Empowerment and regulation – dilemmas in participatory fisheries science

Using a perspective from the sociology of knowledge, this study identifies some ‘dilemmas of participatory research’. We look at how social relationships between fishers and scientists develop around the exchange of fishers’ knowledge in particular institutional contexts. We survey the general types and global examples of fisher–scientist relationships in terms of how they approach the integration of fishers’ and scientists’ knowledge. Based on an empirical study of three European cases of participatory research, we then discuss five dilemmas that tend to characterize fisher–scientist relationships. These dilemmas centre on the relationship between fisheries research, fishery regulations and fishers as subjects of both regulation and participatory research endeavours. We argue that these dilemmas – experienced by both scientists and fishers – express an underlying tension between ‘empowering’ fishers to support the effective management of the fishing commons and the bureaucratic need to regulate the fishery as an industry.     

Seasonal and annual cycles in marine small‐scale fisheries (Ilhéus – Brazil)

Fish stock assessment is a crucial tool for resource management. Small‐scale fisheries are often multispecies and multigear. This study focuses on the search for patterns in the Ilhéus small‐scale fishery using landing data from 2000 to 2006 and climatic data. Ocyurus chrysurus and Ephinephelus spp. were the most commonly landed fish. The number of fishing trips was higher in the winter, when winds were weaker and temperatures lower. When the temperature increased, catches of Seriola dumerili were higher. Coryphaena hippurus and some rays were more abundant in the summer in the presence of stronger winds, intense rainfall and higher air temperature. Large catches of Lutjanus spp. and Scomberomorus spp. were obtained in the autumn. There is an annual seasonality in the fishery, with a cyclical landing pattern regardless of the years considered. These results are important in view of climate change, and specific strategies for better fisheries management are recommended.     

Bycatch Beknown: Methodology for jurisdictional reporting of fisheries discards – Using Australia as a case study

Bycatch remains one of the most important issues in the world's fisheries so its estimation and reporting have been highlighted in many international, regional and jurisdictional guidelines and policies. This paper describes a simple methodology to estimate jurisdictional discards, using Australia's first national bycatch report as a case study. The methodology involves: (a) identifying annual landings for all fisheries and methods; (b) deriving retained:discard ratios for each; (c) where ratios are lacking, using substitute ratios from similar fisheries; (d) applying the ratios from (b) and (c) to the data from (a) to obtain totals; and (e) scoring the quality of the discard information using the US Tier Classification System weighted by estimated discard levels. The results for Australia revealed that, during the last decade, commercial fisheries annually discarded 42.5% of what was caught (87,983t). 70% came from just eight fisheries/methods with 30% coming from the other 299. The Queensland East Coast Prawn Trawl fishery contributed 28.5% of the national total. The quality of discard information was reasonable across most jurisdictions, with a national score of 59.1%. The best quality data came from the Commonwealth due to its observer and (more recent) Electronic Monitoring programmes. Those data also showed that fishers’ logbook information under‐estimated levels of discards (determined from observer data) by 89.7%. This paper provides: (a) the means to develop benchmarks in bycatch management and estimation against which jurisdictions can be compared and performances tracked; and (b) for Australia, priority areas for management intervention to reduce discarding and improve its monitoring.     

Shifting perceptions of rapid temperature changes’ effects on marine fisheries, 1945–2017

Climate‐driven warming has both social and ecological effects on marine fisheries. While recent changes due to anthropogenic global warming have been documented, similar basin‐wide changes have occurred in the past due to natural temperature fluctuations. Here, we document the effects of rapidly changing water temperatures along the United States’ east coast using observations from fisheries newspapers during a warming phase (1945–1951) and subsequent cooling phase (1952–1960) of the Atlantic Multidecadal Oscillation, which we compared to similar recent observations of warming waters (1998–2017). Historical warming and cooling events affected the abundance of species targeted by fishing, the prevalence of novel and invasive species, and physical access to targeted species. Fishing communities viewed historical cooling waters twice as negatively as they did warming waters (72% vs. 35% of observations). Colder waters were associated with a decrease in fishing opportunity due to storminess, while warming waters were associated with the potential for new fisheries. In contrast, recent warming waters were viewed as strongly negative by fishing communities (72% of observations), associated with disease, reductions in abundances of target species, and shifts in distributions across jurisdictional lines. This increasing perception that warming negatively affects local fisheries may be due to an overall reduction of opportunity in fisheries over the past half century, an awareness of the relative severity of warming today, larger changes in American culture, or a combination of these factors. Negative perceptions of recent warming waters’ effects on fisheries suggest that fishing communities are currently finding the prospect of climate adaptation difficult.     

