Estimation of the production ofDaphnia longispinain a mountain lake

Open Access
Publisher Website
Google Scholar
Abstract
The parameters characterizing the processes of birth, growth, death, reproduction and production of Daphnia longispina in Lake Santo Parmense, a mountain lake in Northern Apennines (Italy), have been estimated for the period lasting from June to the beginning of September 1973: in this period the population is mainly constituted by parthenogenetic females and presents the highest seasonal values of density and biomass. The production of D. longispina has been calculated using the compartmental model proposed by De Bernardi and Di Cola (1976) for the study of the biomass dynamics in populations with continuous recruitment. The trend of death rates of the different size classes and in particular of the classes including newborn individuals has been explained by admitting that the population receives an input of individuals hatched from resting eggs over a long period (till the end of August). The total daily production is supplied mainly by the size classes including preadult individuals, over the entire three-month period. The production has also been calculated from smoothed data using the methods by Petrowich et al. (1964) and Winberg et al. (1965): the latter has been applied to the original data too. The values of integrated production obtained with the different methods have been compared.