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Abstract Larval Atlantic sea scallops (Placopecten magellanicus) simulations in the Middle Atlantic Bight (MAB) from 2006 to 2012 were performed to investigate annual and inter-annual dispersal and connectivity patterns among stock regions. These simulations used a circulation model based on the Regional Ocean Modeling System (ROMS) and an individual-based larval model (IBM) that included larval behavior. The circulation model used realistic dynamical forcing (e.g. , winds, tides, and open ocean boundary conditions), thermo-dynamical fluxes (e.g., solar radiations, sensible and latent heating), and hydrological forcing; the larval IBM included vertical swimming and sinking behaviour, temperature-dependent growth, and settlement. Simulated larvae that reach settlement size and suitable habitat in 45 days are considered 'successful', and two regions are considered 'connected' by larval dispersal when larvae successfully disperse from one region to the other. In general, simulated larval dispersal patterns varied seasonally (28% higher in September and October compared to May and June), among years (2007 through 2009 had 5% lower larval success during August and September compared to other years), and spatially, with larvae released from the northern regions like Long Island acting as a substantive larval source with 14% greater dispersal success and 15% greater connectivity with other regions than those released elsewhere. Over the seven years simulated, the MAB scallop stocks showed high rates of connectivity to regions to the south and more limited and variable connectivity to regions to the north. In species like sea scallops with limited adult mobility, larval dispersal supplies recruits, enables range expansion, and connects populations. Thus, appreciation of dispersal patterns are essential for fishery management of this economically valuable stock. [ABSTRACT FROM AUTHOR]

1. Applied ecology, like conservation research, may deal with societal issues if its scientifically based interventions have societal consequences. Human utilization plays a significant role in many ecosystems, so conservation ecologists often have to act on the interface between science and society, where controversies may arise. 2. Using insights from science and technology studies, we have analysed the 15-year controversy on the ecological effects of cockle fishing in the Dutch Wadden Sea, which began around 1990 and involved nature protection and shellfish organizations, as well as several leading Dutch ecologists, in a heated debate. 3. During this controversy, evaluative research on the ecological effects of cockle fishing was undertaken by a consortium of institutes in order to contribute to the process of political decision-making by the Dutch government on cockle fishery in this area. In addition to conservational and commercial interests, ecological research itself became part of the controversy. 4. The research projects on the effects of cockle fishing during this controversy are examples of societally contextualized science, implying that interests and societal disputes are intertwined with scientific arguments. We have applied a dynamic model of contextualization in which societal stakes and scientific uncertainty are considered as the main factors determining the different contexts in which conservation research functions. 5. Synthesis and applications. Conservation research, whether it is fundamental or managerially orientated, is related to greater societal aims and interests and might easily face more or less complex societally contextualized situations. Such situations imply extended responsibilities for scientists. Not only is there a need for sound science, but also for a sound way of interacting and communicating with the societal environment. Some elements of such a notion of extended accountability are presented. [ABSTRACT FROM AUTHOR]

The concept of sustainability has several, sometimes contrasting, meanings that may generate confusion, misunderstanding, and conflict concerning conservation and restoration practices. It is therefore desirable to clarify the concept of sustainability, thereby potentially contributing to mutual understanding, especially when social conflicts arise. This article discusses a recently published typology of three conceptions of sustainability that range from economic to ecocentric valuations of nature. We argue that the typology is incomplete because it does not include the arcadian approaches. For this reason, we introduce a“tripolar model” for conceptions of sustainability, applying it to the debate on shellfish harvesting in the Dutch Wadden Sea. We conclude that the particular visions or conceptions of sustainability held by relevant actors may have an impact on strategies for conservation. [ABSTRACT FROM AUTHOR]

