Fish habitats in a small, human-impacted Sibunag mangrove creek (Guimaras, Philippines): a basis for mangrove resource enhancement
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The fish assemblage of a small, open access mangrove creek highly influenced by aquaculture farms, was studied for the first time in the Philippines as a baseline of such system as well as examining the degree of ecological disturbance among fish habitats, as basis for the necessity to rehabilitate mangrove resources aiming to balance human activities and mangrove functioning. In total, 475 fishes (total weight = 3875 g) were captured and 50 species representing 32 families were identified. Thirty two species were represented by small numbers (< 5 individuals). Commercial species was considerably high (~23 species) but majority were low grade commercial species. Total species, species diversity and fish abundance consistently showed a decreasing pattern from outside creek to inner creek. Fish habitats exhibited substantial differences following a distinct spatial segregation of fish communities, a dominance of non-shared species and a minimal species overlapping inside the creek, which is attributable to the existing mangrove fragmentation associated with aquaculture ponds in the area. Increasing levels of disturbances were observed within the creek indicating ‘stress’ as a result of overutilization of mangroves by aquaculture farms. Our results confirmed the need to rehabilitate mangrove resources in this area. The development of mangrove resources through reforestation, coupled by strict regulation of fishing activities and aquaculture ponds will reduce ecological stress in the area and regain gradually a robust mangrove functioning that will improve fish diversity, fisheries and productivity of adjacent coastal systems by creating a suitable fish nursery, feeding ground and refuge habitat.
CitationAbrogueña, J. B. R., Bagarinao, T. U., & Chícharo, L. (2012). Fish habitats in a small, human-impacted Sibunag mangrove creek (Guimaras, Philippines): a basis for mangrove resource enhancement.
Aquatic habitats; Fisheries; Animal populations; Aquaculture; Rivers; Mangrove swamps; Feeding; Abundance; Habitat; Ponds; Fishing; Species diversity; Commercial species; Mangroves; Biomass; Fish assemblage; Small mangrove creek; Disturbance; Aquaculture pond; Fragmented mangroves; Farms; Reforestation; Philippines
J.B.R. Abrogueña is grateful for the thesis grant given by the Erasmus Mundus Master of Science in Marine Biodiversity and Conservation (EMBC).
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Evaluation of hatchery-based enhancement of the mud crab, Scylla spp., fisheries in mangroves: comparison of species and release strategies MJHL Lebata, L Le Vay, ME Walton, JB Biñas, ET Quinitio, EM Rodriguez & JH Primavera -
Marine and Freshwater Research, 2009 - CSIRO PublishingRanching, stock enhancement and restocking are management approaches involving the release of wild or hatchery-bred organisms to enhance, conserve or restore fisheries. The present study, conducted from April 2002 to November 2005, evaluated the effectiveness of releasing wild and hatchery-reared (HR) mud crabs in the mangroves of Ibajay, Aklan, Philippines where preliminary studies demonstrated declining fishery yields, abundance and size of crabs. Comparison of survival and growth of wild-released and HR Scylla olivacea and HR Scylla serrata demonstrated the effect of nursery conditioning, size-at-release and species differences. Overall yield and catch per unit effort (CPUE) increased by 46% after stock enhancement trials. Recapture rates of released crabs were highest in wild-released S. olivacea and in crabs measuring 65.0–69.9 mm carapace width (CW) and lowest in non-conditioned HR S. serrata. Growth rates were highest for conditioned HR S. olivacea and lowest for conditioned HR S. serrata (11.7 and 3.7 mm month-1 respectively). Fishing mortality was highest for S. olivacea, whereas natural mortality was greater for S. serrata. Conditioning hatchery-bred animals before release is also important in obtaining higher survival. S. olivacea was the more appropriate of the two species for release in mangrove habitats inundated with low-salinity water. However, there is a need for site-specific studies to evaluate the effectiveness of releases.
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Journal of Experimental Marine Biology and Ecology, 1997 - ElsevierThe effect of habitat structure and substratum on predation of the greasyback shrimp Metapenaeus ensis (De Haan), white shrimp Penaeus merguiensis De Man and tiger shrimp Penaeus monodon Fabricius by sea bass Lates calcarifer Bloch and mangrove snapper Lutjanus argentimaculatus (Forsskal) was evaluated. The shrimp juveniles measured 6–15 mm in carapace length; fish measured 6.5–12.5 cm in standard length; structure types were pneumatophores of the mangrove Sonneratia griffithii Kurz and dried coconut leaf bracts; structure densities were 0, 32 and 98 pneumatophores per tank; and sediment particle sizes were pebbles, sand-granules and silt–sand. Predation on shrimp was significantly higher in controls or bare sand (48.7%) than among pneumatophores (29.9%), but not among leaf bracts (43.5%). Shrimp mortality was also significantly higher on bare sand (72.9%) compared to medium-density (54.2%), but not high-density (68.8%), pneumatophores. Fish predation on the burying shrimp M. ensis was affected by predator type but not by sediment size. The generally higher predation rates of snapper may be due to their habit of leaving unconsumed pieces of shrimp, whereas sea bass which devour whole prey require fewer shrimp to reach satiation. Moreover, the presence of structures did not affect sea bass behaviour of chasing prey among pneumatophores and under leaf bracts, but reduced predation by the relatively passive snapper. Predation rates among pneumatophores vs. control, and among medium-density pneumatophores vs. bare sand, were lower for P. monodon but not P. merguiensis. This may be related to the greater and more frequent use of (laboratory) shelters by juvenile tiger shrimp compared to white shrimp. The results demonstrate that the effective provision of shelter depends not only on structure type and density but on the behaviour of predator and prey as well. The use of mangrove structures (pneumatophores) by juvenile shrimp as refuge from predation is also documented for the first time.
Baseline assessment of fisheries for three species of mud crabs (Scylla spp.) in the mangroves of Ibajay, Aklan, Philippines MJHL Lebata, L Le Vay, JH Primavera, ME Walton & JB Biñas -
Bulletin of Marine Science, 2007 - University of Miami, Rosenstiel School of Marine and Atmospheric ScienceStock enhancement through habitat restoration and habitat release have both been considered as approaches to the management of declining Scylla spp. Prior to stock enhancement trials, the present study was conducted to monitor recruitment and yields of three Scylla spp. in ∼70 ha of natural mangroves in Aklan, Panay, Philippines. Results showed that Scylla olivacea (Herbst, 1796) was the most abundant mud crab species, comprising 95% of the catches over the 4 yr sampling period. Size distribution for this species indicated year-round recruitment with peaks in the numbers of smaller, immature crabs during the summer months. The decreasing mean size at capture, yield and CPUE in terms of weight throughout the 4-yr sampling period is an indication that the area has been subjected to heavy fishing pressure. The constant CPUE in terms of numbers of crabs suggests that recruitment is constant, though this is likely to be lower than in other mangrove areas due to the topography of the site with limited access to the open sea, resulting in relatively low crab abundance and yields. Combined with the fidelity of S. olivacea to the mangrove habitat, this indicates a suitable population for investigation of the effectiveness of a hatchery-release program.