I don’t know if you caught the information reported by a local Corpus Christi TV station a couple of months back. “The hatchery,” referring to the Corpus Christi Fish Hatchery, “has a way to track the fish to make sure that their hatchery fish are surviving in the wild. The fish are genetically marked in its DNA and RNA strands, allowing it to be located by satellite.”
Whoa—how in the world are the folks at the TPWD Corpus Christi fish hatchery accomplishing this scientific feat? I’m constantly amazed by the things that the scientific world is coming up with, but this stretches my gray matter really far.
I checked with Ruben Chavez, Natural Resource Specialist at the hatchery, about what they have come up with. Whoops—a mistake by the writer on what Chavez originally said.
“We don’t track fish via satellites,” said a chuckling Chavez. “I think he misunderstood what I said. Fish have genetic markers called microsatellites. In the DNA and RNA strand there are unique markers. For example redfish in general are going to have pretty much in general the same genetic makeup, but there are some unique genes to each fish.
“We first have to catalog our brood fish to create a genetic map of our hatchery fish. When we pair them up and they produce offspring, they have this unique identifiable mark.”
The whole purpose of the identifying mark is to help TPWD fish hatchery people determine what the survival percentage rate of hatchery-reared fish is as compared to native fish reproduced in the bays.
It’s hard to keep track of how hatchery reared fish are doing. “We have tried different methods,” Chavez said, “but it’s really hard to mark or tag a fingerling without doing damage to the fish in the handling process.” Remember that a fingerling redfish or speckled trout is about the size of a finger.
However, when a marked fish is found, that’s solid evidence that hatchery-stocked fish do survive in the wild, but checking for that mark is like finding a needle in a haystack.
Verifying a hatchery-stocked fish is accomplished by taking a scale or tissue from a fish later caught by TPWD fishery management specialists while surveying a bay or from a fish donated by an angler. It has the unique genetic mark noted in the hatchery. Dr. John R. Gold, Texas A&M, a pioneer geneticist in fish genetics. (http://agrilife.org/gold/gold/fish-genetics-laboratory/), has been instrumental in helping TPWD.
It’s interesting to note that the DNA and RNA results vary from bay system to bay system.
Chavez explains the fingerlings only get released back into the bay system that the brood stock came from mainly for genetic differences. “Some of the bays are not connected and the genetic traits are different from the trout you see from bays that are connected,” he said. “You are not going to see that diverse genetic difference in Aransas and Corpus Christi bays.”
Redfish are more migratory. “We used to stock the whole Texas bay systems, but now since we have the additional hatcheries, stockings are more regional.”
The Corpus Christi hatchery stocks more speckled trout than redfish. About 30 million redfish fingerlings were stocked at the beginning. Now redfish stocking is about five million for redfish and about 10 million for speckled trout.
The hatchery is working on culturing southern flounder fingerlings. “We’re trying to produce as many of those guys as possible,” said Chavez. “Our yearly quota is about 25 to 50 thousand. We are still learning that species; we haven’t been doing that too long, still in a learning curve.”
The biggest success story for the Corpus Christi hatchery has been the redfish. Chavez said the hatchery now is more in a maintenance mode. “Fortunately nothing has happened, but just in case something does happen like a killer freeze or bad red tide episode, the hatcheries are here to replenish the system. Where it takes a few years for a fish population to rebound, we can go back and stock the following spring and replenish bays.”
Aransas Bay system is probably the biggest recipient of speckled trout because of the heavy fishing pressure.
Location: Portland Shoreline
Species: Speckled trout, redfish and black drum.
Best Baits: Live shrimp and mullet
Best Time: Dawn to late
Email Tom Behrens at [email protected]