Ecosystem Context for Reducing West Coast Whale Entanglements
California Current Project
The number of large whale entanglements confirmed by NOAA Fisheries has increased off the U.S. West Coast in recent years. This alarming pattern has mobilized efforts to understand and address factors that contribute to whale entanglement in fishing gear. In part, the increase was spurred by a unique combination of variables: environmental conditions, distribution of fishing effort, distributions of important whale prey, and public awareness (Figure 1). In response, multiple government agencies, fishermen, and environmental organizations are actively engaged and committed to finding solutions that reduce the number of entanglements while continuing to support economically valuable fisheries.
A goal of Integrated Ecosystem Assessment (IEA) scientists is to provide science support for Ecosystem Based Management. On this page, we compile timely, relevant, spatially explicit information that can help managers, industry, and other stakeholders better understand and mitigate the causes of large whale entanglements in marine waters of the California Current.
Research by NOAA scientists and partners has shed light on conditions that may cause increases in whale entanglements. The Data Dashboard has a suite of customizable plots that describe environmental conditions, whale and prey populations, and fishing activity along the West Coast in recent decades:
Alternatively, access a complete list of the Full Indicator Suite below, with detailed descriptions, maps, and plots with links to downloadable data.
A spatial time series that tracks the area of coastal upwelling habitat, the Habitat Compression Index (HCI) is a regional indicator used to assess the likelihood of ecosystem shifts and shoreward distribution patterns of top marine predators like whales. Smaller values indicate periods when cool habitat is compressed onshore, heightening whale entanglement risk.
|Habitat Compression Index (HCI) - central CA||maps|
A combination of basin and regional scale indicators used to inform the seasonal development and variability of coastal upwelling, particularly in the spring. For example, the winter North Pacific High (NPH) monitors the area and intensity of atmospheric pressure, indicating whether strong upwelling conditions and krill populations are likely in the spring.
|Upwelling Index - CUTI 39N monthly|
|North Pacific High (NPH)|
|Oceanic Nino Index|
NOAA Fisheries prepares stock assessment reports for all marine mammals in U.S. waters; population size estimates are derived from shipboard surveys and mark-recapture methods.
|Humpback whale - abundance|
|Humpback whale - relative abundance, central CA|
|Humpback whale - stock assessment report|
|Gray whale - stock assessment report|
|Blue whale - stock assessment report|
Compiled by NOAA Fisheries West Coast Region.
Prey indices provide information on the abundance of krill and forage fish, key forage species for whales, and provide context for whether predators may concentrate in particular feeding grounds where these species are likely present. Increased coastal abundance of forage species can heighten whale entanglement risk.
|Krill - central CA|
|YOY anchovy - central CA|
|Adult anchovy - central CA|
Fixed Gear Fishery - Landings
On the U.S. West Coast, whales have been documented entangled with gear and debris associated with numerous fishery and non-fishery sources (Saez et al. 2020). The most common source of entanglements is Dungeness crab gear, but other documented sources include pot/trap gear targeting CA spot prawn, sablefish, spiny lobster, coonstripe shrimp, and rock crab, as well as gillnets targeting highly migratory species, salmon, and other fishes.
|Dungeness crab landings (US West Coast)|
|California Dungeness crab landings|
|Oregon Dungeness crab landings|
|Washington Dungeness crab landings|
Jarrod Santora (SWFSC) and Dan Lawson (NOAA WCR)
- Santora, J. A., N. J. Mantua, I. D. Schroeder, J. C. Field, E. L. Hazen, S. J. Bograd, W. J. Sydeman, B. K. Wells, J. Calambokidis, L. Saez, D. Lawson, and K. A. Forney. 2020. 'Habitat compression and ecosystem shifts as potential links between marine heatwave and record whale entanglements', Nature Communications, 11. DOI.10.1038/s41467-019-14215-w
Figure 1: Factors contributing to whale entanglements in fishing gear. (Click for larger version with additional details)
Figure 2: Graphic depicting how seasonal patterns of climate / ocean conditions, ecological processes, and human activities interact to enhance risk of whale entanglement. (Click for larger version)
More Information: Key Resources
- NOAA Fisheries has a West Coast Large Whale Entanglement Response Program, and produces an annual report on confirmed whale entanglements in West Coast fishing gear. Additional resources provided by state resource management agencies and regional partnerships include:
- PSMFC - Working To Prevent Whale Entanglement
- California Ocean Protection Council - West Coast Entanglement Science Workshop
- Washington - WDFW Coastal Commercial Crab Fishery Letters and Notices
- Oregon - ODFW Reducing Risk of Whale Entanglements
- California - CDFW Whale-Safe Fisheries
- California - Dungeness Crab Fishing Gear Working Group