Species composition of fish in mangrove canals as reflected from coastal land use at Trat Bay

Abstract

The study on species composition of fish in 3 mangrove canals at Trat Bay was conducted during wet season (Aug.-Oct. 97) and dry season (Dec. 97-Feb. 98). All 111 species from 47 families of fish were collected by push net and drift gill net. Basing on the visual interpretation of LAND SAT-TM image of Trat Bay in 1987, 1992 and 1997, the different coastal land use on the both sides of 3 mangrove canals caused the different environment of those canals and reflected in different species composition of fish found. Total 95 species of fish were fond from Bangphra Canal, which runs through the natural recovery mangrove and without shrimp farming on both sides. The index value of species diversity of fish found from this canal was 2.54 in wet season and 3.10 in dry season. Seventy-five species of fish were found from Thaprik Canal, which runs through the destructive mangrove and almost of shrimp farming area on the both sides. The index value of species diversity of fish found from the canal was 2.41 in wet season and 3.02 in dry season. A total of 80 species of fish were found from Thaleuan Canal, which was covered with the abundant natural mangrove and without shrimp farming on the both sides. However, the inner part of the canal was installed by wafer gate, which was opened in wet season and might affect to the distribution of fish, resulting from the lowest species, 39 species, found from Thaleuan Canal in the same season. The index value of species diversity of fish found from the canal was 2.24 in wet season and 2.83 in dry season. From the statistical analysis, total weight of fish collected by push net in both seasons of 3 canals was not different but total weight of fish collected by drift gill net in both seasons of 3 canals was significantly different (P<0.05) The CPUE by drift gill net was 0.12 kg/hr. from Bangphra Canal, 0.09 kg/hr. from Thaprik Canal and 0.06 kg/hr. from Thaleuan Canal. The results of the regression and correlation coefficient analysis showed that species number of fish had relationship with surface and bottom salinity, bottom DO, surface pH, concentration of surface P043- and zooplankton volume.