“Trout have tails…and know how to use them”

Megan Robillard and Greg Stunz, Ph.D.
“Trout have tails…and know how to use them”
A picture of our team (Greg Stunz, Laura Payne, and Megan Robillard) surgically implanting an acoustic tag into a large Lower Laguna 27” 6.5lb spotted seatrout courtesy of Captain Mike McBride.

Weve all had those memorable days where you are in the spot and can do no wrong - fish after fish. You show up the next day for a repeat, same location, conditions, and techniques NOT A BITE! The obvious questions are: where did the fish go, are they still there, are they just not biting?

As avid anglers and scientists, we have envisioned a day where we could track the movements of one of our most prized sportfish, the spotted seatrout, to better understand their behavior. Now with the advancements in fisheries technology, we finally had an opportunity to track these fish real-time to try and answer some of the burning questions most of us have had for years; are trout homebodies, or do they move far distances among neighboring waters? Do tournament fish really survive live weigh-ins? Do surf trout go in and out of tidal inlets spending their time in both the bay and Gulf (aka Tide-Runners)? Well, after 3 years of tracking 81 individual trout (including one of my personal best!), we have some answers. While maybe not the Holy Grail of predicting the exact time and place of the bite, the patterns we found were very enlightening, often surprising, and just may help you catch more fish.

To briefly recap, from 2009 - 2010 we caught and surgically implanted acoustic (sound) transmitters into 81 trout: 31 were from the Laguna Madre (both upper and lower), 30 from the surf beaches, and 20 from live-release tournaments based at Bluffs Landing. Individual fish movements were then tracked using an array of hydrophone receivers we strategically placed on pilings/channel markers in the bays and inlets between Aransas Pass and Port Mansfields East Cut, with the majority in the Upper Laguna Madre (see map). For 3 years we listened for the tagged fish. This acoustic tagging technology works by using internal transmitters that are constantly sending a unique signal through the water every minute. If a tagged fish swims within approximately 1000 yards of a stationary receiver it can hear the ping of the transmitter and records the time stamp and the fishs ID. Each transmitter has enough battery life to last 3 years. During the study we periodically retrieved and downloaded the information collected by the receivers. The tags have now expired, and in summer 2012 we pulled the entire array of receivers and ended the project. Many of the fish that volunteered for our study were still swimming strong with their lifetime souvenir! Im sure there will be more than a few fishermen who unknowingly catch these fish and while filleting them for dinner have quite a surprise when they find a small, black, plastic tag in their fishs abdomen!

First, a few statistics from the study:

Catch-and-Release The Final Chapter It Works! We heard from 59 of the 81 fish, which equals a 73% survival rate. So for those of you who may still be on the fence as to whether a trout survives catch-and-release, we think our study really puts the final nail in the coffin. Our fish were caught with hook-and-line, went through a surgery process, were then released, and they survived. The tournament fish that went through even additional stressors had a 75% survival rate! The other very interesting and related stat is that we had an angler recapture rate of 17%, which is absolutely unheard of in traditional tag-and-recapture studies; typically recapture rates are much lower with 3% considered a high return rate. In fact, just for the 31 fish tagged in the Laguna, there was a 26% recapture rate! One fish was actually captured 3 times. Unfortunately, it was strike 3 for this fish, as it met its fate at the cleaning table. However, this is very telling in terms of the fishing pressure in South Texas waters, when some of our fish are being recycled up to 3 times.

Now on to the really fun partwhere did these fish go? Drum roll pleasetrout have tails, and they sure know how to use them! To better describe what we found it is important to look at the 3 categories of fish tagged: bay, surf, and tournament. Lets talk about the surf fish first their daily movement is unparalleled. They routinely move up and down the coast. The 22 trout tagged in the surf that we heard from swam an average of 2 miles per day. We even had two surf fish that each traveled over 12 miles in one day! The amount of movement these fish do in the surf is fascinating. Every surf fish we detected (75%) were moving into the tidal inlets (often year-round). These results clearly show that inlets are important for fish movement and for Gulf-bay exchange. Interestingly, they didnt stay long in the bay and most headed out after only a short stay. The vast majority of our surf-tagged fish ended up in Packery Channel (a surf trout hot spot), even though we tagged them up and down the surf from Fish Pass jetties down to the 40 mile marker on PINS. What about the tide-runners fish that move through East Cut up through the Land Cut? We did not pick up any surf trout on any of the bay receivers (over 6 miles from an inlet). Surf trout were detected only on the receivers near inlets. Now does this mean tide-runners dont exist? We dont think so. Hindsight is always 20/20 and as with most scientific studies you learn a lot every time you venture out on a new project. The issue was the surf trout would have had to travel a very long way (between 6 30 miles) before getting close to one of the bay receivers to be detected. So a question we still have is how far into the bays do the surf trout come and how long are they staying? However, we did not pick up any surf trout in the Land Cut or Baffin/Upper Laguna Madre areas, where we expected to see a migration route based on anecdotal information. What we do know is that surf trout absolutely use the inlets and these tidal passes are very important to their migration patterns. We will leave it up to you to decide if our evidence helps or hinders the tide-runner theory!

