南极半岛邻近海域南极大磷虾(Euphausia superba Dana)的数量组成和分布

根据2010年1月23日?2月13日在南极南设得兰群岛和南奥克尼群岛邻近海域渔场采集的南极大磷虾(Euphausia superba Dana)样品,分析了南极大磷虾数量、个体体长分布和发育期组成等种群结构特点。样品由330 μm和500 μm浮游生物网垂直拖网和表层水平拖网两种采集方式所获。结果显示,采集样中,南奥克尼群岛水域的南极大磷虾平均密度为1.92 ind/m3,高于南设得兰群岛水域的相应值(0.35 ind/m3);出现的南极大磷虾个体发育期包括CI至CIII期原蚤状幼体、FI至FIV期和FVI期蚤状幼体、未成体、成体(包括雌体和雄体);各发育期个体中,原蚤状幼体数量较多;原蚤状幼体、蚤状幼体、未成体及成体的体长范围(平均体长)分别为1.76–4.96 mm (3.48 mm)、3.95–14.80 mm (5.96 mm)、16.87–39.85 mm (36.10 mm)、40.00–58.96 mm (43.94 mm)。CIII期原蚤状幼体和FI期蚤状幼体的生长率较高。推测,南奥克尼群岛水域南极大磷虾生殖季节始于9月末,集中出现在12月中上旬;而南设得兰群岛生殖季节应早于上述水域。比较两种采集方式,南极大磷虾在水平网中的出现频率和个体出现数量均高于垂直网采集样的相应值,建议传统垂直拖网与水平拖网两种采样方式有效结合,可促进更全面了解大磷虾水平分布和种群结构特点。     

南极半岛邻近海域长臂樱磷虾的数量分布与生长发育

利用2010年1月23日~2月13日在南极半岛邻近海域南设得兰群岛（CCAMLR 48.1亚区内）和南奥克尼群岛（CCAMLR 48.2亚区内）南极大磷虾Euphausia superba Dana渔场采集的浮游动物样品,对长臂樱磷虾Thysanoessa macrura G.O.Sars数量密度、体长分布及发育期组成等进行了研究;样品由330 μm浮游生物垂直拖网和500μm表层水平拖网采集。调查海域表层水温范围为0.37～2.49 ℃,平均1.58℃;盐度范围为32.91～34.32,平均33.88。长臂樱磷虾广泛分布于调查水域;以垂直网样计,48.1亚区的平均密度为261.6 ind/1 000m3,48.2亚区为391.5 ind/1 000 m3,各站位的分布密度与表层水温呈显著正相关（P=0.04）。长臂樱磷虾由CII期原蚤状幼体至成体间的所有发育期个体组成,以蚤状幼体数量居多;蚤状幼体、未成体及成体的体长范围与平均体长分别为2.74～6.80 mm、5.15 mm,6.81～16.20 mm、8.15 mm,15.40～20.70 mm、17.98 mm。蚤状幼体各期生长率范围为0.013～0.064 mm/d,两亚区间无显著差异（P=0.37）,各期均值为0.040 mm/d;48.1亚区长臂樱磷虾生殖季节的估测结果为9月末~10月,48.2亚区内为10月初~11月中旬。长臂樱磷虾在水平网中的出现频率和个体出现数量均高于垂直网,说明在磷虾水平分布和生长发育研究中,水平拖网可作为垂直拖网的有效补充发挥重要作用。     

南极半岛邻近水域南极大磷虾商业捕捞群体的年龄结构时空变化

2009/2010和2010/2011两渔季,我国渔轮在南极公约区内、位于CCAMLR48.1亚区邻近南设得兰群岛和48.2亚区邻近南奥克尼群岛的南大西洋水域开展了南极磷虾捕捞作业。根据两渔季采集的捕捞群体中南极大磷虾体长及性比资料,利用体长频数的混合分布法,比较和分析了两渔季我国商业捕捞所获南极大磷虾Euphausia superba Dana的种群年龄结构特点。结果表明,2009/2010和2010/2011渔季夏至秋初(12月～翌年4月),近南极半岛的南设得兰群岛和南奥克尼群岛附近水域,南极大磷虾捕捞群体中至少有5个年龄组,雌雄性比、种群年龄组成存在较为明显的年间和季节、区域差异。48.1亚区近南设得兰群岛水域,2009/2010和2010/2011渔季的1月和12月,南极大磷虾以5+龄虾数量最多,雌性临产个体占相当比例(>40%),雌性临产个体的年龄分布为3+～5+龄,以5+龄为主。而48.2亚区邻南奥克尼群岛的水域,2009/2010渔季的2月,以5+龄虾数量最多,出现一定比例的5+龄雌性临产个体;2010/2011渔季2～4月连续3月,随时间后移,该水域的大磷虾年龄构成由复杂转为单一;以3+龄虾数量最多,雌雄比值增加;雌性临产个体由很少至基本不出现(<1%);各年龄组生长率随月减少,3～4月均为负值。由上述结果推测,2010/2011渔季南极大磷虾产卵高峰期应早于2011年2月,较2009/2010渔季有所提前。     