Sawfishes in The Gambia and Senegal – shifting baselines over 40 years

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Pre‐impoundment stock assessment of two Pimelodidae species caught by small‐scale fisheries in the Madeira River (Amazon Basin – Brazil)

The middle stretch of the Madeira River has supported an intensive commercial fishery for several decades. Developed in an area of rapids and waterfalls, this fishery focuses primarily on catfish stocks, mainly pimelodids. Data from fish landings collected in the years immediately prior to the start in operations of two large hydroelectric dams were used to estimate growth and mortality rates for Pirinampus pirinampu (Spix & Agassiz) and Brachyplatystoma platynemum Boulenger. In addition, stock assessment was carried out for both species, and the results used to evaluate the status of the fishery. Mean population parameters were L_∞ = 80.85 cm (total length), k = 0.52 year^?1, ? = 3.53, A_0.95 = 6 year, M = 0.87, F = 1.41–1.64 and Z = 2.28–2.51 for P. pirinampu; and L_∞ = 95.55 cm (total length), k = 0.28 year^?1, ? = 3.40, winter point = 0.41, A_0.95 = 11 year, M = 0.55, F = 0.16–0.35 and Z = 0.71–0.90 for B. platynemum. Yield‐per‐recruit analysis indicated P. pirinampu was overfished and that the stock of B. platynemum was under‐exploited. Moreover, overfishing of the P. pirinampu stock and the effects of fragmentation caused by the construction of the dam should be monitored.     

Changes in the fish and fisheries ecology of a large man-made lake in Tanzania, 1965–94

Abstract Nyumba ya Mungu Reservoir in northern Tanzania has a maximum surface area of 180 km², an average depth of 6 m, and contains moderately saline, fertile water. The postimpoundment decade, 1965–74, was characterised by a spectacular rise and fall of a tilapiabased fishery. Since then a gill-net fishery catching large numbers of large, periphyton-grazing tilapias has given way to a mainly beach-seine fishery producing large numbers of small, phytoplankton-feeding Oreochromis esculentus (Graham). Yields remain higher than preimpoundment predictions but the size at maturity of all tilapia species has fallen and few larger than 15 cm TL are caught. These changes, and others in the fish community trophic structure, are chiefly explained by changes in the littoral environment and fishing pressures. Nyumba ya Mungu provides a case history of developments in the tilapia fishery of a man-made river lake conducted on an essentially laissez-faire basis.     

Functional vs scenic restoration – challenges to improve fish and fisheries in urban waters

Abstract Two rehabilitation projects were compared to determine their feasibility for successfully improving habitat for fish in urban waters. The first re‐meandering project involved channel reconstruction in the Müggelspree upstream of Berlin to create an aesthetically pleasing, stable, meandering channel. The second project addressed a typical habitat bottleneck for fish found in urban waterways; that of nursery habitats lost due to river engineering works. Rehabilitated and control sites were sampled before and after in the Müggelspree and once in the urban Spree River. A total of 30 303 fish belonging to 27 species were collected. The fish assemblage was dominated by generalist species with 81% roach, Rutilus rutilus (L.), and perch, Perca fluviatilis L. Species diversity did not improve in either the rural or urban stretch. In the Müggelspree, the loss of riverine habitats was mirrored by significant declines in the densities of chub, Leuciscus cephalus (L.), ide, Leuciscus idus (L.), gudgeon, Gobio gobio (L.), rheophilic and lithophilic species. By contrast, densities of rheophilic species around the artificial structures created in the urban Spree River, although the main effect was an overwhelming increase in roach and perch. The results suggest that if underlying bottlenecks can be identified, artificial structures can provide functional fish habitat that replaces the natural equivalent in urban river stretches. Consequently, even the most heavily degraded waters provide opportunities to improve fish diversity and fisheries using artificial habitat structures.     

On scientists’ discomfort in fisheries advisory science: the example of simulation‐based fisheries management‐strategy evaluations

Scientists feel discomfort when they are asked to create certainty, where none exists, for use as an alibi in policy‐making. Recently, the scientific literature has drawn attention to some pitfalls of simulation‐based fisheries management‐strategy evaluation (MSE). For example, while estimates concerning central tendencies of distributions of simulation outcomes are usually fairly robust because they are conditioned on ample data, estimates concerning the tails of distributions (such as the probability of falling below a critical biomass) are usually conditional on few data and thus often rely on assumptions that have no strong knowledge base. The clients of scientific advice, such as the European Commission, are embracing the mechanization of the evaluation of proposed Harvest Control Rules against the precautionary principle and management objectives. Where the fisheries management institutions aim for simple answers from the scientists, giving ‘green/red light’ to a proposed management strategy, the scientists are forced into a split position between satisfying the demands of their advisory role and living up to the standards of scientific rigour. We argue against the mechanization of scientific advice that aims to incorporate all relevant processes into one big model algorithm that, after construction, can be run without circumspection. We rather encourage that fisheries advice should be a dynamic process of expert judgement, incorporating separate parallel concurrent, lines of scientific evidence, from quantitative and qualitative modelling exercises and factual knowledge of the biology and the fishery dynamics. This process can be formalized to a certain degree and can easily accommodate stakeholder viewpoints.     

