Functional response of Ameca splendens (Family Goodeidae) fed cladocerans during the early larval stage

" We studied the functional response of the goodeid Ameca splendens, an endangered species from rivers Ameca and Teuchitlán (Jalisco, Mexico), from birth until 8 weeks old. The cladocerans, Alona glabra adults, Simocephalus vetulus neonates, Ceriodaphnia dubia adults, Daphnia pulex juveniles and Moina macrocopa adults were used as prey. The prey densities, depending on the species, ranged between 0.25, 0.5, 1.0, 2.0, 4.0, 6.0, 8.0, 16.0 and 32 ind/ml;, with four replicates at each density. We found that all functional responses were Type II. During the feeding period of 30min, the fish larvae consumed about 600 individuals of the smallest prey A. glabra (450 mm). The consumption of larger prey (<1.0mm) such as S. vetulus, C. dubia, D. pulex and M. macrocopa ranged between 150 and 200 prey/larva during the feeding trials. Our study shows that A. splendens reached maximal prey consumption at around 4 weeks of age, after which there was no increase in prey consumption during the feeding period with age until the end of the study period of 8 weeks. Our study indicates that prey digestion rather than handling time determines the functional response in this fish species and that M. macrocopa is most suited as live food for A. splendens "