Abstract
Large whale interaction and entanglement with gear in the ocean poses a major threat to animals worldwide. Entanglement can cause mortality, minor to significant injuries that may compromise the health of the individual animal which may impact their ability to feed or reproduce. There are also economic impacts associated with large whale entanglements. Commercial and recreational fishing industries may incur expenses due to lost gear or potential gear modifications, and increased regulations to reduce future whale entanglements. A significant investment is also needed when a response is undertaken to remove gear from an animal or to remove gear from the water.
Reports from California, Oregon, and Washington were standardized and combined to form a single database. This standard database was then analyzed for spatial and temporal trends in whale species, fishing gear types and associated fisheries, known outcomes of whale entanglements, and entanglement response.
Off the coast of California, Oregon, and Washington, there were 511 whale entanglements reported and 429 confirmed entanglements between January 1, 1982 and December 31, 2017. Whale entanglement reports were confirmed using criteria that include reviewing photos or videos or through direct observation by the National Oceanic and Atmospheric (NOAA) staff or another expert. Data analyses document a recent spike in entanglements, jumping from an annual average of 8 confirmed entangled large whales between 1982 and 2013, to an average of 41 confirmed entangled large whale reports between 2014 and 2017. Multiple factors may contribute to this increase in the number of reported entanglements, including, but not limited to, an increase in public awareness and reporting, changes in the spatial distribution and abundance of whales, fishing effort, and ocean conditions.
Whale species
Gray whales (Eschrichtius robustus) and humpback whales (Megaptera novaeangliae) were the most frequently reported species, with 208 and 165 confirmed entangled whales respectively, between 1982 and 2017. Blue whales (Balaenoptera musculus), fin whales (Balaenoptera physalus), minke whales (Balaenoptera acutorostrata), killer whales (Orcinus orca), and sperm whales (Physeter macrocephalus) have also been reported as entangled in gear.
Whale entanglement report location and timing
Whale entanglements were documented across the entire area off the U.S. West Coast, with additional entanglements reported from bordering countries of Canada and Mexico, of animal’s gear originating from the U.S. West Coast. The majority of confirmed whale entanglements were reported from California (85%), with 7% from Washington, and 6% from Oregon, and 1% from Mexico and Canada. However, these percentages do not always reflect the geographic area where this gear originated. Entanglement reports have been received in every month of the year, with highest numbers of entanglements in March and April. These months correspond with the northern migration of gray whales along the U.S. West Coast, as well as early presence of feeding humpback whales.
Gear types associated with whale entanglement reports
Gear types were coded into general gear types: net, pot/trap, hook and line, other, and unknown. “Net” is the general category describing an entanglement where any type of netting, used for fishing is identified, including gillnet and the California swordfish/thresher shark drift gillnet. “Hook and line” is the general category describing an entanglement where the fishery identified uses hook and line to target fish. “Pot/trap” is the general category describing any entanglement where the identified fishery utilizes a trap or pot to target fish or invertebrates. “Other” is the general category describing an entanglement where the gear type identified is not hook and line, netting, or trap/pot. “Unknown” is the general category for an entanglement report where entangling gear material is unidentifiable to a specific source. Confirmed entanglements were most often attributed to gear that could not be identified (43%), with netting (34%) and pot/traps (22%) accounting for the remainder of the entangled whale reports. Since 2000, the proportion of whales entangled in pot/trap gear has increased, whereas net entanglements have decreased in prevalence. NMFS was able to identify and confirm the specific fishery or gear in 57% of confirmed entanglement reports. Gillnet had the highest number of entanglements, 87, with commercial Dungeness crab pot fishery as second with 73. Other pot/trap fisheries confirmed to be involved with large whale entanglements are commercial spot prawn, commercial sablefish, commercial lobster, recreational Dungeness crab and commercial rock crab. When the gear set location associated with the whale entanglement is known.
Relating entanglement report location to known entanglement (gear set) location
There were 94 records where gear set region was known. Of those 94 records, there were 74 records where the gear set region (and presumably the location of the entanglement) was the same as the region where the whale entanglement was reported, while the remaining 20 had a different gear set region. This suggests that a relationship exists between the patterns of entanglement reporting and the origins of entanglements, at least at a regional level, specifically in those areas where entanglements are commonly reported, such as central California. Whales were also documented carrying gear from the United States (U.S.) for thousands of miles into Mexico and Canada.
Entanglement Response
Trained entanglement responders initiated a response for 39% of the entangled live whales that were reported. Many responses ended with either full (28%) or partial (19%) removal of gear. Of the 243 reports where entangling gear or fishery was confirmed, commercial Dungeness crab gear was associated with entanglements that had the highest number of releases (full, partial, and self-releases), representing a 49% success rate for responses to entanglements with this gear type. The documentation collected during entanglement response is invaluable in gaining an understanding of entanglements towards preventative solutions.
Conclusion/Looking forward
The outcomes of this report should serve as a guide to improve the understanding of the potential for interactions between commercial and recreational fisheries and large whales along California, Oregon, and Washington, recognizing that there are still many challenges in understanding the risk of whale entanglements and identifying gear. Based on the 35 years of whale entanglement data analyzed in this review, future work is recommended in the following areas:
- Improve reporting to NMFS: increasing public awareness and understanding of the need for early and accurate reporting, expanding geographic reporting party coverage, support large whale entanglement response network to gain better documentation (e.g., photo identification, gear identification, injuries) and quality of information collected from each entanglement report;
- Improve understanding of the ecological drivers affecting the distribution of whales and their risks of interaction with U.S. West Coast gear, and develop tools to assist with predicting distributions based on those drivers;
- Improve understanding of the dynamics of the West Coast fixed gear fisheries, and develop tools to assist with monitoring/predicting those distributions;
- Enhance understanding of how behavior of whales and different gear configurations may interact to increase/decrease chances of entanglements occurring;
- Continue gear research and development of innovative ideas in collaboration with fishermen to reduce the number and/or severity of future entanglements, specifically for the U.S. West Coast; and
- Continue and expand fishery gear marking initiatives based on evaluations of whale entanglement report data and success/failure of current marking schemes to identify the origins of entanglements.