青岛文昌鱼体征变化及影响因素探究

Changes of body length and weight of Branchiostoma belcheri tsingtauense outside of Jiaozhou Bay and the environmental factors causing the changes

根据1981年和2004年胶州湾口青岛文昌鱼(Branchiostoma belcheri tsingtauense Tchang et Koo)采集资料,分析了23年来青岛文昌鱼体质量、体长、生物量和栖息密度的变化,发现1981年文昌鱼个体最大体长为55 mm,平均体长为37.63 mm,而2004年个体最大体长仅42 mm,平均体长只有29.82 mm;1981年各月平均体质量范围为0.06～0.14 g,2004年为0.03～0.04 g;1981年平均栖息密度为753个/m2,2004年为1 220个/m2。采用成对数据平均数比较的假设双尾检验法进行数据统计分析结果也表明,文昌鱼的平均体长和体质量在1981年和2004年均有显著的差异,平均分布密度在显著水平a为0.01时,差异不显著,而在a为0.05时,差异显著;说明2004年采集的青岛文昌鱼个体长度和质量都明显变小而分布密度有所增加;而平均生物量,1981年和2004年没有显著性差异。不同体长个体数比例表明,1981年和2004年文昌鱼种群的年龄组成以及各年龄组的生长情况等方面也不相同。引起这些变化的原因初步分析为底质的改变、栖息地萎缩、饵料丰度和组成改变以及人类活动的干扰。

Branchiostoma belcheri tsingtauense Tchang et Koo, a second class protective animal species in China, is one of the four amphioxus species found in Chinese waters. It distributes mainly in the inside and outside of Jiaozhou Bay and adjacent areas. Based on the material collected from the same station （36°02.262＇N, 120°22.771＇E） at the mouth of Jiaozhou Bay in 1981 and 2004, we analyzed the changes of body length and weight and the individual density of the species. The results show that the average body length of B. belcheri tsingtauense was 37.63 mm （maximum 55 mm） in 1981 and 29.82 mm （maximum 42 mm） in 2004; the average body weight in different months ranged from 0.06-0.14 g in 1981 and from 0.03-0.04 g in 2004; the average individual density was 753 ind/m^2 in 1981 and 1 220 ind/m^2 in 2004. The results imply that the body length and weight orB. belcheri tsingtauense decreased distinctly but the individual density increased during the recent 23 years from 1981 to 2004. We also found that the components of the different aged animals changed between 1981 and 2004. The factors caused the changes should be the variations of sediment and food （benthos and phytoplankton）. The variations mainly are caused by the human activities, including marine culture, wharf building and ship anchoring, and industrial and living pollutions.