Ref ID : 6629
Carla Bonacina, Andrea Pasteris, Giulio Di Cola, and Giuliano Bonomi; Production and population dynamics of Tubifex tubifex in the profundal zone of a freshwater reservoir in N.Italy. Hydrobiologia 334:141-146, 1996
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During a study of a pumped storage system from May 1979-June 1980 the profundal macrobenthos of the upper reservoir (Lago di S.Maria Valvestino) was sampled at a fixed station and the population of the tubificid Tubifex tubifex studied in detail. Eggs, embryos and the individuals living in an extra-cocoon stage were counted and individually weighed from monthy samples, according to the methods described in Bonomi & Di Cola (1980). Numerical recruitment during the study period was estimated as 257 000 ind. m-2 yr-1; of which 110 000 died either as egg or as embryos, i.e. inside the cocoons, and a further 128 000 died before they attained sexual maturation. The data seem to confirm the typical demographic strategy of T. tubifex i.e. high fecundity and high mortality in the early life stages. The total annual production of the species was estimated at 91.7 g (w.w.) m-2. The low P/B ratio (2.0 yr-1) is considered to be mainly due to high population densities.