Large-scale changes in the spatial distribution of South African West Coast rock lobsters: an overview

Abstract

A major shift in resource availability in the West Coast rock lobster Jasus lalandii from the traditional fishing grounds on the West Coast to the more southern fishing grounds was observed between the late 1980s/early 1990s and the turn of the century. The contribution of the West Coast region to total lobster landings declined from about 60% to <10%, whereas in the southern region it increased from around 18% to 60% during that period. The early 1990s was also the start of a major influx of lobsters into the area east of Cape Hangklip, an area not previously associated with high lobster abundance. Whereas the 1990s was a period of change, the period 2000 to present has been one of relative stability in lobster catches. The ecological, fisheries and resource management implications of these shifts have been severe and are likely to cause challenges in the future management of both the rock lobster and abalone Haliotes midae resources. The temporal coincidence of the shifts in lobster distribution with events such as the onset of reduced somatic growth and increased lobster walkouts suggests environmental forcing factors, as do congruent changes in other components of South Africa's Western Cape marine ecosystems. However, despite a number of studies on the variability of the physical environment, the causes of these events remain poorly understood.

Keywords: environmental change; Jasus lalandii; southward distributional shift; West Coast rock lobster

African Journal of Marine Science 2008, 30(1): 149–159