人工繁殖鲑鱼威胁野生鲑鱼生存

海外媒体报道称,来自美国阿拉斯加、加拿大不列颠哥伦比亚省、华盛顿、俄勒冈、加利福尼亚、俄罗斯和日本的研究人员进行了20余项研究后表明,人工繁殖鲑鱼争夺野生鲑鱼的食物与栖息地,已严重威胁到了野生鲑鱼种群的生存。俄勒冈州立大学的研究员David Noakes表示,人工繁殖的鲑鱼与野生鲑鱼混合的遗传效应已经显现,而生态效应还仅限于假设。人工孵化鲑鱼所产生的问题需要引起渔业管理人员的足够重视。     

草鱼野生群体和人工繁殖群体遗传结构的比较研究

采用新型分子标记SRAP(Sequence-related amplified polymorphism)对草鱼(Ctenopharyngodon idella)1个野生群体(来自邗江草鱼国家级原种场)和2个人工繁殖群体(分别来自淡水中心良种场和无锡前洲水产良种场)进行遗传多样性分析,从不同引物组合中筛选出8组条带清晰、多态性丰富的引物组合,每个引物组检测到的位点数为12～21个,在3个草鱼群体中共检测到120个位点,其中多态性位点有92个,多态位点比例为76.67%,显示了较高的多态性。野生群体与2个人工繁殖群体多态位点比例分别为67.62%、59.81%、53.33%,平均杂合度分别为0.214 3、0.211 0、0.172 2;邗江野生群体与2个人工繁殖群体间的遗传距离分别为0.098 0、0.115 9,两个人工繁殖群体间遗传距离为0.095 9。结果表明,草鱼人工繁殖群体遗传多样性有所下降。比较各扩增位点显性基因型频率在不同区间的分布发现,人工繁殖群体低频位点明显减少而隐性纯合基因位点显著增加。     

长江口淞江鲈野生种群的采集及人工繁殖研究

淞江鲈(Trachidermus fasciatus Heckel 1840)是一种降海洄游性鱼类,如今在上海内河水系已难见踪迹,为查明长江口水域淞江鲈野生种群是否存在,开展了此项研究。2011年5月,采用拖网方式采得淞江鲈鱼苗51尾;采用淞江鲈工厂化养殖管桶系统模式进行驯养、繁殖和成鱼养殖,至5月底存活40尾,成活率为78.4%,平均全长由(2.9±0.3)cm增长至(3.5±0.3)cm,增长率为20.7%;至10月中旬养成29尾,成活率为72.5%,平均全长为(9.1±1.2)cm,增长率为160.0%。这些成鱼有11对培育成熟用于繁殖,成熟率为75.9%。自行有效产卵6窝,产卵率为54.5%,总产卵量为26 616粒,平均窝卵数为(4 436±647)粒;孵出水花鱼苗24 100尾,孵化率达90.5%。该研究结果表明,目前在东海长江口杭州湾水域,仍有淞江鲈野生种群存在,本研究繁殖的后代原种可作为该种群研究和放流之用。     

硬头鳟人工繁殖技术

硬头鳟为大麻哈鱼属,洄游性冷水鱼类,原产于美国阿拉斯加的Kuskokwin河和加拿大不列颠哥伦比亚省的和平河等水域。硬头鳟与虹鳟亲缘近,体形相似,体表有差异,沿体侧侧线无明显的彩虹带,上半部暗绿色,     

清水江野生大鳍鳠人工繁殖试验

大鳍鳠（Mystusmacropterus）属鲶形目、鲿科、鳠属，俗称江鼠、石扁头、石胡子等，分布于我国长江水系和珠江水系，是一种生长较快、个体较大的经济鱼类。因其无肌间刺，肉质细嫩，味道鲜美，可食部分大，在贵州省清水江等流域是当地群众十分喜爱的土著鱼类。现在由于过度捕捞，江河污染，修建水库（该鱼不能在静水中自然繁殖）等原因，自然资源急剧下降，市场价格不断上升。     

