The dynamics of a population of roach (Rutilus rutilus (L.)) in a shallow lake: is there a 2-year cycle in recruitment ?

摘要: Recruitment success of roach varied dramatically between 1978 and 1985 in Alderfen Broad, a small lake eastern England. All size classes feed to significant extent upon zooplankton, but the underyearling fish have greatest effects abundance, species composition mean zooplankton. During years good recruitment (1979, 1981, 1983 1985) when 0 + age group was abundant, they showed poor growth as result depression their prey populations. Older also tended grow poorly these may been less fecund following year. In (1980, 1982 1984), with release depressive effect zooplankton exerted by fish, older well higher fecundity season, giving rise even number spawners low. The evidence indicates that there is 2-year cycle this will be described.