【作者】 李忠炉；

【导师】 金显仕；

【作者基本信息】 中国科学院研究生院（海洋研究所） ， 海洋生态学， 2011， 博士

【摘要】 鱼类作为海洋生态系统的重要组成部分,为人类提供大量的优质蛋白,在满足市场需求和保障食物安全方面发挥了巨大作用。但是随着人类活动(过度捕捞)和环境变化的加剧,海洋鱼类的生物学特性和种群动态发生了显著变化,进而影响了海洋生态系统的服务和产出功能。因此,本研究以黄渤海三种底层高营养级鱼类小黄鱼、大头鳕和黄鮟鱇作为研究对象,基于其在我国重要的渔业海域黄渤海的底拖网调查和取样资料(小黄鱼、大头鳕和黄鮟鱇资料的时间跨度分别为1960-2010年、1999-2009年和1985-2009年),分析其生物学特征和种群相对资源密度在捕捞和环境变化双重压力下的年际变化,以期为全球变化背景下海洋渔业种群动态的数值模拟提供基础数据,同时也为渔业资源的保护和合理开发利用提供科学依据。从1960年到2010年,多数年份内小黄鱼雌雄个体之间体长-体重关系参数b无显著差异(P>0.05);参数a和b呈极显著负线性关系(P<0.01),参数a的对数lga与b的比值为常数,与鱼体密度有关。小黄鱼黄海北部-渤海群系雌雄群体从1960年到2004年以等速生长为主,参数b在资源严重衰退期(1982-1983年)和资源恢复初期(1993年)有所增大;黄海南部群系雌雄个体从1960年到2010年以负异速生长为主,b在资源严重衰退期(1986年)和资源恢复初期(1994年)呈减小趋势,20世纪90年代后期开始逐渐升高。小黄鱼黄海北部-渤海群系雌雄个体的肥满度从1960年到2004年总体呈减小趋势;黄海南部群系雌雄个体1986年的肥满度极显著小于对应群体1960年的肥满度(P<0.05),此后略有升高,但年间差异不显著(P>0.05)。分析认为,性成熟比例的变化和差异是两个群系参数b变化和差异的主要原因;雄性参数b的变化与捕捞压力呈现较好的协同关系,当资源密度升高时,b值增大。1960年到20世纪80年代中期小黄鱼肥满度的减小主要原因是性成熟年龄的减小,20世纪90年代后小黄鱼两群系肥满度的变化与生活区海表温度(SST)的变化相对应,SST越高,肥满度越高。从1960年到2010年,小黄鱼雌性个体的50%性成熟体长(L50)和年龄(A50)呈减小趋势,其中黄海北部-渤海群系由152.8 mm减小到105.3 mm,黄海南部群系由184.4 mm减小到110.1 mm,A50分别由1.5 a和2.4 a减小到1 a左右。ARSS分析显示,两个群系内性成熟曲线在间隔时间较长时(≥4年)变化极显著(P<0.01),但在较短时间间隔内(<4年)差异不显著(P>0.05);群系之间性成熟曲线差异极显著(P<0.01),表明两个群系的性成熟模式不同。相关性分析表明种群生长参数和SST的变化是L50变化的影响因子。小黄鱼幼鱼生长速度的加快和极限体长的减小,可使其L50减小,由于幼鱼生长速度的加快和种群极限体长的减小主要由过度捕捞引起,说明过度捕捞是小黄鱼性成熟体长减小的原因;海表温度日升高率(TDIR)与黄海北部-渤海群系的L50呈负相关关系,海表温度升高快,L50减小;而SST与黄海南部群系性成熟速率(δ)呈负相关关系,表明较高的SST会使黄海南部群系δ减小,这主要因为黄海南部的SST高于小黄鱼的最佳产卵温度,并使种群向黄海深部和冷水团区域移动导致。此外,小黄鱼承受的持续高强度捕捞压力,会促进其性成熟基因的变化,使A50向低龄进化。2000年以来,小黄鱼黄海北部-渤海群系的相对资源密度较1985年明显升高,且较为稳定;黄海南部群系的相对资源密度从1985年到2010年呈逐年减小趋势。小黄鱼两个群系的相对资源密度通常以秋季最高,这由当年生个体大量进入渔场所致,但部分发生春季厄尔尼诺事件(El Ni?o, EN)的年份,黄海南部群系春季时相对资源密度最高,这可能由SST升高引起东海北部产卵场中的产卵群体向北移动导致。在发生EN事件的年份,江苏省小黄鱼产量在当年和之后1-2年均较高。黄海大头鳕主要分布在35°N以北海区,与20世纪50年代相比向北移动了约0.5°;2007-2009年冬季大头鳕的相对资源密度较1999-2002年升高,优势年龄由I龄组升高到III龄组;体长-体重关系性别间无显著差异(P>0.05),1999-2002年和2007-2009年大头鳕雌雄混合群体的体长-体重关系分别为W=4.564×10-3 L3.333和W=1.550×10-2 L2.994,群体由正异速生长转变为等速生长。两个阶段内,大头鳕主要饵料均为甲壳类,但由于2007-2009年大头鳕分布区转变,摄食了更多的甲壳类生物,饵料多样性指数(H’)由1.0升高到1.9,生境宽度增加。与20世纪80年代相比,黄海大头鳕年龄结构仍然较为简单,资源易受气候变化和人类活动的影响。从1985年到2009年,黄海中南部黄鮟鱇种群结构简单化、个体小型化。体长和体重由负异速生长转变为等速生长;由于雌雄间生长速度的差异和雌性的产卵洄游,导致种群中雄性占优势;2005和2009年秋季黄鮟鱇样品中出现性成熟和产卵个体,预示着黄鮟鱇部分个体的产卵时间发生变化;黄鮟鱇的饵料组成时空异质性强,表明其对饵料的选择主要受生活区饵料种类的易得性影响;但从1985-1987年到2009年,黄鮟鱇的生境宽度持续降低,一定程度上反映了黄海中南部底层生物群落结构的变化;2000年以来,黄鮟鱇的相对资源密度显著升高,从1985年到2009年,多数年份的产量与年均海表温度具有极显著正相关性(P<0.01),但过高的SST会对相对资源密度和产量产生负面影响。更多还原

【Abstract】 As an important part of marine ecosystem, fish plays a significant role in meeting the market demands and ensuring food security, and provides a large amount of high-quality protein for human being. With the serious effects of anthropogenic activities (e.g. overfishing) and environment changes on marine ecosystem, biological characteristics and population dynamics of marine fishes have been greatly changed, which further threaten the service function of marine ecosystem. In the present study, interannual changes in biological characteristics and relative stock densities in three high trophic level demersal fishes in the Bohai Sea and Yellow Sea ecosystem were analyzed, involved in small yellow croaker Larimichthys polyactis, Pacific cod Gadus macrocephalus and anglerfish Lophius litulon. The data for this study were from the bottom trawl data in the Bohai Sea and Yellow Sea (data for small yellow croaker, Pacific cod and anglerfish were 1960-2010, 1999-2009 and 1985-2009, respectively). This study will provide useful information for management of marine living resources and modeling population dynamics.The allometric factors (b) of body weight-length relationship in the small yellow croaker were not significant differences (P>0.05) between sexes in most years from 1960 to 2010; but significantly negative correlations (P<0.01) were found between condition factor (a) and b in two small yellow croaker stocks, the northern Yellow Sea-Bohai Sea stock (NYBS) and the southern Yellow Sea stock (SYS). (lga)/b ratio was constant during the decades, and connected with the fish body density. The isometric growth was found in the NYBS from 1960 to 2004, and b increased during the stock regression stage (1982-1983) and the early recovery stage (1993). The negative-allometric growth was found in the SYS from 1960 to 2010, b showed a decreasing trend during the stock regression stage (1986) and the early recovery stage (1994), increased since the late 1990s. The condition factors of male and female individuals in the NYBS decreased from 1960 to 2004; the condition factors of male and female individuals in the SYS in 1986 were significantly smaller than those in 1960 (P<0.05), Since 1986, the condition factors slightly increased, but no significant differences were found between surveys. These changes were closely related to the variations in the proportion of sexual maturity. The b of male individuals showed better coordination relation with fishing stress, increased with the increase of stock density. The decrease of condition factors of small yellow croaker were mainly caused by the declines in age at maturity from 1960 to the middle 1980s, since the 1990s, the variations in condition factors in both stocks mainly attributed to the changes of sea surface temperature (SST), and the condition factor increased with the increase of SST.As depicted in maturity ogives, body length and age at 50% maturity were studied for female small yellow croaker in the Bohai Sea and the Yellow Sea during the 1960-2010 spawning seasons. Body length (L50) and age at median sexual maturity (A50) were estimated by an arcsin-square-root (ASR) transformative logistic model and an inverse von Bertalanffy growth function, respectively. The results show that L50 decreased from 152.8 mm to 105.3 mm between 1960 and 2003-2005 in the NYBS and from 184.4 mm to 110.1 mm between 1960 and 2010 in the SYS. Over the same period, A50 decreased from approximately 1.5 years in the NYBS and 2.4 years in the SYS to about 1 year in both stocks. Significant intrastock changes (P<0.01) in length-maturation curves were found in both stocks over long time periods (≥4 years); however, there were no significant changes (P>0.05) over short time intervals (<4 years). Significant interstock changes (P<0.01) were observed in length-maturation curves in corresponding sampling years. Significant positive correlations were found between the instantaneous rate of maturation (δ) and the growth potential index (ω) in the NYBS and between L50 and asymptotic body length (L∞) in the SYS. Significant negative correlations were found between L50 and the sea surface temperature (SST) daily rise rate in the NYBS and betweenδand the mean monthly SST in the SYS. These correlations suggest that declines in length and age at maturation primarily reflect changes in growth associated with overfishing and rising SST. Additionally, a fisheries-induced evolutionary response has contributed to changes in maturation schedules in both stocks. The principal pressures are the stress of continuously higher fishing intensity and an increasing proportion of yearling fish in the catches over time.The relative stock density of the NYBS were significantly increased since 2000 when compared with that in 1985, while the relative stock density in the SYS decreased from 1985 to 2010. The highest relative stock density was generally in autumn in both stocks due to the recruitment of yearling fish. However, the highest relative stock density in SYS was found in spring in some El Ni?os year, which might be caused by migration to the north of spawning population for the increase of SST in spawning ground in the northern East China Sea. Generally, the relative stock density and yield were both increased in those years and in 1-2 years after an El Ni?os event.The relative stock density of Pacific cod increased from 1.0 kg/h to 11.7 kg/h, and dominant age increased from 1 year old to 3 years old over 1999-2002 to 2007-2009. Moreover, proportions of females at sexual maturity (maturity degree at IV- VI) were increased from 21.9% to 67.3%. Body weight-body length relationships were W=4.564×10-3 L3.333 in 1999-2002 and W=1.550×10-2 L2.994 in 2007-2009, and no significant differences were found between male and female individuals (P>0.05). The changes of body weight-body length relationships indicated Pacific cod population was from positive-allometric growth to isometric growth. Stomach contents analysis showed that crustaceans were dominant diets of Pacific cod in both periods. The diversity of diet species in Pacific cod increased from 1.9 to 1.0 for the changes of its distribution area, and increased its niche width. The age structure of Pacific cod in the present study was simpler than that in the 1980s, and Pacific cod stock was sensitive to the climate changes and human activities.Anglerfish in the southern Yellow Sea were increasingly characterized by simpler age structure and smaller size from 1985 to 2009.. Body weight and body length were from negative-allometric growth to isometric growth. Male individuals were dominated in the population for the differences of growth speed between sexes. A few individuals reached to sexual maturity in autumn, which indicated the changes in spawning time of anglerfish. Food composition of anglerfish was closely connected with spatio-temporal heterogeneity of diet species, so anglerfish showed low selectivity for prey items and strong adaption to the changes in food-web. The niche width of anglerfish continuously decreased from 1985-1987 to 2009, which also indirectly improved community structure changes of fishery species in southern Yellow Sea. Since 2000, the relative stock density of anglerfish significantly increased, and its yield in year n was extremely positive correlation to SST in year n-2 (P<0.01), however, high SST negatively impacted its relative stock density and catch.更多还原