Marine litter is a global concern. Since most of the litter sinks, understanding the composition of benthic marine litter is crucial for addressing this concern. However, high costs of seafloor ...monitoring inhibit such understanding. Consequently, benthic marine litter in the Baltic Sea has not been comprehensively addressed yet. Here we present data from 2377 hauls, which collected 6828 litter items and 2412 kg on the Baltic seafloor during six years of the Baltic International Trawl Survey (BITS) by seven nations. Our results show lower percentages of plastic (35%) than the widely cited world average (70%) and less fishery-originated litter (2.2–5.6%) than was previously reported for the Baltic Sea (4–24%). Natural products, mostly residuals of burnt coal, were identified as the most common litter category (42–57%) and were largely ignored in the past. Our results highlight the importance of using several evaluation metrics, particularly number of items, weight and encounter probability.
•2377 survey trawl hauls on the Baltic seafloor yielded 6828 litter items (2412 kg).•The plastic share in the Baltic benthic litter (35%) was below world average (70%).•Natural Products, mostly clinker, was the main litter category in the Baltic Sea.•Fishery-originated litter in the Baltic (2.2–5.6%) was lower than in other regions.•Widely differing evaluation metrics hamper comparison among marine litter studies.
The field of behavioural economics holds several opportunities for integrated fisheries management and conservation and can help researchers and managers alike understand fisher behaviour and ...decision-making. As the study of the cognitive biases that influence decision-making processes, behavioural economics differentiates itself from the classical field of economics in that it does not assume strictly rational behaviour of its agents, but rather looks for all mechanisms that influence behaviour. This field offers potential applications for fisheries management, for example in relation to behavioural change, but such applications require evidence of these mechanisms applied in a fisheries context. Thus, we have developed a systematic literature review protocol focusing on the primary question: "Which behavioural economics mechanisms influence fisher behaviour?" The aim is to provide a comprehensive overview of these different mechanisms and how they have been applied in the study of fisher behaviour. The review protocol was developed in close collaboration with the International Council for the Exploration of the Sea (ICES) Working Group on Maritime Systems (WGMARS). WGMARS members were therefore considered the key stakeholders for this study, and were consulted to develop a suitable systematic review question and methodology. Three academic databases will be searched using a customized Boolean keyword search string. Research articles deemed eligible for inclusion in the systematic review are those that studied the influence of behavioural-economics mechanisms on the behaviour of marine fishers in any location, and at any scale. Insights from this literature will be collated in order to provide an overview of the relevant behavioural-economics mechanisms and actions, how effective these mechanisms are and at what scale, geographic region and in which fisheries sector they have been applied. Any fisheries management implications identified by the studies under review will also be outlined. Finally, it will be recorded whether or not ethical considerations were made in the reviewed literature, so that in the discussion it will be possible to reflect on the ethics of conducting behavioural-economics research and policy actions in a fisheries context.
Abstract
The EU deploys technical measures (TMs) to avoid unwanted catches—here, overquota catches and juveniles of commercial species—including gear specifications and closures. In 2012, the ...European Commission had asked its advisory committee, Scientific, Technical, and Economic Committee for Fisheries (STECF), to evaluate the TMs and provide recommendations for improvement. In 2012–2013, STECF judged that the TMs had failed to achieve their objectives and identified approaches for improvement: (1) regionalization and move away from top-down management; (2) bottom-up results-based management to internalize the costs to the resource into individual businesses; and (3) abandon threshold percentages of bycatch leading to perverse incentives. In 2014, the new EU Common Fisheries Policy came in force, with a landing obligation (LO), and regionalization. In 2019, the new TM regulation (TMR) came in force. Besides sets of regional baseline measures, the TMR allows for regional proposals for amendments and results-based bottom-up approaches (“the good”). However, the LO is not enforced, therefore, not providing the incentive for change in fishing practices; and despite avoidance strategies being available regional, innovative bottom-up practices are still rare (“the bad”). TMs still contain threshold percentages (“the ugly”). The onus for bottom-up initiatives is on the industry, although new governance structures are needed to facilitate this.