Intensive fishing in the Dutch Wadden Sea in the late 1980s and 1990, in combination with the effects of storms and ice and low spatfall, has led to an almost complete disappearance of intertidal mussel beds in 1990. Since then, this habitat type has re-established in only very few places, covering some hundreds hectares at the most. Lack of good spatfall in the late 1980s also resulted in low cockle stocks. These stocks were further reduced due to heavy mortality in the 1995/96 winter. These developments yielded very low food stocks for shellfish eating birds in some winters. This paper describes the fishery policy which came into force since 1993 and the effects the low food stocks have had on Eiders and Oystercatchers which are dependent on cockles and mussels. Eiders suffered higher mortality in 1991 and partly emigrated to alternative feeding areas on the North Sea and German Wadden Sea. Oystercatchers suffered higher mortality as well, were found in lower numbers in the Dutch Wadden Sea and in higher numbers in inland feeding areas. This information, together with a comparison of quantitative data on available food stocks and food consumption by birds, indicate that in some winters the number of shellfish eating birds has exceeded the carrying capacity of the Dutch Wadden Sea. Alternative food sources, such as Macoma balthica, Mya arenaria, Scrobicularia plana, Ensis americanus, Nereis spp. and Arenicola marina cannot compensate for low mussel and cockle stocks. Before 1990, intertidal mussel beds must have acted as an important alternative food source. In the current situation, with hardly any intertidal mussel beds in the Dutch Wadden Sea, cockles represent the major food source, especially in winter. Since cockle stocks can be very low in some years they are an unreliable food source at the same time. Intertidal mussel beds represent a winter resistant and a more reliable food source. These considerations are important viewpoints in the discussion on a future fishery policy for the Dutch Wadden Sea. The most important conclusions from the present analysis is that re-establishment of intertidal mussel beds in the Dutch Wadden Sea is essential to allow the area to play its role as vitally important wetland in the East Atlantic flyway. In order to achieve this goal future fishery on intertidal mussel beds should be highly restricted. [ABSTRACT FROM AUTHOR]

Intertidal seagrasses often occupy areas of high ecological importance that are also targeted for human activities, such as shellfishing and leisure walking. These activities could affect the growth or survival of seagrass. The society at large lacks knowledge of the ecological relevance of seagrasses and their vulnerability, presenting an obstacle for their conservation. Here, the Oka estuary (Basque Country, N. Spain) is used as a case study to analyse the spatial extent of shellfishing activities in seagrass (Zostera noltei). This estuary holds 84% of the intertidal seagrass meadows present in the Basque Country and is visited during the year by professional and recreational shellfishers. Bait digging is legal year-round, and clam digging (by professionals only) from October to February. Human presence over 11 years averaged 17 people on the tidal flat in each daylight hours from August to October. Each professional shellfishing daily trip affected 7.4–21.6 m2 by fishing and 110–188 m2 by trampling in seagrass, but was substantially different between clam and bait (crustacean, worm) fishing. Scaling up this area to estimated annual number of shellfishers, 8–69% of the total seagrass area is trampled and 1–9% is dug per year. In comparison to a habitat suitability map for seagrass, 98% of trampling occurred within a very highly suitable area for seagrass presence (i.e., >90%). This pressure could adversely affect seagrass density and prevent the expansion of meadows into areas suitable for seagrass. Management of public impacts to seagrass in this estuary could occur through prohibition of some activities in seagrass and awareness campaigns among shellfishers and walkers. [Display omitted] • Seagrass surface is declining in the Basque estuaries. • Trampling and digging by shellfishers are the main perturbing human factors for Basque seagrasses. • Shellfishers trampling and digging on seagrasses is quantified for the Oka estuary. • Awareness-raising campaign and some banning measures are proposed to protect and conserve seagrasses in the Oka estuary. [ABSTRACT FROM AUTHOR]

Fisheries and other human activities pose a global threat to the marine environment. Marine protected areas (MPAs) are an emerging tool to cope with such threats. In the Dutch Wadden Sea, large MPAs (covering 31% of all intertidal flats) have been created to protect shellfish-eating birds and allow recovery of important habitats. Even though shellfish fishing is prohibited in these areas, populations of shellfish-eating birds in the Wadden Sea have declined sharply. The role of shellfish fisheries in these declines is hotly debated, therefore, we investigated the effectiveness of MPAs for protecting oystercatcher (Haematopus ostralegus) populations. Shellfish stocks (cockles, Cerastoderma edule) were substantially higher in the MPAs, but surprisingly this has not resulted in a redistribution of wintering oystercatchers. Oystercatchers in unprotected areas had less shellfish in their diet and lower condition (a combined measure of mass and haematological parameters), and their estimated mortality was 43% higher. It is likely, therefore, that shellfish fishing explains at least part of the 40% decline in oystercatcher numbers in recent years. Condition and mortality effects were strongest in males, and the population sex ratio was female biased, in agreement with the fact that males rely more on shellfish. The unprotected areas apparently function as an "ecological trap," because oystercatchers did not respond as anticipated to the artificial spatial heterogeneity in food supply. Consequently, the MPAs are effective on a local scale, but not on a global scale. Similar problems are likely to exist in terrestrial ecosystems, and distribution strategies of target species need to be considered when designing terrestrial and marine protected areas if they are to be effective.