Marine Policy 64 (2016) 46-54 Contents lists available at ScienceDirect
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Marine Policy 64 (2016) 46–54 
Contents lists available at ScienceDirect 
Marine Policy journal homepage: www.elsevier.com/locate/marpol Fishing selectivity as an instrument to reach management objectives in an ecosystem approach to fisheries 
Laurence Fauconnet n, Marie-Joëlle Rochet Institution: Ifremer, Unité Écologie et Modèles pour l'Halieutique, Rue de l'Ile d'Yeu, B.P. 21105, 44311 Nantes CEDEX 03, France a r t i c l e i n f o Article history:
Keywords: Catch-related processes Catch utilisation Exploitation pattern Gear technology Integrated scales Management tools a b s t r a c t With the development of the ecosystem approach to fisheries, improving fishing selectivity has in-creasingly been put forward as an objective for management. The aim of this paper is to clarify the limits of fishing selectivity and its use in fisheries management. Fishing selectivity would be better appre-hended if restricted to the catching process only, not to the utilisation that is made of the catch once onboard, which falls under catch utilisation. Confusion would be further limited if fishing selectivity is restricted to the fishing operation scale, while exploitation pattern, i.e. the distribution of fishing mortality at the population or community level, applies to larger scales. Fishing selectively is minimizing bycatch – catching primarily the fishing trip targets. Since the ecological consequences of maximising the target catch relative to bycatch remain unknown at integrated scales, fishing selectivity cannot be used as an objective in itself. However, its small scale, high manageability and good understanding make it a con-venient instrument to reach management objectives at large scales. Selectivity can serve to manage what is extracted from the ecosystem and thus what can be used, and/or to manage what is left in the eco-system and how fishing impacts it. Different factors affect fishing selectivity, catch utilisation and ex-ploitation patterns, some of them are manageable and thus can be used to move towards these objec-tives. Management tools are diverse, but need to be integrated to meet large-scale objectives. The complexity of dealing with large scales incurs a need to develop the available knowledge on exploitation patterns and catch utilisation to be able to adequately manage and monitor progress toward selectivity-related objectives. & 2015 Elsevier Ltd. All rights reserved. 1. Introduction When fishers set out on a trip, they have specific targets in mind – the catch they intend to bring back. But when the gear is hauled there can be less, or more, or something else than the anticipated catch. Bycatch is the part of the catch that was unin-tended, which can then be retained and landed, or returned to the sea; discards are the returned part. Fishing selectively is mini-mising bycatch and discards – catching primarily the trip targets. Improving the selectivity of fishing has been increasingly put forward as an objective of fisheries management, to address the unintended effects of fishing on non-target species, minimise waste, and improve the efficiency of fishing activities [16,22,46,68]. The concern regarding the bycatch of rare and/or vulnerable species appeared on the public agenda as a result of a few highly publicised cases, such as dolphins caught in tuna purse-seine fisheries in the 1960s, and sea turtles in shrimp trawl 
E-mail address: laurence.fauconnet@gmail.com (L. Fauconnet). fisheries [30]. The concern regarding discards of more common species, either commercial or non-commercial, and the sub-sequent waste, arose soon after [55]. However, recent debates have raised the point that ecosystem impacts are more than just the sum of impacts on ecosystem components – and that an uneven distribution of fishing pressure across ecosystem components might have broad scale unintended impacts as well [23].
http://dx.doi.org/10.1016/j.marpol.2015.11.004 0308-597X/& 2015 Elsevier Ltd. All rights reserved.
conservation, etc. This emphasises an important aspect to be considered: the objectives aimed at by fishing activities. Those objectives are likely to differ from different stakeholders' per-spectives. To limit confusion, [43] distinguished different types of selectivity according to the population from which fish were se-lected from, highlighting the importance of the considered scale and perspective. This paper proposes that the term fishing selectivity is most appropriate to the description of the catching process of fishing gear. As such, it should be restricted to the fishing operation scale. The concept of exploitation pattern describes the distribution of fishing mortality over the length or age composition of a popula-tion [35]. It is relevant for scales beyond the fishing operation. The concept of exploitation pattern can be extended to all community components. This enlarged concept would be referred to as com-munity exploitation pattern. The concept of catch utilisation is fur-ther defined to include the fate of the catch once onboard, whe-ther it is kept and used, or discarded. Those three concepts de-scribe catch-related processes under different perspectives or scales. Fishing selectivity, as it determines what is caught, is cen-tral to both catch utilisation and exploitation pattern, what makes it a convenient instrument to act upon them. Fishing selectivity cannot be set as an objective in itself, but can be used to reach management objectives at large scales. As fishing selectivity, catch utilisation and exploitation pattern are closely linked, and even intermingled, the paper starts with definitions. The management objectives related to these processes relevant in an ecosystem approach to fisheries are then discussed. As a help for manage-ment to meet selectivity-related objectives, the factors affecting each process are then listed, emphasising those which can be managed. The knowledge available to manage and monitor pro-gress toward these objectives is finally contrasted across the three concepts. 2. Definitions. A matter of scale and perspective Fishing selectivity, catch utilisation and exploitation pattern operate at different scales (Table 1) and in different dimensions of the socio-ecosystem, but they are closely related. Even if somehow artificial, splitting these highly entangled processes into three discrete concepts is a necessary construct for understanding and management purposes. 2.1. Fishing selectivity restricted to the operational scale Fishing selectivity is the probability of catch resulting from the extraction of some individuals in the environment during the fishing operation. All fishing gears are somehow selective and catch individuals in species, length or age composition that differ from their actual composition in the environment [67]. Fishing selectivity is a measure of the gear selection process [67]. As such, it applies at the fishing operation scale (Table 1). Two components of fishing selectivity should be distinguished. Available selectivity quantifies the catching process of the individuals that were Table 1
present in the path or the surroundings of the gear, but possibly avoided it (Fig. 1; [43]). The individuals that were not able to avoid the gear, came in contact with it where a second selection oc-curred. Contact selectivity quantifies the catch of those individuals that came in contact with the gear [43]. Population selectivity had also been defined to quantify the catch of individuals from the whole population [43,56]. It implies to integrate all catch processes across the different gears occuring in a given fishing ground. The use of the term selectivity for such large scales considerations and integrated processes might lead to confusion and disagreement [23]. The use of another term appears relevant to better distinguish the scales and processes involved. Exploitation pattern as defined below is suggested. 2.2. Exploitation pattern is the cumulative result of gear selectivities at large scales Exploitation pattern describes the distribution of fishing mor-tality across components of a population [35]. Exploitation pattern is the cumulative result of the fishing selectivity of all gears de-ployed at the population scale – generally, a large spatio-temporal scale, even if it can greatly vary from a small coastal population to a wide ocean pelagic population (Table 1). It takes account of how the different gear selectivities concur to determine which in-dividuals are removed from the population, by further considering the availability of individuals to the different gears ([56]; Fig. 1). By integrating fishing selectivity across all gears (or fisheries) that catch the population, the focus shifts from the catch to the po-pulation production and dynamics [56]. The population perspec-tive raises questions related to yields and sustainability, thereby also enlarging the time scale considered. When scaling up to the community level, the community exploitation pattern combines population exploitation patterns of all species in a given area (Fig. 1). The change of organisation level entails a change of scale, towards longer time scales relevant to interspecific processes. Because the different populations which make up the community are likely to occupy different geographical ranges, at the commu-nity level the boundaries of the spatial area are somewhat arbi-trary and need to be decided upon. 2.3. Catch utilisation refers to the fate of the catch once onboard Catch utilisation is the result of the sorting process, i.e. the decision of which parts of the catch are retained and thus landed, and which ones are discarded (Fig. 1). Unlike exploitation pattern, catch utilisation does not directly include fishing selectivity, but depends on it. The more selective the fishing operation, the more the catch should be usable – a catch made up of the target only could be fully utilised. As a result, catch utilisation is often per-ceived as a measure of fishing selectivity: high discard rates in-dicate poor selectivity. However, retention does not depend just on the catch, it is constrained by what can be kept onboard or not. Part of the bycatch, e.g. of high-value species, might be landed even if they were not initially targeted. It is even likely that some bycatch is expected by fishers in order to diversify their landings for markets. Conversely, part of the target catch is sometimes discarded, e.g. individuals that do not meet legal requirements such as minimum landing sizes, or legal-sized individuals that are discarded because they are damaged, or to save quota for larger individuals of higher value, a practice known as high-grading. The decisions made by the fishers while sorting take account of the whole trip, including achieved and expected catch, and the op-portunities and constraints imposed by regulations and markets on a daily, seasonal, and annual basis [17]. Therefore, catch utili-sation involves spatial and temporal scales larger than the fishing operation (Table 1).
…
Fig. 1. Schematic view of available and contact fishing selectivities, population and community exploitation patterns and catch utilisation. The population exploitation pattern is only highlighted for population 1 (shaded area).
Fishing gears have been continuously adapted and modified to improve fishing selectivity. Today, gears that avoid the catch of undesirable species and sizes, i.e. display negative selectivity, while maximising the catch of commercial-sized individuals of the target species, i.e. with positive selectivity, are wanted. Technology and markets have been the main incentives to decide which components of the marine communities should be targeted [30]. Targets were not decided based on ecological considerations, but they do affect the ecosystem. Fishing intention has a strong in-fluence on catch profiles [42], but the large-scale impacts of the combined catch profiles resulting from fishers targeting, i.e. se-lectivity, remain unknown. Thus, for scale reasons, maximising the catch of targeted individuals, i.e. fishing more selectively, appears not relevant as a management objective. At large scales, ex-ploitation pattern and catch utilisation are more appropriate to define objectives. 3.1. Conserving population/community structure and function Increased fishing selectivity can, for example, be implemented to reduce the catch of sea turtles in a fishery that overlaps with a population that is at risk of extirpation. In this example, the ob-jective is to conserve this turtle population. Given the turtle ecology (wide distribution, long lifespan, etc.), it is a large-spatial scale and long-temporal scale objective. For doing so, fishing se-lectivity is adjusted to avoid catching turtles during fishing op-erations, which are fine-spatial and short-temporal scales, because given the turtle life history and the population status, even a single catch could be detrimental to the whole population. If the popu-lation was not at risk of extirpation, the catch of a turtle during a fishing operation, i.e. low selectivity, would not be detrimental in itself. For more abundant and productive species, how to use fishing selectivity to conserve population is more complex. Historically, fisheries management focused on stocks of targeted species. To maintain the abundance and sustainability of a stock, fishing a narrow exploitation pattern at the population scale by avoiding juveniles and/or spawners has long been promoted [2]. However, there are concerns that this could result in fishing-induced evo-lution such as earlier ages at maturity, faster growth rates [12,39], or lower resilience to perturbations [47].
3.2. Making the “best” use of the catch Once the catch is onboard, one might aim at limiting the waste and using it all, or the most part of it, irrespective of the initial expectations. Fishers, consumers, conservationists and the general public may have different expectations from the catch. Fishers
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