Preference for feeding at habitat edges declines among juvenile blue crabs as oyster reef patchiness increases and predation risk grows

Both habitat patchiness and behaviorally-mediated indirect effects (BMIEs; predator- induced changes in prey behavior that affect the prey's resources) are important in many food webs, but the relationships between these 2 factors have yet to be investigated. To explore effects of habitat patchiness and variation in perceived risk of predation on food-web dynamics, we conducted a factorial experiment in a model aquatic food chain of predator-prey-resource using 2 contrasting predators (adult blue crab Callinectes sapidus and toad fish Opsanus tau), juvenile blue crab as prey, and mussel Geukensia demissa as resource. Both predator presence and habitat patchiness influenced the prey's preference for consuming resources at patch edges instead of interiors. The preference of prey for consuming resources at habitat edges was 4 times stronger in continuous oyster reef habitat than in smaller habitat patches. This suggests that interior resources in continuous habitat experience a refuge from consumption, but this refuge is largely lost in patchy habitat. The mere presence of predators reduced the prey's preference for consuming resources at habitat edges. This BMIE was significant for the ambush predator (toadfish) and the treatment containing both predators, but not for the actively hunting predator (adult blue crab). We conclude that habitat patchiness and predator presence can jointly affect resource distribution by inducing shifts in prey foraging behavior, revealing a need to incorporate BMIEs into habitat fragmentation studies. This conclusion has broad and growing relevance as anthropogenic factors increasingly modify predator abundances and fragment coastal habitats. © Inter-Research 2012.

How small-scale variation in oyster reef patchiness influences predation on bivalves

As oyster fishing continues to degrade reef habitat along the US Atlantic coast, oyster reefs appear increasingly fragmented on small spatial scales. In outdoor mesocosms, experiments tested how consumption of representatives of 4 different bivalve guilds by each of 3 mesopredators varies between continuous and fine-scale patches of oyster reef habitat. The mesopredator that fed least (stone crab) exhibited no detectable change in consumption on any bivalve (ribbed mussel, bay scallop, hard clam, and 3 size classes of eastern oyster). Consumption of bay scallops by both blue crabs and sheepshead fish was greater in small patches than in continuous oyster reef habitat. Of the bivalve guilds tested, only the scallop possesses swimming motility sufficient to reduce predation, an escape response that would likely leave the bivalve protected within structured habitat in larger continuous oyster reefs. Sheepshead consumed more small oysters in the continuous habitat than in the fine patches, while no other predator-prey interaction exhibited differential feeding as a function of habitat patchiness. Consequently, predation by mesopredators on bivalves can vary with the scale of oyster reef patchiness, but this process may depend upon the bivalve guild. Understanding the role of habitat patchiness on fine scales may be increasingly important in view of the declines in apex predatory sharks leading to mesopredator release, and global climate change directly and indirectly enhancing stone crab abundances, thereby increasing potential predation on bivalves.

Evaluation of yield parameters and nutritional aspects of different strains of oyster (Pleurotus ostreatus) mushroom

The present study investigates the comparison between three different strains of oyster mushroom Pleurotus ostreatus (oyster (local), WC-537, WC-522) regarding to their yield and nutritional aspects. Four different kinds of substrates (corncob, wheat straw, rice straw, and sugarcane bagasse) were used for the growth of oyster. Oyster strain on corncob was found to be the fast mycelial run in comparison with WC-537 and WC-522. WC-522 on sugarcane bagasse showed the slowest mycellial run. Highest number of flushes was produced by oyster strain on each substrate. Number of days for period between flushes for oyster and WC-537 was about equal on corn cob, wheat straw and rice straw i.e. 4-6 days. Number of days taken for maturation of fruiting bodies of oyster and WC-537 was almost equal 6-7 days. In terms of nutritional aspects all strains have almost the same amount of moisture, fat, ash, fiber and protein with small variation. All the strains have protein content of about 20% by weight.

Oyster (Ostrea edulis) extirpation and ecosystem transformation in the Firth of Forth, Scotland

Marine inshore communities, including biogenic habitats have undergone dramatic changes as a result of exploitation, pollution, land-use changes and introduced species. The Firth of Forth on the east coast of Scotland was once home to the most important oyster (Ostrea edulis Linnaeus, 1758) beds in Scotland. 19th and early 20th century fisheries scientists documented the degradation and loss of these beds, yet transformation of the wider benthic community has been little studied. We undertook archival searches, ecological surveys and shell community analysis using radioisotope dated sediment cores to investigate the history of decline of Forth oyster beds over the last 200 years and the changes to its wider biological communities. Quadrat analysis of the present day benthos reveal that soft-sediment communities dominate the Firth of Forth, with little remaining evidence of past oyster beds in places where abundant shell remains were picked up by a survey undertaken in 1895. Queen scallops (Aequipecten opercularis Linnaeus, 1758) and horse mussels (Modiolus modiolus Linnaeus, 1758) were once common within the Forth but have also markedly decreased compared to the earlier survey. Ouranalyses of shell remains suggest that overall mollusc biomass and species richness declined throughout the 19th century and early 20th century, suggesting broader-scale community change as human impacts increased and as habitats degraded. Inshore communities in the Firth of Forth today are less productive and less diverse compared to past states, with evidence suggesting that most of the damage was done by early bottom trawling and dredging activities. Given the pervasive nature of intensive trawling over the past 150 years, the kind of degradation we document for the Firth of Forth is likely to be commonplace within UK inshore communities.

