Researchers are currently examining the combined USM/GCRL and GADNR conventional tag-recapture datasets to identify seasonal movement and migration patterns. Jim Franks and Dyan Gibson manage an extensive Tripletail conventional tagging program at USM/GCRL that includes data on fish tagged and recaptured throughout the Gulf of Mexico, ranging from Texas to the Florida Keys, and is funded by the Mississippi Department of Marine Resources, Sport Fish Restoration Program. In addition, the GADNR also has an extensive tagging program that covers much of the South Atlantic region. Unfortunately, the strong seasonal site fidelity of Tripletail in certain areas results in many conventionally tagged fish being recaptured near the location of initial tag-release (often the exact location/structure). Therefore, to fully understand the complicated life-history and overall stock structure of Tripletail other tagging methods are needed.

The most recent collaborative work between GSMFC and USM/GCRL, initiated in 2019 aims to better understand both fine-scale and large-scale seasonal movements of Tripletail in the Gulf of Mexico using acoustic telemetry.

In October 2019, the GSMFC and USM/GCRL implanted a total of 31 INNOVASEA V13 acoustic tags in Tripletail caught in Mississippi waters within and directly adjacent to the USM/GCRL acoustic receiver array in the western Mississippi Sound (Total length (TL) = 11-21 inches).  Of those 31 acoustic tags deployed in October 2019, 29 total fish were detected within the USM/GCRL acoustic receiver array logging 8,826 total raw detections before departing the array. In December 2019, an additional 19 acoustic tags were deployed in Florida Bay and the Keys in an attempt to better understand the migration patterns of those fish as they leave their presumed overwintering grounds; no detections reported to date. By learning about the extent of both the northern and southern migratory movement undertaken by tagged individuals researchers hope to gain a better understanding of the stock connectivity, particularly throughout the Gulf of Mexico.

The above map shows Tripletail conventional tag release (blue) and recapture (red) locations in the Gulf of Mexico and South Atlantic for 9,026 fish. Two fish tagged in the Gulf were recaptured along the mid-Florida East Coast but no others have moved between regions. 

Since their exit from the USM/GCRL array in late October/early November 2019, only two of the 31 Tripletail tagged in Mississippi waters in October 2019 have been detected on Mississippi Sound and other iTAG arrays. One fish moved through the Tampa, FL region in December, presumably headed south to the Keys. The last detection for this fish placed it about 370 nautical miles (straight-line distance) from where it was deployed 74 days prior. Without additional detections, it is not clear if this individual traveled along the coastline (450 nautical miles) or directly through the open waters of the Gulf. Interestingly, one other fish was detected off the Texas coast in December. Only a single detection was recorded for this fish outside of the USM/GCRL array where it was originally tagged, so researchers remain skeptical about these data unless they obtain more supporting evidence of its movements west.

The above map shows where Tripletail were acoustically tagged in the western Mississippi Sound and the Florida Keys (red dots) and detected (blue dots), and the location of iTAG acoustic receivers (green dots).

In summary, recapture data from Tripletail conventionally tagged in the northern Gulf indicate a northwest to southeast movement seasonally, but the movements are not well defined. In addition, reports of Tripletail being caught/observed in offshore waters well beyond the reach of acoustic telemetry arrays further complicate the successful detection of acoustically tagged fish as they undergo seasonal migrations. Future satellite tag work and the eventual expansion of acoustic telemetry arrays further offshore may help us resolve such issues by helping to understand if Tripletail use specific travel corridors in open water where acoustic telemetry arrays are largely not present at this time.

The deployed acoustic tags should be active until April 2021, providing for approximately two full migration cycles into and out of the northern Gulf. Contact the GSMFC at svanderkooy@gsmfc.org to get more information on the ongoing Tripletail acoustic tagging research in the Gulf of Mexico, and please forward any Tripletail tag recapture data to USM/GCRL at dyan.gibson@usm.edu.

For more information about this global project please contact itag@myfwc.com to access the full article received by the contributors: Steve VanderKooy (GSMFC), Dr. Jim Franks (GCRL), Paul Grammar (GCRL), Chris Lapniewski (GCRL), Jennifer Green (GCRL/MDMR)