By JoEllen K. Wilson, Bonefish & Tarpon Trust
Once juvenile tarpon emigrate from the nursery habitat (Juvenile Tarpon as they Live and Breathe), they are affectionately known as “sub-adults”. Too big to be considered babies, but not yet sexually mature. Sub-adults are quite mysterious, since we don’t know how far they go from the nursery habitat and where they are most times of the year. Bonefish & Tarpon Trust is using tagging technology to uncover the mystery of their movement patterns.
Acoustic telemetry is an emerging technique used in fisheries science to track movement patterns and behaviors of a variety of species. Because it is becoming so popular, agencies are able to collaborate to greatly expand the detection network while reducing costs. In tarpon, acoustic tags are inserted through a small incision made in the abdomen, followed by a single stitch. Healing time is quite minimal. Each tag transmits a “ping” with its unique identification number and acoustic receivers, or listening stations, that are within range of the tag record the time and date of the “ping” along with the tag ID. Tarpon that we have tagged in Charlotte Harbor have been detected by receivers belonging to FWC and South Carolina’s Department of Natural Resources. BTT receivers in the Harbor have detected spotted eagle rays tagged by Mote Marine Laboratory.
A major benefit to using acoustic tags is the size variability of tarpon that we are able to tag. In the past, BTT funded tarpon research using satellite tags and the size of the tag limited us to tagging fish that were 80 pounds or larger. Acoustic tags are much smaller so that we can target tarpon as small as 20 pounds.
Filling the life cycle gaps for tarpon is essential to the sustainability of the fishery. Most importantly, we could be irreparably damaging essential sub-adult habitat without even knowing it. A functional habitat is critical for any species, particularly those like tarpon which rely on coastal habitats for early life stages and mature relatively late. Healthy habitats mean healthy fisheries.