Preliminary trials to rear the copepod Temora stylifera as food for fish larvae

Abstract

Copepods represent an important natural food supply for many fish larvae but they are not commonly used in aquaculture. The aim of this project is: 1) to set up an experimental re-circulating system to breed the copepod Temora stylifera and 2) to replace Artemia salina with T. stylifera as live food for Sparus aurata larvae. The choice of this copepod species has been based on both its abundance in the Mediterranean as well as its characteristics in terms of size and nutritional value. The re-circulating system consists of a collecting water tank of 1,000 litre of capacity, a thermoregulation system, two 500 litre tanks to rear adults and two 200 litre tanks to collect nauplii. The system allows the computerised water re-circle and to concentrate and collect nauplii through their positive response to light. It can work both in a partial re-circle way, for the thermoregulation only, as well as in a total re-circle way for the water purification through mechanic and biological filters. The culture system can host a minimum of 5,000 T. stylifera females, which will daily produce 75,000 nauplii, approximately. In a preliminary phase of this study, different uni and pluri-microalgal diets have been tested in order to maximise T. stylifera egg production rate and hatching success. Algae with high fatty acids contents were used to improve the nutritional value of nauplii and copepodids. Uni-algal diets, Prorocentrum minimum and Isochrysis galbana, were singularly provided at a mean carbon concentration of 1mg C/l. Egg production and hatching success were 19.4±11.4 eggs/female/day and 63.8% for copepods fed on P. minimum and 4.5±7.8 eggs/female/day and 42.2% for those fed on I. galbana, respectively. In the pluri-microalgal diets, P. minimum was still supplied at 1mg C/l, whereas I. galbana was given as enrichment food at high concentrations based on the size ratio of P. minimum and I. galbana. At present, the best results in terms of egg production (31.8±16.8 eggs/female/day) and hatching success (75.4%) were obtained with the mixed diet of P. minimum and I. galbana.