The redfish is a
favorite with saltwater anglers, ranking with striped bass, bluefish and
weakfish among surf-casting's big four. In their Atlantic and Gulf Coast range
redfish are also known as channel bass and red drum, and they are
hard-fighting, good-eating fish that grow to substantial size; the current
all-tackle record is 90 pounds. But redfish (Sciaenops ocellata) never seemed a
species to make history. Now, however, they may do just that by providing the
necessary clues for turning saltwater game fish into freshwater habitu�s.
Today, hundreds of miles from saltwater, large numbers of redfish are thriving
in Texas lakes, their transfer being an unexpected by-product of a study of
their life cycle made by a Port Aransas laboratory.
Last August three
male and three female redfish spawned naturally under laboratory conditions,
the first time that had happened anywhere. Within a month they had produced 50
million eggs and more redfish than anyone knew what to do with. In September
the first shipment of baby redfish was planted in a freshwater lake in Austin,
and if they grow an inch a month, as scientists expect, Texas freshwater
anglers should have fine new sport by next fall.
Arnold, of the National Marine Fisheries Service lab in Port Aransas, was
studying the eggs, larvae and early life stages of the redfish when he
succeeded in developing the spawning procedure, which apparently is the key to
the successful transfer of the species from salt-to freshwater. Dr. Arnold
remains unawed by the consequences of his findings and, in fact, declares,
"My work ends 10 days after hatching."
The three male
and three female redfish were put in a 6,000-gallon laboratory tank in
September 1974. They had been taken on hooks in the surf off Port Aransas.
Redfish normally spawn in September and October. They do not eat while they are
spawning but come into the surf to feed afterward; it is the time when most of
them are caught With the six captured redfish in the tank, the biologists set
about creating an artificial year in the laboratory, in which water
temperatures and the varying hours of light and darkness approximated those the
fish would have experienced had they remained in the Gulf. Six banks of lights
controlled by timers went on and off with the rising and setting of the sun.
They lighted slowly, one after the other to simulate daybreak, were illuminated
fully through a synthetic day, and turned off one by one as the mathematically
contrived sunsets faded to the total darkness of a submarine night.
"I tried to
re-create their natural light and temperature sequences," Dr. Arnold says.
"I suspected that if we could duplicate nature in the laboratory the fish
would just go ahead and spawn, if everything else was O.K. Something that gave
us a problem was our lack of knowledge of where the fish spawn. Within a mile
of shore? Within 10 miles? No one knew. That created a difficulty with
temperatures. Furthermore, no one knew if they spawn on the bottom or on the
top. Obviously the temperature would be different. How did I decide which to
use? I don't know. I guess intuition. I took the records of temperatures at
various times and depths out there and finally settled on the temperatures we
others of the drum family are noisy fish, communicating with a loud,
bladder-produced drumming and thudding sound, a rhythmical bub-bub bub-bub bum
that reverberates through the Port Aransas laboratory and keeps man and fish
awake. A small school of redfish could provide an unusual backup group for
adventurous rock musicians. The drumming has some connection with the spawning
cycle, but no one knows what it is, and thus far nobody has been able to make
sense of the drum-fish tapes.
The Texas Parks
and Wildlife Department was interested in Arnold's redfish research, having
experimentally planted 200 adult redfish in the Red Bluff Reservoir on the
Pecos River 18 years ago. So far as the fishes' adaptation to fresh water was
concerned, that experiment had been a success: the redfish flourished, growing
up to 12 and 14 pounds. But unlike striped bass, a normally anadromous fish
that has thriven in exclusively fresh water, the redfish never spawned, and the
project was abandoned because of the difficulties in maintaining a stocking
program. Seining small redfish and raising them in ponds was prohibitively
expensive. Milking the females of eggs did not work; it required split-second
timing and the catching of fish when they were ripe to spawn, and it was doubly
wasteful because redfish traumatize easily. In 1972 and '73 Parks and Wildlife
tried hormone injections to induce captive fish to spawn at its marine
fisheries laboratory at Palacios, 70 miles up the coast from Port Aransas.
Hormones have been used successfully to induce other species to spawn,
especially in India and Japan, where aquatic farming is essential to increasing
food supplies. But the experiment at Palacios, as a department publication
reported, had "only limited success...the redfish died from the stress of
The six redfish
in the underwater stage set that Dr. Arnold had built were not handled at all
after they were put in the tank. "It's simple," he says. "I think
that's what's got people sort of bumfozzled. We don't mess with the fish at
all. All I did was duplicate their natural season as best I could." The
fish were taken through a dim synthetic winter, nine hours of daylight and 15
hours of darkness, into a slowly brightening imaginary spring and then to what
biologists call a 12-12 light period, summer days of 12 daylight hours.
"Nothing was known of the spawning of redfish, nothing at all," Dr.
Arnold says. "When they first started, I figured each female would spawn
twice, with a maximum of three times apiece, just from the basic biology of the
fish." But they did not stop spawning. In two months the captive fish
spawned 46 times. For a two-week period they did not eat. "We'd offer them
feed," Dr. Arnold says, "and they wouldn't touch it. When they did
start eating, I said, "Well, that's a good indication they're through
spawning, because they're back eating again.' But now they're eating the way
they used to eat, all the time, and yet they're still spawning."
The eggs floated
to the surface of the saltwater tank and were carried by an overflow pipe to a
filter box, where they collected on the surface and could be scooped up in
containers and placed in glass tanks scarcely larger than an ordinary household
aquarium. At 25� Centigrade (77� Farenheit) they hatched in 24 hours. (In fresh
water the eggs sink and do not hatch.) On August 16 a two-acre saltwater pond
at the Palacios fishery was stocked with 125,000 of these 48-hour-old redfish.
After 30 days the pond was drained, and 4,320 fish, about an inch to an inch
and a quarter long, were recovered. Even this 3.4% recovery rate was considered
encouraging. But then a second stocked pond was drained a few days later and
returned 63,914 fish, an amazing recovery rate of 45%.
Toward the end of
August four additional small ponds were stocked. The first had a return of only
1.9%, the next 2.5%, the third an encouraging 18%. But in one pond there were
no live fish at all. Temperature problems were held partially responsible for
these relatively low returns, but the method of recovering the fish also
influenced the results. It was discovered that the ponds must be drained in
full daylight for best results. Then, when the water begins to flow out, the
tiny fish fight the current with extraordinary strength, until they are finally
swept into the nets with the last gallons. But when the light fades they do not
swim but simply drift up against the drain screens and are killed. Despite such
losses the returns were judged promising. Asked if the project might have been
abandoned had it not been for the 45% return on the second pond to be drained,
Robert Colura, the director of the Parks and Wildlife laboratory, seemed
surprised. "I don't think so," he said. "After all, only 3.4% meant
4,320 fish, and that's a lot of specimens."