Thursday, April 24, 2014
By PAUL KOENIG Kennebec Journal
(Continued from page 1)
Atlantic salmon eggs are ready to be planted by Maine Department of Marine Resources biologists Jan. 15 in the Sheepscot River in Palermo.
Photos by Andy Molloy/Kennebec Journal
Maine Department of Marine Resources biologist Jason Overlock, right, drills a nest, or redd, as Jason Bartlett, center, places a funnel for Paul Christman, left, to insert Atlantic salmon eggs into last week in the bed of the Sheepscot River in Palermo.
The marine resources department, in cooperation with the National Oceanic and Atmospheric Administration Fisheries Service, supplements the wild Atlantic salmon population with different stages of the fish in order to maintain genetic diversity.
The department is in its second year of a five-year NOAA grant, which funds the Atlantic salmon restoration efforts, said Oliver Cox, director of the Sea-Run Fisheries and Habitat Division at the marine resources department.
It received $700,000 this year, a 40 percent reduction from the first year; and the department anticipates similar funding next year, Cox said.
Besides the egg planting, the state biologists release salmon as fry, its first stage after emerging from the egg sac and gravel; parr, the stage living in the river for around two years; and smolt, which are ready to leave for the ocean.
Each year, they stock around 3.5 million fry, 250,000 parr and 650,000 smolt, according to Cox. The advantage of eggs, Christman said, is that the salmon will learn more essential traits -- such as avoiding predators -- that they don't acquire when growing up in the hatchery.
"We put them in as eggs; they're on their own. They've got to emerge," he said. "They've got to fend for themselves, and what we're finding is they're much stronger."
Cox said the trade-off with planting eggs instead of releasing grown fish is that fewer fry will emerge from eggs in the wild compared to in the hatchery.
He said that if they planted 700,000 eggs, around 200,000 fry might emerge. But closer to 90 percent of eggs in a hatchery will yield surviving fry.
Christman said there's very little data on wild spawning and production. But preliminary results of hydraulic planting show that it produces a similar population to what would have survived from eggs brought in by female salmon.
"Once they begin stream life, their survival is much better than stream stocking," he said. "That's what's encouraging, even though we lose some right off."
The Atlantic salmon program's main focus is protecting the genetic diversity of the species to counteract the environment's selective pressure, said Christman. Without the diversity, a drastic change in the environment could be "catastrophic" to the Atlantic salmon population, he said.
"We're in the phase of trying to prevent extinction, if you will," Cox said.
A much larger restoration effort would be needed to begin growing the population to larger than just what is needed for the hatcheries, Cox said.
Maine had a banner year in 2011 for the number of adult Atlantic salmon returning to the rivers to spawn: more than 3,000 fish.
But last year only around 700 salmon -- 624 in the Penobscot River -- returned from sea. The Penobscot River makes up nearly the entire population of returning salmon because it is one of the only waterways stocked with smolt -- those about to leave for the ocean.
Cox said there was no change in supplementation numbers in the previous years, so the difference was in the salmon surviving while at sea.
The cause isn't clear, but he said theories about why the survival rate dropped so significantly range from changes in currents or ocean temperature to prey availability or changes in predator fields.
There isn't much the state can do to fix the low marine survival rate besides trying to grow the river herring numbers to provide alternatives for predators, Cox said.
"We can put a lot of fish in the river, but we can't stock enough to overcome the poor marine survival," he said.
Christman is optimistic that hydraulic planting could replace fry stocking by generating fish more prepared to face the dangers of migrating to the ocean and back.
They won't know until 2017 whether the salmon produced by the eggs planted this year will create the stronger fish Christman is hoping for. Even then, it may be difficult to know whether other variables affected the number of spawners.
During the Palermo outing Tuesday, the biologists planted about 35,000 salmon eggs in their man-made redds in the Sheepscot River. Christman expects to plant about 1 million eggs by the end of the season.
"This a drop in the bucket," Christman said, as he sorted thousands of salmon eggs into beverage coolers from plastic foam trays stationed in the bed of the department's pickup truck. "This is really, really small-time."
Kennebec Journal Staff Writer Paul Koenig can be contacted at 621-5663 or at: