Abstract: Fisheries managers in the United States are required to identify and mitigate the adverse impacts of fishing activity on essential fish habitat (EFH). There are additional concerns that the viability of sessile noncommercial species, animals that are habitat dependent and (or) are themselves constituents of fishery habitat, may be threatened by fishing activities. We propose a system of individual habitat quotas (IHQ) to achieve habitat conservation and species protection cost effectively. Individual quotas of habitat impact units would be distributed to fishers with an aggregate quota set to maintain a target habitat "stock". Using a dynamic, spatially explicit fishery simulation model, we explore the efficiency and effectiveness of an IHQ policy versus marine protected areas (MPAs) for conserving habitat-dependent, sessile species of unknown spatial distributions. Our findings indicate that an IHQ policy with a conservatively established habitat target is better suited to the protection of sessile nontarget species than a rotating or fixed MPA policy.
Resume : Les gestionnaires de la peche aux Etats-Unis doivent identifier et mitiger les impacts negatifs des activites de peche sur l'habitat essentiel des poissons (<< EFH >>). On se preoccupe aussi de savoir si la viabilite des especes sessiles non commerciales, qui sont des animaux lies a l'habitat et (ou) eux-memes des elements constitutifs de l'habitat de peche, puisse etre menacee par les activites de peche. Nous proposons l'etablissement d'un systeme de quotas individuels d'habitats (<< IHQ >>) afin de reussir a conserver les habitats et a proteger les especes de facon efficace a un meilleur cout. Des unites de quotas individuels d'impacts sur l'habitat seraient distribuees aux pecheurs et un quota global fixe de facon a maintenir un << stock >> predetermine d'habitats. Nous explorons, a l'aide d'un modele de simulation de la peche qui est dynamique et explicite en fonction de l'espace, l'efficacite d'une politique d'IHQ par comparaison a l'etablissement de reserves marines (<< MPA >>) pour la conservation des especes sessiles dependantes de l'habitat, mais a repartition spatiale inconnue. Nos resultats indiquent qu'une politique d'IHQ avec un objectif conservateur de maintien des habitats est mieux adaptee a la protection des especes sessiles non ciblees par la peche qu'une politique de MPA fixe ou en rotation.
[Traduit par la Redaction]
Introduction
The provisions added to the Magnuson-Stevens Fisheries Conservation and Management Act (MSFCMA) in 1996 require the eight regional fishery management councils to identify and describe essential fish habitat (EFH) in each fishery management plan (FMP), minimize to the extent practical the adverse effects of fishing on EFH, and identify actions to encourage the conservation and enhancement of EFH. In offshore areas, a primary source of habitat damage is commercial fishing, which can reduce the complexity of the benthic structure (Kaiser and de Groot 2000; McConnaughey et al. 2000), increase the resuspension of benthic sediments (Pilskaln et al. 1998), and alter the community and trophic structure within an ecosystem (e.g., Greenstreet et al. 1999; Rice 2000; Schratzberger et al. 2002). These impacts may vary with the type of gear utilized, as well as with the benthic structure (Collie et al. 2000; Johnson 2002; Kaiser et al. 2002).
Although EFH may be characterized in general terms by the type of substrate or depth, in many cases the utility of these habitats for supporting fish populations, and hence the motivation for habitat protection, relates to the presence of various sessile organisms such as corals, sponges, kelp, rockweed, mussels, marine worms, etc. These organisms may have low rates of reproduction and be highly susceptible to habitat damage (North Pacific Fisheries Management Council 2004). In addition, these species may be important to the overall integrity of the ecosystem and may have unknown future economic value. Exploring methods of protecting these species is the primary focus of this paper.
Proposed actions to mitigate the impacts of commercial fishing consist mainly of gear restrictions and temporary or permanent area closures (i.e., marine reserves and marine protected areas, MPAs) (Gell and Roberts 2003; Kaiser 2005; Sale et al. 2005). However, there are concerns that EFH protection based on area closures could shift and intensify efforts in other areas threatening species that exist primarily, or solely, in those regions (Kaiser 2005). This may have an adverse impact on nontarget species that are part of or dependent on habitat and on general marine biodiversity in benthic habitats (Pope et al. 2000; Powles et al. 2000; Thrush et al. 2001). In addition, a general lack of knowledge regarding the range of marine species in existence and their distributions makes it difficult to provide adequate protection (Kenchington 2003).
