Coral reefs form the basis of many small scale subsistence fisheries throughout the world and therefore are an important food source for coastal communities. The aim of coral reef fisheries management is to increase the sustainable yield. The objective of this pilot project was to explore a general experimental method which can ultimately be used to derive assessment techniques and improve benefits from these fisheries. An experiment was carried out to monitor changes in fish populations before and after fishing within a study area. The study site chosen was situated at the southern end of Zanzibar Island, off the east coast of Tanzania. Transect counts were used to estimate fish abundance inside and around the fishing area. Detailed information was collected concerning the catches, including species, length and weight. The preliminary analysis of the data concentrated on two species, Lethrinus borbonicus, which made up 50% of the catch, and Chaetodon kleinii, which is very rarely caught. As fishing progressed, there was a notable decline in catch per unit effort (CPUE) mainly caused by falling numbers of L.borbonicus in the catch. There was a distinct change in the catch species composition, because L.borbonicus declined at a faster rate than other species. Catches of L.borbonicus dropped during night fishing, suggesting that L.borbonicus dispersed from the reef during night hours, as do other lethrinids. Analysis of the census data showed that there was a large difference between the abundance of fish at different sites in the study area. Numbers of L.borbonicus were lower after fishing even outside the fishing area. In contrast C.kleinii showed no significant decline. The analysis presented here is incomplete. It has, however, been demonstrated that the data from such experiments has an important role in developing new fisheries assessment techniques. The data would allow gear selectivity to be estimated, necessary to interpret catch species composition correctly and to estimate the impact of increased fishing effort on the coral reef community. It should also be possible to develop a model describing the effects of fish distribution and movement, a requirement for setting up fishing reserves as well as interpretation of catch data. However there is a clear need to develop some theoretical models and statistical methods to these data.
TMRU Ltd., University of York, UK, 27 pp.