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
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.derville@ird.fr).
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