Jasus lalandii fishery in post-independence Namibia: monitoring population trends and stock recovery in relation to a variable environment

Abstract

Commercial exploitation of the Namibian Jasus lalandii stock started in the early 1920s. Catches were high until the mid 1960s, with annual landings of up to 9000 t. During 1968 and 1969 the minimum legal size limit was abolished, a collapse occurred in the stock, and annual catches declined to 1000–3000 t. During a 1988 warm-water event mass mortalities of lobsters were recorded, and catches continued to decline over the following three years. In 1992 the total allowable catch (TAC) was set at 100 t, and finally limited catches. Subsequently, TACs have been kept low and some fishing grounds have been closed to the industry. Since 1992 the Namibian lobster research programme has been intensified, incorporating regular environmental and lobster surveys on the main fishing grounds. During the environmental surveys, a seasonal cycle in bottom concentrations of dissolved oxygen observed during the 1980s was confirmed along the southern part of the Namibian coast. This seasonality in environmental parameters is thought to contribute to inshore–offshore migrations of the lobster populations and thus to variable catch rates. Results from commercial and research samples over the past five years indicate improved recruitment and increased, although variable, catch per unit effort.