Changes in enzymatic and structural properties of grass carp fast skeletal myosin induced by the laboratory-conditioned thermal acclimation and seasonal acclimatization

ABSTRACT:   Myosins were prepared from fast skeletal muscles of grass carp thermally acclimated to 10, 20 and 30°C in the laboratory as well as from those seasonally acclimatized and collected in January (winter) 2003 and May (spring), August (summer) and November (autumn) 2002. The maximal initial velocities ( V _max) of actin-activated Mg²⁺-ATPase activity for myosins from the 10°C-acclimated and winter grass carp were 1.7–1.8-fold as high as those from the 30°C-acclimated and summer fish. The inactivation rate constant ( K _D) of Ca²⁺-ATPase for myosin from the 10°C-acclimated grass carp was three to fourfold higher than those for myosins from the fish acclimated to 20°C and 30°C, whereas myosin from winter grass carp was about sevenfold as high as that for myosin from summer fish. Myosins from spring and autumn fish showed K _D values comparable to those of the fish acclimated to 30°C and 10°C, respectively. In differential scanning calorimetry analysis, the transition temperature ( T _m) was observed near 38°C and 45–46°C with most myosins. However, the lowest T _m at 32–33°C was given as one of the major endotherms in myosins from the 10°C-acclimated, autumn and winter fish. These responses of grass carp to changed environmental temperatures were almost similar to those for common carp reported previously.     

Mechanochemical properties of ordinary and dark muscle myosins from seawater fish

Myosin was isolated from two types of muscle, ordinary and dark muscles, of three species of fish living in sea water. The compositions of light chains were visualized by sodium dodecylsulfate-polyacrylamide gel electrophoresis (SDS-PAGE), and the mechanochemical activity was examined by in vitro motility and ATPase assays. Ordinary muscle myosin of either species had three species of light chain, whereas dark muscle myosin had another two species of light chain judged by SDS-PAGE. Sliding velocity of ordinary muscle myosin was in the range of 4.92–6.89 μm/S, whereas that of dark muscle myosin was in the range of 3.07–4.25 μm/s. Therefore, ordinary muscle myosin showed 1.26–1.95 times higher sliding velocity than dark muscle myosin in either species. The ratios of V_max of actin-activated Mg²⁺-ATPase activity of ordinary to dark muscle myosins were correlated quite well to the ratios of sliding velocity. Activity of ordinary muscle myosin was comparable to that of mammalian fast muscle myosin, but that of dark muscle myosin was twice of that of mammalian slow muscle myosin. These results may reflect the essential role of fish dark muscle myosin always used in slow cruising.     

Phytoplankton uptake and growth rate in the Japanese egg cockle Fulvia mutica

To clarify the relationship between the quantity of food ingested by and the growth rate of the Japanese egg cockle Fulvia mutica (Reeve), we conducted a laboratory breeding experiment for 2 weeks and estimated the chlorophyll a (chl-a) concentrations in water and the increments in shell length and soft-body weight of this species under five chl-a concentrations. Moreover, we compared the relationship between cockle growth (changes in soft-body weight and shell length) and their feeding environment observed in the laboratory experiment with the results of a field investigation conducted at two sites in the Sea of Japan, Kumihama Bay (35°38′5″ N, 134°54′00″ E) and Kunda Bay (35°33′30″ N, 135°15′4″ E). The changes in soft-body weight were similar in both laboratory and field investigations, but those in shell length were not. We, therefore, considered shell length changes as unsuitable for evaluating the relationship between growth and feeding in F. mutica. Based on the changes in soft-body weight, it was possible to classify the feeding environment of this species into the following three types: (1) < 1.52 μg chl-a L−1, negative feeding environment for cockle growth; (2) 1.52–5.71 μg chl-a L−1, neutral feeding environment for cockle growth; (3) > 5.71 μg chl-a L−1, positive feeding environment for cockle growth (growth increased with increasing chl-a concentration up to about 11 μg chl-a L−1). These results indicate that maintaining chl-a concentration in the breeding water within 5.71–11 μg chl-a L−1 is desirable for rearing Japanese egg cockle.     

