Effects of feeding copepod and Artemia on early growth and behaviour of the self-fertilizing fish, Rivulus marmoratus, under laboratory conditions

Growth and survival have often been used as parameters to assess the effects of live feeds on marine finfish, however, behavioural effects, which entail energy cost and may have consequences on fish growth have been given less emphasis. Thus, a 20-day feeding experiment was conducted to determine the effects of copepod Acartia tsuensis (104–732 μm), unenriched, and docosahexaenoic acid, DHA-enriched, first instar Artemia franciscana nauplii (656–906 μm) on growth and behaviour of the mangrove killifish Rivulus marmoratus. Growth was significantly higher in Acartia-fed larvae compared with larvae fed Artemia (unenriched and DHA-enriched) until day 10. On day 20, Acartia-fed larvae had significantly lower growth than fish fed DHA-enriched Artemia. Feeding success was highest in larvae fed Acartia on day 1. Ingestion rate and satiation time did not differ among fish fed different types of feeds until day 20. Swimming activity before feeding was significantly lower in larvae fed Acartia compared with larvae fed Artemia (unenriched and DHA-enriched) until day 10. Higher growth in Acartia-fed fish on day 10 is probably due to the suitable size and high DHA content of A. tsuensis, and lower swimming activity of the larvae. However, on day 20, lower growth observed in Acartia-fed fish may be attributed to the shift in the food size preference of the fish. The present study was able to demonstrate the effects of copepods on growth and behavioural development of marine finfish using R marmoratus as a model animal.