The Cutting Edge: Computing / Technology / Innovation : Hatcheries Hail New Study Tool: Identity ‘Tags’ for Fish : Conservation: New technology could help establish whether stocks are interbreeding--and if it matters.


Commercial fish hatcheries in Alaska are using a new technology that will enable them to identify every one of the hundreds of millions of fish they release into the sea each year, and scientists believe the program could have major implications for the industry.

Every salmon released by the privately operated Douglas Island Pink and Chum Hatchery here, for instance, carries a novel biological marker that allows technicians to identify an individual fish years later just as clearly as if it had the hatchery’s logo stamped on it.

The technology, developed almost simultaneously in the states of Washington and Alaska, is expected to help scientists determine if hatchery fish are commingling with wild stocks so much that the genetic pool may be shrinking. Some fear that this could impair the ability of wild fish to survive environmental changes and resist disease.


The development comes at a time of upheaval in the fishing industry. Fish stocks are so low that salmon fishing has been banned in Washington state this year and severely curtailed in Oregon. In Alaska, however, salmon are running in record high numbers--so high, in fact, that the market is glutted and fishermen complain that prices are too low to cover their expenses.

Declining stocks of wild fish have led some depressed areas, especially in Washington and Oregon, to rely more on hatcheries to replace fish stocks wiped out by dams, pollution and overfishing. But that raises the question of whether increasing the percentage of hatchery fish will weaken the species.

“Some people are concerned about the possibility of there being inferior hatchery fish breeding with superior wild fish, and that you could reduce the genetic pool,” said Ladd Macaulay, executive director of Douglas Island Pink and Chum.

“There’s no science behind it,” he said, adding that no one has been able to prove that the gene pool is being weakened. “It’s goofy.”


Others don’t dismiss the idea so easily. The Juneau hatchery’s fish stock originated from eggs collected from just 25 wild salmon, so the entire population of fish produced by the hatchery consists of relatively few families.

One way to reduce the risk of shrinking the gene pool, according to fisheries scientist Robert Burkett of the Alaska Department of Fish and Game, is to restrict hatcheries to areas where the fish are less likely to stray into nearby rivers and reproduce with wild stocks.


“You can’t prevent some of them from straying, but you can site your hatchery in a spot where its zone of influence is not going to carry over into some major producer of wild stock,” he said. But he quickly added that it is impossible to place a hatchery anywhere in Alaska without being relatively close to at least some streams that produce wild stock. Major rivers, however, can be avoided, he said.

Burkett conceded that geneticists have found evidence that some different genes are showing up in the wild population.

“But what does that mean?” he asked. “Is it bad, something neutral, something good? That’s the difficult thing to prove.”

Even Macaulay, who believes there is no evidence that hatcheries are weakening the gene pool, thinks more research is needed. And to do that, scientists need a clearer understanding of what happens to hatchery fish after they are released.

Hatcheries have marked some of their fish for three decades, using coded wire pins that are shot into the snout of the fish before it is released. But that is an expensive process, and it is practical only for larger fish such as the Chinook or coho, known also as kings and silvers. Much of the salmon stock consists of sockeyes, pinks and chums, and these fish are released as fry so small that attaching the coded wire is extremely difficult.


“We’re releasing hundreds of millions of fish each year, and they are fry--just little guys,” said Macaulay, whose hatchery literally started in his back yard many years ago. “How are you going to mark enough to tell you anything? Mechanically, that’s almost impossible.”


Working with biologists at the Juneau Center for Fisheries and Ocean Sciences of the University of Alaska, the hatchery has installed equipment that enables it to mark every fish, no matter how small.

The program grew out of research, begun in Washington, which showed that salmon are affected by even slight changes in water temperature almost as soon as the eggs hatch. The first bone to develop in the fry is the otolith, a small disk in the inner ear, Macaulay said.

Experiments revealed that the otolith forms rings, almost like the rings of a tree, as it grows. Changing the water temperature by a few degrees creates a distinctive ring.

Researchers ran samples of fry through tanks containing water of various temperatures and determined that the changes created marks on the otolith that Macaulay likens to the bar code on a candy wrapper.

“Every single fry had that mark,” he said. “So we knew that for the first time in history, all our fish were marked, and that became pretty exciting to us.”

The new technology is “very significant,” according to Burkett, because it allows hatcheries to mark their entire production, “and that makes things much more simple.”



The code can be tailored to each batch of fish, to record the specific hatchery, the date the fish was released and even the age of the fish at the time of release. By sampling salmon from commercial fishing boats, or in the thousands of rivers and streams in Alaska, fishery managers will be better able to gauge the success of the hatchery and determine how many hatchery fish are straying into wild streams.

The first marked fish began returning to the Juneau hatchery in 1992, and early results have yielded some surprises. Some straying is expected, but records for 1992 and 1993 suggest that the extent of commingling may be influenced by the strength of the overall return.

A higher proportion of hatchery fish strayed into a nearby creek during 1993, when returns were weak, than during 1992, when returns were exceptionally high, Macaulay said.

“That’s strange to us,” he said. “We don’t know what to make of it.”

It will take years of study to determine just how much of an effect--if any--hatcheries are having on wild stocks, but now, at least, managers believe they have the tool to do the job.

It couldn’t come at a better time.

While the Washington and Oregon fishing industries may be facing extinction, catches in Alaska are at record highs.

“There are so many fish that prices are so low that some hatcheries aren’t covering their operating costs, and fishermen aren’t making their boat payments,” said Burkett.


Although the waters of Alaska are rich in salmon now, other years have been exceedingly lean.

“The early ‘70s was such a time,” Burkett said, when about 21 million fish were harvested annually. In those lean years, the state started about two dozen hatcheries since turned over to private operators.