Reproductive biology of christian crabs (Charybdis feriatus, Linnaeus, 1758) in San Miguel Bay, Philippines

Abstract only.The reproductive biology of Charybdis feriatus was investigated from April 2012 to March 2013 to determine gonad maturity, gonado-somatic index (GSI), fecundity, breeding cycle and size at first maturity. Every month, samples of 30 specimens were randomly collected. Gravimetric and volumetric methods were used to estimate fecundity. Results showed that Charybdis feriatus breeds continuously with a distinct period of reproductive activity during the northeast monsoon. Spawning peaks in January where higher values of GSI, mature, and berried female crabs were observed. Female gonad (ovary) weights range from 0.5 to 18.1 grams while mean GSI of female and male were 7.35% and 6.27%, respectively. Berried females were present year round, the highest occurring in December (50%). Fecundity ranged from 1,513,660 to 6,357,133 eggs. The smallest reproductively active female was 8.3 cm. Fecundity was highly correlated with size (r2=0.92). In view of these observations, the following options are recommended for crab fishery resource management: (1) to set a closed season for crab fisheries, (2) to regulate catches by not taking egg-bearing swimming crabs, and (3) to allow egg-bearing crabs to release its eggs and the larvae in fishing grounds and/or marine protected areas

Stock assessment of christian crabs (Charybdis feriatus, Linnaeus, 1758) in San Miguel bay

Assessment of the status of swimming crab fisheries in San Miguel Bay with focus on Christian or Crucifix crab, Charybdis feriatus, was undertaken from November 2011 to January 2013. An analytical length-based fish stock assessment was employed using the FISAT (version 1.2.2). A total of 7,679 length frequencies (3,612 C. feriatus and 4,067 Portunus pelagicus) were used in the analysis. About 15 and 14 percent gravid females were harvested monthly for both species that may contribute to recruitment overfishing. Population parameters showed exploitation rate (E) for P. pelagicus and C. feriatus exceeded the optimum exploitation (E0.5) implying excessive fishing effort and heavily exploited stocks. Size at maturity of C. feriatus and P. pelagicus in San Miguel Bay is 8.3 cm and 8.5 cm, respectively. Doable options for resources conservation and management strategies are proposed and supported by local government units (LGUs) including the Integrated Fisheries and Aquatic Resource Management Council

Occurrence of Anguilla luzonensis in the Tributaries along the Lagonoy Gulf, Philippines

Anguillids are а valuable fish commodity worldwide. Although Anguilla luzonensis have been abundantly found in the northern Philippines and collected for trade, no available records show that it recruited in the midpart where Lagonoy Gulf, Bicol is situated. In this study, we investigated the occurrence of A. luzonensis in the tributaries along the Lagonoy Gulf, Philippines using molecular tools. Glass eel specimens were collected in 2018–2019 from the Comun river, Albay; the Lagonoy river, Camarines Sur; and the Bato river, Catanduanes. Anguilla luzonensis was first reported in Lagonoy Gulf using molecular analysis. A. luzonensis was the second most abundant species in the Comun and Lagonoy rivers (9.5 and 22.4 %, respectively). Anguilla luzonensis collected from the Comun and Lagonoy rivers did not show a significant difference (FST= 0.00825, p>0.05). Anguilla marmorata was the most dominant species in all tributaries (71.1–98.0 %). In the Comun and Lagonoy rivers, A. bicolor pacifica was the third most abundant species (7.7 and 6.5 %, respectively). In addition, Anguilla celebesensis was only found rarely in the Comun river (0.9 %). This study provides important information for sustainable resource management and effective utilization of the eel species in these regions

Status and impacts of tilapia fish cage farming in Lake Bato: Some policy and management options for sustainable development

