Shortfin mako hot sets – Defining high bycatch conditions as a basis for bycatch mitigation

Shortfin mako sharks, Isurus oxyrinchus, were listed under Appendix II of CITES in 2019 in part due to the results of the last stock assessment for the North Atlantic population, which determined the population is overfished and experiencing overfishing. With population numbers expected to continue to decline, the managing body, the International Commission for the Conservation of Atlantic Tunas (ICCAT), has called for efforts to reduce shortfin mako bycatch. We evaluate the potential for reducing mako bycatch by identifying mako hot sets, those with particularly high shortfin mako bycatch. Environmental conditions were evaluated for their influence on catch per unit effort (CPUE) of shortfin mako sharks. Standardized CPUEs were calculated from the US pelagic longline observer program (2004–2012) using a generalized additive model (GAM) with a delta-lognormal approach applied to the environmental variables sea surface height, sea surface temperature, bathymetry, and chlorophyll-a concentration. Quantile regression (QR) was also performed to evaluate whether environmental variables can predict fishing conditions with high CPUE. The results of the GAM and QR methods were compared and assessed for their ability to predict and identify locations where shortfin mako CPUE is particularly high. The results suggest that using the binomial portion of the delta-lognormal model, the probability of positive bycatch, is the best basis to define an algorithm to avoid setting in conditions that might have high mako bycatch. Bycatch avoidance strategies built from probability of positive bycatch perform well enough at identifying hot sets to avoid half the shortfin mako bycatch with only a 20% reduction in effort. •High shortfin mako bycatch in a longline fishery are important, impactful events.•Environmental conditions can be used to design mako bycatch mitigation strategies.•Presence/absence models of mako bycatch can be used to avoid potential high bycatch.•More complex models did not improve the ability to avoid mako bycatch

Ecosystem modeling in the Gulf of Mexico: current status and future needs to address ecosystem-based fisheries management and restoration activities

Many ecosystem-based fisheries management (EBFM) measures and restoration projects have been implemented to address the stressors that have negatively affected the United States (U.S.) Gulf of Mexico (GOM). Ecosystem simulation models are useful tools for tackling EBFM and restoration questions. Here, we review the current status of ecosystem modeling efforts for the U.S. GOM and whole GOM large marine ecosystem and identify future needs to address EBFM and restoration in these regions. Existing ecosystem models of the GOM are diverse, ranging from simple conceptual and qualitative models to biogeochemical-based end-to-end models and coupled and hybrid model platforms. Many models have focused on understanding the structure and functioning of GOM ecosystems and the impacts of EBFM measures such as bycatch reduction strategies and marine protected areas. By contrast, a small number of ecosystem models have been used specifically to address the other EBFM issues of the GOM and to assess restoration efforts (e.g., marsh restoration). The demands for EBFM and state and gulf-wide restoration activities will both be increasing in the GOM. Therefore, there is a critical need to better employ and enhance existing ecosystem models of the GOM, and to develop new ecosystem models, to more comprehensively address the different EBFM and restoration needs in the region. We provide suggestions to facilitate this endeavor. The development of consistent libraries of ecosystem models and gap analyses such as ours will help fisheries scientists to effectively tackle specific resource management questions in the different marine regions of the world

Recommendations on the Use of Ecosystem Modeling for Informing Ecosystem-Based Fisheries Management and Restoration Outcomes in the Gulf of Mexico

Ecosystem-based fisheries management (EBFM) and ecosystem restoration are gaining momentum worldwide, including in U.S. waters of the Gulf of Mexico (GOM). Ecosystem models are valuable tools for informing EBFM and restoration activities. In this paper, we provide guidance and a roadmap for ecosystem modeling in the GOM region, with an emphasis on model development and use of model products to inform EBFM and the increasing investments in restoration. We propose eight “best practices” for ecosystem modeling efforts, including (1) identification of priority management questions, (2) scenarios as simulation experiments, (3) calibration and validation needs, (4) sensitivity and uncertainty analyses, (5) ensuring transparency, (6) improving communication between ecosystem modelers and the various stakeholders, (7) documentation of modeling efforts, and (8) maintaining the ecosystem models and codes. Fisheries management in the USA adheres to a prescriptive set of calculations. Therefore, the use of ecosystem modeling in EBFM for the GOM will likely be incremental, starting with the incorporation of environmental variables into single-species assessments, the provision of background (stage-setting) information on environmental and food web effects (e.g., the impacts of lionfish Pterois spp. invasion), and strategic advice through management strategy evaluation. Management questions related to restoration in the GOM (e.g., the impacts of freshwater and sediment diversions as part of coastal restoration, habitat preservation, and rehabilitation; and measures to mitigate nutrient loading and hypoxia) have more flexibility in how they are addressed and thus are primed for immediate use of ecosystem modeling. The questions related to restoration are appropriate for ecosystem modeling, and data collection at the restoration project level can provide critical information for modeling to then scale up to regional responses. Ecosystem modeling efforts need to be initiated and advanced now in order for the tools to be ready in the near future. Addressing resource management issues and questions will benefit greatly from the proper use of ecosystem modeling

Recommendations on the Use of Ecosystem Modeling for Informing Ecosystem-Based Fisheries Management and Restoration Outcomes in the Gulf of Mexico

Ecosystem-based fisheries management (EBFM) and ecosystem restoration are gaining momentum worldwide, including in U.S. waters of the Gulf of Mexico (GOM). Ecosystem models are valuable tools for informing EBFM and restoration activities. In this paper, we provide guidance and a roadmap for ecosystem modeling in the GOM region, with an emphasis on model development and use of model products to inform EBFM and the increasing investments in restoration. We propose eight “best practices” for ecosystem modeling efforts, including (1) identification of priority management questions, (2) scenarios as simulation experiments, (3) calibration and validation needs, (4) sensitivity and uncertainty analyses, (5) ensuring transparency, (6) improving communication between ecosystem modelers and the various stakeholders, (7) documentation of modeling efforts, and (8) maintaining the ecosystem models and codes. Fisheries management in the USA adheres to a prescriptive set of calculations. Therefore, the use of ecosystem modeling in EBFM for the GOM will likely be incremental, starting with the incorporation of environmental variables into single-species assessments, the provision of background (stage-setting) information on environmental and food web effects (e.g., the impacts of lionfish Pterois spp. invasion), and strategic advice through management strategy evaluation. Management questions related to restoration in the GOM (e.g., the impacts of freshwater and sediment diversions as part of coastal restoration, habitat preservation, and rehabilitation; and measures to mitigate nutrient loading and hypoxia) have more flexibility in how they are addressed and thus are primed for immediate use of ecosystem modeling. The questions related to restoration are appropriate for ecosystem modeling, and data collection at the restoration project level can provide critical information for modeling to then scale up to regional responses. Ecosystem modeling efforts need to be initiated and advanced now in order for the tools to be ready in the near future. Addressing resource management issues and questions will benefit greatly from the proper use of ecosystem modeling