Catch Biomass Research Articles

The Fish Community of the Swartvlei Estuary and the Influence of Food Availability on Resource Utilization

Structural and functional characteristics of the Swartvlei estuary fish community are described. The detritivore group of fishes comprised 49% of the total catch biomass, zoobenthivores 25%, herbivores 18%, piscivores 6%, and epifauna/zooplanktivores 2%. The diets of 18 fish species, based on the analysis of 1,648 stomach contents, are presented. Selection by Swartvlei estuary fishes for zoobenthic invertebrates and aquatic macrophytes in different habitats was calculated using the linear index of selection. Results indicated a strong positive selection for epifaunal invertebrates and poor utilization of infauna and plants. Plant consumption by herbivorous fishes in the estuary centered around filamentous algae and diatoms growing onZostera capensis, rather than seagrass leaf material. The detrital base for both eelgrass- and sand-dominated areas in the Swartvlei estuary is emphasized, and most of the fish biomass was supported directly or indirectly by detritus. Large catches (mass per unit effort) in the macrophyte-free upper reaches site were attributed to the tidal input ofZostera leaves and associated algae to the area and its subsequent utilization by fishes through the detrital food chain.

Population dynamics of dominant demersal fishes caught in Tambelan Islands waters, Riau Archipelago Province

Yonvitner, Fahmi. 2012. Population dynamics of dominant demersal fishes caught in Tambelan Islands waters, Riau Archipelago Province. Biodiversitas 14: 200-204. The population of demersal fishes tends to be decline in the last few decades. The decline was due to the increased of intensive catches, fishing effort and illegal fishing practices. This study aimed to examine aspects of population dynamics such as mortality, recruitment, opportunity capture and population estimation. The study was conducted in six locations at Tambelan waters, on 4-16 November 2010. Collected data included the fish species, size and biomass catch. The analyses performed included mortality, recruitment, opportunity capture and population estimates (VPA). The data indicated that the Genus of Nemipterus and Lutjanus possess the highest total mortality rate that was respectively 1.62 and 2.55. The highest recruitment presentation of the population which has an annual period as Pentapodus was 16%. Catch opportunities tend to be higher than actual fishing, while the alleged biomass of steady state conditions reached 12.2 tons/yr.