Integrated environmental assessment of fisheries management: Swedish Nephrops trawl fisheries evaluated using a life cycle approach
Highlights
► Management of Nephrops trawling in Sweden was evaluated with a Life Cycle approach. ► Environmental impacts and resource use were quantified per kilogram of landing. ► Fish stocks are protected by increased fuel consumption and seafloor disturbance. ► Broader management evaluations facilitate overall sustainable resource use.
Introduction
Managing fisheries is complex. Measures are often determined based on uncertain data, in a limited time, and with a range of different motives – economic, social, and biological – predominantly lacking the integrated perspective [1]. Several of current fishing regimes have been found to have severe negative impacts, not only on targeted species, but also on whole marine ecosystems, and are accordingly being questioned [2], [3].
Discussions of sustainable fisheries management have focused mainly on stock recovery and sustainable exploitation rates [4], whereas possible consequences of measures taken to improve or sustain stock status, such as increased energy consumption or seafloor disturbance, are seldom integrated in the same management context. This may result in incoherent management decisions, which in turn lead to overcapacity and fuel subsidies. Besides improving fisheries economics [5], there is a cumulative need to mitigate the net effects of a range of anthropogenic stressors on the marine environment [6].
The need for an overall evaluation of the impacts of management measures can be seen in recent developments such as increasing consumer awareness and the ongoing reform of the EU Common Fisheries Policy [7], [8]. Broader approaches, such as strategic environmental assessments (SEA), are asked for to pre-evaluate expected impacts of proposed fisheries management measures in the EU [9]. As a complement, there is a need for the post-evaluation of broader environmental impacts of measures taken, in order to increase the transparency of the seafood sector.
Life cycle assessment (LCA) is an ISO standardized methodology that relates resource use and environmental impacts to a product from a cradle-to-grave perspective [10]. In seafood production, early LCAs generally concluded that, of traditional impact categories, such as greenhouse gas (GHG) emissions, the fishing phase dominated the life cycle due to the fuel intensity [11], [12]. Fisheries management, by influencing, for example, the type of gear used, may have implications for the resource use of fisheries. Overcapacity and decreasing fish stocks are expected to lead to excess effort, which could in turn influence fuel consumption [11], [13], [14], [15]. By shifting from a product to a management perspective, LCA could provide a comprehensive and transparent evaluation of the overall environmental implications of fisheries management measures by comparing the environmental impacts per seafood product, revealing the magnitudes of impacts and the potential tradeoffs between them. So far, the only study using LCA to evaluate various fisheries management scenarios identified a range of 17–116 l of diesel per ton of landed herring [16]. However, biological impacts were not to a great extent taken into consideration in LCA's as is attempted here.
If one considers biodiversity loss [17], fish stock depletion [7], trophic interactions [18], size alteration [19], and seafloor disturbance [20], which are not usually considered at present [21], the impacts of fishing become even more serious. The problem has been lack of methodology. One study that tried to gage discards and seafloor area disturbed per kg of landed Norway lobster (Nephrops norvegicus) indicated vastly different biological impacts for different fishing practices: 15,000 m2 of seafloor was found to be affected by trawling while creeling affected only 1.8 m2 of seafloor, with total discards of 4.5 kg versus 0.36 kg [22].
The present study considers differences in appropriation of primary production from discards as a differentiated discard impact for an LCA framework. Primary production requirements (PPR) are considered, because primary production limits global fisheries yield [23] and gives a rough proxy for trophic interactions such as depletion of top predators, an established fisheries impact [17], [18].
A new LCA category included is the potential discard impacts on vulnerable, endangered, and critically endangered (VEC) fish species [24]. Fisheries are often the reason why fish are under threat, so it is important that this impact should inform practice. The International Union for Conservation of Nature (IUCN) Red List is intended to protect species not specifically covered by a management framework, as is often the case with discarded species, and has been shown to be adequately correlated with the results from stock assessments [25], [26]. Landed fish species are not included, but are considered as a managed, hence controlled, impact.
Nephrops is one of the most valuable species in Swedish fisheries. The fishery is located in the western coastal waters, the Skagerrak and Kattegat (ICES area IIIa SD 20 and 21, Fig. 1) and is conducted using demersal trawls and creels. The recommended and agreed-on total allowable catch (TAC) for the area was 5170 t in 2010, of which the Swedish portion was 1359 t [27].
