The perils of relying on handling techniques to reduce bycatch in a partially observed fishery: a potential fatal flaw in the False Killer Whale Take Reduction Plan
Fisheries bycatch is one of the greatest threats facing many cetacean species (Read et al. 2006), and most of what we know of bycatch levels comes from observer programs in the fisheries themselves. In Hawai‘i the only fisheries with observer programs are two longline fisheries, a deep-set fishery targeting bigeye tuna (Thunnus obesus), and a shallow-set fishery targeting swordfish (Xiphias gladius), with some boats switching fishing methods during the year. The observer program in these fisheries was originally implemented to assess bycatch of protected species (Brooke 2015), with the shallow-set fishery having 100% observer coverage, and the deep-set fishery having approximately 20% observer coverage. There were 145 longline vessels in 2017, with most in the deep-set fishery, and some switching between shallow-set and deep-set within the year. While the majority of boats are based in Hawai‘i, the fishing effort is broadly distributed inside and outside the Exclusive Economic Zone (EEZ) surrounding the Hawaiian archipelago, from about 5°N to 35°N, and from about 130°W to 180°W.
Given the size of the fishery, 20% observer coverage allows for the detection of relatively infrequent events such as bycatch of false killer whales (Pseudorca crassidens). While such events are not commonly recorded in the deep-set fishery (e.g., ranging from 4 to 11 records a year in the last 10 years), false killer whales are naturally rare and have a low rate of population growth (Baird 2018), thus even low levels of bycatch have the potential to affect populations. Analyses of bycatch in relation to abundance resulted in the Hawai‘i false killer whale stock being listed as “strategic” under the Marine Mammal Protection Act in 2000, as estimated bycatch rates exceeded the Potential Biological Removal (PBR1) level of the population (Forney et al. 2000). While knowledge of stock structure and abundance have changed dramatically since 2000 (e.g., Barlow 2006; Baird et al. 2008, 2012, 2014; Bradford et al. 2014, 2015), with three different stocks now recognized inside the EEZ (Carretta et al. 2018), what is now known as the Hawai‘i pelagic stock has remained strategic for most years since 2000. This strategic listing eventually led, after legal action, to the formation of a False Killer Whale Take Reduction Team (TRT) in January 2010. The TRT is a multi-stakeholder group including longline fishermen, representation from the Hawai‘i Longline Association, NOAA Fisheries, the State of Hawai‘i, the Marine Mammal Commission and the Western Pacific Fishery Management Council, as well as environmental groups and researchers. In July 2010 the TRT produced a consensus draft Take Reduction Plan (TRP) to reduce false killer whale bycatch in the longline fishery. Although the final TRP that NOAA Fisheries produced did not match the consensus draft TRP entirely2, the TRP went into effect in 2013 and includes both gear “fixes” and handling guidelines, with the combination of the two potentially leading to reduced rates of false killer whale mortality and serious injury in the fishery. Although there are a large number of other fisheries that overlap with false killer whales around the main Hawaiian Islands, and a variety of evidence for fisheries interactions (Baird et al. 2014, 2017), only the longline fisheries are the subject of the TRT and TRP.
With several meetings in the intervening period, five years after the TRP went into effect the TRT met in person in April 2018 to review the success, or lack of success, of the plan. While the overall mortality and serious injury rate on observed trips has declined since the TRP went into effect, I contend that the plan is fatally flawed, as it relies in part on handling techniques of the captain and crew in the 80% of the fishery when no observer is on board. I outline below the primary features of the Take Reduction Plan, its effectiveness in the five years since it went into effect, and why relying on handling techniques to reduce bycatch in a partially observed fishery has the potential to mask the bycatch issue, rather than solve it.