流溪河保护区鱼类群落结构及其时空变动

为了解流溪河光倒刺鲃国家级水产种质资源保护区鱼类群落结构,分析不同河段、不同季节鱼类群落多样性的变化,于2017年12月-2018年10月对保护区上、中、下游的鱼类开展了每个季度一次的调查。调查结果显示,共采集鱼类57种,隶属于5目14科50属,其中鲤形目43种、鲈形目6种、鲇形目5种,合鳃鱼目2种,鳉形目1种;计算57种鱼类的相对重要性指数,结果显示,尼罗罗非鱼、越南■及鲤鱼为2017-2018年度优势种;Shannon-Wiener多样性指数、Margalef丰富度指数和Pielou均匀度指数计算结果显示,下游鱼类群落的多样性及均匀度最高,夏季鱼类群落的多样性、丰富度及均匀度最高;各监测点之间的种类相似性系数显示,保护区上中游、上下游之间鱼类种类组成为中等不相似,中下游种类组成为中等相似,春夏、春冬、夏冬及夏秋季节鱼类种类组成为中等不相似,春秋、秋冬季节为中等相似;ABC分析结果显示,春、夏及冬季鱼类群落处于稳定状态,秋季处于中度干扰状态。     

北部湾西北部近海鱼类资源的时空分布特征研究

根据2012年1月(冬季)、4月(春季)、8月(夏季)、11月(秋季)在北部湾西北部广西近海4个航次的渔业资源调查资料,进一步结合同步测定的水文情况,探讨北部湾西北部广西近海的鱼类资源分布特征和季节变化及其影响因素。调查结果表明,该调查海域共鉴定鱼类125种,鱼类资源质量密度夏季(402.46kg/km^2)>春季(343.22kg/km^2)>秋季(145.13kg/km^2)>冬季(53.99kg/km^2);尾数密度春季(84.34×10~3尾/km^2)>夏季(51.54×10~3尾/km^2)>秋季(26.53×10~3尾/km^2)>冬季(16.81×10~3尾/km^2);平均体长、体质量分别在春季和夏季最大,分别为7.15cm和7.65g;幼体比在夏季最高,为85.86%。从时间上看,春、夏季的鱼类资源密度大于秋、冬季,从空间上看,沿岸水域的资源密度大于近海水域,这与该水域各水团随季节变化的消长密切相关。依据相对重要性指数确定各季节的优势种,二长棘鲷是夏季最重要的优势种,同时也是春、夏、秋3季的共有优势种。通过贡献率β值可知,该区域鱼类总密度变化与主要优势种变化关系密切,且调查海域多为规格较小的幼鱼,其为北部湾渔场重要的产卵场、育幼场和索饵场,对整个北部湾鱼类资源的补充具有重要的作用。     

Differing body size between the autumn and the winter–spring cohorts of neon flying squid (Ommastrephes bartramii) related to the oceanographic regime in the North Pacific: a hypothesis

The neon flying squid (Ommastrephes bartramii), which is the target of an important North Pacific fishery, is comprised of an autumn and winter–spring cohort. During summer, there is a clear separation of mantle length (ML) between the autumn (ML range: 38–46 cm) and the winter–spring cohorts (ML range: 16–28 cm) despite their apparently contiguous hatching periods. We examined oceanic conditions associated with spawning/nursery and northward migration habitats of the two different‐sized cohorts. The seasonal meridional movement of the sea surface temperature (SST) range at which spawning is thought to occur (21–25°C) indicates that the spawning ground occurs farther north during autumn (28–34°N) than winter–spring (20–28°N). The autumn spawning ground coincides with the Subtropical Frontal Zone (STFZ), characterized by enhanced productivity in winter because of its close proximity to the Transition Zone Chlorophyll Front (TZCF), which move south to the STFZ from the Subarctic Boundary. Hence this area is thought to become a food‐rich nursery ground in winter. The winter–spring spawning ground, on the other hand, coincides with the Subtropical Domain, which is less productive throughout the year. Furthermore, as the TZCF and SST front migrate northward in spring and summer, the autumn cohort has the advantage of being in the SST front and productive area north of the chlorophyll front, whereas the winter–spring cohort remains to the south in a less productive area. Thus, the autumn cohort can utilize a food‐rich habitat from winter through summer, which, we hypothesize, causes its members to grow larger than those in the winter–spring cohort in summer.     

