|其他题名: ||Reproductive Ecology of Anadromous Coilia ectenes in the Yangtze River|
|摘要: ||洄游性刀鲚(Coilia ectenes Jordan et Seale)是长江中下游重要的渔业资源，20世纪70年代以来，其资源量严重下降。2006年4月至2007年8月在长江崇明江段(长江口)逐月采集洄游性刀鲚；2006年和2007年分别于刀鲚的洄游季节4~8月在长江靖江和安庆江段采集洄游性刀鲚；2008年，5~6月在崇明江段，7月在靖江和安庆江段采集洄游性刀鲚雌性繁殖群体(性腺发育到Ⅲ期以上的个体)，共采集了1115尾样本。刀鲚耳石年轮的确证采用2006年4月至2007年8月在崇明江段采集的个体；2006年至2008年在三个采样点采集的所有个体都用来分析其年龄、生长和性腺发育；2006年至2008年4~8月在三个采样点采集的所有成熟个体用来分析不同洄游距离繁殖群体的年龄、体长、耳石年轮宽度差异，成熟的雌性个体还用来分析其繁殖策略的；洄游过程中生化组成和能量变化分析，采用2006年4~8月在长江崇明、靖江和安庆江段采集的个体。
2. 目前刀鲚渔获物由0-4龄共五个年龄组组成，以2龄个体为主。而1973至1975年间，刀鲚的渔获物由0龄至6龄共7个年龄组组成，其中以3龄和4龄个体为主(袁传宓等，1978)。本文调查的3龄和4龄雌性个体，2龄、3龄和4龄雄性个体最大标准体长较1973至1975年渔获物的最大体长小10%以上, 表明目前长江刀鲚种群明显低龄化和小型化，刀鲚资源已严重过度利用。
3. 各年龄组雌雄个体体长分析表明， 0龄刀鲚的雌雄个体没有显著差异，1龄、2龄、3龄刀鲚雄性个体显著小于同龄雌性个体，雄性个体拟合的Von Bertalanffy生长方程为：SL=362.55(1-e-0.42(t+0.30)) (n = 392, r2 = 0.65, p < 0.05)。雌性个体拟合的Von Bertalanffy为长方程为：SL=348.25(1-e-0.53(t+0.23)) (n = 723, r2 = 0.73, p < 0.05)。
4. 崇明江段雄性繁殖群体由1~3龄的个体组成，2龄的个体占93.6%；靖江江段雄性繁殖群体由1~3龄的个体组成，以2龄(35.7%)和3龄(57.2%)的个体为主; 安庆江段雄性繁殖群体由1~3龄的个体组成，2龄的个体占92.3%。崇明江段雌性繁殖群体由1~3龄的个体组成，2龄的个体占84.6%；靖江江段雌性繁殖群体由2~4龄的个体组成，以2龄(64.9%)和3龄(31.2%)的个体为主；安庆江段雌性繁殖群体由2~3龄的个体组成，2龄的个体占87.3%。靖江和安庆江段2龄成熟雌雄个体体长显著大于崇明江段的。安庆江段的3龄雌性繁殖群体显著大于靖江江段的。安庆江段雌雄繁殖群体矢耳石横截面上第一个年轮的宽度均显著小于崇明和靖江江段的，安庆江段洄游性刀鲚的繁殖季节晚于崇明和靖江江段的(Li et al., 2007)，该江段出生的后代至第一个年轮形成的生长季节较短，因此第一个耳石年轮半径可能较小，在本研究中我们发现安庆江段繁殖群体耳石第一个年轮的半径小于崇明和靖江江段的，安庆江段繁殖群体与该江段出生的后代耳石第一个年轮半径的一致性说明安庆江段的繁殖群体可能是以前在该江段出生的后代，刀鲚的洄游可能具有回归性。
6. 生化组成和能量分析结果显示，三个江段性腺未成熟个体(Ⅱ期或Ⅲ期)的生化组成和能量存在显著差异：安庆江段鱼体和肝胰脏的蛋白质和脂肪含量显著低于崇明和靖江江段同龄个体的；肠系膜脂肪组织脂肪含量显著低于崇明和靖江江段的同龄个体的，而表明肌肉、肝胰脏和肠系膜脂肪组织中贮藏的脂肪是刀鲚在洄游过程中重要的能量来源。雌性个体洄游过程中消耗的绝对和相对能量 (((绝对能量消耗×100)/洄游初始时的能量)% )都随着体长增加而增加，洄游过程消耗的能量，安庆江段的(16%-50%)显著高于靖江江段的(<12%)。对各个江段未成熟个体和成熟个体(Ⅳ期或Ⅴ期)的生化成分和能量分别比较分析表明：崇明和靖江江段的成熟个体的鱼体空壳和肠系膜脂肪组织脂肪含量显著小于未成熟个体的, 靖江和安庆江段的成熟个体的肝胰脏脂肪含量显著小于未成熟个体的，表明鱼体空壳、肝胰脏和肠系膜脂肪组织中储存的脂肪是性腺发育过程中重要的能量来源。崇明和靖江江段的成熟个体的鱼体总能量显著低于未成熟个体的，性腺发育过程中消耗能量都随着体长的增加而增加，靖江江段为25%~53%，显著高于崇明江段的(＜35%)。安庆江段雌性个体性腺能量与靖江江段的没有显著差异，表明安庆江段的性腺发育消耗的能量应该与靖江江段的相似，而安庆江段未成熟个体和成熟个体的鱼体总能量、能量密度和鱼体脂肪含量均没显著差异，结合胃饱满度分析表明，安庆江段的雌性个体的性腺发育还通过摄食补充能量来完成性腺的发育，否定以前认为刀鲚进入长江后不再摄食(长江水产研究所资源捕捞研究室等，1977)的观点
综上所述，1)刀鲚年龄结构和个体大小与历史监测数据的差异表明，目前长江洄游性刀鲚资源已严重过度利用；2)不同洄游距离繁殖群体的繁殖生物学特征存在显著差异：五月份开始在河口产卵，并随着时间向上游推移，洄游距离较远的繁殖群体，个体较大，洄游过程消耗的能量较多， GSI较小,繁殖力较大，而卵径较小，离河口较远的繁殖群体对种群补充的贡献可能越大，我们更应该加强保护洄游距离较远的繁殖群体；3)我们的结果还表明刀鲚的洄游可能具有回归性，由于洄游距离越远的繁殖群体，受到的捕捞压力越大，过度捕捞可能导致洄游距离越来越短，事实上洄游距离已经大大缩短了(上世纪70年代洄游性刀鲚能洄游到洞庭湖水域，而现在只能洄游到鄱阳湖湖口附近水域) (施德龙和龚洪新，2003)，这对刀鲚的资源管理和保护将是一个严重的挑战，降低刀鲚的捕捞强度是刀鲚资源保护和恢复的基础。长江中下游禁渔期(4月1日～6月30日)仅仅保护了刀鲚的部分产卵季节，就刀鲚保护而言，长江禁渔期应该后延。|
