Species Richness Of Fish Assemblages Research Articles

The influence of depth on the Mediterranean reef fish assemblage revealed by the new video on underwater scooter method

The new video on underwater scooter method in combination with rebreather diving techniques was introduced and applied for visual census of fish assemblages. The presently applied method facilitates deeper visual census studies below 40 m, where they have rarely been done before due to the increasing research challenges with depth. The video on underwater scooter method is also expected to be less disturbing and faster compared to swimming divers. The method was applied in visual census study of fish assemblages from 8 to 50 m depth conducted at two locations in the east Adriatic using 102 video transects. The environmental variables contributing to the variation of the reef fish community in the depth range of the infralittoral and upper circalittoral bottoms were also recorded. Thirty-one fish species were recorded on transects and 10.3% of all individuals were not identified to the species level. The average density on transects was 0.8 individuals/m², with C. chromis, C. julis and G. auratus being both the most abundant and the most frequent species. Three environmental variables, depth, bottom with zoocover and eastern orientation of the coast, were identified as highly significant for species occurrence. Abundance and species richness of fish assemblages showed no significant variation with depths, inclinations, orientations and sites. A significant difference in the fish assemblage structure was found among orientations, depths and inclinations with the gradient change of species composition with increasing depth and with increasing inclination.

Density-dependent effects of non-native brown trout Salmo trutta on the species-area relationship in stream fish assemblages.

The spatial scale and density-dependent effects of non-native brown trout Salmo trutta on species richness of fish assemblages were examined at 48 study sites in Mamachi Stream, a tributary of Chitose River, Hokkaido, Japan. The density of age ≥1 year S. trutta was high in the upstream side of the main stem of Mamachi Stream. Fish species richness increased with increasing area of study sites (habitat size), but the increasing magnitude of the species richness with area decreased with increasing age of ≥1 year S. trutta density. The relationships between age ≥1 year S. trutta, however, and presence-absence of each species seemed to be different among species. Species richness was also determined by location and physical environmental variables, i.e. it was high on the downstream side and in structurally complex environments.

Seychelles' marine protected areas: Comparative structure and status of reef fish communities

Effective management of Seychelles' reef resources is essential because the conflicting demands of fishing, tourism and conservation must be reconciled if sustainable development and the protection of natural resources is to be assured. Marine protected areas play a key role in the existing management strategy and yet there is little quantitative understanding of the benefits they may provide. We compare the biomass and species richness of fish assemblages on coral and granitic reef habitats in four areas which receive different levels of protection from fishing and other human activities. Species richness of the total fish community, biomass of the total fish community and species richness and biomass of many families were higher on both coralline and granitic reefs in two marine protected areas where protective regulations were effectively enforced. However, the biomass of the three principal families of fishes targeted by the fishery was significantly lower in one of these areas. This was attributed to illegal fishing and the fishing concessions offered to local people. We conclude that poaching and minor fishing concessions did not affect the aspects of the fish community which are important to most tourist visitors (biomass and overall species richness), but that they have a statistically significant effect on the structure of the fish community. Furthermore, whilst a small well-patrolled area will provide an effective refuge from fishing, it will often be stocked by larval fishes which are the progeny of adults living many kilometres away. As such, the protected area cannot operate in isolation to maintain biomass and diversity. A valid longterm aim of reserve management may be to assure the protection of a greater proportion of Seychelles' fishes throughout their life history. This may be achieved if current plans for the management of marine protected areas can be instituted.