野生岩原鲤的生物学特性及人工繁殖技术

岩原鲤地方名为岩鲤巴、岩鲤、鬼头鱼,英文名：Rockcarp。分类上属鲤形目、鲤科、鲤亚科、岩鲤属。分布于长江中上游干支流,主要分布在云南金沙江永仁江段,其次在四川乐山、贵州修文六广河等有零星分布。其肉质细嫩,味道鲜美,是金沙江最名贵的野生鱼类之一，笔者于2008年开始在龙开口野生鱼类增殖站对其人工繁殖进行了初步研究和试验。     

挪威：鲑鱼养殖有望成为支柱产业

挪威工业大学下属专门从事渔业和农业研究的机构称,如果挪威的鲑鱼养殖业按照目前的增长速度持续发展,那么到2040年挪威国内鲑鱼养殖业的产值将会达到640亿～870亿欧元,与目前挪威石油开采业的产值相等。2010年,挪威名义国内生产总值约为24000亿挪威克朗（约合3200亿欧元）,其中石油和天然气行业占21．0％．     

中华鲟全人工繁殖获重大突破

文汇报讯：被誉为“水中熊猫”的古老物种——中华鲟全人工繁殖在湖北宜昌中国长江三峡集团公司中华鲟研究所三峡坝区研究基地获得重大突破。日前，该研究所养殖的子一代中华鲟个体成功催产并授精。从此，中华鲟人工繁殖可不再依赖稀有野生亲鱼，这对该物种的保护具有里程碑式的意义。     

日本采集到野生鳗鱼受精卵 全球尚属首次

日本研究人员在近日的英国在线科学杂志《自然·通信》上发表论文说,他们成功采集到野生日本鳗鱼的受精卵,这在世界上尚属首次。     

Release during night enhances survival of wild Atlantic salmon smolts

The effect of nocturnal and diurnal releases on survival and migration of wild and hatchery‐reared Atlantic salmon, Salmo salar, L., smolts (n = 82) was investigated by releasing acoustically tagged smolts at the lower end of the River Vosso, Norway. Hatchery smolts was registered in the estuary within hours of their release, whereas wild smolts migrated over a prolonged period. The time of estuary exit was affected by river discharge but not by time of release. Progression rates were slow through the estuary (0.25 BL/s ± 0.18 SD) and fast through the fjord (1.80 BL/s ± 0.69 SD), and they were not affected by the time of release or origin. Survival to the fjord was low (0%–15%). Survival was not affected by body length but was lower for wild smolts than for hatchery smolts, and survival of the former was lower when the fish were released in daylight.     

Inter-stage survival of wild juvenile Atlantic salmon, Salmo salar L.

A biological model was developed to calculate annual survival between life stages of juvenile Atlantic salmon, Salmo salar L., in Catamaran Brook, a small stream basin (52 km²) in the Miramichi River catchment in New Brunswick, Canada. Seven years’ data (1990–1996) were used in the model. Input variables included: daily fish counts and measurements of parr (3–4 age classes), smolts, and adult salmon at a fish-counting fence near the stream mouth; biennial quantification of all habitat types along the watercourse; fish density estimated by electric fishing at 30 sites; and estimates of young-of-the-year emigration via stream drift. Continuous recording of stream discharge provided data to assist in interpretation of survival estimates. Annual survival for juvenile salmon in their first 3 years of life in the stream averaged between 31% and 34%. The greatest annual variation (CV = 0.699) occurred at the egg to 0+ (summer) stage with a low of 9.2% survival recorded for a winter with an atypical midwinter flood event; parr and pre-smolt survival were similarly affected. Survival from egg deposition (after correction for losses caused by predation and retention/non-fertilization) to smolt emigration was between 0.16% and 0.52%, which is low relative to estimates from many other studies. Survival of smolts to returning 1-sea-winter adults (grilse) averaged 8.5%. Potential errors in the computation of the model are discussed, e.g. inaccurate counts of spawning adults during high autumn stream flow. A possible explanation for the low egg to smolt survival was the environmental conditions experienced during various winters. Mean egg survival was 1.3 times higher (39.3%) and egg to smolt survival increased to 1.03% when the two winters characterized by extremely low discharge or midwinter freshets were excluded from the calculation. Density-dependent factors related to a beaver dam, which limited spawning distribution, may also have contributed to poor survival and increased fry emigration in one year. Environmental factors, particularly winter conditions, in streams such as Catamaran Brook may act as bottlenecks to natural production of Atlantic salmon.     

