Trophic Relationships of Limnoperna fortunei with Larval Fishes

Abstract

This chapter reviews investigations concerning the importance of veligers of the exotic bivalve Limnoperna fortunei in the diets of larval fish in the Río de la Plata basin. These studies have shown that of the 25 fish taxa studied, 18 consumed veligers of L. fortunei. These species included the most abundant members of Characiformes and Siluriformes. The relative frequency and biomass contribution of L. fortunei larvae differed strongly in pimelodid and Prochilodus lineatus larvae at different developmental stages and in different environments. Thus, as fish larvae grew, their diets shifted from veligers to other prey items. The fact that the earliest fish larvae are the most active consumers of veligers is particularly significant because these early larvae usually represent the most vulnerable life stage when mortality rates are the highest. In addition, field data and laboratory experiments indicate that small crustaceans have been largely replaced by L. fortunei veligers in diets of fish larvae, especially when veligers are abundant. Selectivity for feeding on veligers was recorded in the field and in laboratory experiments by manipulating prey density. Experiments also demonstrated that P. lineatus larvae grew to a significantly larger size with a high concentration of veligers in the diet. This new and abundant food resource appears to have a very important impact on the survival and growth of P. lineatus and probably other fish species as well.