珠江中下游鲴亚科鱼苗发生规律与年际变化

Occurrence and interannual variability of larval Xenocyprininae in the mid and lower reaches of the Pearl River

为了解珠江鱼类补充群体发生规律及资源量状况,2005-2011年在珠江中下游肇庆江段设置定点采样点,通弶过定量网连续采集漂流性鱼苗样品,对珠江中下游鲴亚科（Xenocyprininae）鱼苗补充群体进行了调查研究。结果表明：珠江中下游鲴亚科鱼苗稳定出现在4～10月,每年持续（183±12）d,平均出现率为40.1%。在5～8月伴随洪水过程有多个漂流高峰期,鲴类鱼苗密度与径流之间显著正相关（n=876,P〈0.01）。2007年鲴类鱼苗密度显著高于2009年（P=0.012）和2011年（P=0.009）,而与其他各年之间不存在显著性差异。鲴类鱼苗密度峰值出现时,白天平均密度高于早上和晚上,采样期间内整体3个时间段之间不存在显著性差异。鲴类鱼苗资源量总体呈现减少的趋势,长洲水利枢纽可能是最主要影响因素,建议其通过保证鱼道正常运行和生态调度两种途径减小对珠江中下游鱼类资源的影响。

We evaluated the occurrence and stock status of larval Xenocyprininae in the mid and lower reaches of the Pearl River, China. We collected larval samples from Zhaoqing using a Jiang net between 2005 and 2011. The occurrence of larval Xenocyprininae was stable between April and October, with individuals being captured a mean of （183±12） d each year （40.1% occurrence rate）. We observed several peaks in larval drift associated with floods between May and August. There was a significant correlation between Xenocyprininae larval drift density and discharge （n=876, P〈0.01）. The larval density in 2007 was significantly higher than in 2009 （P=0.012） and 2011 （P=0.009）, but was not different from the remaining years. During the drifting peak of larval Xenocyprininae, larval density was higher during the daytime than in the morning or at night, though there was no significant difference between the three time periods over the entire sample period. We observed a decrease in the larval recruitment of Xenocyprininae, likely due to the operation of Changzhou Dam. Given this, we suggest that the operation of Changzhou dam be modified, by opening the fishway and increasing flows, to reduce its effect on fishery resources in the mid and lower reaches of the Pearl River.