[MARMAM] New article: Modeling changes in baleen whale seasonal abundance, timing of migration and environmental variables to explain the sudden rise in entanglements in California

Ellen M Hines ehines at sfsu.edu
Sun Apr 25 13:44:51 PDT 2021

Dear colleagues, we are pleased to present the following open source article.  Thanks to our collaborators at Point Blue Conservation Science and the scientists who climbed to the lighthouse on Southeast Farallon Island every day for sightings since 1993 and through the present.
Modeling changes in baleen whale seasonal abundance, timing of migration, and environmental variables to explain the sudden rise in entanglements in California<https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0248557>
As well as good news from San Francisco:
Endangered humpback whales get extra habitat protection along the West Coast (sfchronicle.com)<https://www.sfchronicle.com/local/environment/article/Endangered-humpback-whales-get-extra-habitat-16115817.php?utm_source=newsletter&utm_medium=email&utm_content=briefing&utm_campaign=sfc_baybriefing_am&sid=53ba8b55a256ab232000006e>
K. Ingman1,2¶, E. Hines2,3¶, P.L.F. Mazzini4&, C. Rockwood1&, N. Nur1¶, J. Jahncke1¶
1 Point Blue Conservation Science, Petaluma, CA, USA
2 Estuary & Ocean Science Center, SFSU, Tiburon, CA, USA
3 Department of Geography & Environment, SFSU, San Francisco, CA, USA
4 Virginia Institute of Marine Science, William & Mary, Gloucester Point, VA, USA
We document changes in the number of sightings and timing of humpback (Megaptera novaeangliae), blue (Balaenoptera musculus), and gray (Eschrichtius robustus) whale migratory phases in the vicinity of the Farallon Islands, California. We hypothesized that changes in the timing of migration off central California were driven by local oceanography, regional upwelling, and basin-scale climate conditions. Using 24 years of daily whale counts collected from Southeast Farallon Island, we developed negative binomial regression models to evaluate trends in local whale sightings over time. We then used linear models to assess trends in the timing of migration, and to identify potential environmental drivers. These drivers included local, regional and basin-scale patterns; the latter included the El Niño Southern Oscillation, the Pacific Decadal Oscillation, and the North Pacific Gyre Oscillation, which influence, wind-driven upwelling, and overall productivity in the California Current System. We then created a forecast model to predict the timing of migration. Humpback whale sightings significantly increased over the study period, but blue and gray whale counts did not, though there was variability across the time series. Date of breeding migration (departure) for all species showed little to no change, whereas date of migration towards feeding areas (arrival) occurred earlier for humpback and blue whales. Timing was significantly influenced by a mix of local oceanography, regional, and basin-scale climate variables. Earlier arrival time without concomitant earlier departure time results in longer periods when blue and humpback whales are at risk of entanglement in the Gulf of the Farallones. We maintain that these changes have increased whale exposure to pot and trap fishery gear off the central California coast during the spring, elevating the risk of entanglements. Humpback entanglement rates were significantly associated with increased counts and early arrival in central California. Actions to decrease the temporal overlap between whales and pot/trap fishing gear, particularly when whales arrive earlier in warm water years, would likely decrease the risk of entanglements.
Please let us know any questions, best Ellen
Ellen Hines, PhD
Associate Director and Professor of Geography & Environment
Estuary & Ocean Science Center
San Francisco State University
3150 Paradise Dr, Tiburon, CA 94920 USA
ehines at sfsu.edu<mailto:ehines at sfsu.edu>
**I formally acknowledge that I reside and work on occupied Tamyen Ohlone and Coastal Miwok land.

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