南极磷虾(Euphausia superba)脂肪与蛋白含量的季节变化

为了有效提取营养功效和附加值均更高的磷虾油,对南极磷虾(Euphausia superba)资源的综合开发利用提供参考,利用2013年7-8月和2013年12月-2014年5月在南乔治亚群岛和南设得兰群岛附近海域采集的南极磷虾样品,采用索氏抽提法,分别用无水乙醇、丙酮、石油醚、正己烷、乙酸乙酯、环己烷6种常见的有机溶剂作为提取试剂,对南极磷虾体内的脂肪进行提取,并确定最佳萃取溶剂.同时对南极磷虾脂肪、蛋白含量的季节变化及其与体长的关系进行了分析.结果显示,无水乙醇为南极磷虾脂肪提取的最佳溶剂.南乔治亚群岛海域7-8月南极磷虾脂肪含量和蛋白含量(干重)分别为(22.03±0.51)％和(64.52±0.16)％;其中,全长小于40 mm的磷虾个体,脂肪与蛋白含量均显著高于全长大于40 mm的个体(P＜0.05).从南极的初夏到秋末,南设得兰群岛海域的南极磷虾脂肪含量呈逐渐上升趋势,由12月的(19.83±0.04)％上升至翌年4月的最大值(30.584±0.02)％;5月则略有降低,为(28.66±0.03)％.与此相反,南极磷虾的蛋白含量则是12月最高、4月最低,分别为(66.75±0.14)％和(58.02±0.23)％;脂肪含量与蛋白含量呈显著负相关(P=0.005).研究结果对南极磷虾渔业及其生产安排具有直接的指导意义.     

南极磷虾(Euphausia superba)脂肪与蛋白含量的季节变化

为了有效提取营养功效和附加值均更高的磷虾油,对南极磷虾(Euphausia superba)资源的综合开发利用提供参考,利用2013年7-8月和2013年12月-2014年5月在南乔治亚群岛和南设得兰群岛附近海域采集的南极磷虾样品,采用索氏抽提法,分别用无水乙醇、丙酮、石油醚、正己烷、乙酸乙酯、环己烷6种常见的有机溶剂作为提取试剂,对南极磷虾体内的脂肪进行提取,并确定最佳萃取溶剂。同时对南极磷虾脂肪、蛋白含量的季节变化及其与体长的关系进行了分析。结果显示,无水乙醇为南极磷虾脂肪提取的最佳溶剂。南乔治亚群岛海域7-8月南极磷虾脂肪含量和蛋白含量(干重)分别为(22.03±0.51)%和(64.52±0.16)%;其中,全长小于40 mm的磷虾个体,脂肪与蛋白含量均显著高于全长大于40 mm的个体(P0.05)。从南极的初夏到秋末,南设得兰群岛海域的南极磷虾脂肪含量呈逐渐上升趋势,由12月的(19.83±0.04)%上升至翌年4月的最大值(30.58±0.02)%;5月则略有降低,为(28.66±0.03)%。与此相反,南极磷虾的蛋白含量则是12月最高、4月最低,分别为(66.75±0.14)%和(58.02±0.23)%;脂肪含量与蛋白含量呈显著负相关(P=0.005)。研究结果对南极磷虾渔业及其生产安排具有直接的指导意义。     

光照条件下南极磷虾的行为观察

2010—2011年随中国大型拖网加工船“安兴海”轮在南极南奥克尼群岛附近进行南极磷虾拖网作业,将作业过程中采集到的鲜活南极磷虾立刻转移至实验水箱,进行暂养并观察其行为。实验样本为45尾,体长为37~50 mm,整个实验持续时间为13 d,水面光照为220 lx,水温恒定在0 ℃。通过观察发现:(1) 南极磷虾进入实验水箱后体色迅速变为透明;(2) 在静水环境中,南极磷虾多数时间位置相对固定,集中于角落,沿箱壁进行角落间游动,较少穿过水箱中央,穿过水箱中央时有加速游动的现象;动水环境中能够顶流游动并形成集群,0.5 m/s时顶流游动,流速超过1 m/s时,集群消失;水流对南极磷虾的集群有极显著影响;(3) 南极磷虾进入水箱后第6天开始蜕壳,第6~9天均发现虾壳,实验对象平均体长增长5~8 mm。     

