By Jenny Neyman
For such mysterious creatures, encased in shells and living buried in the sand, biologists actually have quite a bit of data about razor clams in Cook Inlet.
“The department has been estimating harvest and effort on these beaches since the 1970s and estimating the clams per digger since then, as well,” said Carol Kerkvliet, Alaska Department of Fish and Game assistant area management biologist for the Division of Sport Fish, based in Homer.
Biologists monitor the harvest of razor clams, a popular summer subsistence activity along Cook Inlet’s eastern shore, as well as the effort, measured in days harvesting, put in by clam diggers. They track the size and age of clams. And at the most popular clamming beaches, especially at Ninilchik, they conduct periodic estimates of abundance.
So they know that razors on east-side beaches are struggling, leading to a decision to enact harvest restrictions this year to give the clam population a chance to dig itself out of its population slump.
On Feb. 24, the department issued an emergency order closing east-side beaches to clamming, from the mouth of the Kenai River to the tip of the Homer Spit, effective from March 1 through the end of 2015. Clamming on the west side of Cook Inlet, however, remains open.
Kerkvliet said that two factors contributed to the decision to close the east-side harvest of razors — fewer age classes of clams on the beach, smaller clams, and a higher mortality of the clams that are present.
“What we’re seeing on the beaches right now is a low number of razor clams recruiting to the beaches. (And) once they recruit to the beaches and grow to mature size that they’re just not as long,” she said.
The emergency order notes some discouraging trends. The population of razors at Clam Gulch was found to be 89 percent lower than average. And at Ninilchik South, the most popular clamming beach on the eastern shore, the population was down 82 percent. The number of juvenile clams was also down at both locations, 36 percent below average at Ninilchik South, and 86 percent below average at Clam Gulch. This trend toward smaller, younger clams has been seen at most east-side Cook Inlet beaches, Kerkvliet said.
The decline has worsened over the decades. The peak razor clamming year was 1994, when Fish and Game estimated the harvest at 1.3 million clams collected in 48,000 digger days. By 2013, the harvest was down to 174,000 clams in 24,000 digger days.
And state harvest surveys show that the average number of clams harvested by each digger shrunk from 25 early in the 1990s to seven in 2013. And that’s not because of restrictions, either. The bag limit for razors has been 60 most years, until 2013 when it was lowered to 25.
That leads biologists to think something environmental is inhibiting more razors from arriving and thriving on east-side beaches, rather than a problem of overharvest. A healthy clam population is one with both high abundance and high variety of age classes of clams, so the population continues to replenish itself.
Razors are broadcast spawners, sexually mature by age 3 or 4, with eggs and sperm released into the water around about July. Fertilized larvae are transported by ocean currents for four to six weeks, then form a small shell and settle into a sandy tidal beach, potentially far away from their parents, and are ready to harvest in about four years.
But this doesn’t seem to be happening, as east-side beaches seem to be populated by mostly just one age class of razor clams the last several years.
This pattern became clear following a massive winter storm in November 2010 that uprooted and killed thousands of razor clams at Ninilchik. Biologists did an estimate of abundance in 2011 to gauge the impact of the storm, and were surprised to find the highest abundance of razor clams they’d yet recorded at the Ninilchik South Beach — 1.6 million.
That was the good news. The bad was that the vast majority of those clams were all age 3.
“So that was a red flag to us, when you see a population composed of one age class, how long is that population going to support that fishery?” Kerkvliet said.
They’ve gone back each year since to track that population and haven’t yet seen positive change.
“We haven’t seen sufficient numbers of younger-size clams appearing on beach, and have observed unnatural mortality of this one brood that has supported the fishery,” Kerkvliet said.
Clams tend to have high mortality rates — one reason why they’re such prolific spawners, with females able to release an estimated 5 to 15 million eggs — and populations can naturally fluctuate. Kerkvliet said it will take more study to figure out what might be causing the current east-side population slump, and more time to determine how long it might take for the razors to rebound.
“We’ll be looking at small-size clams, how many clams are recruiting to the beach, what is the natural mortality of the mature-size clams. We’re looking at that now, and we’re looking at the estimates of juvenile-sized clams and from our past surveys and we’ll continue to track the abundance on these beaches, but it looks to be a few years down the road,” she said.