珠江禁渔对广东鲂资源补充群体的影响分析

继我国各大水系实施禁渔期制度之后,珠江水系于2011年4月1日至6月1日实现首次禁渔。广东鲂是珠江中下游地区主要的经济鱼类之一,为分析珠江实施禁渔期制度对广东鲂资源补充群体的影响,于珠江实施禁渔制度前(2006—2010年)和禁渔制度后(2011—2012年)在珠江下游肇庆江段设立固定采样点,利用定量弶网对流经该江段的广东鲂鱼苗补充群体进行调查。结果显示,禁渔前,珠江广东鲂鱼苗集中出现在4月中下旬至10月中旬,持续时间为(189±11)d,高峰期为6—8月。禁渔期制度实施之后,全年广东鲂鱼苗出现的起始时间变化不大,但是结束时间提前,持续时间略有缩短,4—5月份广东鲂鱼苗密度明显增大。广东鲂鱼苗总量及其在鱼苗补充群体中的比例均有所提高。根据禁渔前广东鲂鱼苗发生量与径流量之间存在的回归关系:LgY=0.988Lnx-4.932(R2=0.365,P0.01),结合禁渔后实际调查结果,对禁渔的实际作用进行了估算,2011年和2012年由于禁渔分别增加了9.43×108和651.81×108尾广东鲂鱼苗。研究表明,在径流量有保障的前提下,目前的禁渔制度可以有效增加广东鲂鱼苗补充群体资源量。

Effect of Pearl River closed fishing on Megalobrama hoffmanni recruitment stock

Closed fishing was carried out for the first time in Pearl River April 1, 2011. For analyzing the effect of closed fishing on Megalobrama terminalis recruitment stock, the fish larvae were sampled by Jiang net at Zhaoqing section in lower of Pearl River from 2006~2012. The result showed that Megalobrama terminalis larvae was usually occurrence from mid April to mid October, and breeding period was last 189±11 days before Closed fishing. The density of Megalobrama terminalis larvae was higher from June to Auguest than April and May every year. After Closed fishing, the drift density increased obviously within the banned fishing periods, and the biomass and the relative abundance also rised greatly. For analyzing the effect of closed fishing on Megalobrama terminalis recruitment stock, the regression models was built, and the logarithmic equation was lg(Y)=0.988ln(x)-4.932(R2=0.365,P<0.01),and regression effect was significant. Based on the logarithmic equation the fitted value of Megalobrama terminalis larvae was calculated, and the closed fishing effect was estimated combining actual monitoring value at Zhaoqing sampling station. The increment of Megalobrama terminalis laevae caused by closed fishing was 8.20×108ind in 2011 and 650.57×108ind in 2012 respectively. The result indicated the present regime of closed fishing can effectively increase the Megalobrama terminalis recruitment stock based on the abundance discharge.