Prey selection of juvenile seahorse Hippocampus reidi

The culture of ornamental organisms is seen as a possible alternative to capturing wild specimens. The low newborn survival in seahorse aquaculture may be related to the provision of ideal live food since seahorses do not accept dry food. In most cultures of seahorses, juveniles are fed Artemia sp. nauplii and rotifers however, the newborn survival is not always satisfactory. The use of wild pelagic or cultivated harpacticoid copepods in marine larval fish cultures can promote higher juvenile growth and survival. The objective of this study was to evaluate the ingestion rate and prey selection of juvenile seahorses, Hippocampus reidi, 1, 5 and 10 days after release, for: copepod (Tisbe biminiensis) offspring, Artemia sp. nauplii, enriched Artemia sp. metanauplii and rotifers (Brachionus plicatilis) in relation to prey and mouth size. The experiments tested 4 treatments mixing two live preys at 50% proportion at 10 mL− 1, and were performed on 5 experimental units of 600 mL glass beakers with 10 juveniles each at 26 to 28 °C, 30 salinity. Five beakers with the same mix of food without juveniles were used as controls for each treatment. After 5 h, 3 samples of 10 mL per beaker were collected and fixed to estimate the final food concentration. The ingestion rate, the proportion of offered and ingested preys, Ivlev selectivity indexes (I), prey sizes and mouth sizes of the juveniles were estimated. T. biminiensis offspring and rotifer (B. plicatilis) were positively selected for the 1 DAR, and Artemia were negatively selected. At the fifth and tenth day the negative selection disappeared in treatments, except the treatments with rotifers. The width of most prey items on the first day were compatible with the hypothetical maximal size of the prey estimated from mouth size, thus prey size doesn't appear to be the cause of the prey selectivity of the newly released juveniles. These results indicated that copepods or rotifers were important food items for the feeding of 1 DAR H. reidi.