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Bitter Cold In Early January Takes A Toll On Coastal Fish and Shrimp

Coastal Resources to monitor cold impacts on crustacean and fish populations.

GON Staff | February 23, 2010

The new year arrived with a rude surprise — abnormally cold temperatures. The north Georgia mountains saw temperatures in the single digits while the usually balmy coastal counties suffered through several consecutive nights in the mid to low 20s. As the air temperature plunged, so did the water temperature in coastal estuaries and the near-shore Atlantic Ocean.

“For over 30 years, we’ve measured January water temperatures as part of our coast-wide marine-life survey. We’ve had winters where the water temperature dropped into the low 40s or even upper 30s for a couple of days, but it would bounce back to the low 50s pretty quickly. In early January we had water temperatures between 39 and 45 degrees for almost two weeks,” said Spud Woodward, DNR’s Coastal Resources Division director.

When water temperatures remain well below average for a long time, marine life accustomed to warmer conditions can be stressed or even killed.

Shrimp die when exposed to water temperatures of 47 degrees or lower. Common species such as blue crab and red drum are hardier, surviving until temperatures dip into the mid-30s, but even they become sluggish in the frigid waters, making them more vulnerable to predators like wading birds and dolphins.

Spotted seatrout, a popular fish with coastal anglers, can die when water temperatures fall into the low 40s. Even if they don’t immediately succumb to the cold waters, they can be stressed to the point they may die later. Also, a loss of shrimp can mean less food for trout and other fish during the already lean times of winter.

By the second week of January, there were scattered reports of dead fish — a few trout and mullet — from Savannah to St. Marys.

Bait-shrimp harvesters reported catching dead shrimp in their trawls, and dead shrimp even washed up on the beach at Jekyll Island.

Even the coastal-bird population took a hit as several dead pelicans were observed floating in coastal waterways.

“We’ll be monitoring crustacean and fish populations closely in the coming months. If we see that catches in our scientific surveys are far below average, it may be necessary to take some additional conservation action,” said Woodward.

Exactly what those actions might be remains to be seen. The DNR commissioner has authority to close and open shrimp and blue-crab seasons, but the legislature retains authority over most saltwater fish.

“In the past, the commissioner has closed inshore bait-shrimp harvesting and delayed opening the spring food-shrimp-trawling season after winters when water temperatures dropped far below normal. We’ll consider these measures but only after we have strong evidence that such action is warranted. We realize that closing fisheries will have an adverse economic impact,” said Woodward.

Periodic cold snaps are a natural occurrence, and animal populations can rebound. Short-lived species like shrimp can recover after one spawning season, but sometimes it can take years for fish populations to rebuild.

“We know that water temperatures were cold enough to kill speckled trout even though we didn’t see widespread evidence of fish kills like those that happened in Florida,” Woodward said. “So, it would be wise for anglers to be more conservative with the harvest of larger trout this spring and summer.

“With a few exceptions, trout over 18 inches are actively spawning females. The larger the fish, the more eggs they produce per spawn. Leaving these large fish in the water gives them more chances to spawn, which means more young trout, and hopefully more fish to catch the following year.”

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