The Copper River dip net fishery is re-opening after being shut down for more than a month. A dismal early wild sockeye return, which threatened escapement goals, is rebounding, according to Glennallen area state biologist Mark Somerville.
”We’re monitoring hatchery component and overall escapement here to see if we can keep the fishery open,” Somerville said. “And obviously it looks like right now we can. We’ve opened up the personal use fishery for an 84-hour period here starting Thursday at noon through Sunday.”
Somerville says sport fishing is also re-opening with a Friday start date. With ensuring escapement in mind, he says managers are working to determine the number of hatchery versus wild sockeye stocks moving upriver.
”Trying to figure out whether or not we’re gonna reach that wildstock escapement goal,” Somerville said. “It’s not like the different fish come up in colors or anything like that. They all look the same.”
Somerville says historic return timing, and genetic analysis help biologists sort the returning stocks, noting that hatchery fish are internally marked.
”The hatchery operator puts their outgoing fry into a strontium bath for about 24 hours. Strontium is a salt, and they incorporate that strontium into the bone structure of their otoliths, which we refer to as ear bones, but it’s a bone we look at for aging,” Somerville said. “And then, when those fish return, those otoliths are taken out. They’re sectioned, they’re polished, they’re coated, and then the department sends them to the University of Alaska Fairbanks to look at them under an electron microscope. And when they use a fluorescent light, the strontium actually shows a green band. And so we can tell if that fish came from the hatchery, or is a natural fish.”
Somerville says biologists are also trying to understand why the early part of this season’s run was so weak. He says it may be due to poor ocean survival, but could also reflect its 2013 parent stock, which was heavily harvested in the commercial fishery during the early part of that year’s run.
”We tended to pass early fish at a lower level than we did the later fish, and we could be seeing the result of that as well this year,” Somerville said.
For dip-netters planning to fish this week’s dip net opening, Somerville notes that the Copper River has been running high and fast, conditions that slow fish movement upriver, and make boating and dip netting challenging. Somerville says cloudy cooler weather the early part of this week should ease the situation.
Dan Bross is a reporter at KUAC in Fairbanks.