|英文摘要: ||Anadromous Coilia ectenes (Jordand et Seale) is a commercially important fishery resource in the middle and lower reaches of the Yangtze River, the resource of which has declined dramatically since late 1970s. Fish Sampling were conducted in the Yangtze Estuary at Chongming (31.58oN, 121.73oE), Jingjiang (31.95oN, 120.27oE) and Anqing (30.5oN, 117.05oE) in the lower reach of the Yangtze River as: for females and males at Chongming in each month from April 2006 to August 2007; females and males at Jingjiang and Anqing in each month from April to August in 2006 and 2007; mature females( Stage Ⅳ or stage Ⅴ) at Chongming in May and June 2008 and mature females at Jingjiang and Anqing in July 2008. A total of 1115 individuals were collected. The otolith annuli were validated with the individuals collected at Chongming from April 2006 to August 2007, the age structure, growth and gonad development of the individuals collected at the three locations in 2006, 2007 and 2008 were investigated, the differences in age structure, standard length and the first annuli width among reproductive population with different migration distance were analyzed with the mature males and females collected at the three locations from April to August in 2006, 2007 and 2008, reproductive traits of the mature females collected at the three locations from April to August in 2006, 2007 and 2008 were analyzed and the changes in proximate composition and estimates of energetic costs during the spawning migration were analysed with the individuals collected at the three locations from April 2006 to August 2007.
1. Examination of transverse plane of the sectioned sagittal otoliths revealed a periodic straight/curved growth pattern. The straight zone occurred during April and December, and curved zone during October and June. Marginal increment ratio analysis also showed an annual periodicity of the straight/curved growth increment. The shift from curved growth to the next straight growth occurred during April and June. We defined this shift as an annuli mark.
2. The collected specimens were consisted of 5 age classes ranged from 0 to 4 years, dominated by age-2 individuals, but a harvest of C. ectenes between 1973 and 1975 was consisted of 7 age classes ranged from 0 to 6 years, dominated by age-3 and age-4 individuals (Yuan et al.，1978). Again, the maximum lengths of age 3 and age 4 females and age 2 to age 4 males were at least 10% smaller than the harvest with the same age and gender between 1973 and 1975 (Yuan et al.，1978), revealing that the harvest during the present research was younger in age and smaller in size of the same age class fish. This change in age composition and size structure indicated that the anadromous C. ectenes has been overexploited.
3. The standard length of females and males at age 0 has no difference; but that of age 1, age 2 and age 3 males were smaller than that of the same age females. The standard length (SL) and age (t) data were fitted to the von Bertalanffy growth function, represented as SL=362.55(1-e-0.42(t+0.30)) (n = 392, r2 = 0.65, p < 0.05) for males and SL=348.25(1-e-0.53(t+0.23)) (n = 723, r2 = 0.73, p < 0.05) for females.
