The Dynamic Nature of Nearshore Shark Nurseries in the Northern Gulf of Mexico

Abstract

Aim

Some habitats serve particularly important functions for wildlife. Identifying and appropriately managing these ‘essential habitats’ is critical, especially for wildlife that have faced severe population declines like sharks. Nursery habitats aid in the survival and development of juvenile sharks, which until recently were not formally identified or managed throughout most regions. Managing shark nurseries was in part challenging because there was no standardized quantitative method to delineate these essential habitats prior to the seminal paper written by Michelle Heupel and colleagues in 2007. Management in some regions now includes the protection of shark nurseries; however, changes in nursery dynamics in response to environmental change and human impacts are unclear. Here, we used long-term monitoring data to identify bull shark (Carcharhinus leucas) and blacktip shark (C. limbatus) nurseries and assess how they have changed over time.

Location

Alabama coast and Texas coast, USA.

Time Period

1982–2023.

Taxa

Bull shark, blacktip shark.

Methods

Shark catch records (catch per unit effort) from long-term gillnet monitoring were assessed with general linear models and generalized linear models to determine (1) if shark nurseries exist in the Northern Gulf of Mexico, and (2) if and how they have changed over the study period using the shark nursery criteria established in 2007.

Results

Northern Gulf of Mexico nurseries first (re)emerged in the early 2000s on the Texas coast for bull sharks, followed by a relatively rapid expansion along the Texas and Alabama coast. Fewer nurseries were identified for blacktip sharks, which (re)emerged more recently starting in the 2010s.

Main Conclusions

Improved management has led to the re-establishment of shark nurseries. We expect that changes in these essential habitats will continue as environmental conditions and human impacts shape coastal ecosystems and the dynamics of nurseries within their waters. The delineation, management and reassessment of nurseries will therefore be imperative moving forward as shark populations continue to recover from historic and persistent overfishing and habitat degradation. Predicting where nurseries will (re)emerge in response to improved management and habitat suitability will also be essential to achieve conservation goals.