September 17, 2020 2 min read
Mako sharks are heavily targeted in recreational fisheries and are one of the more common species that occur as bycatch in commercial fisheries. This combined fishing pressure has led to a decline in mako shark populations as a result of overfishing. Because of the slow rate at which sharks reproduce, rebuilding of populations requires many years. In the case of mako sharks, even with fairly stringent regulations aimed at recovery of the stock, it may be as long as 50 years before the mako shark population rebounds. A critical aspect of recovery efforts for a population is understanding where individuals within the population are found and how they move throughout their range. This information sheds light on which countries have the greatest responsibility for management, where different demographics (males, females, mature individuals) spend their time and what types of interactions occur between a species and fisheries in which they are caught.
The Guy Harvey Research Institute (GHRI) and collaborators have been studying the movement patterns and habitat use of mako sharks for over a decade, primarily by tagging mako sharks with satellite transmitters. To date GHRI has tagged 115 mako sharks with satellite transmitters and followed their movements for as long as two years. The tracking data has revealed long distance movements spanning from Venezuela to Canada and provided a huge amount of data to answer the question of: In who’s waters they spend their time? (Largely USA, Canada and Mexico). An unintended consequence of the mako tagging program was documentation of the very high frequency of capture of tagged sharks in commercial and recreational fisheries. Nearly one third of the makos tagged with satellite transmitters were caught and killed in fisheries. This high fishing mortality of tagged mako sharks observed by GHRI was one of the reasons that the status of the mako shark population in the Western North Atlantic was recently reevaluated and that measures were implemented to reduce fishing mortality and enhance recovery of the population.
This past summer GHRI and the University of Rhode Island have collaborated to conduct mako shark tagging expeditions off the coast of Rhode Island and have had great success finding and tagging mako sharks with satellite transmitters. The amount time and effort spent in search of mako sharks over the past decade has been substantial, so the discovery of several mako hot spots off Rhode Island has enhanced the ability of GHRI to access these sharks and expand studies that will continue to provide information about their movements and habitat use into the future. The ultimate goal of the research is to contribute information for the successful management of mako shark populations so that they can be fished sustainably for many years to come.
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