A juvenile Blacktip shark swims freely after being released
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A juvenile Blacktip shark swims freely after being released following surgery.

June 1, 2010
A juvenile Blacktip shark swims freely after being released following surgery. A transmitter was inserted in the shark's abdomen for tracking. An external yellow ID tag is visible to the left of the dorsal fin. The fin was clipped for genetic analysis. [One of three related images. See Next Image.]

More about this Image Dr. Heupel of the Mote Marine Laboratory in Florida, is currently monitoring the movement and behavior patterns of juvenile Blacktip sharks inside a nursery area. The nursery area in Terra Ceia Bay is a small estuary adjacent to Tampa Bay.

The movements of 91 sharks have been monitored within this study site over the past three years. The movements are tracked using an automated system. Sharks monitored by the automated system have transmitters surgically implanted in their abdomen. The invasive procedure is necessary due to the long-term nature of the study; transmitters have a battery life of 18 months.

Once a shark has been fitted with a transmitter, anytime the animal swims within range of the receiver unit, the information is recorded, including the time and date the animal was present. The data is used to examine the movement patterns of sharks throughout the study site.

Blacktip sharks are known to migrate south during winter months. The study hopes to determine if, when they return to the northern areas the following spring, the juvenile sharks will return to the nursery area where they were born. If so, this behavior would be similar to turtles, who return to their nesting beaches in subsequent years.

To date sharks have been monitored within Terra Ceia Bay for periods ranging from 3 to 159 days. Various movement patterns appear to be present with some animals leaving the study site early, some animals remaining in the nursery area for the duration of the summer months and some animals moving into and out of the study site throughout the summer.

In addition to the surgically transmitted sharks, eight sharks have been tracked using traditional manual tracking methods. In this instance, the shark is fitted with a transmitter and then followed by researchers in a small boat. These tracks have consisted of 24 hours or less and are used to examine the short-term movements of these small sharks. Transmitters are attached externally to the first dorsal fin.

Analysis of the genetic makeup of the Terra Ceia shark population and other populations throughout the Gulf of Mexico and southern Atlantic ocean are also being sampled in an attempt to define any genetic trends within these populations. This analysis may further define whether sharks return to the same sites in later years.

This research is currently supported by National Science Foundation grant 99-11295, scheduled to continue until early 2003. Upon completion of the grant, researchers hope to have a much greater understanding of how young sharks utilize the nursery area and how critical the protection of these nursery-area habitats may be to the life history of small coastal sharks. (Year of image: 2002)

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