Dahlheim et al.: Interactions, injuries, and mortalities of Orcinus orca during fishing operations 81 
The North Pacific Observer Program uses a stratified, 
hierarchical sampling design to monitor fishing activities 
in the U.S. exclusive economic zone in Alaska. From the 
development of domestic fisheries in the early 1990s until 
the restructuring of the North Pacific Observer Program 
in 2013, large vessels over 38.1 m (125 ft) in length over- 
all were required to carry an observer on all fishing trips 
(this group of vessels is the full-coverage pool) and vessels 
between 18.2 m (60 ft) and 37.9 m (124.5 ft) length over- 
all were required to carry observers on approximately 30% 
of their fishing days (this group of vessels is the partial- 
coverage pool). The restructuring of the North Pacific 
Observer Program in 2013 redefined these pools such that 
the full-coverage pool consists primarily of vessels that pro- 
cess catch at sea (catcher-processors and motherships) and 
vessels that participate in catch share programs regardless 
of vessel size and such that the partial-coverage pool con- 
sists primarily of vessels that deliver their catch to shore- 
side processors and are over 12.2 m (40 ft) length overall 
(NPFMC?’). Observer deployment rates for partial-coverage 
vessels have varied with management needs for various 
fisheries and are set each year in an annual deployment 
plan (e.g., NMFS°). These changes over time are one of the 
reasons that analyses and results are presented separately 
for the full-coverage and partial-coverage pools. 
Once an observer is on a vessel, a subset of hauls are 
randomly selected to be sampled for catch composition and 
other biological catch data (Cahalan et al., 2014; Cahalan 
and Faunce, 2020). If a marine mammal is caught, the 
observer records this event regardless of whether the 
animal is within the selected hauls; for marine mammal 
bycatch, observers record all known mortalities. Sightings 
of and fishery interactions with marine mammals are also 
recorded; whenever the observer becomes aware of the 
presence of a marine mammal, data for the interaction or 
sighting are recorded. 
Interactions of marine mammals with fishing vessels 
and fishing gear are recorded by observers according to 
the 7 broad categories defined in the observer manual 
(e.g., AFSC*”). These categories are as follows: 1) some 
2 NPFMC (North Pacific Fishery Management Council). 2011. 
Environmental assessment/regulatory impact review/initial regu- 
latory flexibility analysis for proposed amendment 86 to the fish- 
ery management plan for groundfish of the Bering Sea/Aleutian 
Islands management area and amendment 76 to the fishery man- 
agement plan for groundfish of the Gulf of Alaska. Restructur- 
ing the program for observer procurement and deployment in the 
North Pacific, 239 p. North Pac. Fish. Mange. Counc., Anchorage, 
AK. [Secretarial review draft.] [Available from website.] 
3 NMFS (National Marine Fisheries Service). 2017. 2018 annual 
deployment plan for observers and electronic monitoring in the 
groundfish and halibut fisheries off Alaska, 20 p. Natl. Mar. 
Fish. Serv., Juneau, AK. [Available from website.] 
* AFSC (Alaska Fisheries Science Center). 2001. North Pacific 
groundfish observer manual, 571 p. [Available from North Pac. 
Groundf. Obs. Program, Alsk. Fish. Sci. Cent., Natl. Mar. Fish. 
Serv., 7600 Sand Point Way NE, Seattle, WA 98115.] 
° AFSC (Alaska Fisheries Science Center). 2021. 2022 observer 
sampling manual, 496 p. Fish. Monit. Anal. Div. and North Pac. 
Groundf. Obs. Program, Alsk. Fish. Sci. Cent., Natl. Mar. Fish. 
Serv., Seattle, WA. [Available from website.] 
form of deterrence was used to discourage nearby mam- 
mals from interacting with fishing operations, 2) a mam- 
mal was entangled and released without trailing gear, 3) a 
mammal was entangled and released with trailing gear, 
4) a mammal was lethally removed (from gear that was 
not trailing), 5) a mammal boarded the vessel, 6) a mam- 
mal was feeding on catch that had not yet been landed, 
and 7) a mammal was feeding on discards. 
During the course of this study (2001-2016), observers 
used all of these interaction categories with the exception of 
the category for mammals feeding on discards because it was 
not introduced until 2008. Observers also used additional 
interaction categories recorded as other (i.e., observations 
that did not fit the 7 categories listed above) and unknown 
(i.e., interactions observed by the vessel crew but not seen 
by the observer). In addition, mortalities were recorded and 
classified as follows: 1) killed by gear, 2) killed by propeller, 
3) removed lethally from trailing gear (crew killed a mam- 
mal entangled in gear), or 4) removed lethally from gear that 
was not trailing (in spite of efforts by the crew to release 
the mammal, the animal died). For whales entangled in gear 
and subsequently released, an assessment was made by 
scientists at the MML to determine if the injury sustained 
would result in the whale’s death. If there was a high proba- 
bility that the entanglement would result in the death of the 
whale, the incident was listed as a serious injury (serious 
injury criterion are further described in NMFS‘). 
Analysis of fisheries interactions 
The data on fisheries interactions and marine mammal 
sightings collected by observers were summarized within 
sampling strata and fisheries as defined in the LOF. The 
fishery in which a haul or set occurs is determined by the 
NMFS reporting area (Fig. 1), gear type, and trip target 
code (dominant species retained; for additional detail, see 
Cahalan et al., 2014). Additional information collected for 
an interaction with one or more marine mammals may 
include the date, year, latitude, longitude, number of ani- 
mals, vessel and observer identifiers, indication of whether 
photographs were taken, and indication of whether tissue 
samples were taken (Breiwick, 2013). 
Between 2001 and 2016, the number of hauls moni- 
tored by observers fluctuated with varying coverage 
rates and fishing effort; however, these changes were not 
always consistent with changes in fishing effort. There- 
fore, numbers of sampled hauls for which associated 
interactions with killer whales have been recorded have 
to be considered in the context of these changes in sam- 
pling intensity (for summary of annual sampling inten- 
sity, see table 1-1 in AFSC and ARO’). As a result, some 
° NMFS (National Marine Fisheries Service). 2014. Process 
for distinguishing serious from non-serious injury of marine 
mammals. Natl. Mar. Fish. Serv. Policy Directive 02-238, 4 p. 
[Available from website.] 
7 AFSC (Alaska Fisheries Science Center) and ARO (Alaska 
Regional Office). 2018. North Pacific Observer Program 2017 
annual report. AFSC Processed Rep. 2018-02, 136 p. [Available 
from website.] 
