Trait groups as management entities in a complex, multispecies reef fishery.

Localized stressors compound the ongoing climate-driven decline of coral reefs, requiring natural resource managers to work with rapidly shifting paradigms. Trait-based adaptive management (TBAM) is a new framework to help address changing conditions by choosing and implementing management actions specific to species groups that share key traits, vulnerabilities, and management responses. In TBAM maintenance of functioning ecosystems is balanced with provisioning for human subsistence and livelihoods. We first identified trait-based groups of food fish in a Pacific coral reef with hierarchical clustering. Positing that trait-based groups performing comparable functions respond similarly to both stressors and management actions, we ascertained biophysical and socioeconomic drivers of trait-group biomass and evaluated their vulnerabilities with generalized additive models. Clustering identified 7 trait groups from 131 species. Groups responded to different drivers and displayed divergent vulnerabilities; human activities emerged as important predictors of community structuring. Biomass of small, solitary reef-associated species increased with distance from key fishing ports, and large, solitary piscivores exhibited a decline in biomass with distance from a port. Group biomass also varied in response to different habitat types, the presence or absence of reported dynamite fishing activity, and exposure to wave energy. The differential vulnerabilities of trait groups revealed how the community structure of food fishes is driven by different aspects of resource use and habitat. This inherent variability in the responses of trait-based groups presents opportunities to apply selective TBAM strategies for complex, multispecies fisheries. This approach can be widely adjusted to suit local contexts and priorities.

Grupos de Atributos como Entidades de Manejo en una Pesquería de Arrecife Compleja y Multiespecie Resumen Los estresantes localizados agravan la continua declinación de los arrecifes de coral causada por el clima, lo que requiere que los administradores de recursos naturales trabajen con paradigmas en constante cambio. El manejo adaptativo basado en caracteres (TBAM, en inglés) es un marco de trabajo nuevo que ayuda a enfrentar las condiciones cambiantes mediante la selección e implementación de acciones de manejo específicas para grupos de especies que comparten atributos, vulnerabilidades y respuestas al manejo esenciales. En el TBAM, el mantenimiento de los ecosistemas funcionales está balanceado con el suministro para la subsistencia humana. Identificamos mediante un agrupamiento jerárquico los grupos basados en atributos de peces para la alimentación en un arrecife de coral del Pacífico. Al plantear que los grupos basados en atributos que desempeñan funciones comparables responden similarmente a los estresantes y las acciones de manejo, determinamos los impulsores biofísicos y socioeconómicos de la biomasa de un grupo de atributos y evaluamos sus vulnerabilidades mediante modelos aditivos generalizados. Identificamos siete grupos de atributos a partir de 131 especies. Los grupos respondieron a diferentes impulsores y desplegaron vulnerabilidades divergentes; las actividades humanas aparecieron como predictores importantes de la estructuración de la comunidad. La biomasa de las especies solitarias asociadas al arrecife incrementó con la distancia desde puertos importantes de pesca y los piscívoros solitarios de gran tamaño exhibieron una declinación en la biomasa junto con la distancia desde un puerto. La biomasa de los grupos también varió en respuesta a los diferentes tipos de hábitat, la presencia o ausencia reportada de actividad pesquera con dinamita y la exposición a la energía del oleaje. Las vulnerabilidades diferenciales de los grupos de atributos revelaron cómo la estructura de la comunidad de peces para la alimentación está impulsada por aspectos diferentes del uso de recursos y del hábitat. Esta variabilidad inherente en las respuestas de los grupos basados en atributos presenta la oportunidad de aplicar estrategias selectivas de manejo basado en atributos en las pesquerías complejas y multiespecie. Este enfoque puede ajustarse abiertamente para adaptarse a los contextos y las prioridades locales.

Human and environmental gradients predict catch, effort, and species composition in a large Micronesian coral-reef fishery.

The consistent supply of fresh fish to commercial markets may mask growing fishing footprints and localized depletions, as fishing expands to deeper/further reefs, smaller fish, and more resilient species. To test this hypothesis, species-based records and fisher interviews were gathered over one year within a large, demand-driven coral-reef fishery in Chuuk, Micronesia. We first assessed catch statistics with respect to high windspeeds and moon phases that are known to constrain both catch and effort. While lower daily catch success was predicted by higher windspeeds and greater lunar illumination, total daily landings fluctuated less than fishing success across environmental gradients. Instead, daily landings were mainly driven by the number of flights from Chuuk to Guam (i.e., international demand). Given that demand masked local drivers of overall catch volume, we further evaluated species-based indicators of fisheries exploitation. Most target species (75%) had either a positively skewed size distribution or proportional contributions that were dependent upon favorable conditions (i.e. season and moon phases). Skewed size distributions indicated truncated growth associated with fishing mortality, and in turn, suggested that size-based management policies may be most effective for these species. In contrast, environmentally-constrained catch success indicated species that may be more susceptible to growing fishing footprints and may respond better to gear/quota/area policies compared to size policies. Species-based responses offered a simplified means to combine species into fisheries management units. Finally, a comparison of commercial and subsistence landings showed higher vulnerability to fishing among species preferentially targeted by commercial fisheries, offering new insights into how commercial harvesting can disproportionately impact resources, despite having lower annual catch volumes.

The Micronesia Challenge: Assessing the Relative Contribution of Stressors on Coral Reefs to Facilitate Science-to-Management Feedback.

Fishing and pollution are chronic stressors that can prolong recovery of coral reefs and contribute to ecosystem decline. While this premise is generally accepted, management interventions are complicated because the contributions from individual stressors are difficult to distinguish. The present study examined the extent to which fishing pressure and pollution predicted progress towards the Micronesia Challenge, an international conservation strategy initiated by the political leaders of 6 nations to conserve at least 30% of marine resources by 2020. The analyses were rooted in a defined measure of coral-reef-ecosystem condition, comprised of biological metrics that described functional processes on coral reefs. We report that only 42% of the major reef habitats exceeded the ecosystem-condition threshold established by the Micronesia Challenge. Fishing pressure acting alone on outer reefs, or in combination with pollution in some lagoons, best predicted both the decline and variance in ecosystem condition. High variances among ecosystem-condition scores reflected the large gaps between the best and worst reefs, and suggested that the current scores were unlikely to remain stable through time because of low redundancy. Accounting for the presence of marine protected area (MPA) networks in statistical models did little to improve the models' predictive capabilities, suggesting limited efficacy of MPAs when grouped together across the region. Yet, localized benefits of MPAs existed and are expected to increase over time. Sensitivity analyses suggested that (i) grazing by large herbivores, (ii) high functional diversity of herbivores, and (iii) high predator biomass were most sensitive to fishing pressure, and were required for high ecosystem-condition scores. Linking comprehensive fisheries management policies with these sensitive metrics, and targeting the management of pollution, will strengthen the Micronesia Challenge and preserve ecosystem services that coral reefs provide to societies in the face of climate change.