Population Dynamics of the Bream Abramis brama in Lake Peipusстатья
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Дата последнего поиска статьи во внешних источниках: 7 октября 2020 г.
Аннотация:Population dynamics of the bream Abramis brama in lakes Peipsi and Pihkva for the period from1980 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’scurve. 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