山东半岛东南部海域星康吉鳗资源密度时空分布及其与环境因子之间关系

为了解山东半岛东南部海域星康吉鳗资源密度时空变化及其与环境因子之间的关系,实验根据2016年10月和2017年1月、5月、8月山东半岛东南部海域4个航次底拖网调查数据,利用广义可加模型(GAM)分析了星康吉鳗资源密度时空分布特征及其与环境因子之间的关系。结果发现,星康吉鳗资源密度及分布具有明显的季节变化。春季,山东近海星康吉鳗资源密度为66.38 kg/h,夏季资源密度达到一年中最大值,为87.31 kg/h,秋季资源密度为79.01 kg/h,冬季资源密度大幅度降低,仅为10.44 kg/h。GAM模型结果显示,水深和海水底层温度对星康吉鳗资源分布影响最大。春季,星康吉鳗资源密度与水深、底温呈正相关关系,其分布范围较广,主要分布在海州湾中部海域(35°N沿线分布最多);夏季,其空间分布受水深影响,主要集中分布在水深20～30 m的山东半岛南部近岸海域;秋季,水深、底温、饵料生物量与星康吉鳗资源密度呈正相关,此时星康吉鳗分布较分散。冬季,星康吉鳗资源密度与水深呈正相关,此时主要分布在受黄海暖流影响的海州湾北部海域以及123.5°E～124°E海域。研究表明,星康吉鳗资源分布与其洄游习性和海域水温等水文特征的季节性变动有关,其分布特征在春季、冬季分别受青岛冷水团与黄海暖流影响显著。本研究有助于了解山东近海星康吉鳗群体的生活习性,为其资源的养护和管理提供依据。     

北部湾东北部游泳生物资源现状

2009年至2010年对北部湾东北部海域游泳生物调查研究表明,该海域共有游泳生物300种,其中鱼类有209种（硬骨鱼类205种,软骨鱼类4种）,隶属15目、70科、119属;甲壳类76种;头足类15种。底层鱼类100种,近底层鱼类72种,中上层鱼类29种,岩礁性鱼类8种,分别占鱼类总数的47．85％,34．45％,13．87％和3．83％。暖水性鱼类153种,暖温性鱼类55种,冷温性鱼类1种,分别占鱼类总数的73．20％,26．32％和0．48％。游泳生物种类数季节变化为夏季〉秋季〉春季〉冬季;资源密度指数季节变化为夏季〉秋季〉春季〉冬季;渔业资源密度随季节变化为夏季〉秋季〉春季〉冬季,渔业资源年平均资源密度为522．925kg·km^-2,约相当于该海域原始渔业资源密度的1／10;生物多样性指数以夏、秋季最高。估算了北部湾东北部海域潜在渔业资源量为1．092×10^5t·a^-1,最大可捕量为5．460×10^4t·a^-1。比较了北部湾渔业资源的历史变动情况,对渔业资源的进一步养护和管理提出了建议。     

Feed intake,growth and osmoregulation in Arctic charr,Salvelinus alpinus (L.), transferred from freshwater to saltwater at 8°C during summer and winter

