Behavioral analysis of rock bream Oplegnathus fasciatus reveals a strong attraction potential for sea urchin extracts

Abstract

Monitoring fish movement is important to understand how physiology adapts to environmental change. To explore the applicability of a video tracking system for determining if chemical cues attract or repel aquatic animals, the movement patterns of rock bream, Oplegnathus fasciatus, were analyzed upon exposure to various materials, including extracts of sea urchin, rock worm, bait worm, krill, barley kernel, and commercial fish feed. Pellets were prepared by mixing freeze-dried tissues with a cellulose and corn flour mixture. Behavioral analysis was carried out with five fish that had been acclimated in the adaptation zone of a Y-shaped tank. Preference toward chemical cues was quantified by assessing the frequency rock bream were observed in a discrete zone around the test material located at the end of each arm and the duration each fish stayed in each zone. The analysis of fish movement upon exposure to commercial feed and barley kernel at each end, respectively, indicated a clear preference toward the feed relative to the barley kernel. Movement responses were further tested with pellets containing extracts of sea urchin, one of the species collected on a large scale, and other materials including krill and worms. A stronger preference toward sea urchin (100%) was observed based on the duration of stay in the test zone, compared to krill (90.1 ± 44.2%), bait worm (81.1 ± 39.1%), rock worm (73.7 ± 28.9%), and barley (63.9 ± 25.9%), under the conditions tested. A detailed comparison of rock bream movements toward each material revealed significant differences in frequency and duration, respectively, between pairs of test materials including krill (74 ± 29.8 and 375.6 ± 118.9) vs. rock worm (41.5 ± 18.7 and 160.2 ± 42.6), krill (86.3 ± 22.9 and 477.1 ± 84) vs. bait worm (36.2 ± 5.5 and 166.1 ± 50.7), and rock worm (45.9 ± 26.2 and 213.7 ± 100.1) vs. bait worm (34.6 ± 21.7 and 159.5 ± 98.5). Rock bream exhibited preference for the test materials in the following order: commercial fish feed > sea urchin > krill > rock worm > bait worm > barley. The results suggest a higher potency of sea urchin extract as a rock bream fishing bait compared to the other materials that are used as commercial bait.