Hammerhead Shark Research
Project Leader:
Dr. Matt Smukall, PhD
President/CEO Bimini Shark Lab
Project Overview:
The Bimini Biological Field Station Foundation (aka The Shark Lab) is conducting elasmobranch research in the lower Florida Keys, specifically targeting great hammerhead sharks, and scalloped hammerhead sharks. This area is situated at the convergence of two large marine basins, The Gulf of Mexico and the Western North Atlantic, and research indicates the area is important habitat for these species. The Gulf of Mexico and Florida Keys are projected to continue experiencing significant anthropogenic impacts, including warming water temperatures from climate change. This research, supported by the Ocean Mokum Foundation, will help to understand habitat use, identify essential habitats across ontogeny, and determine long-term movements for these focal species. We will use our platform to support several ongoing collaborations and larger research initiatives in the region. The data derived from this research will directly benefit conservation and management of these species through supporting stock management, assess fishery interactions, and estimate the potential effects of climate change in coming decades.
Objectives:
Great hammerhead sharks are listed as ‘critically endangered’ by the IUCN Redlist assessment, indicating a drastic need to understand overall biology and identify essential habitat for the species. Previous research by BBFSF and collaborators showed that the Florida Keys likely serves as an important primary or secondary nursery ground for juvenile great hammerheads. However, the full extent to which juvenile great hammerhead sharks remain in the area across seasons and years, and to where they disperse, is not yet understood. Improving this understanding can be used for fishery management, stock delineation, and overall conservation efforts of the species.
Scalloped hammerheads are currently listed as ‘critically endangered’ by the worldwide IUCN Redlist assessment, with significant information still lacking for the species. The Shark Lab seeks to take advantage of our fishery-independent surveys to also capture and tag large juvenile and adult scalloped hammerhead sharks. We will also collect samples to support investigations of genetic exchange between the Northwest Atlantic and Gulf of Mexico Distinct Population Segment (DPS) with the ESA listed Central and Southwest Atlantic DPS. This data will support effective management and stock assessments, which relies upon accurately distinguishing distinct groupings and the intermixing of fishery zones.
Methods:
The Shark Lab team will deploy additional Vemco acoustic transmitters in great hammerheads, some of which will be equipped with temperature and accelerometer loggers. These transmitters and data loggers will be informative to determine habitat use, how activity varies across habitats and water temperatures, and how these scale across ontogeny. We will also deploy Vemco acoustic receivers strategically in areas we believe to be primary movement corridors, or have a high degree of local residency. The acoustic receivers will benefit overall regional cooperative research efforts in the area, by filling current gaps in the coverage of the FACT and Ocean Tracking Networks. Our data will be combined with previous BBFSF datasets, as well as datasets of collaborators in the area. In addition, baited remote underwater video surveys (BRUVS) and stable isotope analysis will be used to assess trophic ecology of great hammerheads in the area. BRUVS will provide information on the relative abundance of elasmobranchs and potential prey items, such as invertebrates and bony fishes. Stable isotope analysis will provide information on the base habitat of the food web (carbon) and the overall trophic level (nitrogen).
