| 1. |
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| 2. |
- Cardinale, Massimiliano
(författare)
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Rebuilding Mediterranean fisheries: a new paradigm for ecological sustainability
- 2013
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Ingår i: Fish and Fisheries. - : Wiley. - 1467-2960 .- 1467-2979. ; 14, s. 89-109
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Tidskriftsartikel (refereegranskat)abstract
- In Mediterranean European countries, 85% of the assessed stocks are currently overfished compared to a maximum sustainable yield reference value (MSY) while populations of many commercial species are characterized by truncated size- and age-structures. Rebuilding the size- and age-structure of exploited populations is a management objective that combines single species targets such as MSY with specific goals of the ecosystem approach to fisheries management (EAF), preserving community size-structure and the ecological role of different species. Here, we show that under the current fishing regime, stock productivity and fleet profitability are generally impaired by a combination of high fishing mortality and inadequate selectivity patterns. For most of the stocks analysed, a simple reduction in the current fishing mortality (Fcur) towards an MSY reference value (FMSY), without any change in the fishing selectivity, will allow neither stock biomass nor fisheries yield and revenue to be maximized. On the contrary, management targets can be achieved only through a radical change in fisheries selectivity. Shifting the size of first capture towards the size at which fish cohorts achieve their maximum biomass, the so-called optimal length, would produce on average between two and three times higher economic yields and much higher biomass at sea for the exploited stocks. Moreover, it would contribute to restore marine ecosystem structure and resilience to enhance ecosystem services such as reservoirs of biodiversity and functioning food webs.
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| 3. |
- Friedman, Kim, et al.
(författare)
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Management of sea cucumber stocks : patterns of vulnerability and recovery of sea cucumber stocks impacted by fishing
- 2011
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Ingår i: Fish and Fisheries. - : Wiley. - 1467-2960 .- 1467-2979. ; 12:1, s. 75-93
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Tidskriftsartikel (refereegranskat)abstract
- Identifying rates of change in the abundance of sea cucumbers under differing management regimes is fundamental to estimating commercial yields, identifying ecological interactions and facilitating management. Here, we review the status of sea cucumber stocks from a range of Pacific Island countries (Samoa, Tonga, Palau, Fiji and Papua New Guinea), some of which have had a moratorium on exports for up to a decade. We use a time-series approach to look at variation in sea cucumber presence, coverage and density from survey and re-survey data. Results give an appreciation of variation between 'high' status (less impacted) and depleted stocks. Survey data show marked declines in coverage and abundance as a result of artisanal fishing activity, and although species groups were not lost at a country level, local extirpation and range restriction was noted. Resilience and 'recovery' following cessation of fishing varied greatly, both among locations and among the species targeted. Worryingly, even after extended periods of moratorium, the density of some species was markedly low. In many cases, the densities were too low for commercial fishing, and may be at a level where the effective population size is constrained due to 'Allee' affects. From these results, we suggest that management regimes presently employed are generally not well aligned with the level of response to fishing mortality that can be expected from sea cucumber stocks. New adaptive, precautionary approaches to management are suggested, which would allow more timely interventions to be made, while refined information on stock dynamics is sought.
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| 4. |
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| 5. |
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| 6. |
- Piccolo, John J, 1964-, et al.
(författare)
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Conservation of endemic landlocked salmonids in regulated rivers : a case-study from Lake Vänern, Sweden
- 2012
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Ingår i: Fish and Fisheries. - : Wiley. - 1467-2960 .- 1467-2979. ; 13:4, s. 418-433
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Tidskriftsartikel (refereegranskat)abstract
- Conservation of migratory salmonids requires understanding their ecology at multiple scales, combined with assessing anthropogenic impacts. We present a case-study from over 100 years of data for the endemic landlocked Atlantic salmon (Salmo salar, Salmonidae) and brown trout (Salmo trutta, Salmonidae) in Lake Vänern, Sweden. We use this case-study to develop life history-based research and monitoring priorities for migratory salmonids. In Vänern, small wild populations of salmon and trout remain only in the heavily regulated Rivers Klar (Klarälven) and Gullspång (Gullspångsälven), and commercial and sport fisheries are maintained by hatchery stocking. These populations represent some of the last remaining large-bodied (up to 20 kg) landlocked salmon stocks worldwide. We found that one of four stocks of wild fish has increased since 1996; the other three remain critically low. Hatchery return rates for three of four stocks appear stable at roughly 1% and annual fisheries catch is roughly 75 metric tons, with an estimated 7.5% of hatchery smolts being recruited to the fishery; this also appears relatively stable since 1990. Our analysis reveals much uncertainty in key data requirements, including both river return and fisheries catch rates, estimates of wild smolt production and survival, and hatchery breeding and genetics protocols. These uncertainties, coupled with a lack of information on their riverine and lacustrine ecology, preclude effective management of these unique populations. We conclude with a framework for a life history-based approach to research and monitoring for Vänern salmon and trout, which should be applicable for all endemic, migratory salmonid populations.
