[MARMAM] New publication right whale abundance estimates Cape Cod Bay

Laura Ganley laura.ganley at gmail.com
Fri Mar 1 10:54:39 PST 2019

Dear colleagues,

My co-authors and I are pleased to share the recent publication of our
paper in Endangered Species Research:

Ganley LC, Brault S, Mayo CA (2019) What we see is not what there is:
estimating North Atlantic right whale *Eubalaena glacialis* local
abundance. Endang Species Res 38:101-113.

ABSTRACT: Aerial surveys can be used to estimate animal abundance, but
animals unavailable for detection for portions of the survey can cause
biased abundance estimates. Moreover, these biases may be variable owing to
changes in behavior. We conducted focal follows to obtain surface and dive
times of North Atlantic right whales *Eubalaena glacialis* in Cape Cod Bay
(CCB) and measured the aircraft field of view; these metrics were combined
to estimate availability and correct monthly abundance estimates from 1998
to 2017 generated via distance sampling methodology. We used a general
least squares model to test for trends in abundance. Availability varied
with month (0.27-0.85), likely linked to changes in the depth of copepod
food resources. Detection probability varied across the years (0.43-0.87).
Sightings per unit effort and counts of whales were significant, but
downward-biased indicators of abundance and availability caused changes in
bias over the season. Estimated abundance in CCB increased during the study
period (4.9 whales yr-1), and estimated abundance in peak months increased
at a faster rate (10% yr-1 for 1998-2017) than for the overall population
(2.8% yr-1 for 1990-2010). Accurate abundance estimates are necessary to
monitor long-term changes in abundance of right whales in CCB, to
understand the importance of CCB relative to other areas, and improve
management strategies to protect this endangered species from entanglements
in fishing gear and ship-strikes. Failing to correct for seasonal variation
in availability results in substantial and variable underestimation of

A PDF copy of the publication can be downloaded from

Laura Ganley
PhD candidate
University of Massachusetts, Boston
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