Freshwater fish community structured more by dispersal limitation than by environmental heterogeneity

Abstract –  We examined the relative contribution of environmental heterogeneity and dispersal limitation on freshwater fish community composition in 18 Greek protected lakes and reservoirs. Environmental heterogeneity was measured by spatial pattern metrics (calculated by digital map processing, e.g., patch richness density, area-weighted mean patch area), altitude, maximum lake depth and trophic status. Dispersal limitation was measured by straight-line distances among lake centres. Ecosystems were clustered according to species composition. We examined the correlation of similarity in species composition among ecosystems with that of environmental heterogeneity and with straight-line distances, for the entire dataset, as well as for the occurring clusters. Fish species richness increased with ecosystem area and decreased with altitude. The clusters identified (aquatic ecosystems of Northern vs. ecosystems of Western Greece), implied an underlying biogeographical pattern as defined, with Pindus range acting as a natural barrier. Between ecosystems similarity, based on fish species composition, showed a weak to insignificant correlation with environmental heterogeneity, but was significantly correlated to dispersal limitation for the entire dataset as well as within each occurring cluster. Thus, natural barriers, species biogeography and dispersal limitation played a more significant role in shaping freshwater fish communities than environmental heterogeneity.     

Opportunities for agent‐based modelling in human dimensions of fisheries

Models of human dimensions of fisheries are important to understanding and predicting how fishing industries respond to changes in marine ecosystems and management institutions. Advances in computation have made it possible to construct agent‐based models (ABMs)—which explicitly describe the behaviour of individual people, firms or vessels in order to understand and predict their aggregate behaviours. ABMs are widely used for both academic and applied purposes in many settings including finance, urban planning and the military, but are not yet mainstream in fisheries science and management, despite a growing literature. ABMs are well suited to understanding emergent consequences of fisher interactions, heterogeneity and bounded rationality, especially in complex ecological, social and institutional contexts. For these reasons, we argue that ABMs of human behaviour can contribute significantly to human dimensions of fisheries in three areas: (a) understanding interactions between multiple management institutions; (b) incorporating cognitive and behavioural sciences into fisheries science and practice; and (c) understanding and projecting the social consequences of management institutions. We provide simple examples illustrating the potential for ABMs in each of these areas, using conceptual (“toy”) versions of the POSEIDON model. We argue that salient strategic advances in these areas could pave the way for increased tactical use of ABMs in fishery management settings. We review common ABM development and application challenges, with the aim of providing guidance to beginning ABM developers and users studying human dimensions of fisheries.     

Fair trade fish: consumer support for broader seafood sustainability

Sustainable seafood initiatives began with efforts to promote and certify seafood sourced from well‐managed stocks caught with a reduced impact on the marine environment. More recently, social equity in fisheries has been the subject of increased concern with suggestions that seafood cannot be certified as sustainable if its production results in social harm, such as unfair wages or the use of forced or child labour. Together with local seafood, which has been promoted as an eco‐friendly and socially conscious alternative to globally sourced seafood, these initiatives signal a growing interest in fisheries as a social–ecological system. However, this increasingly complex landscape of environmental sustainability and social justice may be difficult for the public and seafood consumers to navigate. Here, we investigate consumer understanding of and responsiveness to a range of seafood sustainability initiatives by testing preferences and willingness to pay (WTP) for seafood across the three types of sustainability: ecological sustainability, local origin and social sustainability. More than half of respondents demonstrated good understandings of both ecological sustainability and social sustainability with respect to seafood, and respondents were willing to pay more for all three types of sustainability. However, WTP for social sustainability benefits was the lowest, and consumers perceived a high degree of overlap of these benefits with those from locally sourced seafood. These results indicate that seafood certification taking a system‐wide approach has potential to succeed, but that it will need to emerge in concert with the increased public education about social problems associated with globalized fisheries.     

Coral reef fish communities in management systems with unregulated fishing and small fisheries closures compared with lightly fished reefs – Maldives vs. Kenya

• 1. This study presents a comparison of the benthic cover and fish communities in three widely different management systems: (1) a heavily utilized subsistence fishery (yields >5 Mg km^?2 yr^?1); (2) moderately sized and well enforced fisheries closures (～9% of the nearshore area) surrounded by heavy fishing; and (3) a more lightly used management system (yields <5 Mg km^?2 yr^?1).
• 2. The objective was to compare management systems of small to moderate‐sized closures surrounded by heavy use in Kenya with a large‐scale light‐use management system in the Maldives.
• 3. Gross level attributes of the fish community suggest that the Maldives reefs had higher numbers of individuals (30%) and species (15%) than the Kenyan closures.
• 4. Maldivian reefs had higher abundance of some carnivores such as emperors (Lethrinidae), jacks (Carangidae), triggerfish (Balistidae), and trumpetfishes (Aulostomidae). Half the biomass of fish in the Maldives was, however, composed of surgeonfish (Acanthuridae), which resulted in a higher abundance of herbivores/detritivores than found in Kenyan closures.
• 5. Apex predator species were not a large portion of the biomass (<10%) in any system and, if remote reefs of the Pacific are examples of undisturbed ecosystems, then neither management system has fully protected apex species.

Copyright © 2011 John Wiley & Sons, Ltd.     