The Nephrops trawl fishery in the North-east Atlantic is known to have one of the highest discard ratios in the world [28]. Discard is the portion of the catch that is thrown back to sea, in amounts that vary strongly with, for example, area fished, season, management policies, economic incentives, and fisherman behavior. In Nephrops trawl fisheries, by-catch consists to a great extent of fish species many of which are restricted with quota. To decouple Nephrops catches from quota-filled fish species and keep the fishery open when quotas on other species are closed, in 2004, the Swedish Board of Fisheries developed and implemented a species-selective grid of Nordmøre type (Fig. 2) which releases fish through an escape window [29].
Fishing days permitted with conventional trawls have gradually been reduced since 2004 in accordance with long-term management for cod recovery by reducing fishing mortality of cod [30], [31]. Vessels trawling without sorting grids are restricted by both TAC and effort measures in line with the updated Cod Recovery Plan. Grid trawling is excluded from effort regulation due to low by-catches of cod, only being subject to a national level effort limitation [32]. Furthermore, vessels with sorting grids are allowed access to some areas closed to conventional trawling, such as a no-trawl coastal zone and parts of a marine protected area in the Kattegat (Fig. 1). From having been mainly a mixed fishery, catching Nephrops and fish, grid introduction has led to the development of a separate single-species fishery for Nephrops [33]. In 2009, grid trawling accounted for 50% of total Swedish Nephrops landings; conventional trawling landed 30%, while creeling landed the remaining part (Fig. 3).
Selective fishing practices, however, may not reduce overall pressure on the marine environment, as landings per effort are lowered for gear that in this case are already characterized by high fuel consumption [11], [14], [22] and seafloor disturbance [20]. Species-selective fishing is more vulnerable when catches of Nephrops are low, and could accordingly increase resource wastage. At the same time, use of sorting grids could represent an improvement, as sorting time decreases, contributing to higher quality and mitigating overcapacity. Expert opinions on marine ecosystem stressors urge immediate action to reduce GHG emissions and restore the structure and function of marine ecosystems [34]. It is therefore important that broader evaluations establish a proper framework for determining whether cutting the fleet or making it less effective would contribute most to reaching management goals.
The present study aims to evaluate the broad environmental implications of having the Nephrops trawl fishery in Sweden structured into two separate fisheries in response to EU regulations to protect cod. This will be done using LCA expanded with potential biological impacts. More specifically, potential tradeoffs between the environmental impacts of introducing the species-selective grid, such as increased seafloor area swept or fuel consumption, are quantified in relation to possible biological implications, such as discard impact on threatened species (VEC) and trophic interactions (PPR).
An additional aim is to advance the development of LCA methodology with regard to the inclusion of indicators of differentiated discard impact (VEC and PPR) in the framework.
Section snippets
General life cycle assessment (LCA) methodology
LCA consists of four phases: goal and scope, inventory, impact assessment, and interpretation of results. During the goal and scope phase, system boundaries for the study are defined and the product of focus, i.e., the functional unit (FU), is specified. In the next step, inventory, all resource use and emissions of interest according to the goal and scope are quantified in relation to the functional unit. In the impact assessment, collected data are grouped in categories of potential
Results
Some of the inventory data are only presented as inventory results, while others are characterized.
Discussion
Grid trawling complies well with management objectives, which are to reduce fishing mortality of cod. However, from a broader perspective, grid trawling has some tradeoffs and there are regional differences for the practice. Resource use in terms of fuel use per total landings is higher using grid trawls, approximately 1 l extra per kilogram landed, but this inefficiency is less important than the superior protection of threatened species contributed by grid practice. In addition, this study
Conclusions and future recommendations
Species-selective trawling for Nephrops fulfils the objectives for fish by-catch management in the area; however, from a broader perspective, it is more resource intensive than conventional trawling in terms of fuel use and seafloor disturbance per landed kilo. Still, per kg of Nephrops (after economic allocation), grid trawling is superior in terms of threatened species affected while being equal in fuel use. Using LCA, the seafood industry can be made more transparent and potential tradeoffs
Acknowledgments
We wish to thank Katja Ringdahl, Johan Lövgren, Patrik Jonsson, and Rickard Bengtsberg for contributing data. Leif Pihl, Mattias Sköld, and Andreas Emanuelsson made valuable comments on the manuscript. Funding is acknowledged from Swedish Research Council Formas and the European Commission (LC-IMPACT FP7 Grant Agreement 243827).
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