Mangrove structure and mud crab population in northern Samar
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This study assessed the mangrove community structure, relative seasonal abundance of all size classes of crabs (catch per unit effort or CPUE) and percent composition of the catch in two collection grounds in Pambujan and Rosario, Northern Samar using cylindrical bamboo traps and lift nets. Mangroves in Pambujan was dominated by Avicennia marina and A. alba. The initial total count of mangrove trees (67 stems ha-1) was slightly higher compared with the final count (61 stems ha-1). On the other hand, mangroves in Rosario was dominated by Rhizophora apiculata and R. stylosa. The total count of mangrove trees was higher in the initial (108 stems ha-1) compared with the final (46 stems ha-1). However, saplings and seedlings increased in both sites after 18 months. Mean CPUE ranged from 0.04 to 0.4 crabs using cylindrical bamboo traps in the monthly spring tide sampling for 19 months in Pambujan. High mean CPUE was recorded in February and August 2008. Mean CPUE ranged from 0.04 to 0.41 crabs using lift nets in the monthly spring tide sampling. The highest mean CPUE was noted in August. The initial and final CPUE were comparable. In Rosario, mean CPUE ranged from 0.3 to 1.78 crabs monthly caught in cylindrical bamboo traps and from 0.04 to 0.77 crabs in lift nets. In general, the number of crabs caught in both traps was higher in Rosario than in Pambujan. Mud crab ranged from 2.02-72.2% of the monthly total catch in lift nets in Pambujan. Other species of crabs ranging from 27.78 to 86.36% were the dominant catch in several months. In Rosario, mud crab ranged from 12.5 to 82.35% of the monthly total catch. The catch composition of the cylindrical bamboo traps was more varied compared with lift nets in both sites. The decrease in the population of mud crabs may also be associated with the decrease in mangrove trees. With the continuous cutting of trees and regular extraction of all sizes of mud crabs, the industry may no longer become sustainable. This paper is the first to be done on the assessment of the mud crab population in Northern Samar and the information gathered can be used as basis for the development and improvement of the existing fisheries legislation for the conservation and management of the remaining wild resources.
Quinitio, E. T., Vista, E. B., Vista, R. C., & Lebata-Ramos, M. J. H. (2017). Mangrove structure and mud crab population in northern Samar. In E. T. Quinitio, F. D. Parado-Estepa, & R. M. Coloso (Eds.), Philippines : In the forefront of the mud crab industry development : proceedings of the 1st National Mud Crab Congress, 16-18 November 2015, Iloilo City, Philippines (pp. 89-98). Tigbauan, Iloilo, Philippines: Aquaculture Department, Southeast Asian Fisheries Development Center. http://hdl.handle.net/10862/3161
PublisherAquaculture Department, Southeast Asian Fisheries Development Center
Catch composition; Catch/effort; Dominant species; Mangrove swamps; Mangroves; Marine crustaceans; Population number; Population structure; Resource conservation; Seasonal variations; Seedlings; Species diversity; Sustainability; Scylla; Avicennia alba; Avicennia marina; Rhizophora apiculata; Rhizophora stylosa; Philippines
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Conference paperJH Primavera - In ET Quinitio, FD Parado-Estepa & RM Coloso (Eds.), Philippines : In the forefront of the mud crab industry development : proceedings of the 1st National Mud Crab Congress, 16-18 November 2015, Iloilo City, Philippines, 2017 - Aquaculture Department, Southeast Asian Fisheries Development CenterThe paper reports the use of mangroves by Scylla species both as wild and culture habitats. Based on published literature, natural mangrove crab populations are described in terms of population density, dispersal and movement within and outside mangroves, crab burrows and associated mangrove species. Strategies for Scylla conservation depend on the kind of mangrove habitat - (mangrove) restoration for open fringing mangroves where crab recruitment and abundance are determined by habitat availability vs stock enhancement in closed basin mangroves with restricted recruitment and limited movement of crabs. Mangrove crabs are also reared in monoculture in mangrove cages and pens, or in polyculture with milkfish in extensive ponds (where mangroves used to thrive). The paper describes a SEAFDEC Aquaculture Department study to evaluate the effects of mud crab net pen systems on mangrove macroflora, and the replacement of dietary trash fish with low-cost pellets. Results showed that incomplete, low-cost pellets can replace fish biomass requirement in mud crab diets, but that crab presence resulted in fewer mangrove seedlings and saplings. Economic analysis showed the viability of crab culture in mangrove pens using a combination of fish biomass and pellets to reduce the requirement for (low-value) fish, which is a food item of poor coastal communities.
Post-August 2006 oil spill populations of Penaeid shrimp in island and riverine mangroves in Guimaras, central Philippines JH Primavera & JB Abroguena -
Philippine Journal of Natural Sciences, 2009 - University of the Philippines VisayasTo evaluate the impact on biota of the release of arrow up million liters of bunker oil off Guimaras Island, Central Philippines, the penaeid shrimp populations in a protected island mangrove (Tandog) and a riverine mangrove (Sibunag) were surveyed by pocket seine 2-3 months after the August 2006 spill; results are compared to 1993 baseline data. A total of 529 individuals belonging to three penaeid species were collected - Metapenaeus anchistus in Tandog, and Metapenaeus ensis and Penaeus merguiensis in Sibunag. Shrimp densities were significantly higher in Tandog Island in 2006 compared to 1993 but remained similar in the riverine mangrove. This suggests that protection may have a greater impact than the Oil Spill per se because Tandog is part of the protected Taklong National Marine Reserve. In contrast to abundance, shrimp sizes (carapace length) were significantly smaller in 2006 compared to 1993 for both sites.
Fish habitats in a small, human-impacted Sibunag mangrove creek (Guimaras, Philippines): a basis for mangrove resource enhancement 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.