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| 7. |
- Sjöstedt, Martin, 1977
(författare)
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Horizontal and vertical resource dilemmas in natural resource management: the case of African fisheries
- 2013
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Ingår i: Fish and Fisheries. - : Wiley. - 1467-2960 .- 1467-2979. ; 14:4, s. 616-624
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Tidskriftsartikel (refereegranskat)abstract
- Abstract The world’s fisheries are under severe pressure. Yet, according to the marine trophic index, the health and stability of marine ecosystems vary greatly across countries. The argument developed and tested in this article holds that some of the sources of this variation can potentially be derived from differences in the character of two fundamental relationships in society – a horizontal one between resource users and a vertical relationship between the government and the resource users. The empirical analysis focuses on sub-Saharan Africa and finds that levels of ethnic and linguistic heterogeneity and levels of democracy in the year that each country declared its exclusive economic zone have a close relationship with ensuing marine exploitation patterns.
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| 8. |
- Alexander, Steven M., et al.
(författare)
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Social ties explain catch portfolios of small-scale fishers in the Caribbean
- 2020
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Ingår i: Fish and Fisheries. - : Wiley. - 1467-2960 .- 1467-2979. ; 21:1, s. 120-131
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Tidskriftsartikel (refereegranskat)abstract
- Small-scale fisheries often involve weak management regimes with limited top-down enforcement of rules and minimal support from legal institutions, making them useful model systems for investigating the role of social influence in determining economic and environmental outcomes. In such regimes, interpersonal relationships are expected to have a strong effect on a fisher's catch portfolio, the set of fish species targeted by an individual fisher. Here, we test three competing hypotheses about social influence using belief propagation network models and show that a peer-to-peer information-sharing social network is key to explaining catch portfolios at a small-scale fishery in Jamaica. We find that experience dictates the direction of influence among fishers in the social network, with older fishers and information brokers having distinct roles in shaping catch patterns for large- and small-sized fish species, respectively. These findings highlight concrete opportunities for harnessing social networks in natural resource management. Our new approach to modelling social influence is applicable to many social-ecological systems with minimal legal and institutional support or those that rely heavily on bottom-up participatory processes.
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| 9. |
- Ammar, Yosr, et al.
(författare)
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Quantifying socio-economic novelty in fisheries social-ecological systems
- 2022
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Ingår i: Fish and Fisheries. - : Wiley. - 1467-2960 .- 1467-2979. ; 23:2, s. 445-461
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Tidskriftsartikel (refereegranskat)abstract
- Socio-economic development has shaped fisheries social-ecological systems (SES) worldwide across different scales. No work has yet undertaken how this development led to novel, not experienced before, systems structure in marine SES. Here, we quantify socio-economic novelty as the degree of dissimilarity relative to a specific spatiotemporal baseline in the Baltic Sea fisheries SES between 1975 and 2015. We used catch by "gears," catch by "commercial groups" and trade ("import" and "export") as respective indicators of novelty at national, regional and international governance levels. We found that socio-economic novelty increased over time nonlinearly in relation to the 1975–1979 baseline. The contribution to total novelty shifted from the dominance of “gears” and “commercial groups” in the late 1990s and early 2000s to “import” and “export” after the mid-2000s, i.e. from national and regional levels to the international level. The fastest increase in novelty occurred with the trade dominance shift, primarily related to monetary value rather than quantity. Spatially, novelty emerged with a large difference across countries, and a major contribution by Sweden, Denmark and Poland. We identified the influence of different management interventions and governance actions on the emergence of novelty in the Baltic SES. The decreasing socio-economic novelty at national and regional levels could indicate reduced variability due to management intervention in recent years which might decrease SES resilience to shocks. Calculating socio-economic novelty and studying its drivers at different scales could provide a better understanding of SES complexity and inform urgently needed adaptation and transformation towards sustainable future pathways.
