山东半岛南部产卵场鳀鱼生殖群体结构及其变化

根据2000～2004年在山东半岛南部鳃鱼（Engraulis japonicus）产卵场多学科综合调查所获得的资料及1991年等相关历史资料，从体长组成、集群特征、年龄结构、性腺成熟度、性成熟系数、性比、摄食强度等多个方面研究了鳃鱼生殖群体结构及其变化特征。结果表明：（1）鳃鱼生殖群体全长组成范围为6～16cm，优势长度9～12cm，长度组成年代际变化明显，生殖群体组成趋向小型化；（2）生殖群体由1-4龄鱼组成，与1991年相比1龄鱼比例增加，生殖群体的平均年龄减小；（3）6月上旬进入产卵盛期，鳃鱼雌性个体性腺成熟度以Ⅳ期、ⅤA期占优势，6月下旬Ⅳ期和ⅤA期比例减少，VB期和Ⅵ—Ⅳ期比例增加，7月上旬Ⅳ—Ⅲ期和Ⅳ—Ⅱ期比例占优势，盛产期结束；（4）鳃鱼生殖期间摄食强度较弱，空胃率超过60％。（5）生殖群体按个体大小集群产卵，各群聚优势长度组成存在明显差别，性腺发育程度不一致。本文还对鲤鱼资源衰退给生殖群体结构和种群补充造成的影响进行了初步讨论。

黄海中南部水域鳀鱼脂肪含量的季节变化

根据 2 0 0 2年 6月～ 2 0 0 3年 5月黄海中南部水域鱼 (Engraulisjaponicus)的调查资料 ,分析其脂肪含量与叉长、性别以及水分含量的关系。产卵前期 (5月)、产卵盛期 (6月 )和越冬期 (1月 )脂肪含量同叉长呈显著正相关 (P <0 .0 1 ) ,而在产卵中后期 (7～ 1 0月 )无显著相关性。在 5～ 1 0月雌性脂肪含量比雄性高 ,其中 5月差异最大。不同季节、不同性别的脂肪和水分含量呈显著负相关(P <0 .0 1 )。脂肪和水分含量变化幅度很大 ,分别为 0 .54 %～42 .97%、36.31 %～ 85 .45%。产卵前期平均脂肪含量最高 ,产卵盛期和越冬期较高 。

Variation in the distribution of wintering anchovy Engraulis japonicus and its relationship with water temperature in the central and southern Yellow Sea

In the present study,we investigated a shift in the spatial distribution of wintering anchovy(Engraulis japonicus)and its relationship with water temperature,using data collected by bottom trawl surveys and remote sensing in the central and southern Yellow Sea,during 2000–2015.Our results indicate that the latitudinal distribution of wintering anchovy varied between years,but there was no consistent pattern in the direction of change(north or south).Wintering anchovy did not move northward with increasing water temperature.However,the latitudinal distribution of wintering anchovy correlated well with 10°C and 11°C isotherms.The results of both a one-step and a two-step generalized additive model indicated that water temperature was associated with both presence and biomass of wintering anchovy.This paper is the fi rst to systematically examine the relationship between anchovy distribution and water temperature using a variety of techniques.All the fi ndings confi rm the impact of water temperature on wintering anchovy distribution,which has important implications for the continued management of the anchovy resource and the enhancement of marine fi shery resources in the Yellow Sea,especially as the climate changes.However water temperature only partly explains the species distribution of anchovy,and stock characteristics also aff ect fi shery distribution.Therefore,other factors should be considered in future research.

Effects of spatio-temporal and environmental factors on distribution and abundance of wintering anchovy Engraulis japonicus in central and southern Yellow Sea

We investigated the spatio-temporal and environmental factors that affect the distribution and abundance of wintering anchovy and quantifi es the infl uences of these factors. Generalized additive models(GAMs) were developed to examine the variation in species distribution and abundance with a set of spatiotemporal and oceanographic factors, using data collected by bottom trawl surveys and remote sensing in the central and southern Yellow Sea during 2000–2011. The fi nal model accounted for 28.21% and 41.03% of the variance in anchovy distribution and abundance, respectively. The results of a two-step GAM showed that hour, longitude, latitude, temperature gradient(TGR), and chlorophyll a(Chl- a) concentration best explained the anchovy distribution(presence/absence) and that a model including year, longitude, latitude, depth, sea surface temperature(SST), and TGR best described anchovy abundance(given presence). Longitude and latitude were the most important factors affecting both distribution and abundance, but the area of high abundance tended to be east and south of the area where anchovy were most likely to be present. Hour had a signifi cant effect on distribution, but year was more important for anchovy abundance, indicating that the anchovy catch ratio varied across the day but abundance had an apparent interannual variation. With respect to environmental factors, TGR and Chl- a concentration had effects on distribution, while depth, SST, and TGR affected abundance. Changes in SST between two successive years or between any year and the 2000–2011 mean were not associated with changes in anchovy distribution or abundance. This fi nding indicated that short- and long-term water temperature changes during 2000–2011 were not of suffi cient magnitude to give rise to variation in wintering anchovy distribution or abundance in the study area. The results of this study have important implications for fi sheries management.

Uncertainties in Stock Assessment and the Precautionary Management Suggestions for the Anchovy (Engraulis japonicus) Stock in the Yellow Sea

Anchovy(Engraulis japonicus) is an abundant fish species in the Yellow Sea,and its natural stock is decreasing rapidly in recent years. Based on the stock-recruitment(SR) data from 1987 to 2002 published in Zhao et al.(2003),the criterion BIC(Bayesian Information Criterion) is applied to selecting a suitable model from six normal and lognormal error structured SR statisti-cal models,the age-structured model is used to calculate the biological reference points(BRPs),and the precision of the SR parame-ters and BRPs are calculated using bootstrap method. The results indicate that the anchovy fishery resource in the Yellow Sea is in an over-fished state. The precaution management principle requires that the fishery should be closed immediately.