3] Who Ate All The Fish? Just About Everybody It Seems
The tens of thousand of missing chinook from this year's upriver Columbia run may still be swimming somewhere off the mouth of the river, but may be in another form, having possibly been eaten as smolts by hordes of hake that have reappeared offshore in huge numbers.
The hake, also known as Pacific whiting for marketing purposes, travel in large schools and usually spawn off the California coast. But they have returned to Northwest waters, which have warmed considerably in the past two years.
Last summer, Canadian researchers found waters off Vancouver Island were even warmer than during the 1997 El Niño. In a recent paper, Frank Whitney, a research scientist with Fisheries and Oceans Canada's Institute of Ocean Sciences, reported that last summer the waters west of Vancouver Island were the warmest in the past 45 years. And though oceanographic data pointed to weak El Niño conditions for the past two years, beachcombers in southern B.C. were finding things usually associated with strong El Niño events, like a species of large squid that is normally seen off San Diego, some over four feet long.
But predation by hake doesn't explain all the mysteries, especially the disconnect between the high jack counts in both 2003 and 2004 and the much smaller-than-expected adult returns. The puzzle points to a combination of high juvenile predation on salmon, coupled with some other type of mortality once the fish reached the high seas.
University of Washington researcher Kate Myers told NW Fishletter that last year's joint cruises with Japanese researchers in the deep ocean showed high salmon abundance, mostly pinks and chums, with a lot of them headed for Asia, without any evidence of extreme mortality to any stocks. Chinook stocks were found to be more abundant in the Central North Pacific than during the years since 1991, with about three-fourths of them showing evidence of two years in the ocean. However, they were a bit smaller than chinook examined in 2003.
Myers and her colleagues reported that chum stocks in 2004 in the central North Pacific have been above the 14-year average since 2001. Sockeye numbers were below average last year, while coho and steelhead abundances were about average.
They also recovered a coded-wire tagged chinook from Idaho south of the Aleutians last August. It's only the fifth chinook from the Spud state to be identified since 1956. All five have been recovered in the northern part of the Gulf of Alaska, one near the western end of the Aleutians at about the 180th meridian, nearly 3,000 miles from its spawning grounds.
Myers said it seemed unlikely that the Columbia River salmon found conditions too poor to stay alive. Rather, they may have succumbed to some large predators, likely marine mammals, possibly fur seals whose winter migration routes can be far out at sea.
It has been reported that a spring chinook stock in Southeast Alaska's Stikine River that is genetically related to Snake River spring chinook is also showing much less than expected returns this year. Some scientists think that the genetic similarities of the fish may mean they spend their ocean lives in the same area, which is still unknown to biologists. However, if both stocks are returning at levels far below pre-season estimates, it could signal a common mortality element in their life-cycle.
Alaska biologists expected 80,000 chinook to return to the Stikine, which enters salt water near Wrangell, and have even opened a small commercial gillnet fishery on the run for the first time in years. Only about one-third of their expected 27,000-fish harvest has been caught so far.
But nearer to home, conditions for salmon have deteriorated the past couple years. Biologists from the NOAA Fisheries research facility in Newport, Ore., report that plankton levels have declined significantly. During the near-ocean's cool water phase after the 1997 El Niño event, plankton levels doubled off the West Coast. Since 1999, this huge increase in primary biological productivity helped boost salmon productivity of Northwest stocks to their highest levels in many years.
But now the warm currents are back, much as they were through most of the 1990s when a seemingly endless series of El Niño events brought mackerel, hake and other predators to waters off the Northwest Coast where they had decimated both hatchery and wild stocks in Washington, Oregon and British Columbia since 1993.
In recent years, large schools of anchovies have also reappeared off the coast, which has led some scientists to hypothesize that juvenile salmon may get a survival break from seabirds when these other species show up, who make use of an expanded menu.
But the hake, aka whiting, have experienced severe ups and downs as well, which seems to be a trait of species with high productivity and a short lifespan. In 1987, the hake biomass was at a historical high, according to the final 2005 harvest rule published in the Federal Register. Stock size moderated in the mid-1990s and declined to its lowest level in 2001, when it was actually declared an overfished species by NMFS. But that assessment was low and the whiting population has jumped so fast that the feds have recommended a total catch this year of nearly 270,000 metric tons. It would likely be even higher except for constraints on the bycatch of other groundfish species like rockfish, which have been severely overharvested.
Jack counts this year have been pretty dismal, only about half of last year's numbers and less than 20 percent of the number that signaled the monster returns in 2001.
As one NMFS scientist pointed out, hake numbers were low back then, with plenty of cold water upwelling to produce nutrients for building plankton diets for migrating salmon. A decent upwelling condition only began off the coast last week, he said, and the millions of young salmon are facing a horde of hake. He said a 400-mm long hake is capable of eating a 200-mm salmon smolt.
It was reported that NMFS scientists are preparing a memo that looks at potential causes for the mysterious fish declines, after earlier comments by NMFS regional administrator Bob Lohn suggested that high-seas fishing might be responsible. But there is little evidence of that occurring, either by foreign ships or the Alaska trawl fleet, which catches few chinook -- 30,000 or less a year -- and most of them are local Alaska stocks. Columbia Basin springers don't appear in the Southeast Alaska troll fishery either, which leads biologists to believe that the stock stays well offshore during most of its life in the ocean.
The trickle of adult springers passing Bonneville Dam, still 1,000 fish a day or better, is normal for this time of year, but the total number is only about one-third of the 250,000 fish expected by harvest managers. Their latest inseason update has pegged the upriver run at about 82,000 fish. So far, less than 74,000 have been counted at the dam. Managers opened the sport steelhead and sport and commercial shad fisheries, expecting little adverse impact on the remainder of the returning chinook run, which was estimated about 80 percent over and done with by the middle of May. - B. R.
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