A little over two years ago, you may have read a blog by Dr. Marcus Drymon about Sea Grant scientists’ efforts to better understand the habitat use of tarpon in the northern Gulf. In summer 2018, we attached satellite tags to 10 individuals and tracked their movement patterns.
Since then, in addition to tagging more tarpon, we’ve had time to sit down and analyze the data transmitted to our computers from the tags, which enabled us to learn where these tagged tarpon went and where they spent much of their time in late summer/early fall. So, what did we discover?
First, we found that the tarpon we tracked were moving from east to west. We tagged the tarpon near Orange Beach, Alabama, and they all moved west toward Louisiana after the tagging procedures. Second, we noticed that the tarpon moved very quickly from Alabama (where most of our specimens were tagged) to Louisiana. The fish sometimes swam as far as 70 miles in a single day!
Finally, and perhaps most importantly, we determined that the waters just off the Pass-a-Loutre Wildlife Management Area -- at the very southeast portion of the Mississippi River Delta in Louisiana -- represented the area that was most frequently used by the tarpon in our study. Interestingly, this area is part of the only known region in the northern Gulf where both the western and eastern Gulf tarpon populations overlap. It is also the only coastal area in the northern Gulf that is in relatively close proximity to deeper waters where tarpon are thought to spawn, which is why this area has previously been hypothesized as a tarpon spawning area.
Unfortunately, we were unable to verify if spawning occurs there, primarily because our satellite tags lacked the capability to track swimming depths. There are certainly other factors that could also attract tarpon to this particular portion of the Mississippi River Delta. Perhaps this area is hyper-abundant in forage fish, a tarpon’s primary food source, or is relatively absent of large sharks, a tarpon’s primary predator.
What we do know is that a large percentage of the tarpon that swim north, and then west, along the Gulf Coast from southern Florida in the early summer do so with the intention of traveling all the way to the Pass-a-Loutre Wildlife Management Area, a one-way trip of over 800 miles! The fact that these tarpon don’t simply stop swimming once they reach the Florida panhandle, which is about the halfway point in terms of distance, speaks to the importance of reaching this specific area in Louisiana.
Even if spawning isn’t actually occurring there, it is clearly one of the most critical areas of habitat use for tarpon in the entirety of the northern Gulf.