Rapid ecological assessment of tropical fish communities in a gold mine area of Costa Rica

Gold mining impacts have generated a great concern regarding aquatic systems and habitat fragmentation. Anthropogenic disturbances on the structure and heterogeneity of a system can have an important effect on aquatic community stability. Ecological rapid assessments (1996, 2002, and 2007) were employed to determine the structure, composition and distribution of tropical fish communities in several rivers and smaller creeks from a gold mining area in Cerro Crucitas, Costa Rica. In addition, species composition and relative abundance were related with habitat structure. A total of 35 species were registered, among which sardine Astyanax aeneus (Charaeidae) and livebearer Alfaro cultratus (Poeciliidae) were the most abundant fish (71%). The highest species richness was observed in Cano Crucitas (s = 19) and Minas Creek (s = 18). Significant differences in ;fish communities structure and composition from Infiernillo river and Minas creek were observed (lambda = 0.0, F-132.66 = 2.24, p < 0.001). Presence and/or absence of certain species such as Dormitor gobiomorus, Rhamdia nicaraguensis, Parachromis loiseillei and Atractosteus tropicus explained most of the spatial variation among sites. Habitat structure also contributed to explain differences among sites (lambda = 0.004, F-60,F-183 = 5.52, p < 0.001). Substratum (soft and hard bottom types) and habitat attributes (elevation, width and depth) explained most of the variability observed in Infiernillo River, Cano Crucitas and Tamaga Creek. In addition, a significant association between fish species and habitat structure was observed. This study reveals a high complexity in tropical fish communities that inhabit a gold mine area. Furthermore,it highlights the importance of habitat heterogeneity in fish community dynamics. The loss and degradation of aquatic systems in Cerro Crucitas can have a strong negative effect on fish community structure and composition of local species. A better understanding of the use of specific habitats that serve as essential fish habitats can improve tropical fish conservation and management strategies, thus increasing local diversity, and thereby, the biological importance of the area. Rev. Biol. Trop. 56 (4): 1971-1990. Epub 2008 December 12.