Population Dynamics of the Bream Abramis brama in Lake Peipus
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lation Dynamics of the Bream Abramis brama in Lake Peipus M. B. Danilova, *, E. A. Kriksunova, A. E. Bobyrevb, c, A. D. Sheremet’evc, M. M. Mel’nikd, S. O. Severind, P. V. Vasileva, and S. V. Chistova aMoscow
State University, Moscow, Russia of Ecology and Evolution, Russian Academy of Sciences, Moscow, Russia c Federal Research Institute of Fisheries and Oceanography, Moscow, Russia dRussian Federal Research Institute of Fisheries and Oceanography, Pskov branch, Pskov, Russia *e-mail: [email protected] bInstitute
Received July 25, 2019; revised August 6, 2019; accepted August 7, 2019
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. Keywords: bream Abramis brama, stock status, recruitment, Lake Peipus DOI: 10.1134/S0032945220040049
INTRODUCTION The organizational and regulation issues of fishery in Lake Peipus, including the ones on the bream Abramis brama as one of the main objects of fishing, have drawn immense interest of specialists (Kangur, 1996; Pihu, 1996; Pihu and Kangur, 2001; Mel’nik and Kontsevaya, 2005; Kangur et al., 2007; Kontsevaya, 2009; Saat et al., 2010; Bobyrev et al., 2013). In the framework of the studies on the population dynamics of the main commercial fish species of Lake Peipus we made an attempt to analyze the state of the stocks, fishery, and reproduction of zander Sander lucioperca in 1980–2009 (Danilov et al., 2018) based on the methods of retrospective analysis, as well as on some traditional models of interactions in the stock-recruitment system. Using this methodological approach, we continued the studies and in this work we paid attention to the bream population, whose share in the total fish catch of Lake Peipus can reach 30%, averaging about 9 and 15% of the annual catch for Peipsi and Pihkva lakes, respectively. Although the processes of population changes are still too complicated for their reliable predictability, a retrospective analysis of fishery statistics
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