Pen culture of mud crab Scylla serrata in tidal flats reforested with mangrove trees
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Growth and survival of mixed sex mud crabs Scylla serrata (Forskal), held in 200 m2 pens located in reforested mangrove tidal flats, were evaluated. The effects of stocking density (0.5 or 1.5 m−2) and feed (salted fish bycatch or a mixed diet of 75% salted brown mussel flesh and 25% salted fish bycatch) were determined in a replicated factorial experiment. Duration of the experiment was 160 days. There were no significant differences (P>0.05) in growth, apparent feed conversion ratio (FCR), survival, and production among the two types of feed. Regardless of feed, the mean±SE FCR of 5.30±0.34 and survival of 56.00±1.90% at 0.5 m−2 stocking density were significantly better (P<0.05) than at 1.5 m−2 stocking density (7.6±0.63 FCR and 33.00±3.61% survival). However, growth was not significantly affected by stocking density. Cost–return analysis on a per crop per 200 m2 basis showed that the use of either of the two stocking densities with either diet was economically viable with a return on capital investment of 49–68%. However, crabs stocked at 1.5 m−2 and fed a mixed diet of 75% salted brown mussel flesh and 25% salted fish bycatch is more profitable. The integration of crab aquaculture within natural mangroves is therefore feasible in the Philippines, providing both immediate and long-term commercial and environmental benefits.
CitationTriño, A. T., & Rodriguez, E. M. (2002). Pen culture of mud crab Scylla serrata in tidal flats reforested with mangrove trees.
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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.
Mud crab pen culture: replacement of fish feed requirement and impacts on mangrove community structure. JH Primavera, JB Binas, GPB Samonte-Tan, MJJ Lebata, VR Alava, M Walton & L LeVay -
Aquaculture Research, 2010 - Blackwell PublishingBrackishwater pond culture has been a major factor in mangrove loss in Southeast Asia, hence, the need to develop environment-friendly technologies such as mud crab Scylla (Portunidae) culture in mangrove pens exists. This study evaluated the effects of mud crab netpen systems in central Philippines on mangrove macroflora, and the replacement of dietary fish with low-cost pellets. Wild or hatchery-sourced Scylla olivacea and Scylla serrata were stocked at 0.5–0.8 m-2 in 167–200 m2 nylon netpens (2.3 cm stretched mesh) in Avicennia-dominated mangrove habitats. The feeding treatments were: (A) Zarraga: (1) no feeding (natural productivity), (2) no feeding for 1 month+supplementary feeding, (3) fish biomass and (4) low-cost pellets, and (B) Batan: (1) fish biomass and (2) pellets+fish biomass. Feeds were given ad libitum twice daily. Growth and survival rates of S. olivacea in Zarraga pens were not significantly different among treatments, although crabs fed fish biomass had the highest survival, body weight and production. Similarly, growth and survival of S. serrata were not significantly different between the Batan treatments. Economic analysis of the latter gave a 38.5% return on investment (ROI) and 2.6 years payback period (PP) for pellets+fish biomass treatment compared with 27.5% ROI and 3.6 years PP for fish alone. Sensitivity analysis showed an improved economic performance of the pellets+fish biomass treatment by increasing the survival rate. Evaluation of mangrove community structure showed that crab culture reduced species diversity, numbers and biomass of seedlings and saplings, but not of mangrove trees. Therefore, mud crab pen culture is recommended for mangrove sites with mature trees, but not seedlings and saplings, and low-cost pellets can reduce dependence on fish biomass.
Conference paperAT Triño & EM Rodriguez - In JH Primavera, LMB Garcia, MT Castaños & MB Surtida (Eds.), Mangrove-Friendly Aquaculture : Proceedings of the Workshop on Mangrove-Friendly Aquaculture organized by the SEAFDEC Aquaculture Department, January 11-15, 1999, Iloilo City, Philippines, 2000 - Southeast Asian Fisheries Development Center, Aquaculture DepartmentThe performance of the mud crab Scylla serrata (Forsskal) in 200 m2 pens installed in tidal flats with existing mangroves was determined in a factorial experiment with stocking density (0.5 or 1.5/m2) and feed (salted fish by-catch or a mixed diet of 75% salted brown mussel flesh and 25% salted fish by-catch) as main factors. Duration of the experiment was 160 days. Results showed no interaction between feed and stocking density so data were pooled for each feed and stocking density treatment. There was no significant differences in growth, feed conversion ratio (FCR), survival, and production among two types of feed. Regardless of feed, the FCR was significantly more efficient and survival significantly higher at 0.5 than at 1.5/m2 stocking density. Growth, however, was not significantly different. Cost-return analysis on a per crop/200 m2 basis showed that the use of either of the two stocking density levels with either of the two types of feed was economically viable with a return on capital investment of 65-87%. Partial budgeting analysis, however, revealed that net earnings were increased by P1,128.00 if crabs were stocked at 1.5/m2 and P881.00 if fed a mixed diet of 75% salted brown mussel flesh and 25% salted fish by-catch compared with crabs stocked at 0.5/m2 and fed salted fish by-catch alone.