Prey preference and the consumption of sea urchins and juvenile abalone bycaptive rock lobsters (Jasus lalandii)

Recent studies on the diet of the South African rock lobster ( Jasus laland ii) have shown an increase in the consumption of sea urchins in certain are as relative to earlier assessments. Concurrent ecological surveys have demo nstrated the dependence of juvenile abalone on urchins for their survival, and a radical increase in the abundance of lobsters in the area that is the main abalone fishing ground. This paper describes laboratory experiments o n the consumption of urchins by lobsters, and the preferences for different prey species. Small lobsters (<68 mm carapace length) ate no urchins. Larg er lobsters ate urchins of all sizes, although small urchins were preferred . The consumption rate was easily sufficient for the lobsters to have cause d the documented disappearance of urchins ( and juvenile abalone) in the ma in abalone fishing area. Lobsters showed a strong preference for mussels ov er all other prey offered, and for juvenile abalone over urchins, although previous field observations and laboratory experiments have shown that urch ins provide shelter for juvenile abalone. However, if black mussels were av ailable in addition to sea urchins and juvenile abalone, consumption of sea urchins and juvenile abalone declined.