Figure 1.
Example species of beaked whales occurring in the California Current Large Marine Ecosystem.
(a) group of Baird's beaked whales, Berardius bairdii; (b) Cuvier's beaked whale, Ziphius cavirostris, the most abundant species in our study system; (c) Blainville's beaked whale, Mesoplodon densirostris, a warmer-water species rare in our study area (Photo credits – a: Bob Pitman, SWFSC; b and c: Bahamas Marine Mammal Research Organisation).
Figure 2.
Map of study area, survey effort, and beaked whale sightings.
Study area (A≈1.142×106 km2) demarcated by extent of on-effort transect lines, US EEZ boundary (dotted line), and sighting locations of Cuvier's beaked whale (Z. cavirostris), Baird's beaked whale (B. bairdii), and Mesoplodon spp., from 1991–2008 (from US Marine Mammal Stock assessments [16]).
Table 1.
Survey data summary.
Table 2.
Estimates of trackline detection probability, g(0).
Figure 3.
Summary of beaked whale detection distances and detection function.
Histograms of beaked whale group detection distances and mean probability density curve, f(y), of the observations, based on coefficient estimates in (Table 3). Plots are shown for observations in calm (Beaufort 1–2) and rough (Beaufort 3+) sea state conditions, and for small (1 or 2 individuals) and larger (3+ individuals) groups.
Figure 4.
Detection probability through time.
Average detection probability of Cuvier's beaked whale and Mesoplodon groups occurring within the truncation distance (4 km) of the research vessel. Plotted values are the medians and 95% CRI of the Bayesian posterior distributions.
Table 3.
Posterior distribution summaries for coefficients of the covariate-dependent detection function (see equation 4 in text).
Figure 5.
Abundance and trend estimates for beaked whales in the California Current, 1991–2008.
Z. cavirostris and Mesoplodon spp. estimates are pro-rated to include a proportion of the abundance estimated for the “unidentified ziphiid” group. For each year, the Bayesian posterior median (•), mean (X) and mode (*) abundance estimates are shown, along with 90% CRIs. Trend lines depict median and 90% CRI estimates of fitted abundance without process error (e.g., equation 1, with γt = 0). Gray points for median estimates in 1991 and 1993 denote that the total abundance estimate for the study area reflects extrapolated density estimates to the Oregon-Washington survey stratum.
Figure 6.
Historical beaked whale stranding records.
Number of unique stranding events reported along the west coasts of U.S. and Canada, 1900–2009, for the four most common beaked whale species in the region. Apart from the first data bin (1900–1969), data are binned by decade (e.g., 1970–1979, …, 2000–2009). Data were from two sources: regional stranding networks (black) and museum collections (gray) (Table S1); there is some data redundancy between these two source types. Bottom panel for each species, “Total CA Current”, is the sum of records from OR-WA and CA.