An assessment and impact analysis of the fish cage arming in Lake Bato was conducted from October 1999 to January 2000 through a field survey and personal interviews with fish cage farmers, operators and key informants in 10 lakeside communities bordering Lake Bato. Tilapia fish cage farming was the most dominant activity undertaken in the lake owing to its economic contribution and performance. It is sad to note, however, that the management and protection of the lake has been neglected. Results showed that the lake is experiencing serious stress and degradation as a result of fish cage congestion numbering to more than 21,820 units indiscriminately installed all over the lake. The same is also the cause of conflicts (i.e., marginalized small-scale fishers, obstruction of navigational route, and proliferation of dummy fish cage operators) among lake users. As a consequence of expanded technology application, slow fish growth, algal bloom, fish kill, and the apparent shallowing of the lake have become alarming concerns among resource users. It is also worth noting that the industry s sustainability is now under serious threat if not properly planned, managed, and protected. It is therefore recommended that alternative policy and management options be institutionalized. This would include formulation of a lake-wide inter-Local Government Unit (LGU) fisheries ordinance, implementation of Lake Bato Resource Management Plan, organization of a lake-wide fish cage farmers and operators, conduct of collaborative and interdisciplinary research and development initiatives, conduct of technical and management training for Best Fish Cage Practice, and massive information-education-communication (IEC) for concerned municipalities

Economic, Ecological and Institutional Impacts of Super Typhoon Reming on a Mangrove Rehabilitation Community in Malinao, Albay, Philippines

Arresting the decline of mangrove forests and mainstreaming people‟s participation in their management provided the rationale for community-based mangrove rehabilitation in the Philippines. Mangrove rehabilitation aims to re-establish habitat and functions that have been lost. In the context of coastal resource management, the risk that typhoons could alter socioeconomic and institutional goals of communitybased mangrove rehabilitation and the dearth of information on impacts of typhoon on such goals and combined income-asset shocks on households presents a great challenge. This paper analyzed the economic effects of typhoon and its impact on community-based mangrove rehabilitation community in the coastal municipality of Malinao, southeastern Luzon. Key informant interview, household and mangrove transect surveys were used in data gathering. Valuation of damaged crops and lost assets were used in quantifying direct economic effects. A time-one, time-two comparison technique was used in quantifying impacts. The results showed the direct damage on crops was highest in rice. The damage on physical assets was highest in fishing gears. The damage on livestock was highest in small animals. The cost of repair was highest for concrete houses, although native houses had the highest proportion of damage. Total direct damage cost valued at PhP 24.33 million justifies public investment in disaster risk management. Per capita damage cost at PhP 12,581 equivalent to 3-month household income shortfall can derail early recovery. The indirect social impacts increased access on social services as window of opportunities brought by the disaster event but are ad hoc in nature. The old mangrove forest population was very slightly impacted but the reforested mangrove was dramatically reduced. Most of the institutional performances in resource management and livelihood sustainability plans were negatively impacted. Livelihood projects with live production assets were more vulnerable and incurred heavy losses from typhoon. The typhoon resulted to very minimal gains on overall natural resource management goals posting slight positive changes on stakeholders influence on mangrove resource management, control over resources, collective decision-making, and knowledge. Coping mechanisms and implications for disaster mitigation and sustainable management were discussed

Challenges and Opportunities for Giant Freshwater Prawn Culture through Participatory Learning and Fish Farmer Engagements

This paper provides a review of on-farm studies conducted to explore the viability of giant freshwater prawn (Macrobrachium rosenbergii, locally known as ulang), culture in six regions in the Philippines. We adopted a participatory action learning approach aimed at improving pond productivity through engagement of 17 small-scale fish-farmer cooperators to adopt different ulang culture systems—ulang monoculture, ulang-rice polyculture, and ulang-tilapia polyculture. This paper focuses on comparing the production and profitability of ulang monoculture and ulang-tilapia polyculture. The cooperators were guided to follow proper protocols in pond preparation, feeding, and water management. Results showed an average survival rate of 65 percent for ulang monoculture; and 59 percent and 77 percent survival rates for ulang and tilapia in polyculture system, respectively. The major problems encountered across regions were unavailability of post-larvae; distance of post-larvae source; water availability; presence of predators; and inconsistent implementation of technical interventions by the cooperators. This paper also presents research and policy recommendations toward sustainable development of freshwater prawn culture which include establishment of a network of hatcheries and broodstock development; technology promotion and extension services; and improving value chains and market strategy