Individual study: Effects of depth and marine reserve fishing restrictions on the structure of a rocky reef fish assemblage at Banyuls-Cerbère marine reserve, Languedoc-Roussillon, France
Bell J.D. (1983) Effects of depth and marine reserve fishing restrictions on the structure of a rocky reef fish assemblage in the north-western Mediterranean Sea. Journal of Applied Ecology, 20, 357-369
There have been few attempts to evaluate the effects of restricted fishing activity in marine reserves on fish populations. Scuba diving censuses, in which abundance and size class of conspicuous fish species were determined, was used to assess the effects of depth and reserve fishing restrictions on the structure of a Mediterranean rocky reef fish assemblage by comparing communities at sites from two depth ranges inside and outside a marine reserve.
Study site: This study was undertaken within and adjacent to the Banyuls-Cerbère marine reserve (3º08'E, 42º29'N) on the French Mediterranean coast. The reserve (mostly rocky reef) encompasses approximately 5 km of foreshore extending into the sea for approximately 2 km. The reserve was declared in February 1974 and spearfishing was prohibited. Amateur angling and commercial fishing with gill nets were permitted to continue. In August 1979 a central area (1 x 1.5 km) was closed to all fishing. Shallow (7-10 m) and deep (15-20 m) sites with reefs of comparable structure were selected in an area subject to fishing outside the reserve 4 km to the north.
Transects: Transects (4 m wide x 150 m long) were delineated with cords. Sampling was conducted by swimming slowly along a transect, recording abundance of small, medium and large individuals of each conspicuous fish species. A transect generally took 25 minutes to complete.
A total of 35 ‘conspicuous’ fish species was recorded dominated by two families: wrasses Labridae (13 spp.) and seabream/porgies Sparidae (9 spp.). Average species richness and diversity did not differ significantly between the two areas. Samples from the same depth were similar as the majority of species showed a preference for either deep or shallow areas. Reserve transects however, had higher densities of fish species sought after and/or vulnerable to local fishing methods, than those from non-reserve sites of similar depth. Size frequency distributions of vulnerable species at reserve sites were generally in larger size class than non-reserve sites.
Conclusions: This study suggests that within this marine reserve, reduced fishing pressure has provided at least some protection for species vulnerable to fishing.