Dear MARMAM community,
We are pleased to announce the publication of a new study that focuses
on a key prey item for cetaceans in the California Current System... krill!
Derville, S., Fisher, J. L., Kaplan, R. L., Bernard, K. S., Phillips, E.
M., & Torres, L. G. (2024). A predictive krill distribution model for
/Euphausia pacifica/ and /Thysanoessa spinifera/ using scaled acoustic
backscatter in the Northern California Current. /Progress in
Oceanography/, 103388, https://doi.org/10.1016/j.pocean.2024.103388
<https://doi.org/10.1016/j.pocean.2024.103388>
*Abstract: *Euphausiids (krill) are globally significant zooplankton
prey for many commercially important or endangered predator species. In
the productive upwelling system of the Northern California Current
(NCC), two krill species, /Euphausia pacifica/ and /Thysanoessa
spinifera,/ dominate the preyscape and constitute an important food
resource for many seabirds, cetaceans, and fish. In this study, we use
five years of hydroacoustic and net tow data collected in the NCC to
develop integrative models predicting acoustic backscatter scaled for
/E. pacifica/ or /T. spinifera/ separately. Boosted Regression Trees and
Generalized Additive Models are applied in an original ensemble hurdle
framework to predict krill presence and abundance from a diverse set of
topographic and oceanographic predictors. Krill metrics had significant
relationships with seabed depth, distance to submarine canyons, and
variables indicative of dynamic ocean conditions (e.g., total deviance
explained in acoustic data: 25 % in the presence-absence model & 49 % in
the abundance model). Predictions of krill abundance at 5 km resolution
averaged by month indicate differential habitat preferences between the
two species: /T. spinifera/ was constrained to the continental shelf,
around and inshore of the 200 m isobath, whereas /E. pacifica/ was found
in greater abundances just offshore of the 200 m isobath and into
offshore water in lower abundances. /E. pacifica/ was generally more
abundant than /T. spinifera/ (10:1.3 ratio). Both species increased in
abundance in the spring and summer, followed by a rapid decline in the
fall, and lowest abundances in the winter. These models can produce
fine-scale spatial and year-round weekly predictions of /E. pacifica/
and /T. spinifera/ abundance in the NCC, which will provide essential
knowledge and new spatial layers about critical ecosystem components to
support research and management.
Note that predicted weekly krill layers are freely available at
https://figshare.com/projects/OPAL_Overlap_Predictions_About_Large_whales/161137
The article is available online in open access but please feel free to
get in touch for any further information (solene.dervi...@ird.fr
<mailto:solene.dervi...@oregonstate.edu>).
Best,
--
*Dr Solène Derville * *Chargée de recherche - Ecologie marine *
*Research scientist - Marine ecology * UMR ENTROPIE - Institut de
Recherche pour le Développement ENTROPIE Lab - French National Research
Institute for Sustainable Development 101 promenade Roger Laroque, BPA5
98848 Nouméa, Nouvelle-Calédonie Tel +687 50.12.45 >> Researchgate
<https://www.researchgate.net/profile/Solene-Derville-2>
****
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