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| 10. |
- Boonstra, Wiebren J., et al.
(författare)
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Classifying fishers' behaviour. An invitation to fishing styles
- 2016
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Ingår i: Fish and Fisheries. - : Wiley. - 1467-2960 .- 1467-2979. ; 17:1, s. 78-100
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Tidskriftsartikel (refereegranskat)abstract
- The study and classification of fishers’ behaviour remains a much debated topic. There is a tension between detailed empirical studies, which highlight the variety and diversity of fisheries, and the parsimony and generalization required to satisfy science and policy demands. This study contributes to this debate. The first sec- tion reviews quantitative methods currently used for classifying fishing practices. The review uncovers significant weaknesses in quantitative classification methods, which, we argue, can be improved through the complementary use of qualitative methods. To this purpose, we introduce the concept of ‘fishing style’, which integrates quantitative classification methods with qualitative analysis. We explain the scientific premises of the fishing-style concept, outline a general methodological framework and present a fishing-style analysis of Swedish Baltic Sea fisheries. Based on these results, we conclude that it is possible to classify fishing practices in a rel- atively uniform and limited number of styles that can highlight the rich, empirical diversity of fishers’ behaviour. We therefore propose that fishing-style analysis, based on an integration of quantitative and qualitative methods, can be an impor- tant step towards more effective and sustainable fisheries management.
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| 11. |
- Boonstra, Wiebren J., et al.
(författare)
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The quality of compliance : investigating fishers' responses towards regulation and authorities
- 2017
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Ingår i: Fish and Fisheries. - : Wiley. - 1467-2960 .- 1467-2979. ; 18:4, s. 682-697
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Tidskriftsartikel (refereegranskat)abstract
- A substantial amount of scientific effort goes into understanding and measuring compliance in fisheries. Understanding why, how and when fishers follow or violate rules is crucial for designing effective fishery policies that can halt overfishing. Non-compliance was initially explained almost exclusively with reference to economic and self-interested motivations. More recently, however, most explanations involve a combination of economic, social, political and environmental factors. Despite this recent development towards more holistic explanations, many scientists continue to frame the issue in binary terms: fishers either follow rules, or they don't. In this article we challenge this binary interpretation and focus attention on the diversity of fishers' dispositions and perceptions that underpin compliant behaviour. To this aim we construct a typology of fishers' responses towards regulation and authorities, thereby developing conceptual tools to understand different motivations and attitudes that underlie compliance outcomes. For this purpose, we identify the motivational postures of 'creativity' and 'reluctance', and then highlight their empirical relevance with an interview study of Swedish fishers. Reasons for studying the quality and diversity of fishers' motivations and responses are not purely academic. Conceptualizing and observing the quality of compliance can help policymakers and managers gauge and anticipate the potentiality of non-compliant fishing practices that may threaten the resilience of marine ecosystems.
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| 12. |
- Cardinale, Massimiliano, et al.
(författare)
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A centurial development of the North Sea fish megafauna as reflected by the historical Swedish longlining fisheries
- 2015
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Ingår i: Fish and Fisheries. - : Wiley. - 1467-2960 .- 1467-2979. ; 16:3, s. 522-533
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Tidskriftsartikel (refereegranskat)abstract
- Historically, to compensate for declining catches, fishers have usually shifted from species characterized by high catch rate onto less easily caught species or have moved into new fishing grounds. Such shifts are poorly documented for areas with a long history of exploitation (i.e. North Sea) as they occurred long time before the start of the regular assessments of the marine resources. The Swedish longline fisheries in the Kattegat-Skagerrak and North Sea have a long history that spans over several centuries. These fisheries have historically targeted large demersal predator fish as ling (Molva molva), cod (Gadus morhua), Atlantic halibut (Hippoglossus hippoglossus) and skates (mainly Dipturus spp.). In this study, data from the Swedish longline fisheries from 1859 to 1960 have been collated. The data show that the geographical expansion of the fishery was extensive. At the turn of the 20th century, offshore longlining became concentrated north and west of the Shetlands and Hebrides, and after the WWII, the fishery expanded to Iceland and Rockall. In the offshore fishery, CPUE for the main target species, ling, remained stable, whereas for the other species, with the exception of tusk (Brosme brosme), CPUE showed a dramatic decline over time. In contrast, in the coastal longlining fishery, severe declines were revealed for all major target species except cod. We argue that the constant search for new fishing grounds in the Northeast Atlantic reflects a dwindling resource, where the fishermen kept the catch rates of ling high by travelling to more and more distant fishing grounds. © 2014 John Wiley & Sons Ltd.
