The rise of tropical fish and fish diversity in Texas

The Texas Slam, which includes the combined catch of a Spotted Seatrout, Redfish, and Southern Flounder in a single day, holds a special place in the culture and pride of Texan anglers. While there is no replacing this iconic trio, are there other notable species to catch here?

In recent years, there has been an interesting development: the rise of tropical fish and an increase in overall fish diversity here on the Texas coast. Fishery biologists at Texas Parks and Wildlife Department - Coastal Fisheries Division (TPWD-CF) are finding an increasing occurrence of fish like Common Snook and Gray Snapper in our long-term dataset, a phenomenon called tropicalization. Even species like Permit and juvenile Bonefish are making appearances in our bays! The northern movement of these tropical species may offer anglers opportunities to catch ‘bucket-list’ worthy fish right in our back yard.

Tarpon, Bonefish, Permit, Snook, and Snapper are some of the most popular game fish in the world. Anglers travel far and wide to have the opportunity to bring these fish to hand. There is still a lot to learn about the life history of these tropical species in Texas waters. Some species are likely using our estuaries as nurseries, then leaving to the Gulf once they are adults. Given the potential increase in sightings of these migratory fish, it is essential for Texan anglers to familiarize themselves with the identification of these possible catches and to adhere to any relevant regulations. One notable example is the occurrence of anglers unintentionally catching juvenile Tarpon while cast netting for mullet. Therefore, the ability to recognize such bycatch is of utmost importance.

The rise of these tropical fish species in Texas can be attributed to a combination of climatic and environmental factors. As temperatures increase, coastal waters experience changes in chemistry and biology, which, in turn, affect the entire ecosystem. Tropical species thrive in warmer climates that support year-round growth, sustained by higher temperatures and ample sunlight. As Texas experiences rising temperatures, it becomes a more suitable habitat for these tropical visitors, resulting in their northward migration.

 As these more tropical populations trend upward, TPWD-CF as a management agency want to know how they will affect other resident populations. For example, here pictured (Figure 2) is a Common Snook’s stomach contents- a juvenile Spotted Seatrout. This snook was caught in the Upper Laguna Madre, an area heavily fished for seatrout. Seeing this reminds us that we need to consider the food web impacts that tropic expansion might have and what the priorities of Texan anglers are.

It is not only about who is eating whom, there are also questions about how resident and visiting populations are going to respond to our changing climate. It is well known that there are preferential temperature ranges for certain species to spawn, indicating there could be temporal and spatial population shifts. This may be concerning for some of our resident species like Blue Crabs and Southern Flounder that are known to rely on relatively cool winters for their spawning and there has been an observed decrease in their numbers. There are, of course, other environmental factors to consider beyond just temperature, such as salinity. Freshwater inflow manipulations (e.g., dams, diversions) and changing precipitation patterns may also affect the ecology of our bays. In response to observed declines in these specific stocks, TPWD-CF has implemented management strategies such as various minimum size regulations with the goal of allowing a large proportion of spawning stock (of species like flounder) from being harvested. The interplay among competition, fishing pressure, and range shifts due to climatological factors creates a lot of scientific questions that are being addressed by a multitude of agencies and institutions alike.

I’ve mentioned increased temperature driving these patterns several times, so I’d be remiss to ignore the fact that with a changing climate comes more extreme weather events like the freeze of 2021. TPWD-CF wants to know if these tropical populations will become more resilient to these swings in temperatures, and if so, how to properly manage these fisheries. Mangrove Snapper, for example, are known to be particularly sensitive to cold snaps, henceforth bag and size limits have not been implemented because it is unclear still how they will fare in our waters long-term irrespective of fishing pressure. Implementing standards on size and bag limits is one of the tools in our kit used to hedge the loss of opportunity to catch species like these, though, so TPWD-CF keeps a close eye on our resource monitoring data to see what we can realistically manage.

Tropicalization in general may very well bring unique angling opportunities to the Texas coast. We are excited to explore the relationships among habitat use by various species, species interactions (predator prey interactions), and functional impacts to local fish communities and share these findings with Texan anglers. I can’t ever picture a change to what we consider our Texas slam, but we may be afforded the opportunity to more ‘catches of a lifetime’. As always, size and bag limits of these less-common catches should be kept in mind should you be lucky to land something new.