Highly migratory species predictive spatial modeling (PRiSM): an analytical framework for assessing the performance of spatial fisheries management

Stephen J. Durkee,John K. Carlson,Daniel P. Crear,Tobey H. Curtis

doi:10.1007/s00227-021-03951-7

Abstract

Spatial management for highly migratory species (HMS) is difficult due to many species’ mobile habits and the dynamic nature of oceanic habitats. Current static spatial management areas for fisheries in the United States have been in place for extended periods of time with limited data collection inside the areas, making any analysis of their efficacy challenging. Spatial modeling approaches can be specifically designed to integrate species data from outside of closed areas to project species distributions inside and outside closed areas relative to the fishery. We developed HMS-PRedictive Spatial Modeling (PRiSM), which uses fishery-dependent observer data of species’ presence–absence, oceanographic covariates, and gear covariates in a generalized additive model (GAM) framework to produce fishery interaction spatial models. Species fishery interaction distributions were generated monthly within the domain of two HMS longline fisheries and used to produce a series of performance metrics for HMS closed areas. PRiSM was tested on bycatch species, including shortfin mako shark (Isurus oxyrinchus), billfish (Istiophoridae), and leatherback sea turtle (Dermochelys coriacea) in a pelagic longline fishery, and sandbar shark (Carcharhinus plumbeus), dusky shark (C. obscurus), and scalloped hammerhead shark (Sphyrna lewini) in a bottom longline fishery. Model validation procedures suggest PRiSM performed well for these species. The closed area performance metrics provided an objective and flexible framework to compare distributions between closed and open areas under recent environmental conditions. Fisheries managers can use the metrics generated by PRiSM to supplement other streams of information and guide spatial management decisions to support sustainable fisheries.

Highlights

Migratory species (HMS) including tunas, sharks, swordfish and billfishes are, by definition, broadly distributed and have large migratory ranges
For bottom longline (BLL) models, the deviance explained for the best models were 49, 38.3, and 47.2% for sandbar shark, dusky shark, and scalloped hammerhead, respectively (Table 2)
Marginal mean prediction plots indicate the relationship between species probability of occurrence and each covariate, while all other covariates are at their mean

Summary

Introduction

Migratory species (HMS) including tunas, sharks, swordfish and billfishes are, by definition, broadly distributed and have large migratory ranges. There are worldwide calls to expand spatial protections for such species, including marine protected areas (MPAs), shark sanctuaries, and other designations; there are a number of challenges to delineating appropriate locations and boundaries that will tangibly enhance conservation (Davidson and Dulvy 2017; Derrick et al 2020). The U.S National Marine Fisheries Service (NMFS) uses spatial management areas and/or measures (e.g., closed areas, gear-restricted areas, essential fish habitat, etc.) to achieve a variety of conservation goals for HMS (e.g., Charleston Bump Closed Area; NMFS 2019). These areas were designed to reduce bycatch of overfished stocks and/or species protected under the Endangered Species Act (ESA) or Marine Mammal Protection Act (MMPA). Some of the existing static areas along the U.S east coast that restrict HMS fishing have been in place for extended periods of time (15–20 years) and the ability to evaluate their continued effectiveness is hampered

Methods

Results

Conclusion