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| 13. |
- Cardinale, Massimiliano
(författare)
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'Drivin' with your eyes closed': Results from an international, blinded simulation experiment to evaluate spatial stock assessments
- 2024
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Ingår i: Fish and Fisheries. - 1467-2960 .- 1467-2979. ; 25, s. 471-490
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Tidskriftsartikel (refereegranskat)abstract
- Spatial models enable understanding potential redistribution of marine resources associated with ecosystem drivers and climate change. Stock assessment platforms can incorporate spatial processes, but have not been widely implemented or simulation tested. To address this research gap, an international simulation experiment was organized. The study design was blinded to replicate uncertainty similar to a real-world stock assessment process, and a data-conditioned, high-resolution operating model (OM) was used to emulate the spatial dynamics and data for Indian Ocean yellowfin tuna (Thunnus albacares). Six analyst groups developed both single-region and spatial stock assessment models using an assessment platform of their choice, and then applied each model to the simulated data. Results indicated that across all spatial structures and platforms, assessments were able to adequately recreate the population trends from the OM. Additionally, spatial models were able to estimate regional population trends that generally reflected the true dynamics from the OM, particularly for the regions with higher biomass and fishing pressure. However, a consistent population biomass scaling pattern emerged, where spatial models estimated higher population scale than single-region models within a given assessment platform. Balancing parsimony and complexity trade-offs were difficult, but adequate complexity in spatial parametrizations (e.g., allowing time- and age-variation in movement and appropriate tag mixing periods) was critical to model performance. We recommend expanded use of high-resolution OMs and blinded studies, given their ability to portray realistic performance of assessment models. Moreover, increased support for international simulation experiments is warranted to facilitate dissemination of methodology across organizations.
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| 14. |
- Cardinale, Massimiliano, et al.
(författare)
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Something old, something new: Historical perspectives provide lessons for blue growth agendas
- 2020
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Ingår i: Fish and Fisheries. - : Wiley. - 1467-2960 .- 1467-2979. ; 21, s. 774-796
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Tidskriftsartikel (refereegranskat)abstract
- The concept of "blue growth," which aims to promote the growth of ocean economies while holistically managing marine socioecological systems, is emerging within national and international marine policy. The concept is often promoted as being novel; however, we show that historical analogies exist that can provide insights for contemporary planning and implementation of blue growth. Using a case-study approach based on expert knowledge, we identified 20 historical fisheries or aquaculture examples from 13 countries, spanning the last 40-800 years, that we contend embody blue growth concepts. This is the first time, to our knowledge, that blue growth has been investigated across such broad spatial and temporal scales. The past societies managed to balance exploitation with equitable access, ecological integrity and/or economic growth for varying periods of time. Four main trajectories existed that led to the success or failure of blue growth. Success was linked to equitable rather than open access, innovation and management that was responsive, holistic and based on scientific knowledge and monitoring. The inability to achieve or maintain blue growth resulted from failures to address limits to industry growth and/or anticipate the impacts of adverse extrinsic events and drivers (e.g. changes in international markets, war), the prioritization of short-term gains over long-term sustainability, and loss of supporting systems. Fourteen cross-cutting lessons and 10 recommendations were derived that can improve understanding and implementation of blue growth. Despite the contemporary literature broadly supporting our findings, these recommendations are not adequately addressed by agendas seeking to realize blue growth.
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| 15. |
- Crona, Beatrice I., et al.