The purpose of the current study was to examine seasonal changes in seawater tolerance and growth performance of anadromous Arctic charr (Salvelinus alpinus L.) held at the same temperature (8°C) during winter and summer. Charr (20–27 cm), previously reared in freshwater under natural photoperiod, were transferred either directly (DT) from freshwater to seawater (35 ppt), from freshwater to brackish water (20 ppt), or were gradually adapted (GT) to seawater over a period of 10 days. Control fish were held in freshwater. Feed intake and osmoregulatory ability were then monitored on three occasions during the following 59 days. Two experiments were carried out, one during winter (December–January) and the other during summer (June–July). In both experiments fish mortality was low. Plasma osmolalities recorded in fish transferred to seawater were within normal ranges, but osmolalities on day 10, were significantly lower in summer (313 mOsm/kg (DT), 328 mOsm/kg (GT)) than in winter (323 mOsm/kg (DT), 352 mOsm/kg (GT)). In winter, feed intake and growth rates were high in fish kept in fresh and brackish water, but charr transferred directly to seawater ate little and lost weight. Fish that were gradually adapted to seawater occupied an intermediate position. During summer the observed differences in feed intake were small and all fish had relatively high growth rates. These results suggest that Arctic charr display seasonal changes in feed intake and growth performance that parallel seasonal changes in hypoosmoregulatory capacity. The ability to survive and hypoosmoregulate in full strength seawater does not, however, seem to be a particularly good indicator of successful seawater adaptation with respect to the ability to display high rates of feed intake and growth. During winter, a gradual transfer to seawater appeared to lead to improved feeding and growth compared to direct transfer.     

三都澳四个水产养殖点水质周年变化分析

2011年8月-2012年7月对三都澳四个水产养殖点的营养盐(N、P)、溶解氧(D0)、化学需氧量(COD)、pH值进行了分析,结果表明,无机溶解氮(DIN)组成结构在春、秋、冬季节中主要以NO3-N为主,其次为NH4-N和NO2-N.夏季营养盐结构,NO3-N所占比例明显减低,NO2-N所占比例超过NH4-N.营养盐NO3-N浓度的周年变化为:冬季＞秋季＞春季＞夏季;NO2-N的浓度为:夏季＞秋季＞春季＞冬季;NH4-N浓度:夏、秋偏低,春、冬较高;P04-P的浓度:冬季＞秋季＞夏季＞春季.水体中DO浓度的周年变化为:冬季=春季＞秋季=夏季.pH变化的周年变化为:春季＞冬季＞夏季＞秋季.三都澳四个养殖点周年属于中度营养状态.     

Seasonal adjusted diets to Atlantic salmon (Salmo salar): Evaluations of a novel feed based on heat-coagulated fish mince, fed throughout 1 year in sea: Feed utilisation, retention of nutrients and health parameters

The present paper reports the results of a 1 year experiment using Atlantic salmon with a starting weight of 1.7 kg, and final weight of 7.4 to7.8 kg dependent of diet group. The experiment aimed to evaluate a direct production method of feed where landings from fishing vessels are used directly in feed processing. The dietary compositions followed the natural rhythm in lipid level of the catches of herring in the North Sea (Catch group) adjusted to be stable throughout one season only, and compared to a control diet (constant composition throughout the year) and a designed diet (opposite to the natural biorhythm of salmon lipid stores) (diet group Design). Four seasons were defined: spring (March, April, May), summer (June July August), autumn (September, October, November), winter (December, January, February). All diets varied in protein and lipid due to the adjustment according to season. The experiment was run in triplicate sea cages for each diet, using natural light and temperature regimes (21°N). All diet groups showed equal growth throughout each season, except for the Catch group during autumn showing lower SGR-values. SGR values varied significantly also between seasons for all diet groups, ranging from 0.29 during spring to 0.81 during autumn. Feed conversion ratio varied dependent on season and the dietary protein to energy ratio, at all seasons except winter. Quite a large variation between diet groups and seasons were registered in condition factor. Whole body lipid varied between seasons, as a consequence of dietary lipid levels, and increased as fish weight increased. After autumn growth only, whole body protein levels were significantly lower in the Catch group compared to the two other diet groups. Muscle lipid levels did not vary as a consequence of fish size alone, but varied substantially between seasons in both the Catch and Control groups, but not in the Design group. Muscle alpha-tocopherol and fatty acid profile varied due to diet in spring and autumn seasons, but with minor variations due to diet in summer and winter periods. Only minor influences from diet were registered in liver and heart compositions. Haematological parameters and plasma nutrient values ranged within normal values for salmon, and together with close to no mortality throughout the experiment, fish health was concluded to be good in all diet groups at all seasons. However, plasma asparagine aminotransferase (ASAT) values were quite high during summer and autumn, especially in the control group. These results point to the need of optimizing antioxidant composition of diets during the summer and early autumn season. Overall results show the possibility to obtain acceptable production results when feeding Atlantic salmon a diet adjusted to each season, as long as the fish protein to energy (P:E) requirements are met, further that total body lipid stores varied more than muscle lipid concentrations, and that the lipid levels were highly dependent on season, diet composition and fish size.     

