[MARMAM] New publication: Seasonal differences in cetacean distributions off California

Elizabeth Becker ebecker77 at cox.net
Mon May 15 07:19:53 PDT 2017

Dear Colleagues,


We are pleased to announce the publication of the following paper in
Frontiers in Marine Science:

Becker EA, Forney KA, Thayre BJ, Debich AJ, Campbell GS, Whitaker K, Douglas
AB, Gilles A, Hoopes R and Hildebrand JA.  (2017) Habitat-based density
models for three cetacean species off Southern California illustrate
pronounced seasonal differences. Front. Mar. Sci., 4:121. doi:

Abstract - Managing marine species effectively requires spatially and
temporally explicit knowledge of their density and distribution.
Habitat-based density models, a type of species distribution model (SDM)
that uses habitat covariates to estimate species density and distribution
patterns, are increasingly used for marine management and conservation
because they provide a tool for assessing potential impacts (e.g., from
fishery bycatch, ship strikes, anthropogenic sound) over a variety of
spatial and temporal scales. The abundance and distribution of many pelagic
species exhibit substantial seasonal variability, highlighting the
importance of predicting density specific to the season of interest. This is
particularly true in dynamic regions like the California Current, where
significant seasonal shifts in cetacean distribution have been documented at
coarse scales. Finer scale (10 km) habitat-based density models were
previously developed for many cetacean species occurring in this region, but
most models were limited to summer/fall. The objectives of our study were
two-fold: 1) develop spatially-explicit density estimates for winter/spring
to support management applications, and 2) compare model-predicted density
and distribution patterns to previously developed summer/fall model results
in the context of species ecology. We used a well-established Generalized
Additive Modeling framework to develop cetacean SDMs based on 20 California
Cooperative Oceanic Fisheries Investigations (CalCOFI) shipboard surveys
conducted during winter and spring between 2005 and 2015. Models were fit
for short-beaked common dolphin (Delphinus delphis delphis), Dall's porpoise
(Phocoenoides dalli), and humpback whale (Megaptera novaeangliae). Model
performance was evaluated based on a variety of established metrics,
including the percentage of explained deviance, ratios of observed to
predicted density, and visual inspection of predicted and observed
distributions. Final models were used to produce spatial grids of average
species density and spatially-explicit measures of uncertainty. Results
provide the first fine scale (10 km) density predictions for these species
during the cool seasons and reveal distribution patterns that are markedly
different from summer/fall, thus providing novel insights into species
ecology and quantitative data for the seasonal assessment of potential
anthropogenic impacts. 


The paper can be downloaded from:



or contact me directly at Elizabeth.Becker at noaa.gov
<mailto:Elizabeth.Becker at noaa.gov> 





Elizabeth A. Becker

Contractor, Marine Mammal & Turtle Division

Southwest Fisheries Science Center, NMFS, NOAA

c/o MLML Norte

7544 Sandholdt Rd

Moss Landing, CA 95039 USA

Elizabeth.Becker at noaa.gov <mailto:Elizabeth.Becker at noaa.gov> 



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