(författare)
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Masked, diluted and drowned out : how global seafood trade weakens signals from marine ecosystems
- 2016
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Ingår i: Fish and Fisheries. - : Wiley. - 1467-2960 .- 1467-2979. ; 17:4, s. 1175-1182
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Tidskriftsartikel (refereegranskat)abstract
- Nearly 40% of seafood is traded internationally and an even bigger proportion is affected by international trade, yet scholarship on marine fisheries has focused on global trends in stocks and catches, or on dynamics of individual fisheries, with limited attention to the link between individual fisheries, global trade and distant consumers. This paper examines the usefulness of fish price as a feedback signal to consumers about the state of fisheries and marine ecosystems. We suggest that the current nature of fisheries systems and global markets prevent transmission of such price signals from source fisheries to consumers. We propose several mechanisms that combine to weaken price signals, and present one example - the North Sea cod - to show how these mechanisms can be tested. The lack of a reliable price feedback to consumers represents a challenge for sustainable fisheries governance. We therefore propose three complimentary approaches to address the missing feedback: (i) strengthening information flow through improved traceability and visibility of individual fishers to consumers, (ii) capitalizing on the changing seafood trade structures and (iii) bypassing and complementing market mechanisms by directly targeting citizens and political actors regarding marine environmental issues through publicity and information campaigns. These strategies each havelimitations and thus need to be pursued together to address the challenge of sustainability in global marine fisheries.
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| 16. |
- Defeo, Omar, et al.
(författare)
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Co-management in Latin American small-scale shellfisheries : assessment from long-term case studies
- 2016
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Ingår i: Fish and Fisheries. - : Wiley. - 1467-2960 .- 1467-2979. ; 17:1, s. 176-192
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Tidskriftsartikel (refereegranskat)abstract
- Co-management (Co-M), defined as the sharing of management tasks and responsibilities between governments and local users, is emerging as a powerful institutional arrangement to redress fisheries paradigm failures, yet long-term assessments of its performance are lacking. A comparative analysis of five small-scale Latin American shellfisheries was conducted to identify factors suggesting success and failure. In Chile, Uruguay and Mexico Co-M produced positive effects, including stabilization of landings at low levels, increase in abundance, CPUE, unit prices and revenues per unit of effort, and reduced interannual variability in several fishery indicators, particularly in landings. Co-M was successful because it was mainly bottom-up implemented and accompanied by-catch shares (spatial property rights and community quotas). By contrast, Co-M implementation was unable to prevent the collapse of the Galapagos sea cucumber fishery, as reflected by a decrease in abundance and CPUE. Negative effects were also observed in the Galapagos spiny lobster fishery during Co-M implementation. However, recovery was observed in recent years, reflected in a stabilization of fishing effort and the highest CPUE and economic revenues observed since the beginning of the Co-M implementation phase. The combined effects of market forces, climate variability and a moratorium on fishing effort were critical in fishery recovery. We conclude that Co-M is not a blueprint that can be applied to all shellfisheries to enhance their governability. These social-ecological systems need to be managed by jointly addressing problems related to the resources, their marine environment and the people targeting them, accounting for their socioeconomic and cultural contexts.
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| 17. |
- Eriksson, Hampus, et al.
(författare)
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The sea cucumber fishery in Australia's Great Barrier Reef Marine Park follows global patterns of serial exploitation
- 2015
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Ingår i: Fish and Fisheries. - : Wiley. - 1467-2960 .- 1467-2979. ; 16:2, s. 329-341
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Tidskriftsartikel (refereegranskat)abstract
- Tropical sea cucumber fisheries follow a predictable pattern of serial depletion. Overfishing is exacerbated in developing countries where management systems lack capacity to control large numbers of fishers influenced by poverty. In contrast, the tropical sea cucumber fishery in Australia's World Heritage listed Great Barrier Reef Marine Park (GBRMP) is operating in a developed high-income country with relatively few licensed fishers to manage. The development of this fishery is reviewed here in a meta-analysis of catches from 1991 to 2011. The fishery expanded to replace high-value teatfish species (Holothuria whitmaei and H.fuscogilva), fished heavily in initial stages of the fishery, with newly commercialized medium-value species such as burying blackfish (Actinopyga spinea) and curryfish (Stichopus herrmanni). These two species now constitute 80% of total catch. The annual average catch of burying blackfish was 208tonnes years 2004-11 and curryfish catches increased rapidly at an average annual pace of 200% from 2007-11. This serial harvest pattern occurred in the absence of baseline studies and without independent resource assessments, information required to inform relevant harvest predictions and to determine fishery impacts. This situation does not support ecologically relevant and adaptive decision-making in management and the unfolding catch patterns in the GBRMP follow those in low-income developing countries. The missing knowledge and lack of data serve as arguments to support precautionary reductions in harvests and extending fallow periods in fishing zones.
