence of spinal injuries in migratory Yellowstone cutthroat trout captured at electric and waterfall‐velocity weirs

The South Fork Snake River (Idaho, USA) supports a native Yellowstone cutthroat trout (YCT) population Oncorhynchus clarkii bouvieri (Richardson) threatened by non‐native rainbow trout O. mykiss (Walbaum). Electric weirs prevent rainbow trout passage into YCT spawning tributaries but may cause spinal injuries. YCT captured at electric weirs on Palisades and Pine Creeks and a control waterfall‐velocity weir on Burns Creek were X‐rayed in 2012 and 2013 to estimate spinal injury rates. Electrical pulse frequency was increased from 2012 to 2013 at the Palisades (from 11.5 to 20 Hz) and Pine weirs (13–20 Hz), and spinal injury rates were found to increase from 11.3 to 21.3% at Palisades and from 6.5 to 14.7% at Pine, while Burns injury rates remained constant (4.5% in 2012 and 6.0% in 2013), suggesting the electric weirs caused spinal injuries in YCT. Lower pulse frequencies may minimise YCT spinal injury but still prevent rainbow trout from accessing YCT spawning tributaries.     

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.     

Physiological condition and migratory experience affect fitness‐related outcomes in adult female sockeye salmon

Relating fish physiology, behaviour and experience to fitness‐related outcomes at the individual scale is ecologically significant, but presents difficulties for free‐ranging fishes in natural systems. Physiological state (e.g. level of stress or maturity) and experience (e.g. habitat use or exposure to stressors) may alter the probability of survival or reproduction. This study examined the relative influence of physiology and migratory experience on survival, migration duration, reproductive longevity, and egg retention in adult female sockeye salmon (Oncorhynchus nerka) from a Fraser River population. One hundred and thirty‐five females were plasma sampled and tagged with radio transmitters and archival temperature loggers. Fish were tracked 55 km through two natal lakes to spawning grounds, following passage of a hydroelectric dam. For 39 females, we assessed the proportion of time within an optimal temperature (T_optAS) window (13.4–19.5°C), which provides ≥90% of maximum aerobic scope. Females with lower plasma glucose concentrations were more likely to reach spawning grounds. Early migrants spent longer in natal lakes. More time in the T_optAS window was associated with greater reproductive longevity and lower probability of egg retention. Later arriving females had reduced longevity on spawning grounds, as did females that retained eggs. Exposure to higher dam discharge was associated with reduced reproductive longevity and greater probability of egg retention, but not lower survival, indicating a delayed effect of dam passage. Our results underscore the complexity of factors governing fitness‐related outcomes for salmonids, particularly the importance of female experience in the days and weeks prior to spawning.     

Early assessment of gilthead sea bream (Sparus aurata) spawning dynamics by mini‐broodstocks

The implementation of any sustainable breeding program requires a maximization of effective size (Ne) to maintain inbreeding rate at minimum levels. However, the control of Ne remains a major challenge for those species whose reproduction in captivity is based on a spawning strategy where there is no control over the established matings. The present study aims to assess the spawning dynamic of gilthead sea bream (Sparus aurata) at different dates from two mini‐broodstocks (4 ♀ and 4 ♂). Here we report the use of a simple protocol based on the genotyping of fertilized eggs from a reduced set of microsatellite loci which provides a quick evaluation of daily spawning in terms of family structuring (number of active breeders and number and family size). According to our results, the daily spawning dynamics is characterized by a fluctuation in the number of active breeders, reaching maximum values (until 100%) during peak production phase. However, the proportion of possible mating (families) in a single daily spawning never exceeded more than 81%. Unbalanced parental contributions were highly frequent, with extreme cases involving the assignment of 50%–90% of the offspring to a single family. Therefore, the use of mini‐broodstocks and the grouping of spawning harvested at different dates are proposed as strategies to minimize the inbreeding risk by providing a more optimal pattern of family structuring (increase in the number of families obtained and a more balanced parental contributions) that entails a more conservative Ne/N ratio.     

Artificial reproduction protocol,from spawning to metamorphosis,through noninvasive methods in Patella caerulea Linnaeus, 1758

Controlled reproduction is a requirement for developing effective mollusc cultivation for commercial or restoration purposes. In this study, a protocol for spawning induction using noninvasive methods in limpets was developed, using the common Mediterranean species, Patella caerulea Linnaeus, 1758. Six nonlethal spawning induction treatments were tested: three chemical (two concentrations of H₂O₂ and KCl) and three physical (bubbling, warm and cold thermal shock). All treatments, except thermal shocks, induced the spawning of fertile gametes. Bubbling resulted the best treatment in providing spawning response, being the easiest and least invasive method tested. After eggs fertilization, larval development was followed until metamorphosis, testing fed and unfed conditions. Settlement took place after 7 days. The developed protocol represents a benchmark for further application to other limpets, for aquaculture or repopulation.