In deriving this estimate, they “assumed that the number of carcasses drifting out of the study area equaled the number drifting in” (Dean et al., 2000, p. 284). This assumption is unlikely to be true because prevailing Selleck INK 128 currents flowed into this area from the origin of the spill (Fig. 1). Moreover, shortly after the spill, PWS was struck by a large storm with northerly winds that pushed the floating oil southward, explaining
why the north-facing shorelines were most heavily oiled (Galt and Payton, 1990). As otters died in the path of the spill, they either drifted out to sea and eventually sank or washed up on beaches. Oil landed disproportionately at NKI (Fig. 1), so it follows that dead and moribund otters drifted on a similar course (Hill et al., 1990). With these currents selleck chemical and wind conditions, the number of sea otter carcasses collected at NKI could have been substantially higher than the number living there at the time of the spill. Counts made at NKI in 1984, just 5 years before the spill, provide a better indication of the number of otters living there at the time of the spill. Irons et al. (1988) counted 2.5 times more otters than did Pitcher for the whole of PWS, but saw only 58 otters at NKI, suggesting that the NKI population had declined since the early 1970s and that both of the Dean et al. (2000) pre-spill estimates were too high. Herring Bay on NKI (Fig. 1) captured large
amounts of oil, and thus attracted disproportionate cleaning efforts and later research work. At the height of the spill response, nearly 1000 people worked in this bay (Hooten and Highsmith, 1996). Anecdotal reports indicate that clean-up boats herded oil, floating debris, and some wildlife carcasses into this area in order to contain them. Some scientists have drawn particular attention to the 38 sea otter carcasses known or estimated to have come from Herring Bay (Rice et al., 2007), suggesting this as a minimum baseline number of otters present in that bay at the time of the spill. This value, though, is more than five times higher than the seven otters that Irons
et al. (1988) counted in this bay during the summer of only 1984. Either otter numbers in Herring Bay had increased dramatically between 1984 and 1989 or, more likely, the number of carcasses found in this bay in the months following the spill represented an accumulation of individuals that died in the expanse of water to the north. Depending on which pre-spill values are used, otter numbers in Herring Bay and other parts of NKI could have been above the pre-spill baseline as early as 1991, or could have been below baseline for two decades post-spill (Table 1 and Fig. 3b). Trends in otter abundance in the NKI area have also been subject to debate. Counts of otters sharply declined across a broad region of WPWS, including unoiled Montague Island, from 2001 to 2002 (Fig. 3a; Bodkin et al., 2011).
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