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| 18. |
- Fetterplace, Lachlan
(författare)
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Continental‐scale acoustic telemetry and network analysis reveal new insights into stock structure
- 2021
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Ingår i: Fish and Fisheries. - : Wiley. - 1467-2960 .- 1467-2979. ; 22, s. 987-1005
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Tidskriftsartikel (refereegranskat)abstract
- Delineation of population structure (i.e. stocks) is crucial to successfully manage exploited species and to address conservation concerns for threatened species. Fish migration and associated movements are key mechanisms through which discrete populations mix and are thus important determinants of population structure. Detailed information on fish migration and movements is becoming more accessible through advances in telemetry and analysis methods however such information is not yet used systematically in stock structure assessment. Here, we described how detections of acoustically tagged fish across a continental-scale array of underwater acoustic receivers were used to assess stock structure and connectivity in seven teleost and seven shark species and compared to findings from genetic and conventional tagging. Network analysis revealed previously unknown population connections in some species, and in others bolstered support for existing stock discrimination by identifying nodes and routes important for connectivity. Species with less variability in their movements required smaller sample sizes (45-50 individuals) to reveal useful stock structure information. Our study shows the power of continental-scale acoustic telemetry networks to detect movements among fishery jurisdictions. We highlight methodological issues that need to be considered in the design of acoustic telemetry studies for investigating stock structure and the interpretation of the resulting data. The advent of broad-scale acoustic telemetry networks across the globe provides new avenues to understand how movement informs population structure and can lead to improved management.
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| 19. |
- Flink, Henrik, et al.
(författare)
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Recreational fisheries selectively capture and harvest large predators
- 2024
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Ingår i: Fish and Fisheries. - : John Wiley & Sons. - 1467-2960 .- 1467-2979.
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Tidskriftsartikel (refereegranskat)abstract
- Size- and species-selective harvest inevitably alters the composition of targeted populations and communities. This can potentially harm fish stocks, ecosystem functionality, and related services, as evidenced in numerous commercial fisheries. The high popularity of rod-and-reel recreational fishing, practiced by hundreds of millions globally, raises concerns about similar deteriorating effects. Despite its prevalence, the species and size selectivity of recreational fisheries remain largely unquantified due to a lack of combined catch data and fisheries-independent surveys. This study addresses this gap by using standardised monitoring data and over 60,000 digital angling catch reports from 62 distinct fisheries. The findings demonstrate a pronounced selectivity in recreational fisheries, targeting top predators and large individuals. Catch-and-release practices reduced the overall harvest by 60% but did not substantially alter this selectivity. The strong species- and size-specific selectivity mirror patterns observed in other fisheries, emphasising the importance of managing the potential adverse effects of recreational fisheries selective mortality and overfishing.
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| 20. |
- Freitas, Tiago Magalhaes da Silva, et al.
(författare)
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Quantifying shortfalls in the knowledge on Neotropical Auchenipteridae fishes
- 2021
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Ingår i: Fish and Fisheries. - : John Wiley & Sons. - 1467-2960 .- 1467-2979. ; 22:1, s. 87-104
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Tidskriftsartikel (refereegranskat)abstract
- The Neotropics harbour the greatest diversity of freshwater fish on Earth. Despite recent advances in characterizing the fish fauna, the total number of species, distributional range, evolution and ecological traits remain uncertain. Thus, we quantify shortfalls in the knowledge of taxonomy (Linnean shortfall), geographic distribution (Wallacean shortfall), evolutionary relationships (Darwinian shortfall) and feeding habits (Raunki AE ran shortfall) of Auchenipteridae driftwood catfishes, one of the most representative groups of the Siluriformes family in the Neotropics. We find a steep increase in the historical accumulation of valid species over time, suggesting that 45% of the total number predicted remains to be described. Auchenipterids also remain under-collected; only 45% of the ecoregions and less than 3% of the one-degree grid cells covering the Neotropics are reasonably sampled. The topologies of recent phylogenies are more similar to each other than former ones, showing a tendency towards a robust phylogenetic hypothesis for this family. Current knowledge on feeding habits is biased towards a few genera and species and is still expanding with every new published study. Our study highlights specific knowledge gaps that need to be addressed: a considerable number of Auchenipteridae species remain to be described; and most of valid species lack reliable information on their geographic distribution and feeding habitat. It implies that research on fish systematic biology needs to advance and it will require a concerted effort of taxonomists, ecologists and biogeographers to reduce these gaps.