Thermal ecology of subadult and adult muskellunge in a thermally enriched reservoir

The movement of adult muskellunge, Esox masquinongy Mitchill, has been investigated in a variety of systems, but temperature selection by muskellunge has not been examined where well‐oxygenated waters were available over a range of temperatures for much of the year. Thirty subadult and adult muskellunge tagged internally with temperature‐sensing radio tags were tracked from March 2010 to March 2011 in a Tennessee reservoir. Mean tag temperatures were 18.9 °C in spring (March to May), 22.1 °C in summer (June to August), 16.5 °C in autumn and 9.8 °C in winter (December to February). When the greatest range in water temperatures was available (7.1–33.3 °C; May to early August 2010), their realised thermal niche (mean ± 1 SD) was 22.3 °C ± 1.8; the realised thermal niche was affected by fish size (smaller fish selected slightly warmer temperatures) but not sex. An electric generating steam plant discharging warm water resumed operation in January 2011, and most (86%) tagged fish occupied the plume where temperatures were ≈10 °C warmer than ambient water temperatures. No mortalities were observed 15 days later when plant operations ceased. Their affinity for the heated plume prompted concerns that muskellunge will be too easily exploited when the plant operates during winter.     

流沙湾浮游动物群落特征及与鱼贝养殖的关系

为了解流沙湾养殖活动对浮游动物群落的影响,于2015—2016年对流沙湾海区进行了夏(8月)、秋(11月)、冬(2月)、春(5月)4个季度的浮游动物调查,分析了浮游动物群落特征及其与环境因子的相关性。共记录浮游动物18大类119种、浮游幼体17种。浮游动物种类组成以桡足类(45种)和端足类(20种)为主,其次为毛颚类(15种)、水螅水母类(12种)、等足类(6种)等。十足目幼体(Decapod larvae)为春、夏两季的主要优势类群,亚强次真哲水蚤( Subeucalanus subcrassus)、微驼隆哲水蚤(Acrocalanus gracilis)为秋季主要优势种,夜光虫(Noctiluca scintillans )为冬季主要优势种。年均浮游动物丰度和生物量分别为151.53个·m^-3 和73.48 mg·m^-3 。多维尺度分析(nMDS)结果表明,除春季外,流沙湾内湾浮游动物群落组成与外湾差异明显。典范对应分析(CCA)显示,溶解氧、磷酸盐、透明度、温度和硝酸盐等环境因子是影响浮游动物优势种分布的主要因素。在流沙湾海区,鱼类小网箱的养殖活动在夏秋两季对浮游动物群落组成和结构影响较大;贝类养殖区的浮游动物的丰度和生物量明显降低,但浮游动物群落组成及多样性与其它采样点差异不大。     

长江口沿岸碎波带仔稚鱼分布的季节性变动

为进一步探明长江口沿岸碎波带仔稚鱼种类组成和数量分布的季节性变化特征,2006年11月至2007年10月,在长江口沿岸碎波带的13个站位用小型拖网(1 m×4 m,网目1 mm)共采集到仔稚鱼77种,隶属于13目27科63属。各季节出现仔稚鱼种数分别为37、20、13和7种。仔稚鱼是以暖温性种类占绝对优势,按生态类型划分,河口性和淡水性种类为主,其次为海洋性种类,洄游性种类最少。根据优势度曲线可看出,夏季优势种最突出,秋季优势种最不明显。夏季与秋季的共有种最多,均为27种;冬季与春季,冬季与秋季间的共有种最少,均为11种。从数量分布来看,冬季仔稚鱼数量最少,且分布较分散,春季数量有明显增加,夏季数量达最大值,且分布趋于集中。在低盐和淡水的站位St.4、St.5、St.7和St.10,形成了以刀鲚为主要种类的仔稚鱼密集区,平均密度高达2 729尾/站。     

Annual variations in hepatic antioxidant defenses and lipid peroxidation in a temperate fish,common bream Abramis brama (L.)