The surf trout definitely used their tails and moved large distances up and down the surf zone, but we also found that the bay trout had extensive movements, just not nearly as dramatic. Unlike the surf trout that routinely entered the inlets, bay-tagged trout NEVER left the estuary and never registered on any of the inlet receivers. This suggests that the surf and bay trout may actually be different sub-groups. The other notable finding was that one bay trout was recaptured by a recreational angler up to 6 months later only a few hundred yards from where we originally tagged it. Traditional tagging would have suggested this trout moved very little, but when we downloaded the receivers we found that this fish made at least a 70-mile track back and forth along the King Ranch shoreline and down into the Baffin area over the 6 months. This technology shows how much these fish really move and how previous studies using traditional tag-and-recapture methods left a big question about what the fish actually do between the tag event and subsequent recapture. Interestingly, several of our fish have been recaptured at almost the same spot they were originally tagged, despite having many long-distance forays in the meantime. This does suggest some type of preferred feeding area, and why certain locations may produce better than others.

Now on to the last group of tagged fishthe tournament fish. The neat thing about tagging these fish was they were obviously the biggest fish we tagged averaging 25 and larger, and not surprisingly had very large migration patterns. We heard from 15 of the 20 fish tagged and 2 were recaptured by anglers. These large tournament fish, which were all released from the same spot near Pita Island, greatly dispersed after release. Most went south into the Baffin area and even the Land Cut headed toward Lower Laguna, while one went north into Corpus Christi Bay, and we never heard from her again.

From the scientific standpoint what does all of this mean? We have a few take-home messages:

1) Catch-and-release works! No ifs, ands, or buts about it.

2) Surf trout move between the Gulf and our bays, frequently. Although we were not able to absolutely confirm or deny the tide-runner theory, we did show how critical our tidal inlets are to Gulf-Bay exchange.

3) We now better understand trout movements and our findings contradict previous studies that said trout rarely leave their natal estuaries. Although some trout did like to stay closer to home, others absolutely move among nearby bays and are willing to make large extensive migrations over very short time periods.

What makes fish venture out or stay home? Most of the movement was largely unpredictable, and most likely this is due to the wide tolerance range trout have evolved. Early on, we speculated environmental conditions would greatly affect movement. Despite a wide variety of extreme weather events, conditions played little role in trout movement. A notable exception was the widespread flooding during 2010 in Lower Laguna Madre, where we observed movements northward through the Land Cut to more salty realms. However, that was the exception rather than the rule. For example, we had some very cold weather during our study period the coldest weve seen in many years. We anticipated seeing a major migration of fish out of the bay to the Gulfs warmer waters; that egress never materialized, not a single fish. Likewise, several strong Gulf storms produced rough surf and very high tides, but they didnt cause any unusual movement into the bays/inlets. Since spotted seatrout do not make spawning migrations, our best guess is their movement is largely in response to locating their preferred food supply or just simply random movement. So the moral of the trout story is when youre on them take advantage of the opportunity while it lasts, because individual fish may not stick around for long. However, keep that spot in your memory bank, because they often come back to the same feeding areas even after long travels.

Whats next? The value of the data collected was so informational, we will be expanding this network with even more coverage and species. Were thinking of calling it the TEXAAN (Texas Acoustic Array Network) - we like the name at least. The TEXAAN will wire the Texas coast and allow us to examine very large-scale movements along large stretches of the Gulf and facilitate collaborations with other researchers. We have been and will continue using this technology with red snapper offshore, and we are planning another project within our Texas bays looking at juvenile trout and redfish movements starting in 2013; so, stay tuned. Ultimately we hope the information from this and our future studies will be useful to our TPWD resource managers as they consider future management strategies for Texas sport-fishes.

Finally and most important, this type of work would not have been possible without the generous support of several groups and individuals. In particular, the CCA, the Rotary Club of Corpus Christi, and Texas A&M University-Corpus Christi who all helped fund this project were essential. Texas Saltwater Fishing Magazine and David Sikes (Caller Times) kept everyone updated and on the lookout, for tagged fish. However, most essential were the TSFM guides who helped us catch our study subjects and supported this project is many ways: Mike McBride, David Rowsey, Billy Sandifer, and Jay Watkins. A major fringe benefit of our job is getting the opportunity to fish with the best trout fisherman in the business. Scientists are not always easy to work with, especially when the captains had to keep straight faces when we asked them to routinely put us on fish of a particular size, in a particular location, on a particular date; however, they always came through for us! Stay up-to-date on our latest sport-fish projects by visiting us at: www.harteresearchinstitute.org/fisheries


Dr. Greg Stunz is a marine biologist that specializes in sport-fisheries. He holds the Endowed Chair of Fisheries and Ocean Health at the Harte Research Institute for Gulf of Mexico Studies and is a Professor of Marine Biology at Texas A&M University-Corpus Christi. Megan Robillard is a Research Associate with over 8 years of sport-fish research experience. Their research program is diverse but recently focuses on migration patterns of marine life using a variety of state-of-the-art electronic tracking devices for fish such as sharks, red snapper, and dolphin-fish. In addition, they have also begun assessing the role of artificial reefs in the Gulf.