The blue shark, a wide-ranging oceanic predator, plays an important role in marine ecosystems. Growing concerns about marine life populations have brought increased attention to species like the blue shark. Understanding their biology and conservation status is crucial for assessing the challenges these sharks face.
Understanding the Blue Shark
The blue shark, Prionace glauca, is a requiem shark known for its slender body and distinctive indigo blue coloration, fading to lighter blue on its sides and white underneath. This countershading provides camouflage in the open ocean. They possess long, pointed pectoral fins and a conical snout.
Blue sharks are primarily pelagic, inhabiting the open ocean from the surface down to depths of about 350 meters. They are found worldwide in temperate and tropical oceans, undertaking extensive migrations. Their diet mainly consists of small fish and squid, but they are opportunistic feeders that also consume crustaceans and seabirds.
Current Conservation Status
The blue shark is classified as “Near Threatened” globally by the International Union for Conservation of Nature (IUCN) Red List, an assessment last updated in 2018. This classification indicates the species is not immediately endangered but is close to qualifying for a threatened category, meaning its population is declining and requires close monitoring. A global population decline over three generations was estimated.
Regional populations can face more severe situations. For instance, the Mediterranean population of blue sharks is considered “Critically Endangered” due to intense fishing pressure. The North Atlantic stock has also experienced an estimated 50% decline in the last three generations, which would typically qualify it as “Endangered.” This highlights the varying health of blue shark populations across different ocean basins.
Primary Threats to Blue Sharks
Overfishing stands as the most significant threat to blue shark populations worldwide. This includes both targeted fishing, driven by the demand for shark meat and fins, and, more substantially, bycatch in fisheries aimed at other species like tuna and swordfish. Blue sharks are among the most frequently caught sharks globally, with estimates suggesting millions are caught annually.
Longline fishing, which uses lines with numerous baited hooks stretching for miles, is particularly problematic. Blue sharks are highly susceptible to being caught as bycatch in these operations. Large numbers of blue sharks are caught as bycatch annually. Even when released, many do not survive due to injuries or stress.
Shark finning, the practice of removing a shark’s fins and discarding the body at sea, also contributes to population declines. Blue shark fins are among the most heavily traded in the global fin market, and this demand fuels fishing pressure. While some fisheries are managed, many remain unregulated, allowing unsustainable catches to continue.
Global Conservation Efforts
Conservation efforts for blue sharks involve a combination of international agreements, regional management, and research initiatives. The blue shark was added to Appendix II of the Convention on International Trade in Endangered Species (CITES) in November 2022. This listing means that international trade in blue sharks is monitored and regulated to ensure it does not threaten the species’ survival.
Regional Fisheries Management Organizations (RFMOs) also play a role in managing highly migratory species like blue sharks. For instance, the International Commission for the Conservation of Atlantic Tunas (ICCAT) has implemented measures to reduce catch quotas for blue sharks in the Atlantic Ocean. ICCAT introduced total allowable catches and quota limits for North and South Atlantic blue sharks.
National regulations further support conservation by establishing measures such as mandating that all harvested sharks be landed with fins naturally attached. Research and monitoring programs are ongoing to better understand blue shark movements and population dynamics, providing data for more effective management.