Worldwide, fisheries produce ~27 million tons of by-catch yr -1 . By-catch is defined as unwanted fish that are accidentally caught, or discarded carcasses of target species. In Bonaire, N.A., by-catch is produced on a relatively small scale, by artisanal fishermen cleaning fish that they caught and discarding the remains back into the ocean. This study examines the feeding behaviors of fish in Bonaire and the effect fishermen’s by-catch has on these behaviors, and also investigates the potential for fish to learn about sites of by-catch input. This study was performed in two parts, the first assesed the effects of established by-catch sites, while the second part focused on learning behaviors of fish. Bites per minute, time of arrival to the food source and fish population data was collected at sites along Kaya Playa Lechi where fishermen were present daily. The same data was collected 30 m away from the fishermen at simulated by-catch sites, as well as at control sites where no by-catch was present. In part II, the discarding of fish was simulated at sites that do not receive it on a normal basis, to obtain observations on fish reactions to a new food source. It was found that densities and biodiversity were significantly greater at by-catch treatments vs. control treatments for part I. Bites min-1 was greatest when by-catch was present and the time of arrival data showed that the greatest proportion of fish arriving for the fishermen’s by-catch was within the first 15 s. For part II, densities and biodiversity were greater at control treatments than at simulated by-catch treatments. Bites min-1 was greater at simulation treatments, and there was a decrease in the time of arrival over the three day observation period. This data shows that relatively greater fish densities were seen at sites of food input, that fish were more aggressive when by-catch was present, and that fish can learn that to respond to sites with a consistent input of by-catch.
This student research was retrieved from Physis: Journal of Marine Science VII (Spring 2010)19: 21-26 from CIEE Bonaire.