辽东湾斑海豹历史种群数量的估计

辽东湾斑海豹(Phoca largha)在本世纪里由于过度捕杀,种群数量下降比较严重。本文利用1930～1990年的捕获统计数据,对1930年以来辽东湾斑海豹的种群数量变化进行了估计。该种群在30年代初有7100头,并于1940年达到最高峰8137头,40～70年代末,由于过度捕杀,种群数量几度下降,1979年只有2269头(以上结果依据R=0.09413的种群更替率算得)。经1979～1982年徘徊以后,该种群数量迅速回升,并达到50年代末期的水平。根据0.09413,0.1163的种群更替率,对生殖力及特定年龄的死亡率进行估计。结果表明,在高比例的雌性生殖力情况下,辽东湾斑海豹幼体死亡率低于52％,成体死亡率低于16％。

ESTIMATES OF HISTORICAL POPULATION SIZE OF HARBOUR SEAL(PHOCA LARGHA) IN LIAODONG BAY

The harbour seal (Phoca largha) population in the Liaodong Bay area has been dwindling in this century due to excessive hunting pressure. Statistics of the hunted seals during 1930-1990 are used to estimate changes in population size over the past century. This population consisted of about 7100 animals (R = 0.094 13) in the early of 1930s, and amounted to the highest level, which consisted of 8 137 animals (R = 0.094 13) in 1940. The population appeared to decline several times from 1940 to the end of 1970s, and decreased to the lowest level in 1979, which consisted of only 2 267 animals. After loitering at the level of 2300 ones between 1979 and 1982 (R = 0.09413), the population increased rapidly, and amounted to the level of the end of 1950s. The net recruitment rate of 0.094 13, 0.1163 is used for modelling the influence of fertility and age-specific mortality. It is found that the observed high rate of increase is only realistic if female fertility rate is very high, the juvenile mortality rate is less than 52%, and the adult one is less than16%.