云南抚仙湖鱼类的若干生物学特性及其对湖泊环境的适应

THE BIOLOGICAL CHARACTERS OF FISHES OF FUXIAN LAKE,YUNNAN,WITH COMMENTS ON THEIR ADAPTATIONS TO THE LACUSTRINE ENVIRONMENTS

作者于１９８８年１１月至１９８９年１１月逐月取样研究了抚仙湖鱼类的生物学特性。在此基础上，本文尝试从生物与环境相统一的观点出发，结合湖泊环境的演变历史，进一步探讨了其生物学特性对湖泊环境的适应。研究结果表明，抚仙湖鱼类具有一系列共同的生物学特性。依其性质可把这些生物学特性区分为原始性状或特化性状。原始性状提示了抚仙湖现生鱼类主要是源自该湖所属的江河鱼类区系。特化性状则是鱼类在长期的进化过程中适应相同湖泊环境的具体表达。随着湖泊的由浅变深和贫营养化，先后由江河溪流进入抚仙湖的鱼类逐渐分化为沿岸浅水区生活类型、敞水区中上层生活类型和敞水区中下层生活类型；种间的食性出现多种多样的分化；鱼类的体型普遍较细长，滤食性种类的生长速度较慢、体型较小；每年的繁殖期较长，而且每两个产卵群体之间的产卵时间间隔有明显的规律性；个体繁殖力较低；种群的性比较悬殊，雌性较多。尤其值得注意的是，上述适应性状的特化程度依种而异，呈现明显的种间差异。这种差异在一定程度上进一步表明了各种鱼类进入抚仙湖的时间是各不相同的。正是上述综合分化的结果才形成了目前抚仙湖鱼类的多样性。诸种鱼类各得其所，各就其位，保持一种相对稳定而复杂的网络关系。

Based on the data obtained by monthly samplings from Fuxian Lake in the duration of one year (Nov. 1988 to Nov. 1989),the author has investigated into the biological characters of fishes of Fuxian Lake.From the viewpoint that organisms evolve along with their environments, the adaptative significance of these characters are further explained with reference to the geological history of Fuxian Lake. It is found that a series of common characters are shared by all or many species of fishes. These common characters can be further recognized as original or derived ones according to the principle of character analysis. The original characters suggest that the extant fishes of Fuxian Lake be originated from the ichthyofauna of rivers connected to the lake. The derived characters are supposed to be evolved from adaptations of the fishes to the deepening and oligotrophic development of the lake. According to the data in living spaces, the adults of all species can be divided into three types,they are:coastal dwellers, offshore mid-upper dwellers and offshore mid-lower dwellers.However,the larvae of all species live together in coastal zone of the lake.Differentiations in adults'living spaces should be a derived characters and represent their adliving spaces should be an original characters and suggest that the ancestors of extant fishes be hill-stream dwellers. This differentiation in living spaces can be shown as Fig.1.When companng to their congeners,most fishes share a slower growth rate,a more slender body and a small body size(Table 1,2,3,4,5).The oligotrophic development of the lake must have lead food shortage to the fishes.It was the increasing food shortage that had caused the fishes to grow more slowly and to form a smaller body size. The fishes of the lake are characterized by having long spawning seasons and the existence of a regular interval between the spawning activities of any two breeding populations.These breeding habits can ensure that the limited spawning sites would be fully used and that the limited food resources would be effectively used by the larvae.Some species of fishes have relatively lower individual fecundities than their congeners.This is closely related to the oligotrophic development of the lake.Increasing food shortage can usually cause fishes to have lower individual fecundities.The sexual ratios of most species show great disparity and the females are usually dominant in a population(Table 6).It is those differentiations mentioned above that have resulted in the diverse extant fishes of Fuxian Lake.