Browsing by Author "Findlay, Ken"

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    Abundance of blue whales off Chile from the 1997/98 SOWER survey
    (2007) Branch, Trevor A; Zerbini, Alexandre N; Findlay, Ken
    The 1997/98 SOWER survey in Chile searched the region from 18°30′S to 38°S. Although the primary intention of the surveys was to maximize blue whale encounters, survey coverage was sufficient to estimate abundance using line transect methods. The baseline abundance estimate, excluding transit legs, was 452 (CV = 0.56, 95% CI: 160–1300). This abundance estimate is negatively biased because inshore regions including Chiloé Island and the Gulf of Corcovado, where blue whales are now known to aggregate, were outside the survey area. If it is conservatively assumed that the baseline estimate applied to the entire population, then the population was at a minimum of 7–23% of pre-exploitation levels in 1997.
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    Updated application of a photo-identification based assessment model to southern right whales in South African waters, focussing on inferences to be drawn from a series of appreciably lower counts of calving females over 2015 to 2017
    (2018) Brandão, Anabela; Vermeulen, Els; Ross-Gillespie, Andrea; Findlay, Ken; Butterworth, Doug S
    This paper extends the analyses of Brandão et al. (2013) which applied the three-mature-stages (receptive, calving and resting) model of Cooke et al. (2003) to photo-identification data available from 1979 to 2012 for southern right whales in South African waters, by taking five further years of data into account. The lower counts of calving females over 2015 to 2017 are indicated to be a reflection of time variability in the probability that a resting whale rests another year, rather than of any mass mortality. The 2017 number of parous females is estimated to be 1 765, the total population (including males and calves) 6 116, and the annual population growth rate 6.5%. This reflects a small decrease to the 6.6% increase rate estimated previously; even in the instance of lesser numbers seen in recent years than estimated previously. Information from resightings of grey blazed calves as adults with calves allows estimation of first year survival rate of 0.852, a slight increase from the previous estimate of 0.850, compared to a subsequent annual rate of 0.988.