[MARMAM] New Publication: Spatiotemporal patterns of overlap between short-finned pilot whales and pelgaic longlines off of the US East Coast

Julia Stepanuk julia.stepanuk at stonybrook.edu
Fri Sep 7 11:10:10 PDT 2018

Dear MARMAM readers,

We are pleased to announce the recent publication of the following
paper in *Fisheries

Stepanuk, JEF; Read, AJ; Baird, RW; Webster, DL; Thorne, LH (2018)
Spatiotemporal patterns of overlap between short-finned pilot whales and
the U.S. pelagic longline fishery in the Mid-Atlantic Bight: An assessment
to inform the management of fisheries bycatch.* Fisheries Research*, 208,
309-320. https://doi.org/10.1016/j.fishres.2018.07.008.

Abstract: Short-finned pilot whales (Globicephala macrorhynchus) depredate
pelagic longlines along the shelf break of the Mid-Atlantic Bight. The
mortality and serious injury of short-finned pilot whales in the U.S.
pelagic longline fishery recently exceeded Potential Biological Removal
levels defined under the U.S. Marine Mammal Protection Act, and bycatch
mitigation techniques developed to date have been unsuccessful. We examine
the spatial and temporal characteristics of pilot whale habitat use and
longline fishing effort, quantify spatiotemporal patterns of pilot whale
bycatch based on environmental factors, and assess the potential for a
spatial management approach to mitigate pilot whale bycatch. We assess
patterns of overlap and bycatch of pilot whales and longlines by applying
Area Under the Curve and Williamson’s Spatial Overlap Index analyses to
telemetry data from short-finned pilot whales, along with longline fishing
effort and Pelagic Observer Program (POP) fisheries observer data from 2014
and 2015. We found that proximity to the 1000 m isobath, season, and sea
surface temperature (SST) were important variables influencing pilot
whale-longline overlap and POP bycatch rates. Pilot whale density was
consistently highest immediately inshore of the 1000 m isobath, but
longline effort varied seasonally relative to the 1000 m isobath. Resultant
seasonal patterns in pilot whale-longline overlap relative to the 1000 m
isobath were strongly and significantly correlated with POP bycatch rates;
the highest bycatch rates primarily occurred in fall and winter months,
when longline effort shifted inshore near the 1000 m isobath. We observed
differences in the distribution of logbook and POP longline sets relative
to the 1000 m isobath; POP sets were more dispersed relative to this
feature while the overall distribution of longline effort was typically
focused at the 1000 m isobath. Since bycatch primarily occurred close to
the 1000 m isobath, more bycatch might be observed if the observer effort
better reflected the overall distribution of longline effort. In winter
months, POP bycatch occurred in cooler waters than most observations of
tagged pilot whales, and therefore the relationship between bycatch and SST
during winter months requires further exploration. Together, our results
suggest that a spatial management approach could be effective in reducing
pilot whale bycatch in the pelagic longline fishery, and an improved
understanding of the relationships between pilot whale bycatch and dynamic
variables might allow high-risk regions for pilot whale bycatch to be
further delineated.

The paper has 50 days free access at the following link:

*Julia Stepanuk*
PhD Student
M.S. Marine Science
Stony Brook University
Department of Ecology and Evolution
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