As an alternative approach, we propose an individual habitat quota (IHQ) system to provide habitat protection and to protect sessile nontarget species that are habitat dependent. Whereas individual transferable quotas (ITQs) provide a property right for the stock of a harvestable resource, an IHQ program would be based on the degree of habitat impacts, denoted habitat impact units (HIUs), allowed in a given fishery. Individual quotas of HIUs, based on a proxy for marginal habitat damage resulting from a given fishing activity, would be distributed to fishers with an aggregate quota set to maintain a target habitat "stock" within the fishery. The system is designed to achieve a given average level of habitat quality without dictating the spatial distribution of fishing effort or habitat quality.
To investigate how the IHQ system might perform, we develop a dynamic spatially explicit fishery and habitat simulation model consisting of three primary components: a target species, a habitat stock, and a number of habitat-dependent, sessile, nontarget species. The survival rate of the habitat-dependent species is assumed to depend on whether the habitat quality where they are located is maintained above a specified minimum habitat-quality threshold. Acknowledging the general lack of accurate information regarding the biological characteristics and distributions of sessile organisms in most marine environments, we model a number of stylized sessile organisms with random spatial distributions and varying degrees of global versus local recruitment.
The performance of the IHQ system with different average habitat targets (30% and 50%) is compared with two alternative management regimes, fixed and rotating MPA policies. This extends analysis by Holland and Schnier (2006), which focused simply on the cost effectiveness of achieving a given average level of habitat quality but did not consider the impacts on habitat-dependent species. Our inclusion of habitat-dependent species allows us to explore the relative effectiveness of IHQ and MPAs at conserving a diverse community of habitat-dependent species of unknown spatial distribution.
Materials and methods
An IHQ management system requires the definition and monitoring of habitat impacts that will be allocated and traded. Because it is unlikely to be feasible or cost effective to directly monitor habitat impacts, we propose that a proxy for habitat impacts, denominated in habitat impact units (HIU), be utilized. HIU would represent the marginal damage that the habitat incurs from a single fishing event and would vary depending on the ecological characteristics of the region fished, as well as the amount of fishing that has recently occurred within the region. The habitat impact units used by a vessel might differ with the type of gear utilized and would be based on empirical studies of the marginal physical damage associated with fishing particular gears in particular types of habitat. Suppose, for example, that empirical research showed that a heavily fished area takes 10 years to regenerate to a "pristine" state and that each pass of a bottom trawl over an area removes 80% of the remaining habitat structure. If HIU are denominated in square metres of bottom contacted, a vessel towing a bottom trawl over 10 000 [m.sup.2] of "pristine" habitat would use 8000 HIU leaving the proxy for the habitat "stock" in that area at 2000 HIU. If the vessel made a second pass over the same area they would use only 1600 units leaving a stock of 400 HIU. After 1 year, if left unfished, the habitat stock in the 10 000 [m.sup.2] area would have increased by 10% of the pristine level of habitat (1000 HIU) leaving a habitat stock of 1400 HIU.
The rate of habitat recovery and damage resulting from fishing activity will invariably be linked to the type of benthic habitat present and the gear utilized (Collie et al. 2000; Hiddink et al. 2006; Kaiser et al. 2006). The use of an 80% habitat reduction, although not identical to recent empirical research, is consistent with recent findings in the literature (Collie et al. 2000; Hiddink et al. 2006). In addition, the 10% recovery rate is similar to the recovery rates of slowgrowing biota; however, sandy sediments do recovery much faster (Collie et al. 2000; Kaiser et al. 2006). Given these habitat dynamics and the habitat quota system, it is evident that it is economically cost effective to continually fish in a location previously fished by others because the HIU costs incurred will be lower. In addition, this behavior will generate proportionally less damage then the previous fishing event, which is consistent with the general findings in the literature (Kaiser 2005). However, this will only be rationale provided that the marginal gains from fishing in a region with higher habitat levels are lower than in previously fished locations.
Each year a total quota of habitat units would be set and distributed. Individuals might have an ongoing right to a proportional share of that total quantity or might purchase or be allocated shares of the total quota annually to complement their fishing rights. The total quantity of HIU distributed each year would be set to maintain a given level of habitat protection as measured by the total remaining "stock" of HIU. The total stock of HIU would be made up of a combination of totally and partially regenerated areas. The quantity of HIU allocated each year would depend on the regeneration rate of habitat, the standing stock of habitat, and the target level of the habitat stock. However, the definition of HIU, setting the target stock, and determining the total HIU quota would not require regulators to determine either the total or the marginal value of habitat protection.
HIU use could be monitored remotely using a vessel monitoring system (VMS). For example, trawlers might be charged HIU any time they are in fishable areas moving within a range of speeds feasible for fishing. More sophisticated systems could be developed using sensors on gear. To be effectively used by fishers, this system would require real-time updating of the state of the habitat. This would not be the true …
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