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| 21. |
- Fulton, Christopher J., et al.
(författare)
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Macroalgal meadow habitats support fish and fisheries in diverse tropical seascapes
- 2020
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Ingår i: Fish and Fisheries. - : Wiley. - 1467-2960 .- 1467-2979. ; 21:4, s. 700-717
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Tidskriftsartikel (refereegranskat)abstract
- Canopy-forming macroalgae can construct extensive meadow habitats in tropical seascapes occupied by fishes that span a diversity of taxa, life-history stages and ecological roles. Our synthesis assessed whether these tropical macroalgal habitats have unique fish assemblages, provide fish nurseries and support local fisheries. We also applied a meta-analysis of independent surveys across 23 tropical reef locations in 11 countries to examine how macroalgal canopy condition is related to the abundance of macroalgal-associated fishes. Over 627 fish species were documented in tropical macroalgal meadows, with 218 of these taxa exhibiting higher local abundance within this habitat (cf. nearby coral reef) during at least one life-history stage. Major overlap (40%-43%) in local fish species richness among macroalgal and seagrass or coral reef habitats suggest macroalgal meadows may provide an important habitat refuge. Moreover, the prominence of juvenile fishes suggests macroalgal meadows facilitate the triphasic life cycle of many fishes occupying diverse tropical seascapes. Correlations between macroalgal canopy structure and juvenile abundance suggests macroalgal habitat condition can influence levels of replenishment in tropical fish populations, including the majority of macroalgal-associated fishes that are targeted by commercial, subsistence or recreational fisheries. While many macroalgal-associated fishery species are of minor commercial value, their local importance for food and livelihood security can be substantial (e.g. up to 60% of landings in Kenyan reef fisheries). Given that macroalgal canopy condition can vary substantially with sea temperature, there is a high likelihood that climate change will impact macroalgal-associated fish and fisheries.
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| 22. |
- Griffiths, Christopher, et al.
(författare)
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Including older fish in fisheries management: A new age-based indicator and reference point for exploited fish stocks
- 2024
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Ingår i: Fish and Fisheries. - 1467-2960 .- 1467-2979. ; 25, s. 18-37
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Tidskriftsartikel (refereegranskat)abstract
- Larger and older fish contribute disproportionately to spawning and play an important role in the replenishment of exploited stocks. Fishing often removes specific size- and age-classes, with direct impacts on stock productivity and population resilience. Despite this, fisheries advice is commonly based on estimates of spawning stock biomass (SSB) and fishing mortality (F) and makes little reference to the importance of size and/or age structure. Consequently, there is a need for indicators of size and/or age structure to better inform fisheries management and help assess global sustainability goals. Here, we introduce a new age-based indicator ABI(MSY) that monitors age structure relative to the equilibrium age structure at F-MSY. We apply this new indicator to 72 commercially important stocks in the Northeast Atlantic, covering 26 species, which collectively contributed 86% of all commercial catches in the region in 2019. We estimate that 62% (45 stocks) currently have proportionally fewer older fish relative to F-MSY conditions, whereas 38% (27 stocks) have proportionally more older fish; we also note patterns with respect to geographic area and taxonomic family. Simulation testing demonstrated that ABI(MSY) is responsive to overfishing and generally tracks (with high sensitivity and specificity) a common measure of stock depletion, SSB relative to B-MSY. Throughout, we show that ABI(MSY) provides information on the age structure of exploited stocks that is complementary to conventional reference points for SSB and F. Further, the framework used to estimate ABI(MSY )make it well placed for integration into current advisory frameworks on fisheries management.
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| 23. |
- Hamilton, P. B., et al.
