Cannibalistic interactions among young anchovy: A first attempt to apply laboratory behavioural observations to the field

Abstract

It has been established from laboratory observations that anchovy larvae longer than about 15 mm SL are capable of cannibalizing eggs and smaller larvae. The probability that such predation will occur when an encounter takes place in a laboratory tank is dependent on relative predator and prey size and on the abundance of alternative prey. This attempt to apply laboratory observations to the field employs a model based on best available estimates of predation probability, predator search rate and food consumption rate, predator and prey growth rates and rate of prey total mortality. For simplicity, it was assumed that predator and prey stages are distributed randomly with respect to each other or that patches of predator and prey are distributed randomly. Alternative food was set at 2, 25 mg dry mass·m−3. The model predicted that all predator anchovy up to 35 mm SL (completion of metamorphosis) would account for only about I percent of total daily mortality of prey stages between spawning and 20 days post-hatch. Juvenile anchovy between 35 and 50 mm SL were predicted to account for 3–6 per cent of mortality of those prey stages. Situations that would lead to increased levels of cannibalism are discussed. © 1987 Taylor & Francis Group, LLC.