2005-2006: Tarpon Catch-and-Release Study—TAMPA BAY
Biologists at the Florida Fish and Wildlife Conservation Commission's Fish and Wildlife Research Institute continue their study in the Tampa Bay area to evaluate the effects of catch-and-release fishing on the short-term survival and movement of tarpon, Megalops atlanticus. Data collection begun in the spring of 2005 focused on the fishery in the bay and adjacent gulf waters from Longboat Key to Anclote Key. Unlike the 2005 season in which tracking opportunities were few because of a persistent, wide-spread red tide bloom that made baitfish and tarpon scarce, the 2006 season was refreshingly productive with 15 released tarpon tracked.
Tarpon and anglers seemed to be everywhere in 2006. Baitfish were plentiful and the tarpon were busy feeding, rolling, leaping and generally having a great time just being tarpon. Some noteworthy observations of fish tagged and tracked included:
- tarpon that resumed feeding immediately after being tagged and released
- one tarpon that escaped from the jaws of an attacking hammerhead shark and survived
- a tarpon that traveled nearly 11 miles from the Manatee River to Ft. DeSoto (Mullet Key) in 4 hours
- One tagged tarpon was seen at the surface 50 times during a single tracking event!
Preliminary results indicate about a 90% survival rate for released tarpon in the Tampa Bay area.
As with previous seasons, in 2007 fishing guides and recreational anglers who target tarpon will be asked to participate in the study by allowing state scientists to shadow their vessels during fishing trips. Once a tarpon has been hooked and brought to the side of the boat, researchers will approach the angler's boat, if permitted, to tag the fish from an FWC vessel by inserting a VEMCO brand ultrasonic continuous transmitter into the musculature just below the dorsal fin.
When the researcher pulls back on the tagging applicator stick, the v-notch of the tag's stainless steel anchor will hook onto a pterygiophore (internal portion of the fin ray) of the dorsal fin. This causes no damage to the fish's organs. The tag is also inserted in a manner that causes no damage to the fin as the tarpon swims away with the tag in its back.
Immediately upon release, the tarpon will be acoustically tracked for a maximum of six hours to determine if the fish recovers or dies as a result of being captured and released. Every fifteen minutes, biologists will record the tagged tarpon's GPS position, bearing and swimming direction relative to the current and other tarpon in the vicinity to aid in the final determination of the fate of the tagged fish (survivor or mortality). Biologists hope to tag 20 more tarpon in the Tampa Bay area. Other important information, such as fight time (in minutes), hook position (e.g., hooked in the mouth, gills, fins, or elsewhere on the body), and general health prior to release, will also be recorded and examined as possible factors contributing to tarpon mortality.
Scientists monitoring tag signals may suspect that a fish has died if its tag signal stops moving. In such cases, a remotely operated vehicle (ROV) will be lowered into the water to visually confirm or deny a suspected death. A small float is attached to the tags, so that, if a tag falls out of the tarpon, the tag will float to the surface and not be mistaken as a fish mortality. Previous work showed that these fish might sometimes swim back into the school and just "mingle" with cohorts as opposed to actively swimming away from the area.
Previous studies conducted in Boca Grande Pass appear to indicate that tarpon are relatively hardy and have a high probability of surviving after being hooked and released. With that understanding, researchers are adding a new genetic tagging component to the study this year in order to look at recapture rates and estuarine connectivity of tarpon stocks within the state of Florida. The technology exists for FWRI biologists to identify and track individual tarpon with the odds of being in error at less than one in one-billion (1 : 1,000,000,000)!
The hook-and-release mortality rates estimated during a similar study completed in Boca Grande Pass (2002-2004) ranged between 7.3% and 17.1%; 83% to 93% survival. Of the 41 tagged tarpon tracked during that study, those that researchers visually confirmed as mortalities all died as a result of shark attacks. If the potential effects of predation are removed from these estimated mortality rates, the mortality rate drops to 4.9%. It is important to note that studies like this provide only an estimated range of fishing mortality rates and not an absolute number. Another tarpon hook-and-release study conducted in Boca Grande Pass in 1992 found a mortality rate of 3.7%.
Thank you to all of the anglers and guides who assisted with this study in 2006. Look for the "Marine Research" boat out on the water again in Spring 2007.