Comparison of techniques for correlating survival and gene expression data from wild salmon

Abstract – In laboratory and field studies of survival, one of two alternative analytical techniques is often used to estimate survival rates and identify covariates, namely parametric survival analysis or Cormack–Jolly–Seber models. These techniques differ in algorithms and assumptions of the data. They also tend to be used under different circumstances depending on whether the intention is to demonstrate group‐specific differences or to predict survival variables. Here, we apply and compare both analytical techniques in a study that couples functional genomics with biotelemetry to ascertain the role of physiological condition on survival of adult sockeye salmon (Oncorhynchus nerka) migrating in the Fraser River, British Columbia, which builds on the growing concern over the decline in numbers of spawning fish. Herein, we show a high level of quantitative and qualitative agreement between the two analytical methods, with both showing a strong relationship exists between the genomic signature that accounts for the largest source of variance in gene expression among individuals and survival in one of the three populations assessed. This high level of agreement suggests the data and the approaches are generating reliable results. The novel approach used in our study to identify physiological processes associated with reduced fitness in wild populations should be of broad interest to conservation biologists and resource managers as it may help reduce the uncertainty associated with predicting population sizes.     

Fecundity, egg size and early hatchery survival for wild Atlantic salmon, from the River Bush

Abstract  A total of 118 wild Atlantic salmon, Salmo salar L., females were stripped at the River Bush Salmon Station. The total number of eggs (fecundity) and egg diameters were compared for three age groups of adults. Adult length explained the majority of the variation in fecundity whilst freshwater age explained the majority of the variation in egg diameter. Parallel regression analysis for the total number of eggs on fish length relation for 3 years (2000–2002) showed significant temporal variation among years. Larger eggs from 2.1+ adults produced longer and heavier swim-up fry than smaller eggs from 1.1+ adults. There was also the suggestion that the survival of eggs from 1.1+ adults was lower than eggs from 2.1+ adults to the swim-up stage.     

Seasonal differences in smolt traits and post-smolt survival of wild Atlantic salmon, Salmo salar, migrating from a northern boreal river

Abstract  Seasonal differences in smolt traits and the post-smolt survival of wild Atlantic salmon, Salmo salar L., were investigated by smolt trapping and Carlin-tagging in the River Simojoki, northern Finland between 1991 and 2004. The annual trapping season was divided into two halves based on the median catch date. Smolt length was significantly higher during the first half of the season, while differences in smolt weight were typically small. Smolt age was always significantly higher during the first half of the season because older smolts tended to migrate earlier in the season. Many smolts migrating during the early season and almost all smolts migrating later had started their new growth, indicating that smolts grow in the spring before sea entry. The differences in recaptures between smolts tagged during the first and second halves were insignificant. Although variations in smolt traits and environmental conditions can produce inter-annual variation in post-smolt survival, their seasonal differences seem to be too small to have an effect.     

Evaluation of partial water reuse systems used for Atlantic salmon smolt production at the White River National Fish Hatchery

