Protecting species requires an understanding of their population biology and their ecology. The Conservation Research program studies population growth rates, age structures, sex ratios and mortality rates of species of concern including southern sea otters, bluefin tuna and sharks. Those data inform models of future population growth and the vulnerability of these species to harvests, pollution, climate change and other threats.
Population Biology of Sharks
Sharks are top predators in marine ecosystems around the world, from coral reefs and kelp forests to the open ocean. They reproduce slowly and can't keep up with fishing that claims tens of millions of sharks each year. The Aquarium collaborates with other shark researchers to study the life history of sharks, with a current focus on white sharks in the eastern Pacific Ocean. We use unique markings on sharks to count them, develop sophisticated instruments to record swimming behavior and obtain at-sea video images, document migrations and use our knowledge to inform conservation policies.
Tracking the population size of marine animals with large oceanic ranges requires sophisticated methods. We are refining and using a "mark-recapture" method that relies on resightings of sharks identifiable by natural markings on their skin.
Population Biology of Bluefin Tuna
Bluefin tuna are fast, wide-ranging animals, capable of crossing the Pacific Ocean in 21 days. They can maintain body temperatures warmer than the waters through which they swim, giving them wide access to feeding grounds that are unavailable to cold-blooded fishes. They are also the target of incredibly lucrative global fisheries. And fishing pressure has pushed Pacific Bluefin tuna populations to less than 5 percent of their historic levels.
The Aquarium operates the Tuna Research and Conservation Center (TRCC) as a joint enterprise with Stanford University's Hopkins Marine Station. The TRCC conducts field and laboratory studies to inform conservation of bluefin tuna. The TRCC is documenting the physiology and migrations of Pacific Bluefin tuna. And we're using this rigorous science to help policymakers understand how best to restore healthy tuna populations across the Pacific.
Populations are subsets of species and the most appropriate units for conservation. Distinguishing between populations is often challenging, especially in the ocean. We are using molecular genetics to determine the boundaries of populations and the amount of gene flow between tuna populations.
Large seawater tanks at the TRCC and the Aquarium's Animal Research and Conservation Center allow scientists to improve husbandry and veterinary techniques, investigate the physiology of swimming and test telemetric tags prior to use in the field. Studies of the cardiac physiology of tunas have provided important new information on habitat use and the impacts of oil contamination on tuna species.
Population Biology of Sea Otters
Southern sea otters once ranged from Baja California to the Pacific Northwest. Today, they're a threatened species, recovering slowly from near-extinction due to intensive hunting by 19th century fur traders. The species is at 95 percent of the number targeted by a recovery plan but only 20 percent or less of its historical numbers.
Recent research by the U.S. Geological Survey and the Aquarium suggests that the sea otter population growth rate is limited in the center of the range by food availability and at the periphery of the range by shark attacks. The risk of a major oil spill in their limited range along California's Central Coast also remains a threat.
Population recovery depends on accurate assessment of threats to the health of the population. Our animal care specialists and research veterinarian monitor the health of southern sea otters and their prey. They monitor disease and other health threats and assess the impacts on population recovery. The team has also developed the ability to foster orphaned pups using sea otters from our exhibit as surrogate mothers. Someday, orphans raised in captivity may contribute to population recovery.