8 
National Marine 
Spencer F. Baird 
r \ 
Fisheries Service 
Fishery Bulletin 
First U S Commissioner 
NOAA 
established in 1881 -e. 
of Fisheries and founder 
of Fishery Bulletin 
* 
Interactions between fisheries and early life stages 
of skates in nursery areas of the eastern Bering Sea 
Duane E. Stevenson 
Gerald R. Hoff 
James W. Orr 
Ingrid Spies 
Christopher N. Rooper 
Email address for contact author: duane.stevenson@noaa.gov 
Abstract —From late 2014 through 
2017, fishery observers in the North 
Pacific Observer Program, Nation¬ 
al Marine Fisheries Service, were 
trained in the identification and 
sampling of skate egg cases to inves¬ 
tigate the interactions between fish¬ 
eries and skate nursery areas in the 
eastern Bering Sea. Trained observ¬ 
ers identified and assessed 2887 egg 
cases in a wide range of fisheries 
across all gear types, with the ma¬ 
jority of egg cases being encountered 
on vessels targeting deepwater spe¬ 
cies, such as the arrowtooth floun¬ 
der ( Atheresthes stomias), Greenland 
halibut ( Reinhardtius hippoglossoi- 
des ), Pacific cod (Gadus macroceph- 
alus), and sablefish (Anoplopoma 
fimbria). A large proportion of the 
egg cases identified were reported 
on boats using bottom trawling gear, 
but an even greater proportion were 
reported on longliners. Egg cases 
identified represent 10 skate taxa. 
Over half (67%) of them were iden¬ 
tified as Alaska skate ( Bathyraja 
parmifera), and 19% were identified 
as either Aleutian skate (B. aleuti- 
ca) or Bering skate ( B. interrupta). 
More than 42% of all the egg cases 
assessed were viable (contained a 
living skate); over 50% of egg cases 
of Alaska skate and of egg cases en¬ 
countered on longliners were viable. 
The highest concentrations of egg 
cases generally were reported near 
known skate nursery areas, par¬ 
ticularly in the Bering, Pribilof, and 
Pervenets Canyons. 
Manuscript submitted 28 June 2018. 
Manuscript accepted 29 October 2018. 
Fish. Bull. 117:8-14 (2019). 
Online publication date: 21 November 2018. 
doi: 10.7755/FB.117.1.2 
The views and opinions expressed or 
implied in this article are those of the 
author (or authors) and do not necessarily 
reflect the position of the National 
Marine Fisheries Service, NOAA. 
Alaska Fisheries Science Center 
National Marine Fisheries Service, NOAA 
7600 Sand Point Way NE 
Seattle, Washington 98115-6349 
Skates (Rajiformes) form an impor¬ 
tant and diverse component of the 
ichthyofauna in the eastern Bering 
Sea (EBS). At least 12 species of 
skates are currently known to occur 
in the EBS (Stevenson et al., 2007), 
and the overall biomass of skates in 
this region is currently estimated at 
about 600,000 metric tons (Ormseth, 
2017). On the EBS shelf, the skate 
fauna is dominated by the Alaska 
skate (Bathyraja parmifera), which 
accounts for over 90% of the skate 
biomass at depths <200 m (Steven¬ 
son et al., 2008). In the deeper wa¬ 
ters of the EBS outer shelf and up¬ 
per continental slope, skate diversity 
increases as other species, such as 
the Aleutian skate ( B. aleutica), Ber¬ 
ing skate 1 (B. interrupta), mud skate 
(B. taranetzi), Commander skate (B. 
lindbergi), and whiteblotched skate 
(B. maculata), are encountered more 
frequently (Hoff, 2016). The conti¬ 
nental slope of the EBS is an area 
of particularly high skate diversity, 
1 We recognize Bathyraja kincaidii on the 
west coast of North America as a species 
distinct from B. interrupta in Alaska wa¬ 
ters; therefore, we retain the common 
name Bering skate, rather than sand¬ 
paper skate, for this species (see Ebert, 
2003; Stevenson et al., 2007). 
and as many as 7 species have been 
encountered in a single haul (Steven¬ 
son et al., 2008). 
Skates are oviparous, depositing 
their eggs in egg cases on the sea¬ 
floor. In the Bering Sea, several spe¬ 
cies of skates congregate in small, lo¬ 
calized nursery areas along the outer 
continental shelf and upper slope to 
deposit their eggs (Hoff, 2008, 2010). 
These sites may reach densities of 
800,000 eggs/km 2 , are occupied by 
skates continuously throughout the 
year, and have been persistently 
used by skates for decades (Hoff, 
2010). For at least some species of 
skates, the incubation time from 
egg deposition to hatching may be 
3-4 years (Hoff, 2008), and hatch¬ 
lings are relatively large (14-25 cm 
in total length) and fully developed 
(Hoff, 2009). These early life history 
characteristics, combined with the 
adult characteristics of large size, 
slow growth, late maturation, and 
low fecundity, make skates particu¬ 
larly vulnerable to both natural and 
anthropogenic disturbances (Dulvy 
et al., 2000; Frisk et al., 2005; Matta 
and Gunderson, 2007). 
Alaska’s marine ecosystems are 
highly productive, supporting nu¬ 
merous fisheries for benthic and 