Eight of the existing 9.1 m (30 ft) diameter circular culture tanks at the White River National Fish Hatchery in Bethel, Vermont, were retrofitted and plumbed into two 8000 L/min partial water reuse systems to help meet the region's need for Atlantic salmon (Salmo salar) smolt production. The partial reuse systems were designed to increase fish production on a limited but biosecure water resource, maintain excellent water quality, and provide more optimum swimming speeds for salmonids than those provided in traditional single-pass or serial-reuse raceways. The two systems were stocked with a total of 147,840 Atlantic salmon parr in May of 2005 (mean size 89 mm and 8.5 g/fish) and operated with 87–89% water reuse on a flow basis. By the time that the smolt were removed from the systems between March 28 to April 12, 2006, the salmon smolt had reached a mean size of 24 cm and 137 g and hatchery staff considered the quality of the salmon to be exceptional. Overall feed conversion was <1:1. The Cornell-type dual-drain circular culture tanks were found to be self-cleaning and provided mean water rotational velocities that ranged from a low of 0.034 m/s (0.2 body length per second) near the center of the tank to a high of 39 cm/s (2.2 body length per second) near the perimeter of the tank. The fish swam at approximately the same speed as the water rotated. System water quality data were collected in mid-September when the systems were operated at near full loading, i.e., 24 kg/m³ maximum density and 52.1 and 44.1 kg/day of feed in system A and system B, respectively. During this evaluation, afternoon water temperatures, as well as dissolved oxygen (O₂), carbon dioxide (CO₂), total ammonia nitrogen (TAN), and total suspended solids (TSS) concentrations that exited the culture tank's sidewall drains averaged 14.8 and 15.9 °C, of 7.9 and 8.2 mg/L (O₂), 4.0 and 3.2 mg/L (CO₂), 0.72 and 0.67 mg/L (TAN), and 0.52 and 0.13 mg/L (TSS), respectively, in system A and system B. Dissolved O₂ was fairly uniform across each culture tank. In addition, water temperature varied diurnally and seasonally in a distinct pattern that corresponded to water temperature fluctuations in the nearby river water, as planned. This work demonstrates that partial reuse systems are an effective alternative to traditional single-pass systems and serial-reuse raceway systems for culture of fish intended for endangered species restoration programs and supplementation programs such as salmon smolt.     

From Atlantic to Pacific: Price links in the US wild and farmed salmon market

Abstract

In 1990, the US International Trade Commission stated that Atlantic and Pacific salmon species did not share a substitute relationship in any of the product forms. This result is contrary to economic demand studies that show a substitute relationship for Atlantic and Pacific salmon species. Time‐series results reported in this paper are consistent with the earlier demand studies and show evidence of an equilibrium price system that includes Atlantic, chinook and coho salmon species for the US market. For these three salmon species a substitute relationship cannot be rejected. However, we observe only weak price links across the three different species in the different US regional markets.     

Thyroid hormone concentrations in the gonads of wild chum salmon during maturation

Changes in gonadal and plasma concentrations of thyroid hormones were examined at various stages of maturation in chum salmon (Oncorhynchus keta) caught in the Bering Sea and the Bay of Alaska. Plasma concentrations of thyroxine (T₄) were less than 5 ng ml⁻¹, and those of 3,5,3′-triiodo-L-thyroxine (T₃) were less than 2 ng ml⁻¹ I in both males and females, regardless of the degree of sexual maturity or the gonadosomatic index (GSI). There was no clear relationships between circulating thyroid hormone levels and tissue levels. The ovarian T₄ concentrations were undetectable (less than 0.2 ng g⁻¹) or less than 2 ng g⁻¹ when GSI was lower than 1%, but increased thereafter and reached a plateau of 8–10 ng g⁻¹ when GSI became 2%. The ovarian T₃ concentrations were about 5 ng g⁻¹ when GSI was 1%, increased to a maximum level (20 ng g⁻¹) when GSI was about 2%, and decreased to a constant level of 10 ng g⁻¹ thereafter. The T₄ and T₃ content in single oocyte increased proportionally to the oocyte volume, indicating a constant incorporation of the hormones into the oocyte. The T₄ concentrations in the testis were 1 ng g⁻¹ or less regardless of the GS1. On the other hand, the T₃ concentrations were highest (15 ng g⁻¹) when the GSI was less than 1%, decreased thereafter when spermatocytes appeared in the testis, and became about 5 ng g⁻¹ I in testes containing spermatozoa, raising the possibility of a role for T₃ during early gamete and/or gonad maturation of testes.     

Dominance and predator avoidance in domesticated and wild masu salmon Oncorhynchus masou

ABSTRACT:   Dominance, aggression and predator avoidance were compared among farmed, sea-ranched and wild juvenile masu salmon Oncorhynchus masou in laboratory experiments. Domesticated fish (farmed and sea-ranched), which had been exposed to artificial selection, were not dominant against wild fish in pairwise contests, nor did they show greater aggressiveness. Farmed fish did show greater feeding than wild fish. Under chemically simulated predation risk, farmed fish were more willing to leave cover and feed than wild fish, indicating reduced predator avoidance in the farmed fish. Our results indicate that selection for fast growth (domestication) in masu salmon favors fish that respond to food quickly and ignore predation risk.