Abstract
This article describes a method for the quantitative analysis of fish behaviour relative to selection devices in trawl gears. Based on video observations, the method estimates probabilities ...for a given event to happen and establishes behavioural tree diagrams representing and quantifying behavioural patterns in relation to the selection device under assessment. Double bootstrapping is used to account for the uncertainty originating from a limited number of fish observations and the natural variation in fish behaviour. The method is used here to supplement standard analysis of catch data for the performance assessment of a flatfish excluder (FLEX). The Baltic Sea trawl fishery targeting cod (Gadus morhua) provides the pilot case. Results obtained by comparing catches with and without FLEX installed revealed that >75% of bycaught flatfish individuals escaped through the device, while no evidence was found that catches of cod in the targeted sizes were reduced. The behavioural analysis produced values of escape efficiency comparable to those obtained in the catch analysis. Furthermore, it revealed that ∼80% of the flatfish went calmly into the excluder, while most of the roundfish displayed avoidance swimming reactions. The method provides quantitative information of fish behaviour that can be relevant for developing and optimizing selection devices.
Abstract
Conference participation is an important part of academic practice and contributes to building scientific careers. Investigating demographic differences in conference participation may ...reveal factors contributing to the continued under-representation of women in marine and ocean science. To explore the gender and career stage dimensions of participation in an international marine science conference, preferences of presentation type (oral/poster) as well as acceptance and rejection decisions were investigated using 5-years of data (2015–2019) from an International Marine Science Conference. It was found that early career scientists were more likely to be women, while established scientists were more likely to be men. Although overall, gender did not show a significant effect on the decisions to “downgrade” requests for oral presentations to poster presentations, early career scientists were significantly more likely to be downgraded than established scientists. Given that more women were often early career scientists, more women than men had their presentations downgraded. Other indicators and evidence from conference prize-giving and recognition awards point to a gender gap remaining at senior levels, highlighting the need for further actions as well as monitoring and researching conference participation from a gender perspective.
Abstract
When size-selective fishing removes faster-growing individuals at higher rates than slower-growing fish, the surviving populations will become dominated by slower-growing individuals. When ...this “Rosa Lee phenomenon” is ignored, bias may occur in catch and stock projections. In a length-and-age-based model we quantified the effects through simulations of a simplified fishery on a stock that resembles Western Baltic cod. We compared outcomes of runs with and without taking account of the Rosa Lee phenomenon in scenarios of changes in fishing mortality. We found that, when only fishing rate was changed, the biases in predictions of spawning-stock biomass (SSB), yield and catches of undersized fish were relatively small (<10% in absolute values). When the selectivity parameters of the gear were increased, the bias in the prediction of the catches of undersized fish was very substantial (+120 to 160%). When the selectivity parameters were decreased, the biases in the predictions of SSB, yield and catches of undersized fish, were substantial (25–50% in absolute values). With slower mean growth the biases became more pronounced. We conclude that in short-term forecasts, medium-term projections, and MSE simulations featuring selectivity changes, the Rosa Lee phenomenon should be accounted for, ideally by using length-based models.
Abstract
The EU discard ban and its high-survival exemption exposed our lack of scientific evidence on discard survival in the fisheries. Discard survival is known to be highly variable and ...influenced by numerous factors, including conditions during the catch, on-board the fishing vessels, and post-discard. Therefore, obtaining unambiguous results in discard survival experiments is challenging. We conducted the first systematic year-round discard survival study of flatfish in the Western Baltic Sea on-board a commercial stern trawler under realistic fishing conditions (13 monthly hauls from May 2015 to May 2016) to test whether delayed mortality can be predicted by vitality scores and reflex action mortality predictor (RAMP) scores in combination with variable conditions during catch, processing, and post-release. The factors vessel type, gear, haul duration, fishing ground, depth, handling time, and processing procedures were kept constant as much as possible. On-board, live individual flatfish were tested for vitality and the presence of reflexes for RAMP, then “discarded” and kept in cages on the bottom of the seafloor for about a week after which the delayed mortality was determined. The proportions of “discarded” plaice, flounder, and dab that were dead after being kept in the cages ranged from 5% to 100%, 0% to 96%, and 33% to 100%, respectively. Higher mortalities occurred in summer-autumn when air and water temperatures were higher, catches smaller, and catches contained smaller proportions of roundfish. Relationships between RAMP scores and mortality probabilities varied substantially across the monthly trials. Indeed, in addition to RAMP or vitality scores and individual reflexes, the factors air and water temperature and catch weight and catch composition were significant in logistic GLMs explaining delayed mortality. Cross-validations indicated that delayed mortality could be predicted by these models with a reasonable accuracy. Nevertheless, the presence of possible confounding effects calls for caution in inferring causality and extrapolating the conclusions on predictability.
