IS CLIMATE CHANGE CONTRIBUTING TO RANGE REDUCTIONS AND LOCALIZED EXTINCTIONS IN NORTHERN (HALIOTIS KAMTSCHATKANA) AND FLAT (HALIOTIS WALALLENSIS) ABALONES?

摘要

Abalone abundance surveys from the 1970s were repeated 30 yrs later following a period of increased sea surface temperatures along the Pacific coast of the United States. Northern abalone, Haliotis kamtschatkana (Jonas, 1845) once abundant enough to support commercial fishing in Washington and Canada, are now extremely rare in the southern portion of their range in southern and central California. They have also declined 10 fold in northern California in the absence of human fishing pressure. In Washington, northern abalone are in decline and exhibit recruitment failure despite closure of the fishery. Flat abalone, Haliotis walallensis (Stearns, 1899) no longer occur in southern California, and in central California have declined from 32% to 8% of the total number of abalones, Haliotis spp., inside a marine reserve. The distribution of flat abalone appears to have contracted over time such that they are now only common in southern Oregon where they are subject to a new commercial fishery. Given these range reductions, the long-term persistence of flat abalone and northern abalone (locally) is a concern in light of threats from ocean warming, sea otter predation, and the flat abalone fishery in Oregon. The likelihood of future ocean warming poses challenges for abalone restoration, suggesting that improved monitoring and protection will be critical, especially in the northern portions of their distributions.