TPWD’s Response to Coastwide Freeze, 2010

Steven Mitchell, Aquatic Biologist | Upper Coast Kills and Spills Team | Dickinson Marine Laboratory
TPWD’s Response to Coastwide Freeze, 2010
Prior to the 1950s, biologists along the Texas coast were few and far between and getting to a fish kill or even knowing that one had occurred was often difficult. Even though a few historic freezes were fairly well documented, the true extent of the early freezes will never be known since quantitative estimates were never made or data were inadequate. A standardized approach to estimate the number of animals killed during catastrophic events, such as freezes, was developed and used during the 1983-84 freeze and in all subsequent freeze events. Because of this standardization and TPWD staff that are distributed coastwide to respond to these events, we are able to better assess the impacts and respond with appropriate management action, if necessary.

On January 8, 2010 the National Weather Service issued a hard freeze warning for coastal counties creating conditions for a potential freeze kill in coastal waters. With this advance notice, TPWD Kills and Spills Team (KAST) biologists and other Coastal Fisheries staff began preparing for potential coast wide impacts to inland and coastal fisheries resources. TPWD staff began monitoring air and water temperatures and the projected time period for freezing temperatures to occur. During the period of January 8 through January 11 the air temperature in Port Arthur was recorded at a record low of 18 F; the air temperature in Galveston was recorded at a low of 27 F and Corpus Christi hit a record low of 24 F.

Beginning January 9th, TPWD started receiving reports of dead, dying or cold stunned fish. Reports of impacted species along the coast included mullet, various drum species (spotted seatrout, sand seatrout, black drum, red drum, and silver perch), gray snapper, sheepshead, spadefish, striped burrfish, blue crabs and sea turtles. Reports varied from stunned to dead fish in areas along the entire coast, with higher impacts along the mid to lower coasts. TPWD staff (KAST, Game Wardens and Coastal Fisheries Ecosystem teams) began responding to reports of fish kills and began reconnaissance of areas where freeze impacts have occurred historically.

A total of 50,971 fish of 18 species were estimated to be impacted during the 2010 freeze event. Table 1 shows the comparison of mortality between freezes from 1983 to 2010. We suspect the weeks of cool weather that preceded the 2010 freeze event (with December 2009 being one of the coolest on record) allowed fish to acclimate to lower temperatures and move to deeper water. The 1983 and 1989 events were preceded by warmer water temperatures and the fish did not have time to acclimate. Day time air temperatures were also higher during the freeze of 2010 compared to 1983. All these factors further minimized the impact on mortality.

The following is an estimate of fish mortality based on field observations and data collected by TPWD staff from the bay systems along the Texas coast. As with previous freeze counts, these are conservative estimates of freeze killed fish.

Sabine Lake
Only one fish kill was reported for the Sabine Lake bay system. Two black drum and 24 spotted seatrout were observed in the Bridge City area.

Galveston Bay
The Galveston Bay system had several reports; most of which were within local bayous and canals. One snook, 32,364 striped mullet, and 105 spotted seatrout were observed.

Matagorda Bay
One snook and 1,000 mullet were observed in Caney Creek within the Matagorda Bay system.

San Antonio Bay
Impacts in the San Antonio Bay system were limited to Espirito Santo Bay and Pringle Lake where 198 spotted seatrout and 1,200 mullet were observed.

Aransas Bay
The Aransas Bay system lost 3,012 mullet, and 400 cabbagehead jellyfish were found stranded along Mesquite Bay shoreline.

Corpus Christi-Upper Laguna Madre
The combined Corpus Christi Upper Laguna Madre Bay systems had the largest variety of species impacted including 34 Atlantic spadefish, 284 snook, 5 tarpon, 118 hardhead catfish, 9 pigfish, 11 red drum, 55 stone crabs, 9 striped burrfish, 10,983 mullet, 214 Irish pompano, 26 gray snapper, one gray triggerfish, one spotted seatrout, one black drum, and one pinfish.

Lower Laguna Madre
Lower Laguna Madre Bay system lost 750 gray snapper, 23 striped burrfish, 137 hardhead catfish, one lane snapper, and one mullet.

In addition to finfish, the cold weather impacted sea turtles. Overall 438 cold stunned sea turtles, ranging from five to 200 pounds, were recovered from the bays and beaches of East Matagorda Bay to the lower Laguna Madre. Of those recovered, 436 of were green sea turtles and two were loggerhead sea turtles. Approximately 2/3 of the recovered sea turtles were dead which included many young green sea turtles. The fact that so many young green sea turtles were impacted during this event compared top previous freezes suggests the green sea turtle population is on the rise.

Even though the sea turtles were highly impacted, we appear to have been lucky and dodged a bullet with respect to fisheries. Because the total mortality was low for fish species, we don't expect to see major impacts to fish populations.
With the Coastal Fisheries long term monitoring program, we will be watching to see if our expectations are correct, especially with more tropical species such as snook and gray snapper. TPWD and other resource agencies will continue to work to determine the impacts of this freeze on the population of the threatened green sea turtle.