MARINE, BRACKISH, AND FRESH-WATER FISH COMMUNITIES IN THE VEGETATED AND BARE SHALLOWS OF AN AUSTRALIAN COASTAL RIVER

Fish communities found in the marine, brackish, and freshwater shallow s of the Clarence River (New South Wales, Australia) were sampled over a 12-mo period to compare communities inhabiting bare and vegetated s ubstrata. A total of 26,107 fish representing 57 species and 36 famili es was collected bimonthly using a 6-mm mesh seine. Permanent resident s (i.e., species found throughout the year) were primarily gobies (Gob iidae) and gudgeons (Eleotridae). Juveniles of many species found as a dults in other parts of the river were seasonally abundant in the shal lows. Most numerous was a small ambassid, the glassy perchlet (Ambassi s jacksoniensis), the majority of which was collected from marine and brackish regions of the river. Firetail gudgeons (Hypseleotris compres sus) were caught in highest numbers at the freshwater sites. Cluster a nalysis suggested that fish communities in widely separated vegetated sites were more similar to each other than to those in adjacent bare s ites. Shallow vegetated (Zostera capricorni) habitats in the marine re gion of the river had greatest diversity and highest abundances of fis h, particularly during recruitment periods. At these times, juveniles of many commercially important species were captured, including yellow fin bream (Acanthopagrus australis), sea muller (Mugil cephalus), flat -tail mullet (Liza agentea), tarwhine (Rhabdosargus sarba), luderick ( Girella tricuspidata), silver biddy (Gerres subfasciatus), and sand wh iting (Sillago ciliata). The vegetated (Vallismeria gigantea) sites in the brackish region also had significantly more species and individua ls during recruitment periods (spring) than bare sites. Although fresh water vegetated sites consistently had more individuals than freshwate r bare sites, there were no significant differences in species richnes s between vegetated and bare habitats. The need to conservatively mana ge shallow-water fish habitats is stressed.