Restoration of the European flat oyster Ostrea edulis using elevated broodstock reefs

The precarious status of flat oyster Ostrea edulis stocks in Europe is widely acknowledged. To build a scientific basis for oyster restoration, an elevated experimental reef stocked with O. edulis was established within Poole Bay (Dorset, UK). Oysters were planted out on twenty four oyster reef modules (80cm above sea bed) and compared with oysters held on the sea bed close to each reef module to test the hypothesis that a reef habitat enhances physiological performance of O. edulis and improves local biodiversity. The environmental data indicated that there was no significant difference in temperature or salinity between the elevated reefs and sea bed. Whilst total suspended solids were significantly higher at the sea bed than at 80 cm above the sea bed at every sampling interval. The filtration rates of oysters varied with elevation (reef/sea bed) and months. Filtration rates of reef oysters were significantly higher than sea bed oysters. Respiration rates varied among months but were not significantly affected by elevation. Elevation and month also affected the total number of haemocytes and the granulocyte population; reef oysters had significantly higher numbers of haemocytes than sea bed oysters. Althought geographical variation in filtration rate was also observed, this study suggested that the improved physiology of reef oysters in summer was still notable when comparing between different populations. An increase in filtration rate for reef oysters may, however, increase the likelihood of uptake of the protozoan parasite, Bonamia sp.. However, haemocyte and haemolymph protein data suggested that there was no differential impact on physiology between reef and sea bed oysters as a result of Bonamia sp. infection. Fifty-four epifaunal species including oyster spat were found on oyster valves in reef boxes whilst only 23 species with no oyster spat were found on oyster valves in oyster cages laid on sea bed. The epifaunal community on oyster valves on reefs was significantly different from those sea bed valves but also had some species in common. Sixty-five mobile species were observed in reef boxes, whilst 47 species were recorded in oyster cages. These differences in faunal communities observed on the elevated reefs and sea bed implied that the presence of elevated reef habitats created by O. edulis valves can enhance or accelerate local diversity in Poole Bay. As current stocks of European flat oysters (O. edulis) in Europe have declined in both abundance and distribution, the results of this pilot study suggest that the culture of oysters on elevated reef structure represents at least a partial solution to improve O. edulis physiology for restoration in Europe

Fishing Status and Management Proposal in Bandon Bay, Suratthani Province, Thailand

Bandon bay is one of the importance and high-pressure fishing grounds of southern Thailand in the Gulf of Thailand. The present fishing grounds are under threat due to three main issues. Firstly, the fishing area has been minimized because some parts of the fishing grounds are now used for clam-culture. Secondly, fishery resources per se are in a vulnerable state because the catch is largely composed of unsalable and immature fish, resulting in a noticeable decrease in the fisherman’s income. Lastly, the growth in the price of gasoline (i.e. marginal cost) index was higher than the growth of catch price index. Thus, the short- and a long- term plans for the fishery management of Bandon bay are urgently required. This article presents the current threats in detail and develops management plans for the purpose of a sustainable fishing industry in Bandon bay, in terms of socio-economics, environmental and fishery resources as well as policies aspects

Chronicle of marine fisheries in the Gulf of Thailand: variations, trends and patterns

1302-1309A comprehensive picture of marine fisheries in the Gulf of Thailand (GoT), within Thailand’s boundary, has been described by using fish landing data for 26 years, between 1984 and 2009. Thirty-five (35) species/groups of fish landings were used in analysis. Rastrelliger brachysoma showed the lowest long-term variation (CV) in fish landings at 15.53% and the highest CV was observed in Lates calcarifer at 146.16%. The relationship between CV and fish landings showed a negative trend with a high correlation (r = 0.62) and was associated with species life-history strategies. For short-term variations, the means of the relative variation (28%) were higher than the absolute variation (25%), indicating a higher uncertainty when catches are low. Three trends in fish landings were analyzed by Spearman’s rank correlation. Seven (7) and 3 species/groups trended to decrease and increase, respectively, over the studied period. Meanwhile, 15 species/groups showed a trend of inversion, i.e. increased then decreased. The self-organizing map was used to cluster patterns of fish landings, which indicated temporal trends of chronological order, i.e. 1985-1990, 1992-1998, 1999-2007 and 2008-2009

Determination of short mackerel Rastrelliger brachysoma (Bleeker, 1851) stocks in the Gulf of Thailand using otolith microchemistry

The short mackerel Rastrelliger brachysoma (Bleeker, 1851) is a commercially important fish in the Gulf of Thailand (GoT). The management strategy for this species in the entire GoT is based on the single-stock approach, which may not be efficient or effective. This study aims to identify the stock structure of short mackerel in the GoT. A total of 55 samples of short mackerel were collected throughout the GoT, sexed, weighed and measured. The pair of sagittal otoliths were removed from individual fish. The left sagittae were used for stock identification via microchemistry elements. The microchemical composition of the otoliths from four locations (Eastern, Upper, Central and Lower GoT) was different (MANOVA, P < 0.01) for both sexes. The linear discriminant function analysis (LDFA) using eight microchemical elements in the edge zone showed high classification accuracy of short mackerel with regard to their sampling location (89 % for males and 79 % for females). The LDFA results also showed high classification accuracy in both sexes (more than 85 %) and indicated that there were four short mackerel stocks in the GoT. The right sagittae, meanwhile, were used for fish ageing. Results showed that the adults had resided in the stock more than 50 % of their life before being captured

Improvements in the physiological performance of European flat oysters Ostrea edulis (Linnaeus, 1758) cultured on elevated reef structures: Implications for oyster restoration

The precarious status of flat oyster Ostrea edulis stocks in Europe is widely acknowledged. To build a scientific basis for oyster restoration, an elevated experimental reef stocked with O. edulis was established within Poole Bay (Dorset, UK). Oysters were out planted on twenty four oyster reef modules (80 cm above sea bed) and compared with oysters held on the sea bed close to each reef module to test the hypothesis that a reef habitat enhanced physiological performance. Filtration and respiration rates, condition index, haemolymph protein concentration, haemocyte counts and gonad maturation were measured as indicators of physiological performance. During the first 15 months of oyster reef deployment, water samples were collected at regular intervals at the sea bed and at a height of 80 cm from the sea bed to determine chlorophyll a concentration, total suspended solids and bacterial abundance. Total suspended solids were significantly higher at the sea bed than at 80 cm above the sea bed at every sampling interval, while bacterial abundance adjacent to the sea bed was significantly higher than 80 cm above the sea bed in August and November 2013 when temperature was 18 °C and 15 °C, respectively. The filtration rates of oysters varied with elevation (reef/sea bed) and months. Filtration rates of ‘reef oysters’ (oysters on elevated reefs) were significantly higher than ‘sea bed oysters’ (oysters held on the sea bed). Respiration rates varied among months but were not significantly affected by elevation (reef/sea bed). Elevation and month also affected the total number of haemocytes and the granulocyte population; reef oysters had significantly higher numbers of haemocytes than sea bed oysters. As current stocks of European flat oysters (O. edulis) in Europe have declined in both abundance and distribution, the results of this pilot study suggest that the culture of oysters on elevated reef structure represents at least a partial solution to improve O. edulis physiology for restoration in Europe