Distribution pattern of shrimps and fish among Avicennia and Rhizophora microhabitats in the Pagbilao mangroves, Philippines

For sustainable management of mangrove ecosystems, there is a pressing need to increase our knowledge of fish and invertebrates associated with this s ystem. This study sampled microhabitats (89-258 m(2)) inside the mangrove f orest at Pagbilao, the Philippines, on two consecutive spring tides using s take nets. Distribution patterns of shrimps and fish were compared among fo ur microhabitats that differed in dominant mangrove species (Avicennia mari na, A. officinalis or Rhizophora apiculata), structural complexity of the r oot system, and proximity to open water habitat. A 5 to 6-year-old replante d Rhizophora microhabitat was also sampled to study faunal recolonization f ollowing replantation. The mean (+/- SE) density of the shrimp community wa s 1.5 +/- 0.2 shrimps m(-2), dominated by Palaemonidae, followed by Acetes sp., Penaeus merguiensis and Metapenaeus ensis. The highest shrimp density was observed in the replanted Rhizophora habitat, which also had the highes t structural complexity. The mean (+/- SE) density and biomass of the fish community was 5.1 +/- 2.0 fish m(-2) and 10.4 +/- 3.3 g m(-2), respectively , dominated by Ambassis kopsi, A. urotaenia and Atherinomorus balabacensis. The fish community preferred the pneumatophore (Avicennia) microhabitats t o the prop root (Rhizophora) habitats. Highest fish abundance and biomass w ere observed in the most inland habitat, which also lacked larger (total le ngth >100 mm) carnivorous fish. The results demonstrate the extensive use o f intertidal mangrove forests by vagile fauna, as well as the successful re colonization by shrimps and fish of replanted Rhizophora habitat. The role of mangroves as predation refuges, based on the distribution pattern of shr imps and fish, is discussed. Sampling strategies in mangrove intertidal hab itat are also outlined. (C) 1999 Academic Press.