Abstract

Population dynamics of the bream Abramis brama in lakes Peipsi and Pihkva for the period from 1980 to 2009 has been studied by means of cohort models. Bream stock increased steadily in Lake Pihkva until 1999 and in Lake Peipsi until 2004, however then a trend towards a decrease of stock down to the level of early 1980s has been detected. In the 2000s a decrease in the population average age has been registered; it could be explained by both an increase in fishing intensity and high recruitment rates of the late 1990s. Highly abundant bream generations emerged in both lakes simultaneously. In late 2000s low level of recruitment was noted in both lakes. The qualitative relationship between stock and recruitment is best described by Ricker’s curve. It has been shown that bream recruitment depends on water transparency, water temperature, average annual number of days with air temperature above 20°С, and average annual water level. The existing fishery pressure on the stock of bream is close to optimal. A further increase in fishing intensity in both lakes is impractical. The current level of equilibrium yield can be achieved with much lower fishing intensity.

中文翻译：

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培比斯湖theAbramis brama的种群动态

摘要

braAbramis brama的种群动态通过队列模型研究了1980年至2009年期间Peipsi和Pihkva湖中的水。直到1999年，皮克瓦湖和2004年直到2004年的皮皮斯湖的stock鱼种群都稳定增长，但是随后发现了种群减少到1980年代初的趋势。在2000年代，人口平均年龄有所下降。1990年代后期捕鱼强度的增加和高招募率都可以解释这一点。两个湖同时出现了高度丰富的abundant鱼世代。在2000年代后期，两个湖泊的征兵水平都很低。里克曲线可以很好地描述股票与招聘之间的质量关系。研究表明，的吸食取决于水的透明度，水温，气温高于20°С的年平均天数，以及年平均水位。on鱼现有的渔业压力接近最佳水平。在两个湖泊中进一步增加捕鱼强度是不切实际的。较低的捕捞强度可以达到当前的平衡产量水平。