Alternation of physiological states during the annual cycle (pre-spawning mobilization, spawning energy loss, post-spawning accumulation of energy reserve, declined metabolic activity during the wintering) occurring in the wide temperature range requires high plasticity of fish defense systems. The article presents a 2-year study of hepatic antioxidant defenses and lipid peroxidation in the temperate cyprinid fish, common bream Abramis brama (L.), in relation to basic annual rhythms, such as photoperiodic and temperature cycling, reproduction and feeding activity. The objective of the study was to evaluate the plasticity of antioxidant defenses in bream under normal conditions throughout the annual cycle, by measuring hepatic antioxidants (superoxide dismutase, catalase, glutathione-S-transferase activities and reduced glutathione concentrations) and products of lipid peroxidation (thiobarbituric acid reactive substances concentrations). The results suggested that hepatic levels of antioxidants in bream varied dramatically during the annual cycle allowing bream to develop necessary adaptation and implement reproduction program. The lowest values of all studied antioxidants were witnessed in the middle of winter. In early spring, antioxidant enzyme activities increased rapidly reaching their maxima in late spring and summer. Toward the end of autumn, enzyme activities were declining toward the levels observed before the ice breakup. Spring–summer up-regulation of antioxidant defenses along with increased lipid peroxidation indicated bream to be experiencing mild oxidative stress.     

福建台山列岛周边海域鱼类群落分类多样性研究

根据2012年~2013年在台山列岛周边海域进行的4个航次底拖网调查资料,并结合该海域的历史资料系统整理了台山列岛周边海域鱼类总名录,使用PRIMER 5.0软件计算了该海域鱼类的分类多样性指数,研究了分类多样性指数的季节变化。结果显示,台山列岛周边海域共记录鱼类2纲20目81科150属208种,以鲈形目种类占绝对优势;2012年~2013年调查记录到鱼类2纲11目40科63属77种。台山列岛周边海域鱼类的平均分类差异指数（△+）和分类差异变异指数（+）的理论平均值分别为63.14和378.4。鱼类分类多样性指数（△）秋季最高,春、夏季次之,冬季最低;鱼类分类差异指数（△*）秋季最高,春季次之,夏、冬季较低。研究结果表明,春季鱼类种类数最多,夏、秋季次之,冬季最少,水温和饵料决定了研究海域鱼类种类组成。     

长江口渔场渔业生物群落结构的季节变化

利用2000～2002年在长江口渔场的底拖网调查资料,运用多样性指数和相似性指数,对该水域的渔业生物群落结构季节变化进行了研究。结果表明:该域的渔业生物群落以鱼类为主要生物类群,占有绝对优势;甲壳类和头足类为其次要组成部分,处于生态劣势。群落生物量以秋季最大,春季最小。渔业生物群落的丰度、多样性以及均匀度以春冬季较高,夏秋季较低,造成这种趋势的原因可能是与带鱼(Trichiurusjaponicus)和小黄鱼(Larimichthyspolyactis)的洄游有关。渔获物组成春冬季之间、夏秋季之间的相似性指数较高。     

