Taste attractivity of tropical echinoderms for barramundi Lates calcarifer

Abstract

Fish meal has become the suppressing factor for fish feed development. The current practice of using forage fish as the protein source in fish feed is not sustainable and is one of the major bottlenecks in the aquaculture industry. Numerous researchers have aimed to find newer, less expensive, and more widely available sources of protein, such as food industry by-products and other local raw materials. Echinoderms (sea stars, sea urchins, and sea cucumbers) are common and abundant in marine shallow and intertidal areas, but only some of them are harvested and cultivated. An experiment was conducted with barramundi Lates calcarifer juveniles (7–9 cm total length) to examine the taste attractivity of several echinoderm species, including the pest crown-of-thorns sea star Acanthaster planci, which devastated live coral reefs during population outbreaks. Feeding behavior that accompanies fishes' responses to agar pellets flavored with hydrophilic extracts of echinoderms was evaluated. It was found that extracts of 5 out of 6 species (sea stars Linckia laevigata, A. planci, Culcita novaeguineae, Fromia milleporella, holothurian Holothuria atra) had an aversive taste for barramundi. In contrast, extract of sea urchin Diadema setosum was highly palatable. The barramundi repeatedly grasped the pellet with an aversive taste before rejecting it. Palatable pellets were swallowed after a single grasp but were retained in the fishes' mouth much longer than less palatable ones. Pellets having a size about 5% of the fish's body length (4 mm) were often fragmented by fish during intraoral processing. Fragmentation of pellets correlates negatively with pellet retention time but positively with repeated grasps performed. The present study has shown that most of the echinoderms examined are unpalatable for barramundi and the use of these animals as an ingredient in barramundi feed is not recommended.