Archive for the 'Research' Category

Alligator Gar and Thermonuclear Weapons Testing

Thursday, September 12th, 2019
Alligator Gar

Alligator gar: What a lovely smile.

This is Passport to Texas

Here’s a fish story about alligator gar, a curious biologist and thermonuclear weapons testing.

We’ve done a lot of work recently on the alligator gar. Being able to accurately age these fish is important. Because it tells us not only how long they live, but how they grow and in what years they were produced.

Dan Daugherty is a biologist with Texas Parks and Wildlife.

Fish have structures called otoliths that are like the bones in our inner ear – they accrue a layer of calcium carbonate each year of the fish’s life. If you remove the otolith and section it, you can see growth bands like the rings on a tree stump. Count the rings and estimate of the age of the fish. We estimate that some Alligator Gar caught in recent years at over 60 years old. But counting that many rings on a small structure is difficult. So, to verify our ages, we turned to radiocarbon.

You may know it as Carbon-14. But how is it used to age this fish?

Radiocarbon, or carbon-14, is a rare carbon isotope, naturally occurring at about 1 part per trillion. However, thermonuclear weapons testing in the 1950’s released massive amounts of this isotope into the environment, which was absorbed by all organisms at that time. Given that some of these fish were estimated to be over 60 years old, they would have hatched around that time. And, if the fish were truly that old, then we should measure high levels of radiocarbon in their otoliths. When we analyzed the radiocarbon concentrations in the otoliths, they matched the levels found in the environment in the 1950s, confirming the accuracy of these Alligator Gars’ age.

Now that’s a fish story for the ages.

For Texas Parks and Wildlife…I’m Cecilia Nasti.

Feline City Slickers

Wednesday, August 21st, 2019
Bobcats serve an ecosystem function.

Bobcats serve an ecosystem function.

This is Passport to Texas

According to the US Census Bureau, the Dallas-Ft. Worth metro area leads the nation in population growth. But this growth has fragmented wildlife habitat, and as a result wildlife have become more visible. Now sightings of one particular species has citizens concerned.

There have been some neighborhoods in the DFW area that have seen a lot of bobcats.

Richard Heilbrun is the urban wildlife program leader at Texas Parks and Wildlife.

If you’re in an urban area and you happen to see a bobcat, the most important thing you can do is to stop and enjoy the moment. Keep your distance. Take a photo, but don’t approach it. The bobcat will probably run away.

To answer growing public inquiry, Texas Parks and Wildlife partnered with Utah State University to capture and study urban bobcats.

We caught 12 bobcats in the middle of the metroplex and we radio-collared 10 of them. And we followed them for a year. We found out that bobcats are good at living in the city. They use greenbelts and golf courses, cemeteries, river corridors, and when you stitch all those habitats together they actually form a functioning ecosystem for a wide variety of wildlife.

Understanding urban bobcats is an important first step in achieving a conflict-free coexistence with humans.

The Wildlife Restoration program supports our series and funds bobcat research in Texas.

For Texas Parks and Wildlife…I’m Cecilia Nasti.

Aoudad Sheep Study

Wednesday, July 10th, 2019
Aoudad Sheep

Photo by Glen Mills, TPWD

This is Passport to Texas

Aoudads, also known as Barbary Sheep, were originally imported to Texas from North Africa as game animal over 50 years ago. But for native species like Mule deer and Desert Bighorn Sheep, the ever-increasing Aoudad population has become a threat.

They pose, not only a competition threat, as far as competition for resource, but they can also be socially disruptive.

Froylan Hernandez is Desert Bighorn program leader for Texas Parks and Wildlife. His team initiated a tri-species study to determine if Aoudads could also introduce a disease threat.

This is the first project of its kind of Bighorn Sheep, Mule deer and Aoudad. We’re looking at some of these areas that have Aoudad infestations and taking tissue samples and investigating potential diseases that could pose threats to our native wildlife.

Disease aside, the sheer number of Aoudad have already changed the landscape.

Sometimes we’ll see them in herds of two to three hundred in one herd and so they can definitely degrade the habitat rather quickly. And it’s almost like a gravel bed out on the hillside. It’s peeled, I mean essentially bare ground.

The study will provide valuable information to biologists and help educate landowners on the importance of managing Aoudad populations.

The Wildlife Restoration Program supports our series.

For Texas Parks and Wildlife…I’m Cecilia Nasti.

Rebuilding Texas’ Oyster Habitat

Thursday, June 27th, 2019
Sampling Gulf Oysters

Sampling Gulf Oysters

This is Passport to Texas

Texas has been one of the country’s top oyster producing states since the late 1800’s. Oysterman, Mauricio Blanco has worked the Port Lavaca region for over 30 years.

It’s been a pretty good place over the years. We got so much salt in our blood. That’s what I love to do

But, declining limits on commercial harvests have been signaling a problem for years.

Most oyster reefs are operating on the border of sustainability. Everyone realizes that something needs to be done.

Bill Rodney is a costal ecologist

They’ve been suffering from a number of stressors including drought and hurricanes. On top of that, there’s a lot of fishing pressure being put on.

A historic restoration plan is now in place to rebuild the reefs. A new law requires oyster dealers to recycle their old shell or pay a restoration fee.

The key to restoring the habitat is putting fresh cultch out there. Cultch can be any material that oysters can grow on.

Crushed limestone and recycled oyster shells make an excellent substrate for oyster larva to attach to and grow into spat, which are baby oysters

The site will be closed to commercial harvest for two years, allowing the baby oysters time to grow to adulthood. By the fall, there should be millions of baby oysters growing on this rock out here.

The sport fish restoration program supports our series.

For Texas Parks and Wildlife…I’m Cecilia Nasti.

Hatchery Raised Red Drum and Spotted Sea Trout

Wednesday, June 26th, 2019

CCA Incubation Room. Image courtesy of Texas Saltwater Fishing Magazine.

The CCA Marine Development Center in Corpus Christi produces juvenile red drum and spotted sea trout for release into Texas bays. They do it by tricking wild brood stock.

We put them through a 150-day light and temperature cycle to condense their year down and get them to spawn when we want them to.

Ashley Fincannon is Hatchery Manager

It’s volitional spawning so they are just freely spawning freely in the tanks at night. When the eggs are fertilized, they are buoyant, and they end up at the top of the tanks and end up going in to our egg collectors.

We take those eggs into our incubator room where we hatch them out. They are pretty rapidly developing fish so if we had fish that spawned last night, by this afternoon around six, those fish would be hatching out, they would be feeding on their yolk sack, by three days, they have consumed their yolk sack, their eyes are formed, their mouth is formed, their gut is formed and they are ready to go out and eat.

On the third day, we stock them to our outdoor rearing ponds where we grow them out about 35-40 days where they reach that targeted 35-40-millimeter mark for size at release.

Go to the Texas Parks and Wildlife website to learn more about the hatchery or to plan a visit; search for CCA Marine Development Center.

The Sport Fish Restoration Program supports our series.

For Texas Parks and Wildlife…I’m Cecilia Nasti.