南极磷虾调查CPUE指数变动的影响因素初步分析

根据2010年1月~2月在南极南设得兰群岛和南奥克尼群岛周围水域开展的南极磷虾拖网调查期间收集的数据,对南极磷虾CPUE指数变动的影响因素(包括表温、水深、拖速和拖曳深度)进行了分析。结果表明:(1)开始捕捞至结束捕捞的表温相差较小时,平均CPUE相对较高(250 kg/min);(2)起放网表温在0.5~1.0℃和1.0~1.5℃时,平均CPUE均较高(250 kg/min);(3)当海底平均深度大于2 000 m时,CPUE均最低(100 kg/min);(4)随着拖速和拖曳深度的增加,平均CPUE逐渐减小,当拖速小于2.5 kn及拖曳水深小于25 m时,平均CPUE达到最大,分别为364.46 kg/min和347.59 kg/min。本研究结果可为开发南极磷虾资源提供基础数据,并为海上生产提供指导性参考。     

从拖网逃逸南极磷虾的死亡率评估

正本研究的总体目标是估算在目前的商业捕捞渔业中从采用最常用网目尺寸(16 mm)的网囊中逃逸的南极磷虾的死亡率。在南奥克尼群岛外进行了试验,试验使用了一项网囊包覆采样技术保留住从网囊逃逸的磷虾,随后在容留池中观察,监测磷虾的死亡率。结果表明,体长较小的磷虾死亡率较高。但采样水深、拖网持续时间和渔获积聚,还有船上的处置方式如暴露在不同温度下等差异,可能增加了实     

2010/2011年夏季南设得兰群岛北部水域南极磷虾的种群组成

为了解中国南极磷虾渔业主要渔场——南设得兰群岛水域南极磷虾种群动态,利用渔业科学观察员收集的生物学数据,在将研究区域划分成10′×10′小尺度单元的基础上,实验分析了南设得兰群岛夏季南极磷虾种群组成的时空特征。结果表明,23个单元中,雌性未成体(F₂)的比例最高(42.1%),其次为雌性成体(F₃,35.6%),雄性个体所占比例不足20%,且均为未成体(M₂),而幼体(I₁)的比例仅占2.7%。12月中旬,I₁阶段的磷虾个体占有一定的比例(9.6%),M₂阶段磷虾个体比例较F₃阶段高。12月下旬的情况与1月上旬较为相似,I₁个体未出现在调查样本中,M₂阶段磷虾个体比例下降,F₃阶段磷虾个体比例明显上升。M₂、F₂和F₃阶段的磷虾个体在各水层中的分布模式较为相似(PSI=90.9～97.7)。I₁阶段磷虾个体主要分布在60～80 m水层(66.9%),而其它3个性成熟度的磷虾个体主要分布在40～60 m水层。     

基于渔业调查的利文斯顿岛西南部2012年秋冬季南极大磷虾体长时空分布

基于南极磷虾渔业科学观察员收集的南极大磷虾(Euphausia superba)体长数据,将研究区域划分成经纬度10'×10'小尺度单元,分析了利文斯顿岛西南部水域2012年秋冬季南极大磷虾体长分布的时空特征。结果表明,10个单元的平均体长范围为35.3～51.0 mm,其中最小体长为23.1 mm,最大体长为61.0 mm,各单元间体长分布存在显著性差异。由秋末转至冬初,南极大磷虾平均体长及优势体长范围均呈逐渐减小趋势。14～16时和22～24时南极大磷虾个体较小,而4～6时、8～10时以及20～22时的南极大磷虾则以大个体为主。一半以上(72%)的样本分布于40～80 m水层。80 m以深水层,南极大磷虾个体均大于38 mm。随着海区水深的增加,南极大磷虾平均体长逐渐减小,且南极大磷虾体长组成在不同水深海区呈现不同的分布模式。     

Age,growth, maturity and the overfishing of the iconic sciaenid,Argyrosomus japonicus,in south-eastern,Australia

