Tracking Shark Populations Off Delaware's Coast

This summer, a team of National Aquarium biologists spent a week aboard our research vessel, the R/V Carcharhinus, conducting shark conservation research off the coast of Delaware.

Published November 19, 2015

shark-conservation-research

A generous grant from Yamaha provides the engines that power R/V Carcharhinus, allowing our staff to collect and tag sharks, gather data and assist other scientists in the field!

Throughout the week, Aquarium staff partnered with scientists from other institutions, and biologists new to the work were trained in shark tagging. Out on the R/V Carcharhinus, they gained valuable experience through the handling of 35 sand tiger sharks and 31 sandbar sharks—the team’s all-time record for a 3-day period of shark tagging in the Delaware Bay!

After being caught, basic measurements were taken and the sharks were tagged and released. The information was provided to the National Marine Fisheries Service (NMFS) Cooperative Shark Tagging Program. If researchers or fishermen recapture these animals, the visible tags instruct them to collect the same information and report it to NMFS. That data is critical to understanding species growth, migration and habitat usage to help guide appropriate fisheries management decisions.

Globally and in the Northwest Atlantic, sand tiger sharks are listed by the IUCN as a vulnerable species. In the Southwest Atlantic and off the east coast of Australia, these animals are considered critically endangered. In U.S. waters, sand tiger sharks are a prohibited species, meaning they can’t be fished, and are considered a species of concern. Reproduction of sand tiger sharks in captivity has been very limited, with only a small number of successes at institutions in Australia, South Africa and Kuwait.

shark

Blood samples were also collected from the sharks caught and released over the course of the week. The samples will be used in several projects led by National Aquarium researchers, including an examination of reproductive steroid hormone levels in both species. To date, the only published values of reproductive steroid hormone levels over the course of the reproductive cycle in sand tiger sharks are those from sharks at the National Aquarium.

The newly collected blood samples will be added to previous samples from fellow researchers and help scientists better understand the endocrine cycle in wild sand tiger sharks. In addition, the blood samples will be used in ongoing investigations into shark hematology. 

Onboard the R/V Carcharhinus, partnerships were strengthened with the Delaware State University and the University of Delaware’s College of Earth, Ocean and Environment, where the field station is located. Two doctoral candidates working on tracking sand tiger sharks using acoustic telemetry joined the Aquarium’s expedition.

Acoustic telemetry is a method of using transmitters and receivers to track a fish’s movement using sound. The researchers used a hydrophone, a tool used to detect sound underwater, to locate sand tiger sharks that were previously tagged. The data logged in their tags is intended to capture how the sharks utilize habitat and interact with other species, valuable information for the conservation of this threatened species.

While many have been located, of the 20 sharks tagged in 2012, only two have been successfully recaptured so far to collect the tracking log data. The National Aquarium is committed to the continued support of these efforts and partnerships for the conservation of all sharks.

Stay tuned for updates!

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