Ecosystem-Based Fishery Management

Many of the worlds fish populationsare overexploited, and the ecosystemsthat sustain them are degraded (1). Unintended consequences of fishing, includinghabitat destruction, incidental mortalityof nontarget species, evolutionary shiftsin population demographics, and changes inthe function and structure of ecosystems, arebeing increasingly recognized. Fisheries management to date has oftenbeen ineffective; it focuses on maximizingthe catch of a single target species and oftenignores habitat, predators, and prey ofthe target species and other ecosystemcomponents and interactions. The indirectsocial and economic costs of the focus onsingle species can be substantial. For example, over 90% of the annual mortality ofwhite marlin, a species petitioned for listingunder the U. S. Endangered SpeciesAct, occurs through incidental catch inswordfish and tuna longline fisheries. Thisthreatens a recreational fishing industryworth up to U. S. 2 billion annually (2). To address the critical need for a moreeffective and holistic management approach, a variety of advisory panels (39) have recommended ecosystem considerationsbe considered broadly and consistentlyin managing fisheries. Ecosystem-basedfishery management (EBFM) is a new directionfor fishery management, essentiallyreversing the order of management prioritiesto start with the ecosystem ratherthan the target species. The overall objective of EBFM is tosustain healthy marine ecosystems and thefisheries they support. In particular, EBFMshould (i) avoid degradation of ecosystems, as measured by indicators of environmentalquality and system status; (ii) minimize the risk of irreversible change tonatural assemblages of species and ecosystemprocesses; (iii) obtain and maintainlong-term socioeconomic benefits withoutcompromising the ecosystem; and (iv) generateknowledge of ecosystem processessufficient to understand the likely consequencesof human actions. Where knowledgeis insufficient, robust and precautionaryfishery management measures that favorthe ecosystem should be adopted. We need to derive and develop communityand system-level standards, referencepoints, and control rules analogous to singlespeciesdecision criteria (1012). We maywant to ensure that total biomass removed byall fisheries in an ecosystem does not exceeda total amount of system productivity, afteraccounting for the requirements of otherecosystem components (e. g. , nontargetspecies, protected species, habitat considerations, and various trophic interactions). Maintaining system characteristics withincertain bounds may protect ecosystem resilienceand avoid irreversible changes. EBFM must delineate all marine habitatsutilized by humans in the context ofvulnerability to fishing-induced and otherhuman impacts, identify the potential irreversibilityof those impacts, and elucidatehabitats critical to species for vital populationprocesses. Protecting essential habitatfor fish and other important ecosystemcomponents from destructive fishing practicesincreases fish diversity and abundance (13, 14). Thus, ocean zoning, inwhich type and level of allowable humanactivity are specified spatially and temporally, will be a critical element of EBFM. The impacts of fisheries on endangeredand protected species, including ecologicalprocesses that are essential for their recovery, should be managed through an EBFMapproach. Single-species management hasbeen successful at reducing incidentalcatch of protected species in some cases (e. g. , with turtle excluder devices intrawls), but EBFM would also manage indirecteffects (e. g. , protecting forage fishnear sea lion rookeries). Another goal of EBFM is to reduce excessivelevels of bycatch (i. e. , killing ofnontarget species or undersized individualsof the target species), because juvenile lifestages and unmarketable species often playimportant roles in the ecosystem (15, 16). Globally, discards in commercial fisherieshave been estimated at 27. 0 million metrictons, accounting for about one-fourth ofthe worlds marine fish catch (17). Bycatchproblems can be ameliorated throughocean zoning that would prohibit use ofnonselective or destructive gear in criticalareas, as well as through the development and deployment of more selective and less damaging fishing technologies.