Retrospective evaluation of data-limited fisheries: a case from Hong Kong

This study reconstructs the likely historical changes of the data-limited Hong Kong's inshore fisheries and evaluates their probable effects on the marine ecosystem, based on multiple information sources. Local knowledge on changes in the fisheries and the marine ecosystem is collected from commercial fishers, recreational divers and fishery officials. We combine this knowledge with results from simulation modelling and information from published and unpublished literature and reports to generate hypotheses on the historical changes in the fisheries and ecosystem between 1950 and 2000. The analyses suggest that traditionally targeted fishes had already been over-exploited by the 1970s, following a rapid drop in catch per unit effort in the 1960s. This paralleled a dramatic expansion of fishing effort. Ecosystem structure shifted as the large predatory species became depleted and small fishes and benthic invertebrates gained dominance. High demand for small fishes as fish-feed for aquaculture farms, high market price of benthic invertebrates, and reduced operational costs of fishing by smaller boats evidently provided support and incentives for continued depletion. We develop fishery management policy options that aim to reverse the depletion trend. This approach of retrospective evaluation combines fragmented information from multiple sources to generate management policy options that should be useful to assess fishery status and history in a data-poor fishery. It can be used to obtain insight into a fishery from a region in which little formal scientific study has been conducted, although it is no substitute for rigorous analyses when sufficient data are available.