Stevenson et al.: Interactions between fisheries and early life stages of skates in nursery areas of the Bering Sea 
9 
benthopelagic species, such as walleye pol¬ 
lock ( Gadus chalcogrammus), Pacific cod ( Ga- 
dus macrocephalus), sablefish ( Anoplopoma 
fimbria), and several species of rockfishes 
(Scorpaenidae) and flatfish (Pleuronectidae). 
Although they are not targeted, significant 
numbers of skates are encountered as by- 
catch in a number of the fisheries of Alaska, 
particularly the longline fishery for Pacific 
cod (Stevenson and Lewis, 2010). These fish¬ 
eries regularly encounter skate egg cases, in 
addition to adult and juvenile skates (senior 
author, personal observ.; North Pacific Ob¬ 
server Program 2 ). Egg cases are brought to 
the surface when they are captured in trawl 
nets or entangled in longline gear. Egg cases 
captured during fishing operations are gener¬ 
ally returned to the sea. Unknown are the 
proportion of captured egg cases that contain 
viable embryos and the mortality associated 
with viable eggs that are subjected to capture 
and subsequent release by fisheries. 
At least 26 nursery areas for 6 species 
of skates have been identified in the EBS 
(Rooper et al., in press). These sites are lo¬ 
cated along the outer continental shelf and 
upper slope, at depths ranging from -150 m to 1069 
m. In 2015, the North Pacific Fishery Management 
Council designated 6 of the known skate nursery ar¬ 
eas in the EBS (Fig. 1) as habitat areas of particu¬ 
lar concern (HAPC), suggesting that these areas “are 
rare and provide an important ecological function” 
(Federal Register, 2015). Although this designation 
did not provide any protection for these 6 HAPC, it 
included a recommendation that the National Marine 
Fisheries Service monitor these sites for potential ef¬ 
fects of fishing. The overall goal of this study was to 
provide additional information on fishery interactions 
with skate egg cases and skate nursery areas in the 
EBS, by using data collected by fishery observers in 
the North Pacific Observer Program. Specifically, the 
objectives of this study were 1) to identify the species 
of skates for which fisheries encounter eggs, 2) to 
determine the proportion of skate eggs encountered 
by fisheries that are viable, and 3) to identify poten¬ 
tially unknown nursery areas by determining the lo¬ 
cation of viable skate eggs encountered by fisheries 
relative to documented skate nursery areas. 
Materials and methods 
All data used in this study were collected by fishery 
observers in the North Pacific Observer Program, 
which monitors commercial fishing activity in the fed¬ 
eral waters of the U.S. exclusive economic zone of the 
2 North Pacific Observer Program. 2018. Unpubl. data. 
North Pac. Obs. Program, 7600 Sand Point Way NE, Seattle, 
WA 98115. 
North Pacific Ocean, Gulf of Alaska, Aleutian Islands, 
and EBS. All vessels over 12 m (40 ft) in length that 
participate in federally managed commercial ground- 
fish fisheries are required to carry a fishery observer 
for at least a portion of their fishing activity. Observ¬ 
ers record data on fishing effort and catch composition, 
using a variety of subsampling methods depending on 
gear type and logistical constraints, as detailed in the 
sampling manual produced annually by the program 
(AFSC 3 ). To the extent possible, observers identify 
sampled individuals of all federally managed groups 
(e.g., rockfish, flatfish, skate) to the species level and 
other species to the family level. Skate egg cases ap¬ 
pearing in observer samples are counted and recorded 
simply as skate egg case unidentified, regardless of spe¬ 
cies or condition. 
Data collection for this study was restricted to the 
EBS and occurred from 15 November 2014 through 
15 November 2017. During this period, over 500 ex¬ 
perienced observers were trained in the species-level 
identification of skate egg cases. Trainees were issued 
several tools for the identification of skate egg cases, 
including a dichotomous key, a picture guide, and a 
length-width chart. They were also given data forms, 
on which they were instructed to record observer 
name, gear type, cruise number, permit number, haul, 
date, species, total number non-viable, total number vi¬ 
able, and comments. An egg case was considered viable 
if it contained a yolk mass or a skate embryo in any 
3 AFSC (Alaska Fisheries Science Center). 2016. 2017 ob¬ 
server sampling manual, 585 p. Fish. Monit. Anal. Div., 
North Pac. Groundfish Obs. Program, Alaska Fish. Sci. 
Cent., Seattle, WA. [Available from website.] 