东海生态系统中鱼卵、仔稚鱼种类组成、数量分布及其与环境因素的关系

为了解当前东海生态系统中鱼卵、仔稚鱼种类组成和数量分布的现状及其变化与物理环境因素的关系,根据2006年11月—2008年6月5个航次的鱼卵、仔稚鱼和物理环境调查资料,对鱼卵、仔稚鱼种类组成、数量分布与产卵场物理环境进行分析,探讨不同季节、不同年份鱼卵、仔稚鱼种类组成和数量分布的变化及其与物理环境的关系。结果显示,5个航次采集到74 813粒鱼卵、16 826尾仔稚鱼,共有135个种类。其中,鉴定到种的有109种,隶属于15目67科99属,还有17个种类仅能鉴定到属、6个种类仅能鉴定到科和3个种类仅能鉴定到目。2006年—2007年秋季、冬季和春季鱼卵、仔稚鱼的种类和数量随着季节变化逐渐增多;2008年春季的种类和数量较2007年春季明显偏少;2008年初夏种类的数量与2008年春季基本相近,但鱼卵的数量明显增多,仔稚鱼的数量基本相近。42种优势种类、重要种类和主要种类构成当前东海生态系统中鱼卵、仔稚鱼种类组成的主要成分。东海表层水温和盐度分布有显著的季节变化。秋、冬季表层水温锋面强度最强,春季次之,初夏最弱;锋面的位置秋季离岸最近,冬季次之,春季和初夏离岸最远,冬季偏南,初夏季节北移。表层盐度锋面主要分布在近岸区域,与岸线大致平行,其强度冬季最强,春、秋季次之,初夏季节最弱。秋、冬季节陆架深水海域的水温较沿岸海域高,鱼类生殖群体在陆架深水高温区产卵;春季和初夏季节沿岸海域明显升温,鱼类生殖群体由深水区向近岸海域进行生殖洄游,产卵场分布由陆架中部向近岸海域扩展,并在近岸海域形成了中心产卵场。鱼卵和仔稚鱼的分布与温、盐锋面和种类的温、盐属性的关系密切,主要分布在温度锋面暖水一侧,并有各自最适宜的温度和盐度范围。水温、盐度与种类的繁殖生物学特性是导致鱼卵和仔稚鱼种类组成与数量发生变化的主要因素;适宜的温度和盐度范围、锋区的辐聚和卷夹作用以及种类的生物学属性是影响鱼卵和仔稚鱼数量分布以及密集分布区形成的主要因素。     

东海有尾类数量分布

根据1997~2000年东海23°30′~33°N、118°30′~128°E海域4个季节海洋调查资料,探讨了东海有尾类数量分布和季节变化。结果表明:秋季有尾类丰度最高,均值为149 ind/100m3,夏季38 ind/100m3,冬季20 ind/100m3,春季9 ind/100m3;有尾类数量在冬春夏季与水温和盐度相关关系不显著,秋季与表温有显著的正相关关系。有尾类数量季节变化机制具有暖水种的特征,这些特征形成与其优势种适温适盐特性有密切的关系。东海有尾类的数量波动,与东海暖流势力消长有密切的联系,也同暖流势力从夏到秋季维持一段时间有密切的关系。在东海,暖流势力较强的海域往往可以成为有尾类高丰度分布区域。秋季有尾类高分布区出现,对东海北部外海绿鳍马面鲀(Navodon septentrionalis)渔场和东海南部的带鱼(Trichiurus lepturus)和日本鲭(Scom ber japonicus)等多种经济鱼类渔场的形成有重要意义。     

胶州湾鱼类资源量的时空分布特征

为了解胶州湾海域鱼类资源数量的时空分布特征,2016—2017年利用底拖网对胶州湾海域开展了4个航次的渔业资源调查。结果显示,胶州湾海域鱼类资源密度存在明显的季节变化。鱼类资源尾数密度以夏季最高(233 427尾/km~2),春季最低(18 080尾/km~2),秋季和冬季分别为32 246、40 746尾/km~2;鱼类资源质量密度以冬季最高(1 593.16 kg/km~2),秋季最低(337.91 kg/km~2),春季和夏季分别为681.96和825.55 kg/km~2。其中,冬季鱼类平均个体质量最大(39.10 g),夏季最小(3.54 g),春季和秋季分别为37.72 g和10.48 g。与历史调查资料相比,30多年来胶州湾鱼类资源发生了较大变化。本次调查鱼类资源密度(1 593.16 kg/km~2)低于1981—1982年(10 857.00 kg/km~2)和2008—2009年(2 196.00 kg/km~2);鱼类平均个体质量为10.60 g,低于1981—1982年(37.70 g),鱼类群落结构明显呈现小型化和低质化趋势。这些变化可能主要是由于人类活动对鱼类栖息地的破坏和海洋生态环境恶化造成的。