Abstract
Recent research on harvest-induced evolution of behaviour in (especially aquatic) animals has focused on the shy-bold axis, but foraging and dispersal behaviour have received little ...attention. Here, we consider the selective effect of systematically localised trawl harvesting from a wild population of mobile animals that vary phenotypically in their range of movement (resulting in a continuum between wide-ranging and sedentary behaviours). We use a spatially explicit individual-based model of an empirically-based demersal fish population and trawl fishing in a realistic seascape. We test whether a sustained spatially concentrated pattern of fishing can select for or against wide-ranging vs. more sedentary behaviour as the fish perform biased random foraging in a seascape of spatially varying resource quality, leading to an approximation of the ideal free distribution. The simulation predicted a strong micro-evolutionary shift towards more sedentary behaviour as wide-ranging animals flow into a population sink caused by concentrated fishing. The shift towards short-rangers increased with fishing intensity and spatial precision with which fishing activity matches fish abundance; it decreased with habitat spatial complexity (fragmentation of suitable habitat). Most cases led to the effective extinction of the trait values at the upper end of the ranging continuum, indicating important implications for the management of exploited fish stocks.
Age and size at maturation decreased in several commercially exploited fish stocks, which, according to life history theory, may be due to fisheries-induced evolutionary change. However, the observed ...changes may also represent a plastic response to environmental variability. To disentangle phenotypic plasticity from evolutionary change, the probabilistic reaction norm approach was applied to 43 cohorts (1960 to 2002) of female sole Solea solea from market samples. The reaction norm for age and size at first maturation has significantly shifted towards younger age and smaller size. Size at 50% probability of maturation at Age 3 decreased from 28.6 cm (251 g) to 24.6 cm (128 g). This change was even stronger when condition was included as a third dimension in the reaction norm estimation. The influence of alternative factors was tested on the population level by regression of reaction norm midpoints on annual estimates of condition, temperature and competitive biomass. Although effects of temperature and competitive biomass were significant, the variation in the midpoints was best explained by the decreasing time trend. Therefore, the results provide strong evidence for a fisheries-induced evolutionary change in the onset of sexual maturity.
Increased larval viability with increased spawner age (i.e., maternal effects) have been observed in Atlantic cod (Gadus morhua) and Pacific rockfish (Sebastes spp.) stocks. Analytical results from a ...Beverton–Holt recruitment model indicate density-independent maternal effects affected the relative stock productivity and fishing rate reference points. We simulated populations based on Pacific cod (Gadus macrocephalus) and Pacific ocean perch (Sebastes alutus) to explore how estimates of reference points F
msy
and F
crash
are affected by maternal effects and potential interactions with life-history pattern, recruitment autocorrelation, and exploitation rate. Estimates of F
msy
and F
crash
were made from populations with maternal effects using either total larvae (proportional to eggs) or viable larvae (incorporating the maternal effect). Maternal effects have the largest impact upon estimated population productivity at high fishing rates. Estimates of F
msy
and F
crash
for cod were also affected by autocorrelated recruitment variability because of their reduced longevity compared with Pacific ocean perch. These results suggest the importance of evaluating the influence of maternal effects on estimated stock productivity on a case-by-case basis, particularly for depleted stocks composed of relatively young spawners.
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