(författare)
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Population-level consequences for wild fish exposed to sublethal concentrations of chemicals : a critical review
- 2016
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Ingår i: Fish and Fisheries. - : Wiley. - 1467-2960 .- 1467-2979. ; 17:3, s. 545-566
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Forskningsöversikt (refereegranskat)abstract
- Concentrated chemical spills have been shown to impact adversely on fish populations and even cause localized population extinctions. Evaluating population-level impacts of sublethal exposure concentrations is, however, complex and confounded by other environmental pressures. Applying effect measures derived from laboratory-based chemical exposures to impacts in wild fish populations is constrained by uncertainty on how biochemical response measures (biomarkers) translate into health outcomes, lack of available data for chronic exposures and the many uncertainties in available fish population models. Furthermore, wild fish show phenotypic plasticity and local adaptations can occur that adds geographic and temporal variance on responses. Such population-level factors are rarely considered in the chemical risk assessment process and can probably be derived only from studies on wild fish. Molecular technologies, including microsatellite and SNP genotyping, and RNASeq for gene expression studies, are advancing our understanding of mechanisms of eco-toxicological response, tolerance, adaptation and selection in wild populations. We examine critically the application of such approaches with examples including using microsatellites that has identified roach (Rutilus rutilus) populations living in rivers contaminated with sewage effluents that are self-sustaining, and studies of stickleback (Gasterosteus aculeatus) and killifish (Fundulus heteroclitus) that have identified genomic regions under selection putatively related to pollution tolerance. Integrating data on biological effects between laboratory-based studies and wild populations, and building understanding on adaptive responses to sublethal exposure are some of the priority research areas for more effective evaluation of population risks and resilience to contaminant exposure.
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| 24. |
- Hentati Sundberg, Jonas
(författare)
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Seabird-induced natural mortality of forage fish varies with fish abundance: Evidence from five ecosystems
- 2021
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Ingår i: Fish and Fisheries. - : Wiley. - 1467-2960 .- 1467-2979. ; 22, s. 262-279
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Tidskriftsartikel (refereegranskat)abstract
- Forage fish populations often undergo large and rapid fluctuations in abundance. However, most of their predators are buffered against such fluctuations owing to their slower pace of life, which allows them to maintain more stable populations, at least during short periods of food scarcity. In this study, we investigated top-down processes exerted by seabirds on forage fish stocks in five contrasted marine ecosystems, compiling numerous data sets on seabird counts, diets, energetic needs and prey energy content and abundance. Off Norway, South Africa, Peru, Sweden and Scotland, we found that predation pressure-estimated as the proportion of a fish stock consumed by seabirds-was generally low (median = 1%), but increased sharply at low levels of prey abundance. When prey biomass decreased below 15-18% of its maximum recorded value, predation by seabirds became a source of important additional pressure on prey stocks (similar to 20% of prey biomass is consumed by seabirds). An earlier empirical study advocated for keeping forage stocks from falling below a threshold of 33% of long-term maximum prey biomass in order to safeguard seabird breeding success, but here we further suggest that a threshold of 18% should be considered as a limit not to be exceeded for the sake of the forage fish themselves, and below which extra cautious management of fisheries may be required. Nevertheless, despite exceptionally high rates of predation on some occasions, predation pressure was not correlated with prey dynamics, suggesting an absence of prey entrapment due to seabirds alone in these five ecosystems.
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| 25. |
- Hilvarsson, Annelie, et al.
(författare)
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Multidecadal changes in fish growth rates estimated from tagging data: A case study from the Eastern Baltic cod (Gadus morhua, Gadidae)
- 2021
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Ingår i: Fish and Fisheries. - : Wiley. - 1467-2960 .- 1467-2979. ; 22, s. 413-427
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Tidskriftsartikel (refereegranskat)abstract
- Long time series of reliable individual growth estimates are crucial for understanding the status of a fish stock and deciding upon appropriate management. Tagging data provide valuable information about fish growth, and are especially useful when age-based growth estimates and stock assessments are compromised by age-determination uncertainties. However, in the literature there is a lack of studies assessing possible changes in growth over time using tagging data. Here, data from tagging experiments performed in the Baltic Sea between 1971 and 2019 were added to those previously analysed for 1955-1970 to build the most extensive tagging dataset available for Eastern Baltic cod (Gadus morhua, Gadidae), a threatened stock with severe age-determination problems. Two length-based methods, the GROTAG model (based on the von Bertalanffy growth function) and a Generalized Additive Model, were used to assess for the first time the potential long-term changes in cod growth using age-independent data. Both methods showed strong changes in growth with an increase until the end of the 1980s (8.6-10.6 cm/year for a 40 cm cod depending on the model) followed by a sharp decline. This study also revealed that the current growth of cod is the lowest observed in the past 7 decades (4.3-5.1 cm/year for a 40 cm cod depending on the model), indicating very low productivity. This study provides the first example of the use of tagging data to estimate multidecadal changes in growth rates in wild fish. This methodology can also be applied to other species, especially in those cases where severe age-determination problems exist.
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