Key attributes related to fishery improvement project (FIP) effectiveness in promoting improvements towards sustainability

Fishery improvement projects (FIPs) are emerging as a popular market‐based means to improve fisheries sustainability and have been employed in scores of fisheries around the world; however, project ability to realize improvements has been highly variable, and little is known about how fishery and project conditions affect improvement efforts. In order to evaluate the effectiveness of the FIP model as a tool for improving diverse fisheries around the world, we compile a unique dataset of social, ecological and economic characteristics for over 60 FIPs globally, which we use to identify key attributes correlated with improvements in fishing practices, management and/or on‐the‐water outcomes. Using a random forest classifier, we identify three important attributes related to FIP effectiveness in demonstrating improvements. Specifically, FIPs are more likely to have achieved improvements with increased cumulative project time, when regional‐level management arrangements are present and when the target species has a moderate inherent vulnerability to fishing. Interestingly, improvements were not correlated with a number of expected features, including a fishery's socio‐economic setting or baseline performance against the desired sustainability standard (e.g. the Marine Stewardship Council fisheries standard). This study improves our understanding of factors related to FIP effectiveness in improving fisheries practices and management and provides key insights for practitioners into important attributes to consider when implementing the FIP model to promote fisheries sustainability.     

Bottlenose dolphins share fish farm areas while maintaining sexual segregation: Investigating group memberships through spatially and temporally explicit parameters

1. Group membership is a key attribute of animal societies and central to the study of social structure in several taxa. However, social structure analyses are sensitive to the way data are collected and associations defined.
2. In this study, a time–space method was used to investigate the social structure of common bottlenose dolphins Tursiops truncatus observed and photographed across 7 years in the semi-enclosed Gulf of Corinth, Greece. Instead of adopting traditional group definitions, individuals were considered as being members of the same group if photographed within a specific time and space window. This approach can be applied post hoc across studies and can offer advantages under challenging sampling conditions (e.g. when dealing with groups spread over vast areas or when group membership is otherwise hard to assess).
3. Dolphins were mostly found around coastal cage aquaculture facilities farming European sea bass Dicentrarchus labrax and gilthead seabream Sparus aurata.
4. Dolphins formed clusters largely or entirely composed of individuals of the same sex, suggestive of sex-based homophily. Habitat partitioning was not detected: there was substantial spatial overlap among dolphin clusters, with all individuals using a relatively small area in the northern portion of the Gulf, where most of the productive fish farms were located. Associations between females were stronger than those between males, and daughters tended to stay in the group of their mothers.
5. Sex-based social clustering may allow females and calves to limit interactions with potentially aggressive males, while individuals of both sexes benefit from prey concentrated around fish farms.
6. Adaptation to foraging around farms can result in trade-offs between the costs and benefits of nourishment and social interaction. This may have both positive or negative effects on the animals that should be considered in the context of ensuring their favourable conservation status.

     

Seasonal and spatial bank habitat use by fish in highly altered rivers – a comparison of four different restoration measures

Pander J, Geist J. Seasonal and spatial bank habitat use by fish in highly altered rivers – a comparison of four different restoration measures.
Ecology of Freshwater Fish 2010: 19: 127–138. © 2009 John Wiley & Sons A/S
Abstract –  River regulations have resulted in substantial modifications of the characteristics and the diversity of stream ecosystems. Fish habitat use in the context of species life histories and temporal habitat dynamics are crucial for the development of sustainable measures of habitat restoration in degraded rivers. The objective of this study was to compare the effects of introducing four different in-stream structures (bank ripp-rapp, benched bank ripp-rapp, successively grown riparian wood and artificial dead wood, nine replicates each) on the seasonal fish community distribution in a heavily modified stream ecosystem. Species richness and diversity, fish biomass and density showed strong variation (i) between habitat types, (ii) among replicates of the same habitat type, and (iii) in different seasons. The current low abundance of historical widespread rheophilic and migratory fish species in the study stream suggests that technical bank habitat restoration measures are only of limited use for the restoration of highly specialised target species in conservation such as Barbus barbus and Chondrostoma nasus . However, introduction of particular artificial stream structures (in particular of artificial dead-wood fascines) was found to concentrate biomass and density of none-specialised fish species like Squalius cephalus , Alburnus alburnus , Gobio gobio or Rutilus rutilus .     

Implementing ecosystem‐based management: evolution or revolution?

As a dominant paradigm, ecosystem‐based fisheries have to come to terms with uncertainty and complexity, an interdisciplinary visioning of management objectives, and putting humans back into the ecosystem. The goal of this article is to suggest that implementing ecosystem‐based management (EBM) has to be ‘revolutionary’ in the sense of going beyond conventional practices. It would require the use of multiple disciplines and multiple objectives, dealing with technically unresolvable management problems of complex adaptive systems and expanding scope from management to governance. Developing the governance toolbox would require expanding into new kinds of interaction unforeseen by the mid‐twentieth‐century fathers of fishery science – governance that may involve cooperative, multilevel management, partnerships, social learning and knowledge co‐production. In addition to incorporating relatively well‐known resilience, adaptive management and co‐management approaches, taking EBM to the next stage may include some of the following: conceptualizing EBM as a ‘wicked problem’; conceptualizing fisheries as social‐ecological systems; picking and choosing from an assortment of new governance approaches; and finding creative ways to handle complexity.     

Human‐induced gradients of reef fish declines in the Hawaiian Archipelago viewed through the lens of traditional management boundaries

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