Mulloway (Argyrosomus japonicus) occur in estuarine and coastal waters surrounding Australia, Africa, India, Pakistan, China, Korea and Japan, where they are important in fisheries. This study identified that mulloway in south-eastern Australia had similar growth rates, but matured at smaller lengths and younger ages, to those in South Africa and Western Australia. Growth of both sexes was similar to about 5 years, after which females grew faster and attained a greater maximum length than males. Female mulloway matured at 4–5 years of age with a L₅₀ of 68 cm, whereas males matured at 2–3 years of age with a L₅₀ of 51 cm. The commercial fishery in New South Wales was characterised by declining catches and a reduction in the proportion of mulloway of mature lengths in landings. During 2002–2005 commercial landings were dominated (83%) by fish within 15 cm of the current minimum legal total length of 45 cm and aged 2 and 3 years (>80%), even though mulloway can attain lengths of 200 cm and live >30 years. Estimates of the rates of instantaneous total mortality ranged between 0.34 and 0.45, whilst the rate of instantaneous natural mortality (M) was estimated to be approximately 0.12. Yield-per-recruit analyses indicated that mulloway in New South Wales are being growth overfished and substantial increases in yield could be achieved by increasing the length at first harvest. Values of the spawning potential ratio were below 0.2 under a range of mortality estimates, suggesting that mulloway are at risk of recruitment overfishing. These results suggest that the spawning stock of mulloway in south-eastern Australia has been depleted and that remedial management action is required to protect this iconic species.     

Factors influencing the abundance of the common bully, Gobiomorphus cotidianus McDowall, in small, North Island, New Zealand, lakes

Adult common bullies, Gobiomorphus cotidianus McDowall, are small (total length =  30–120 mm), benthic fish commonly found in the littoral zones of New Zealand lakes where they are a major prey species for trout and eels. Differences in their relative abundance (CPUE) were determined between 21 shallow North Island lakes. Mean CPUE ranged from 2 to >  1000 fish net^{− 1} night^{− 1} and was inversely related to water transparency. The abundance of bullies was not reduced in lakes containing rainbow trout, Oncorhynchus mykiss (Walbaum), but was reduced in all lakes containing self-recruiting populations of eels, Anguilla spp. Mean densities of planktonic larval bullies in the limnetic zone were also inversely related to water transparency. Since low water transparency is related to increased trophic status for these lakes, the abundance of bullies is likely to be related to lake productivity, rather than turbidity.     

Nitrite Toxicity to the Razorback Sucker,Xyrauchen texanus,and the Bonytail,Gila elegans

ABSTRACT

Aquaculture for the purpose of supplementing natural recruitment is one approach used to assist the recovery of endangered fish populations. A common consequence of high-density culture is the accumulation of nitrite in the water. Razorback suckers (Catastomidae; Xyrauchen texanus) survived a 72-hour exposure to 25 mg/L nitrite-N. Bonytails (Cyprinidae; Gila elegans) died within 48 hours of exposure to 10 mg/L and 25 mg/L nitrite-N. A chloride:nitrite ratio of 5 (as either calcium chloride or sodium chloride) protected bonytail from nitrite toxicity. This study provides some basic knowledge that can be applied to the culture of these two endangered species and raises some interesting questions about the nature of nitrite toxicity and inhibition of toxicity in these two species.     

Interspecific competition between the round goby,Neogobius melanostomus,and the logperch,Percina caprodes,in the Duluth‐Superior Harbour

The Laurentian Great Lakes have been the site of numerous aquatic invasive species such as the sea lamprey, zebra mussel and round goby. To further understand interactions between invasive and native species in situ, competitive interactions between native logperch (Percina caprodes) and invasive round goby (Neogobius melanostomus) were examined using submerged enclosures in the Duluth‐Superior Harbour. Experiments were conducted on rocky or sandy substrate throughout the spring and summer months. Trials consisted of single fish, paired conspecifics or round goby/logperch pairs with weight change determined after 28 days. The round gobies were able to outcompete and/or negatively affect logperch on rocky substrates as a direct result of round goby/logperch interactions, as logperch fared well when round gobies were excluded from the enclosures. Although there is evidence that round gobies exclude logperch from rocky substrates, the logperch population remains close to pre‐invasion levels in the predominantly soft‐bottomed harbour. The continued coexistence of the logperch with the round goby is attributed to the vastly greater area of soft‐bottom vs. rocky substrate in the harbour, with the round gobies in the soft bottom younger and smaller than those in the rocky substrate. Recent evidence suggests that the round goby population is declining on the soft substrates indicating that the two populations will continue to coexist in the harbour.     

