12 
Fishery Bulletin 11 7(1 -2) 
Figure 3 
Maps of the geographic distribution of skate egg cases 
(gray circles) identified as (A) Alaska skate ( Bathy- 
raja parmifera), (B) Aleutian skate {B. aleutica), and 
(C) Bering skate ( B. interrupta) by fishery observers 
aboard commercial fishing vessels in the eastern Ber¬ 
ing Sea from November 2014 through November 2017. 
Open stars represent skate nursery areas designated 
as habitat areas of particular concern. The gray lines 
indicate the 200-m isobath. 
that it sweeps over; however, longline gear catches fish 
by attracting them to bite baited hooks, an action skate 
egg cases obviously cannot take. Still, although long- 
line gear does not sweep the seafloor in the same way 
that trawling gear does, the groundline of a longline 
gear can move considerable distances across the bot¬ 
tom, under the influence of currents or large hooked 
fish and during gear retrieval (High 4 ). As a result, ses¬ 
sile benthic organisms, such as corals and sponges, are 
commonly caught with longline gear (Duran Munoz et 
ah, 2011; Sampaio et ah, 2012), and clearly skate egg 
cases fall into this category as well. In fact, the struc¬ 
ture of egg cases—with long, curled horns on the ends 
and sticky byssal threads attached along the margins 
(Stevenson et ah, 2007), adaptations that presumably 
keep them from being swept into less favorable areas 
by bottom currents—makes them ideally suited to cling 
to passing lines and hooks as well as to other egg cas¬ 
es. These results indicate that the effects of longline 
fishing on skate nursery areas may be similar to the 
effects of bottom trawling. 
The relative abundance of skate egg cases identified 
to the species level by observers in this study is consis¬ 
tent with abundance patterns reported for adult skates 
in the EBS. The Alaska skate is by far the most abun¬ 
dant skate on the EBS shelf, accounting for 95% of the 
overall skate abundance at depths <200 m (Stevenson 
et al., 2008; Stevenson and Lewis, 2010), and it is also 
by far the most common species of egg case identified 
by observers in this study. In the deeper waters of the 
continental shelf and upper continental slope, other spe¬ 
cies of skates, such as the Aleutian, Bering, Commander 
, and whiteblotched skates, become more abundant (Ste¬ 
venson et ah, 2008), and egg cases of these species were 
identified with regularity by observers in this project. 
Both for the taxon that combined the Commander 
and whiteblotched skates and for B. minispinosa, over 
80% of all the egg cases identified for this study were 
reported by a single observer on a single cruise, indi¬ 
cating the possibility that the abundance of these taxa 
may be inflated by misidentification. Likewise, a small 
number of egg cases were identified by observers as 
deepsea skate ( B. abyssicola), and one egg case was 
identified as an Arctic skate (Amblyraja hyperborea, 
previously known as A. badia in the North Pacific). 
Both of those species are extremely rare in the Ber¬ 
ing Sea and are found only in very deep water (Ste¬ 
venson et al., 2007). Because none of these specimens 
were photographed or collected for species verifica¬ 
tion, the possibility remains that they could have been 
misidentified. 
Less than half of the egg cases examined by ob¬ 
servers in this study were classified as viable; there¬ 
fore, most of the fishery interactions documented 
here involved empty egg cases. However, for one spe- 
4 High, W. L. 1998. Observations of a scientist/diver on fish¬ 
ing technology and fisheries biology. AFSC Proc. Rep. 98-01, 
48 p. Alaska Fish. Sci. Cent., Natl. Mar. Fish. Serv., Se¬ 
attle, WA. [Available from website.] 
