Tripletail, Lobotes surinamensis, have long been called a “bonus fish,” a lagniappe catch after a long day on the water. Anglers often catch them after spotting them basking at the surface lying in wait for unsuspecting prey.

Tripletails are short-lived, fast-growing marine fish, living only about five years but growing up to 18 kg (40 pounds). It is generally accepted that tripletail spawn offshore, which is also where most juveniles grow to maturity. However, our understanding of adult movements is incomplete. Tripletail make seasonal movements inshore into the estuaries and river mouths, but it is not known how frequently this happens.

Dr. Jeffrey Plumlee and his lab are looking to answer those mysteries surrounding tripletail movement patterns. With funding from the Louisiana Board of Regents and the RNR, Plumlee hopes to determine how frequently tripletail come inshore over their short lives and where they go after they leave inshore waters.

Some evidence of tripletail movement is recorded in otoliths, or ear stones, located in the fish’s inner ear. Otoliths are made of calcium carbonate and other trace elements that grow continuously and incorporate the chemistry of the water around them. This chemical fingerprint in the otolith can give clues to the characteristics of a fish’s environment throughout its life, like the temperature and salinity of the water. Tripletail movements from high salinity offshore waters to low salinity inshore waters are recorded in their otoliths, allowing Plumlee and his lab to determine how frequently that behavior happens by analyzing sections of otoliths with mass spectrometry. For this component of the project, the Louisiana Department of Wildlife and Fisheries has donated tripletail otoliths collected over the past decade for this analysis.

Plumlee’s lab is also using more conventional satellite tags to determine tripletail movements after the fish leave the estuary. Plumlee’s lab is catching tripletail before the end of their seasonal inshore residency and attaching a pop-off archival satellite tag on each fish that will provide a location at a predetermined future date. A tag from one fish caught in September popped off 98 days later just offshore in Mexico, 874 km away from where it was tagged.

For fish we know little about, collecting life history data is critical to answering questions about fishery sustainability. If only a fraction of Gulf tripletail makes the annual migration to estuaries, harvest by Louisiana fishers would likely be a sustainable option with minimal impact to stock productivity

Technician Owen Henderson, left, and graduate student Emily Robicheaux preparing to affix a tripletail with a popoff satellite archival tag and releas

A tripletail with a pop-off satellite archival tag attached ready to be put back in the water.