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Population abundance and trend estimates for beaked whales and sperm whales in the California Current from ship-based visual line-transect survey data, 1991-2014
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    For several species -- fin whale, sperm whale, and beaked whales -- Bayesian trend models were previously fit to data from six visual line-transect surveys conducted in the California Current between 1991 -- 2008. In 2014, the NOAA Southwest Fisheries Science Center conducted another, seventh, comparable line-transect survey: the California Current Cetacean and Ecosystem Assessment Survey (CalCurCEAS). Updated trend estimates incorporating the new survey data have been published for fin whales but not yet for beaked whales or sperm whales. Here, new trend model estimates (of population trend and abundance) are presented for beaked whales and sperm whales. There is little evidence of trends in overall sperm whale abundance, but the new analysis supports prior evidence for an increasing number of sperm whales that occur in small groups (presumed to be adult or near-adult males). Cuvier's beaked whales appear to have decreased in abundance from high values in 1991-93, but that decline now appears to have leveled off. There is some weak evidence of an increasing trend in Baird's beaked whales. Mesoplodon beaked whales showed markedly higher abundance in 2014, reversing a declining trend from 1991-2008 that had been noted in a previous analysis. The increase may have be driven by an influx of tropical species of Mesoplodon during the unusually warm ocean conditions in 2014. [doi:10.7289/V5/TM-SWFSC-585(]
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