Improving Protections for Threatened Shark Nursery Grounds Off the Pacific Coast of Northwest Mexico

In 2021, The PEW Charitable trusts commissioned the Duke Marine Geospatial Ecology lab (MGEL) to conduct a literature review of existing scientific research on nursery and spawning grounds for a select group of threatened marine species. This project was developed with the following goals: A) Identify a set of focal marine species that are of conservation concern. B) Conduct a global-scale review of scientific literature to identify where nursery, pupping, and spawning grounds for these species are located, how these areas are impacted by fisheries and how they are protected by existing management measures. C) Use this information to develop recommendations for how these areas can be protected more effectively to prevent further population declines. Fundamentally, PEW intended this report to help determine how their own resources can be allocated most efficiently in the future to maximize conservation benefits, both in terms of where new initiatives should be located and what they will work to achieve. The following report is a supplementary document to the global MGEL study that helps further this underlying goal by providing a more focused analysis of an area with outstanding conservation importance identified in the global review: the coastal waters of northwest Mexico. By incorporating data from the literature review and additional research, this study develops more detailed recommendations for this area within the original project framework. The first section explains why protecting shark nursery grounds is a critical conservation concern, especially in the northwest Mexican Pacific (NMP). Nursery grounds facilitate growth and development of juveniles, allowing them to reach the spawning stage. However, when fishers land large volumes of juvenile sharks, they accelerate population declines by eliminating the specimens themselves and their potential offspring, a prevalent problem in the NMP. Because nursery grounds for multiple threatened shark species in this area are targeted directly by artisanal fishers, reducing or eliminating these fishing threats will be critical to ensuring the survival of underlying populations. The following two sections define the species composition and spatial distribution of focal shark nursery grounds in the NMP while identifying proximal fishing threats. Protecting juvenile shark aggregations requires a consideration of how they are distributed across the study area. Based on the literature review data, focal shark nursery grounds are concentrated in three specific regions of the NMP, which likely hold disproportionate conservation importance. While existing research is limited, available data suggests that all three regions are subject to concentrated fishing activity. The next section outlines the existing regulatory framework for the NMP shark fishery. Understanding this regulatory framework is necessary to develop realistic and effective management recommendations that are within the purview of existing regulatory bodies. Two central regulatory bodies are identified, both of which have authority to institute new protection measures for local shark nursery grounds. The final two sections synthesize the preceding research to provide recommendations for how the Mexican government can protect focal shark nursery grounds in the NMP more effectively. Recording the species composition and corresponding locations of juvenile shark landings in logbook reports can inform the placement of new, small-scale area closures, a feasible means of protecting these nursery grounds from artisanal fishing. The conclusion further outlines how non-governmental organizations (NGOs) like PEW can collaborate with the Mexican government to ensure the success of these new measures.