Winter Weather Impacts on Coastal Wildlife: What Does Texas Parks and Wildlife Do to Mitigate Losses?

TPWD Coastal Fisheries Division Staff
Winter Weather Impacts on Coastal Wildlife:  What Does Texas Parks and Wildlife Do to Mitigate Losses?

Figure 1. Catch of Spotted Seatrout in TPWD gill nets, 1980 – 2019.  Note the decline in catch following severe winter storms in 1983/84 and 1988/89, followed by recovery in abundance in less than 2 years.  Subsequent freeze events have had minimal impact on short-term abundance.

As we continue to thaw out from the winter storm that impacted the state of Texas this year, one question readers may have is how Texas Parks and Wildlife (TPWD) responds to and mitigates the loss of coastal marine wildlife during extreme cold fronts. When winter weather is predicted to significantly lower coastal water temperatures, staff from TPWD’s Coastal Fisheries Division work closely with TPWD game wardens and external agencies to put together a plan to assess the potential threat to wildlife and minimize the long-term impacts. Here’s how.

First, an effort is made by agency staff to assess the length of the winter event, and the potential for water temperatures to remain below lethal thresholds for some of our more common game fish. Lethal threshold temperature varies on a species-by-species basis; where a more tropical species such as a Gray Snapper or Common Snook might perish anywhere from 45 – 55o F, a more temperate species such as Southern Flounder can survive right down to freezing (32o F). Spotted Seatrout and Red Drum fall somewhere in between.

In the event that water temperatures are forecast to remain critical for a long period of time and for a wide range of species, TPWD can implement emergency fishing closures in deep, protected waterways that have historically harbored fish in colder weather (think harbors, basins, and wind-protected bayous). One of the ways that fish naturally cope with extreme cold is to find deeper water. The thermal layers (called thermoclines) that develop in deep areas result in warmer water near the bottom, and fish tend to take refuge in these areas during severe winter events. Limiting fishing in these areas during extreme weather limits the scale of the mortality event. In the 2021 winter storm, coastal water temperatures averaged between 37 – 41o F on the upper coast (north of Port Aransas) and 44 – 48o F on the lower coast, over a four-day span. As a result, TPWD anticipated a fish kill risk, and invoked a coastwide emergency fishing closure in 21 deep-water areas. Additionally, as has occurred in past events, TPWD was in touch with the Gulf Intracoastal Canal Association (GICA) which voluntarily suspended tow operations from the JFK Causeway in Corpus Christi south to Port Isabel, to further reduce stress on fish in some of these areas. Partnerships such as those with GICA enhance the measures put into place by TPWD to mitigate damage to wildlife.

In addition to fishes, some of the hardest hit wildlife species during winter freezes are the five species of marine turtles that occur in Texas, including the highly-endangered Kemp’s Ridley. Prolonged water temperatures below 50o F cause marine turtles to lose function and either freeze on land or drown in shallow water. The coastal fisheries division of TPWD works with local TPWD game wardens and multiple external partners to assist with turtle search and rehabilitation efforts coordinated by United States Fish and Wildlife Service, Padre Island National Seashore and the Sea Turtle Stranding and Salvage Network. As of press time, over 12,000 marine turtles had been recovered in Galveston Bay, East and West Matagorda Bay, Aransas and Corpus Christi Bay, and the Laguna Madre during the winter of 2021, representing the largest prolonged marine turtle cold-stunning event in Texas’ history. The TPWD is proud to be on the front lines of search, recovery, and rehabilitation for these ancient mariners.

The work is not done once the storm passes.  After a winter storm, work begins in earnest to assess the damage that has been done to Texas’ coastal fish species. One of the ways that TPWD does this is by observing the size and number of fish kills that have occurred. Each major bay in Texas has its own team of TPWD fishery management professionals that are tasked with assessing the health of fish communities through routine sampling. Following freeze events, these same teams fan out and systematically assess fish kills in their respective bays. This effort is coordinated through the TPWD Kills and Spills Team (KAST) and uses standard fish kill assessment procedures recommended by the American Fisheries Society. To narrow in on areas to investigate, the team fields reports from staff in the field, public calls through the hotline (512-389-4848), and social media. The number of fish involved, as well as the various species impacted are estimated and compared to previous kills to assess severity and potential long-term impacts. These data can also be used to focus stock enhancement efforts towards mortality “hot spots.” That is, stock enhancement of Red Drum and Spotted Seatrout can be tuned on an emergency basis in any given year to have the greatest effect in bays that had the heaviest storm impacts. For the February 2021 storm, fish kill assessments began in earnest on the first day of the arctic front (February 14), and were in progress as this magazine issue went to press.

So, the final question that is likely on everyone’s mind is….what impact will the storm have on fishing this year? First, the bad news. Historically, catch of popular species like Spotted Seatrout has declined in the year directly following freeze events. The “cold standard” of the most severe Texas freeze events were  winter storms that occurred in 1983/84, and subsequent harsh winters in 1988 and 1989. In those cases, catch of Spotted Seatrout in TPWD samples the following year declined dramatically each time (Figure 1). But here’s the good news – Texas coastal fish communities are surprisingly resilient.

In the case of both of the 1980s winter storms, catches rebounded to the historical average within 2 years. More recent freeze events (1997/98, 2010/11 and 2017/18) have seen recovery spans of 1 year or less.  The average size of catch lags somewhat slower, but generally speaking larger trout begin appearing in numbers within a few years after each event as well. Other popular species tend to follow similar patterns. Texas’ marine fish communities have probably experienced extreme winter events for millennia, and they have adapted in such a way that recovery can be very fast. The outlook for fishing in Texas continues to be a good one in the long term, as TPWD biologists anticipate that recovery from the 2021 storm will look similar to previous severe winter events. As TPWD biologists continue the assessment of this event and determine the impact to the overall fish populations, they will brief the Texas Parks and Wildlife Commission (TPWC) on those impacts, and the TPWC will determine what actions, if any, may be needed to accelerate recovery, and to help address future events.