The reason of crab return into Kachemak Bay may be the change is just a consequence of fishing closures letting the crabs bounce back. Or is the crab revival linked to broader long-term cycles of water temperatures in the region, something oceanographers have come to describe as the Pacific Decadal Oscillation? Whatever be the reasons, the mix of species along the northern Gulf of Alaska is starting to look a bit more like the early 1970s, when local crab and shrimp fisheries were big, cod were rare, salmon runs were weaker and winters were clear and cold.
That was the last time the North Pacific was in a cold phase of the PDO, which is a cycle of temperatures and currents that seems to shift every 20 to 30 years. Tom Weingartner, University of Alaska Fairbanks oceanographer, said that the PDO has apparently switched now but it is difficult to say it’s going to stay until some years have passed. Predicting the future lives of crabs and salmon, like predicting future cold snaps, is ridiculously complicated and still beyond the reach of the super-computers.
Gordon Kruse, a fisheries professor at the University of Alaska Fairbanks, informed that one difficulty with detecting a PDO shift is that weather changes come and go, regardless of any decades-long trend. Then there are the short-range annual shifts known as El Nino (warm) and La Nina (cool), which can temporarily push Pacific water temperatures and weather patterns in a new direction.
University of Alaska salmon expert Milo Adkison told that the present position is quite better and that’s not going to last. He also added that if finfish such as salmon, cod, halibut and pollock do less well in the cool-water phase, shelfish tend to thrive. Indeed, surveys are planned that could lead to revival of a non-commercial fishery for Dungeness crab in Kachemak Bay, something that disappeared in 1997.
