Assessment of the abundance and distribution of burrowing sandprawns and mudprawns (Callichirus and Upogebia species) in Langebaan Lagoon, South Africa

摘要

A survey of sandprawns and mudprawns was undertaken in intertidal and subtidal zones in Langebaan Lagoon, West Coast National Park, South Africa, to determine their stock status and to gain an understanding of the spatio-temporal patterns in abundance and distribution. Four species were recorded: Callichirus kraussi, C. rotundicaudata, Upogebia africana and U. capensis. Callichirus kraussi was broadly distributed, occupying most of the intertidal area, whereas U. africana was confined to the head of the lagoon or beds of eelgrass in the upper sections of intertidal zones. Upogebia capensis was prominent in subtidal areas, occupying deeper areas below the zonation of C. kraussi. Callichirus rotundicaudata was rare. The distribution of the different species of prawns was related to sediment characteristics, with C. kraussi dominant in intertidal sandy areas, U. africana in high-shore vegetated zones and intertidal areas at the head of the lagoon where sediments were finer and had a high mud content, and U. capensis in subtidal areas with similarly fine sediments. Sediment characteristics were dictated by shore height, differences between east and west banks, and distance from the lagoon mouth. For the whole of Langebaan Lagoon, stocks of C. kraussi, U. africana and U. capensis were estimated to be 8 800 million, 380 million and 660 million animals respectively. Assessments of the proportions of the stocks protected in 'no take' zones of the system (82-98%), and of rates of removal by bait collectors (<0.01% per annum), indicate that the resources are being sustainably harvested.