Naturally-occurring stable isotopes as direct measures of larval feeding efficiency, nutrient incorporation and turnover

environmental conditions on stable isotope incorporation will be of broad relevance not only in terms of larval nutrition but can also more broadly inform the design and interpretation of ecological studies

Review of current evidence to inform selection of environmental predictors for active management systems in classified shellfish harvesting areas

Summary: This scoping report explores the potential influences on E.coli concentrations in Shellfish around the UK in the context of new management approache

Baseline assessment of fisheries for three species of mud crabs (Scylla spp.) in the mangroves of Ibajay, Aklan, Philippines

The full text is free.Stock 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.This study was supported by EU-INCO contract IC-CT-2001-10022. We thank the crab collectors in the villages of Naisud and Bugtong Bato, Ibajay, Aklan for collecting crabs during sampling regardless of time and weather, J. Altamirano, J. Inguillo, R. Ramos, W. Sayson, and A. Traje for the assistance with mapping the study site

Evaluation of hatchery-based enhancement of the mud crab, Scylla spp., fisheries in mangroves: comparison of species and release strategies

Ranching, 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

Approaches to stock enhancement in mangrove-associated crab fisheries

non-SEAFDEC main author, ISI-CC covered journal.Over the last decade, hatchery production of mud crabs has become technically and economically more feasible, enabling evaluation of the potential effectiveness of hatchery release in fisheries enhancement. The high growth rates and limited movement of released crabs means that fisheries’ yields an isolated mangrove systems with restricted recruitment can be enhanced with a few months. Thus, a release program may be an effective strategy for short-term enhancement in carefully selected specific areas. To date, results are very promising; with recovery rates up to 50% and increases in fisheries’ yield up to 46% over baseline catches. In contrast, mark-recapture studies in more open mangrove system populations shows that recruitment success and subsequent stock abundance may be largely determined by habitat availability. For these populations, restoration of lost o degraded mangrove areas has been show to be effective in promoting stock recovery through natural recruitment, with replanted mangroves supporting fisheries of equivalent economic value to that of natural mangroves, though it may take some years to reach these levels. Thus, a balanced approach to stock management could integrate both hatchery-release and habitat restoration programs, depending on local conditions and over different thin scales, with parallel-co-management to support effectiveness.European Commission through INCO DC contracts ERB-IC18-CT97-0189 and ECA4-CT-2001-10022