|Document Type:||Journal Article|
|Title:||Indirect effects of conservation policies on the coupled human-natural ecosystem of the Gulf of California|
|Author:||Hem Nalini Morzaria-Luna, C. H. Ainsworth, I. C. Kaplan, P. S. Levin, E. A. Fulton|
|Keywords:||ecosystem based management,bycatch,fisheries policies,indirect effects,Vaquita,Gulf of California|
High bycatch of species of non-target species and species of conservation concern often drives the implementation of fisheries policies. However, species- or fishery- specific policies (e.g., shifts in effort or target species, increased protection) may lead to indirect consequences, positive or negative, for other species or fisheries. Here we use an Atlantis ecosystem model of the Northern Gulf of California to evaluate the effects of fisheries policies directed at reducing bycatch of vaquita (Phocoena sinus), a Critically Endangered porpoise endemic to the Upper Gulf of California. Vaquita have declined severely because they are frequently entangled by finfish gillnets and shrimp driftnets. We tested five fishery management scenarios, projected over 30 years, that are directed at vaquita conservation and that consider progressively larger spatial restrictions for finfish gillnets and shrimp driftnets. We evaluated the effect of these scenarios on species of conservation concern, priority target species and metrics of ecosystem function. For species of conservation concern, the most restrictive spatial closure scenario resulted in the highest biomass; the scenario without any conservation measures in place resulted in the lowest. Vaquita experienced the largest population increase of any functional group; their biomass increased 2.7 times relative to initial (2008) levels under the most restrictive spatial closure scenario. Bycatch of all species in finfish gillnets and shrimp driftnets also decreased under spatial management. We found indirect effects on species and ecosystem function and structure in the Upper Gulf of California as a result of vaquita management actions. Biomass and catch of forage fish experienced negative effects, which could affect lower-trophic level fisheries, while other species such as skates, rays, and sharks increased in both biomass and catch. When comparing across performance metrics, we found that scenarios that increased ecosystem function and structure resulted in lower economic indicators, underscoring the need for vaquita management actions to be part of the integrated management of the Upper Gulf of California.
|Theme:||Recovery, Rebuilding and Sustainability of Marine and Anadromous Species|
Investigate ecological and socio-economic effects of alternative management strategies or governance structures.