4. Mature males were consisted of individuals aged 1 to 3 years, including 3 age classes, which were of age 1 (3.2%), age 2 (93.6%), and age 3 (3.2%) at chongming, age 1 (7.1%), age 2 (35.7%) and age 3 (57.2%) at Jingjiang, and age 1 (2.6%), age 2 (92.3%) and age 3 (5.1%) at Anqing. Mature females were consisted of individuals aged 1 to 4 years, including 4 age classes, which were of age 1 (13.2%), age 2 (84.6%), and age 3 (2.2%) at chongming, age 2 (64.9%), age 3 (31.2%) and age 4 (3.9%) at Jingjiang, and age 2 (87.3%) and age 3 (12.7%) at Anqing. While Standard lengths of age 2 mature females and males were significantly larger at Anqing than at Jingjiang and at chongming, that of age 3 mature females were significantly larger at Anqing than at Jingjiang. The first annular radius in sectioned sagittal otoliths of females and males were significantly smaller at Anqing than at Jingjiang and at chongming. As the spawning season at Anqing was delayed than at Chongming and at Jingjiang (Li et al., 2007), growth season of the offspring from birth to the first annulus formation was shorter for offspring at Anqing, which might have resulted in a smaller first annular radius, which were corresponding to the smaller first annulus radius of the spawning females at Anqing indicated that they may be offspring born there, giving evidence for a homing migration.
5. The gonado somatic index (GSI) at Chongming peaked in May and June, that at Jingjiang in June and July, and at Anqing in July and August. The gonad development revealed that a major part of the individuals at Chongming matured in May and June, that at Jingjiang in June and July, and at Anqing in July and August, indicated that the population at Chongming reproduced in May and June, that at Jingjiang reproduced in June and July, and at Anqing reproduced in July and August. For age 2 mature females, condition factor was smaller at anqing than at Chongming and Jingjiang, GSI was highest at Anqing, egg diameter was highest at Jingjiang, while fecundity was higher at Anqing than at Chongming and Jingjiang.
6. The proximate composition and total energy of immature females (stageⅡand Ⅲ ) among the three locations had some significant differences: the protein and lipid contents of somatic tissue and liver-pancreas were lower at Anqing than at Chongming and Jingjiang and the lipid content of mesenteric lipid tissue was lower at Anqing than at Chongming and Jingjiang, indicated that the lipid stored in the somatic, liver-pancreas and mesenteric lipid tissue were an important energy source during the course of migration. Both the absolute and relative energy loss (absolute energy loss×100)/ initiative energy at the beginning of migration%) increased with standard length. Both these values were higher at Anqing (16%-50% for relative energy loss)than at Jingjiang (<12% for relative energy loss). The proximate composition and total energy content of mature and immature females (stageⅡand Ⅲ ) in each location also had significant differences: the lipid contents of somatic and mesenteric lipid tissues of mature females at Chongming and Jingjiang were lower than that of immature females and the lipid contents of liver-pancreas of mature females at Jingjiang and Anqing were lower than that of immature females, indicated that the lipid stored in the somatic, liver-pancreas and mesenteric lipid tissue were also an important energy source during the course of gonad development. Both the absolute and relative energy loss increased with standard length. Both these values were higher at Jingjiang (25%~53% for relative energy loss)than at Chongming (＜35% for relative energy loss). The ovarian energy of mature females at Anqing were similar to that at Jingjiang which indicated that the energy loss during the course of gonad development at Anqing should be similar to at Jingjiang, while the total energy, energy density and lipid contents of mature females were similar to that of immature females at Anqing. Furthermore, the stomachs of 33% females were full of food, indicated that the females at Anqing should supply additional energy to fulfill the needs of gonad development by feeding, rejecting the viewpoint that anadromous C. ectenes do not feed after entering the estuary (The research labs of resource and catch in Yangtze River Fisheries Research Institute, 1977).
In conclusion, anadromous C. ectenes has been overexploited presently. This fish has some special reproductive strategies: spawning occurs in the estuary in May, which will be delayed with increasing migratory distance from estuary to freshwaters. The females with increasing migration distance would spend more energy, so will have lower GSI, smaller egg diameter but higher fecundity, which all indicated that they would contribute more to the population recruitment. Considering this, we should strengthen measures to conserve the spawners with longer migration distance. The offsprings born at Anqing might be homing to Anqing itself for reproduction when they grow up (homing migration). The individuals with longer migration distance may suffer higher catching pressure, and the overfishing of these populations may induce shorter migration distance, in fact the migration distance had shortened from Dongting Lake to the area near to Poyang Lake(Shi and Gong，2003), which would be a challenge to fisheries management and conservation for anadromous C. ectenes. Reducing fishing intensity is the fundamental fisheries management and resource conservation option for this fish in the Yangtze River. The annual closed season for fishing in the middle and lower reaches of the Yangtze River (April 1 to June 30) covers only part of the spawning season of anadromous C. ectenes. The ban on fishing this species should be expanded typically to the upper spawning grounds.|
|Appears in Collections:||中科院水生所知识产出（2009年前）_学位论文|
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