Critical evaluation of the nursery role hypothesis for seagrass meadows

The vast majority of published papers concerning seagrass meadows contain statements to the effect that seagrass beds serve as important nurseries for many species. We reviewed more than 200 papers that were relevant to the nursery role hypothesis. We used both vote counting and meta-analytic techniques to evaluate whether the body of previous studies that report seagrass meadows to be nursery grounds actually contain data that support this proposition. We restricted our analyses to papers that compared seagrass beds to other habitats, and examined data on a variety of well-studied species concerning their density, growth, survival and migration to adult habitat. Within this group of papers, we considered potential factors that could influence the nursery function (e.g. location, or laboratory vs field studies). We also evaluated case histories of well-documented large-scale seagrass losses on the nursery function. Major results were consistent with the expectations that abundance, growth and survival were greater in seagrass than in unstructured habitats. Abundance data also suggested that seagrass beds in the Northern Hemisphere might be more important as nursery areas than those in the Southern Hemisphere. Surprisingly, few significant differences existed in abundance, growth or survival when seagrass meadows were compared to other structured habitats, such as oyster or cobble reefs, or macroalgal beds. Nor were there decreases in harvests of commercially important species that could clearly be attributed to significant seagrass declines in 3 well-studied areas. However, there were decreased abundances of juveniles of commercially important species in these areas, suggesting a strong link between seagrass abundance and those of juvenile finfish and shellfish. One important implication of these results is that structure per se, rather than the type of structure, appears to be an important determinant of nursery value. Clearly, more rigorous studies that test all aspects of the nursery role hypothesis are clearly needed for seagrass meadows as well as other structured habitats. The results of such studies will allow better decisions to be made concerning the conservation and restoration of marine habitats.

Developing a marine conservation program in temperate Australia: determining priorities for action

The temperate seascapes of southern Australia have, until recently, received less conservation attention than the country's tropical waters. Here, we describe the results of an expert elicitation aimed at identifying gaps and opportunities in marine conservation for temperate waters. The process highlighted the need for focusing conservation attention on temperate bays, estuaries and inlets. The subsequent development of the Great Southern Seascapes program by The Nature Conservancy is aimed at beginning to address this need. The program focuses on the following actions for temperate Australian bays, estuaries and inlets: (a) increased protection, (b) ‘in the water’ restoration, (c) initiatives to address sea-level rise, (d) improved management and increased stakeholder involvement, (e) science and monitoring, and (f) community, government, and corporate engagement and funding. Actions taken to date, including commencing Australia's first ever oyster reef restoration project, and future directions, are outlined.

Incorporating historical data into aquaculture planning

Marine historical research has made progress in bridging the gap between science and policy, but examples in which it has been effectively applied remain few. In particular, its application to aquaculture remains unexplored. Using actual examples of natural resource management in the state of South Australia, we illustrate how historical data of varying resolution can be incorporated into aquaculture planning. Historical fisheries records were reviewed to identify data on the now extinct native oyster Ostrea angasi fishery throughout the 1800 and early-1900s. Records of catch, number of boats fishing, and catch per unit effort (cpue) were used to test fishing rates and estimate the total quantity of oysters taken from select locations across periods of time. Catch quantities enabled calculation of the minimum number of oysters per hectare for two locations. These data were presented to government scientists, managers, and industry. As a result, interest in growing O. angasi increased and new areas for oyster aquaculture were included in regulatory zoning (spatial planning). Records of introductions of the non-native oyster Saccostrea glomerata, Sydney rock oysters, from 1866 through 1959, were also identified and used to evaluate the biosecurity risk of aquaculture for this species through semi-quantitative risk assessment. Although applications to culture S. glomerata in South Australia had previously been declined, the inclusion of historical data in risk assessment led to the conclusion that applications to culture this species would be accepted. The examples presented here have been effectively incorporated into management processes and represent an important opportunity for the aquaculture industry in South Australia to diversify. This demonstrates that historical data can be used to inform planning and support industry, government, and societies in addressing challenges associated with aquaculture, as well as natural resource management more broadly.