Optimizing the essential fatty acids, eicosapentaenoic and docosahexaenoic acid, in the diet of the prawn, Penaeus monodon

The dietary requirements of Penaeus monodon for eicosapentaenoic (20:5n‐3; EPA) and docosahexaenoic (22:6n‐3; DHA) acids were examined. These requirements were examined when dietary levels of linoleic (18:2n‐6; LOA) and linolenic acids (18:3n‐3; LNA) were also provided at previously established optimal levels of 14 and 21% respectively of the total lipid fatty acids. A 5 × 5 factorial design was used with incremental amounts (0, 4, 8, 12 and 16% of total fatty acids) of EPA and/or DHA. An additional diet containing cod‐liver oil was provided as a reference diet. The total lipid content of all of the 25 treatments and reference diets was maintained at the same level of 75 g kg^?1. Growth of prawns fed with the reference diet after 50 days was 244 ± 21%. The greatest response to singular additions of EPA or DHA was with a 12% inclusion of either fatty acid, resulting in 287 ± 21 and 293 ± 18% weight gain, respectively. Growth was generally better when combinations of EPA and DHA were used, the optimal combination being EPA 4% and DHA 4%, resulting in 335 ± 25% weight gain. Addition of high levels of either of the highly unsaturated fatty acids (HUFA) in the diet had a negative effect on growth. Digestibilities of the total neutral lipid and specific fatty acids were examined during the growth trials. The digestibility of total neutral lipid was usually higher when either or both HUFA were present, however there were few significant differences between treatments that contained either or both HUFA. Following the growth trials, digestive glands (DG) of prawns fed with the various diets were analysed to determine the total lipid content and fatty acid composition. Total lipid in the digestive gland increased with the inclusion of DHA, but was not significantly affected by the addition of EPA. The fatty acid composition of the digestive gland lipid generally reflected that of the diet. However, the maximum retention of EPA (11.1% of total DG fatty acids) and DHA (10.7% of total DG fatty acids), was not directly proportional to the amount of either fatty acid present in the diet. These results demonstrate that both EPA and DHA have considerable growth promoting capacity. This growth promoting capacity is enhanced when an optimal balance of both fatty acids are incorporated into the diet.     

Differences in the digestive biochemistry between the intertidal clam, Ruditapes decussatus, and the subtidal clam, Venerupis pullastra

The present study was aimed to evaluate differences in physicochemical characteristics (pH and temperature optima) of the main digestive enzymes (amylase, cellulase, laminarinase, and protease) in two commercially important bivalves, the intertidal clam, Ruditapes decussatus, and the subtidal clam, Venerupis pullastra, as well to assess individual variability of such activities. The assays were performed on extracts obtained from the digestive glands and crystalline styles of individuals collected in the wild and laboratory-conditioned during 1 week. In both species, maximum activity for amylase and cellulase was measured at pH 6 and that of laminarinase at pH 5.5, while pH profiles of protease activity showed important differences between them. Temperature profiles also showed interspecific variations, mainly in laminarinase. Carbohydrase activities were comparatively much higher in R. decussatus and proteolytic activities in V. pullastra. The observed differences both in physicochemical characteristics and relative importance of digestive enzymes are discussed in relation to the amount and type of food available in their respective habitats.     

Population structure,genetic diversity,and colonization history of the eastern pondmussel,Sagittunio nasutus,in the Great Lakes drainage

1. The eastern pondmussel, Sagittunio nasutus (Bivalvia: Unionida), has declined in abundance and distribution in eastern North America over the last few decades. The declines are predominantly the result of infestation by invasive dreissenid mussels and changes in habitat. The species is now considered imperilled across large portions of its distribution, especially in the Laurentian Great Lakes region.
2. The genetic diversity and structure of the remnant populations in the Great Lakes region were assessed using 10 newly developed microsatellite DNA loci for S. nasutus. Understanding the remaining populations can inform future management projects and determine whether the remnant populations have experienced a genetic bottleneck or a founder effect. We hope that this will inform the conservation of other species in regions founded by, and isolated from, a more genetically diverse source population or with disjointed geographical distributions.
3. Focusing on the Great Lakes region, samples (n = 428) from 62 collection sites in 28 water bodies were collected. Across the locations sampled for S. nasutus 11 genetic populations were identified, with significant genetic differentiation among them. The genetic structure of the species was assessed, with genetic similarities among populations compared and with geographical routes of colonization and gene flow evaluated.
4. Initial colonization from the Atlantic coast into Lake Erie and Lake Ontario is evident, followed by colonization events into nearby inland rivers and lakes. Analyses found evidence of inbreeding in all but one population and evidence of past genetic bottlenecks or strong founder effects in all but four populations. This study deepens our understanding of the genetic past and present of this imperilled species, providing conservation suggestions for the future management of the species.