Impacts of introducing Nile tilapia on the fisheries of a tropical reservoir in North‐eastern Brazil

Abstract Nile tilapia, Oreochromis niloticus (L.), has been introduced in most tropical and subtropical regions of the world to improve inland fisheries and aquaculture. This species is generally viewed as beneficial where introduced, but the environmental impacts of its widespread introductions are uncertain and not well understood. In this study, a 30‐year time series of fisheries records from a tropical reservoir was divided into five equal periods of 6 years and compared. The introduction of Nile tilapia did not increase the total catch‐per‐unit‐of‐effort (CPUE), the number of fishers actively fishing or their per capita income. Conversely, a significant reduction in the CPUE of other commercially important species was observed after the introduction of Nile tilapia in the reservoir. Although other factors cannot be rule out as possible explanations of the observed changes in the reservoir fisheries, the results are consistent with the hypothesis that these changes may have been caused, at least partially, by the introduction of the Nile tilapia.     

Realizing the potential of trait‐based approaches to advance fisheries science

Analysing how fish populations and their ecological communities respond to perturbations such as fishing and environmental variation is crucial to fisheries science. Researchers often predict fish population dynamics using species‐level life‐history parameters that are treated as fixed over time, while ignoring the impact of intraspecific variation on ecosystem dynamics. However, there is increasing recognition of the need to include processes operating at ecosystem levels (changes in drivers of productivity) while also accounting for variation over space, time and among individuals. To address similar challenges, community ecologists studying plants, insects and other taxa increasingly measure phenotypic characteristics of individual animals that affect fitness or ecological function (termed “functional traits”). Here, we review the history of trait‐based methods in fish and other taxa, and argue that fisheries science could see benefits by integrating trait‐based approaches within existing fisheries analyses. We argue that measuring and modelling functional traits can improve estimates of population and community dynamics, and rapidly detect responses to fishing and environmental drivers. We support this claim using three concrete examples: how trait‐based approaches could account for time‐varying parameters in population models; improve fisheries management and harvest control rules; and inform size‐based models of marine communities. We then present a step‐by‐step primer for how trait‐based methods could be adapted to complement existing models and analyses in fisheries science. Finally, we call for the creation and expansion of publicly available trait databases to facilitate adapting trait‐based methods in fisheries science, to complement existing public databases of life‐history parameters for marine organisms.     

Allozyme variation and stock structure in the black bream, Acanthopagrus butcheri (Munro) (Sparidae) in southern Australia: implications for fisheries management, aquaculture and taxonomic relationship with Acanthopagrus australis (Günther)

An investigation of allozyme variation at 32 loci in the black bream, Acanthopagrus butcheri (Munro), and the yellowfin bream, Acanthopagrus australis (Günther), revealed heterozygosities (H) equal to 0.035 and 0.065, respectively, and polymorphism (P_0.95) equal to 0.067 and 0.200, respectively. The genetic data confirm the very high level of genetic similarity previously found between the two species, but nevertheless also support their recognition as separate species. The finding of only limited allozyme differentiation at three polymorphic loci amongst six black bream samples from south-eastern Australia is consistent with the existence of a single panmictic population in this region. This would require that adult black bream have a greater capacity to survive in near-shore marine environments than previously realised and that dispersal between estuaries is more extensive than was shown by tagging studies. In contrast, significant differences were found at two loci between black bream from south-eastern Australia and a sample from south-western Australia. The degree of genetic divergence between stocks in south-eastern and south-western Australia suggests that only local brood stock should be used for aquaculture or re-stocking as a precaution until further investigations with DNA-based techniques are conducted. The genetic divergence detected supports separate management for populations in Western Australia and Victoria.     

Comparative Susceptibility of Channel Catfish,Ictalurus punctatus; Blue Catfish,Ictalurus furcatus; and Channel (♀) × Blue (♂) Hybrid Catfish to Edwardsiella piscicida,Edwardsiella tarda,and Edwardsiella anguillarum

Members of the genus Edwardsiella are important pathogens of cultured and wild fish globally. Recent investigations into the phenotypic and genotypic variation of Edwardsiella tarda have led to the segregation of E. tarda into three distinct taxa: E. tarda, Edwardsiella piscicida, and Edwardsiella anguillarum. In catfish aquaculture in the southeastern USA, E. piscicida has been more commonly associated with disease than E. tarda or E. anguillarum, and recent research has demonstrated E. piscicida to be more pathogenic in channel catfish than E. tarda or E. anguillarum. Anecdotal reports from industry suggest an increased prevalence of E. piscicida associated with the culture of channel (♀) × blue (♂) hybrid catfish. This work investigated the comparative susceptibility of channel catfish, blue catfish, and their hybrid cross to molecularly confirmed isolates of E. tarda, E. piscicida, and E. anguillarum. There was significantly higher mortality in hybrid catfish compared to channel catfish following intracoelomic injection of E. piscicida. To our knowledge, E. piscicida is the first bacterial pathogen to demonstrate increased pathogenicity in hybrid catfish compared to channel catfish.