10 
Fishery Bulletin 11 7(1-2) 
Table 1 
Number of egg cases of skates identified by observers aboard commercial fishing vessels in the eastern Bering Sea from 
November 2014 through November 2017, by gear type and presumed target species. 
Predominant (target) species 
Deepwater Other 
Pacific flatfish Walleye Pacific flatfish Rockfish 
Gear type 
cod 
species 
Sablefish 
pollock 
halibut 
species 
species 
Other 
Total 
Longline 
1514 
308 
1 
17 
i 
27 
1868 
Bottom trawl 
3 
612 
39 
91 
71 
59 
1 
876 
Pelagic trawl 
5 
133 
2 
1 
141 
Pot 
1 
1 
2 
Total 
1518 
617 
309 
173 
108 
74 
60 
28 
2887 
stage of development; an egg case was deter¬ 
mined to be non-viable if it was empty or full 
of sediment. Observers trained for this project 
recorded species identifications and viability 
assessments of skate egg cases on data forms, 
and they turned in their forms during post¬ 
cruise debriefing. Ultimately, these data forms 
were returned to the main office of the North 
Pacific Observer Program in Seattle. 
Only species-level data recorded by project 
participants were used to create distribution 
maps for individual species. The position of 
each haul was determined by the deployment 
latitude and longitude recorded by the observer 
in the field. Because observers did not record 
the target species of commercial fishing opera¬ 
tions, the predominant species was used to in¬ 
fer target species for each haul. Nonparametric 
Mann-Whitney U tests were conducted to de¬ 
termine the significance of differences among 
proportions of egg cases that were viable. 
Results 
A 
Alaska 
Bering Sea 
m& 
'_A< 
Figure 2 
Map of the locations (gray dots) of all hauls from which egg 
cases of skates were identified and assessed by fishery observ¬ 
ers aboard commercial fishing vessels in the eastern Bering Sea 
from November 2014 through November 2017. The gray line in¬ 
dicates the 200 m isobath. 
Fishery observers in the EBS identified and as¬ 
sessed the viability of 2887 skate egg cases from 
408 hauls of commercial fishing vessels for this project 
(Fig. 2). Sampled hauls were distributed broadly across 
the continental shelf and upper slope, ranging in depth 
from 45 to 684 m, but they were concentrated near the 
break between the shelf and slope. The number of egg 
cases in a single sampled haul ranged* from 1 to 204 
(mean: 5.4 egg cases), and as many as 3 species of skates 
were identified from egg cases sampled in a single haul. 
Observers identified egg cases from a wide variety of 
fisheries and gear types, but over half of all egg cases 
identified for this study were encountered on longline 
vessels targeting Pacific cod (Table 1). Smaller num¬ 
bers of egg cases were encountered on vessels using 
bottom trawling gear, particularly those targeting 
deepwater flatfish species (arrowtooth flounder, Ather- 
esthes stomias, and Greenland halibut, Reinhardtius 
hippoglossoides), and on vessels using pelagic trawls 
and even pots. 
Egg cases identified by observers represent 10 puta¬ 
tive taxa (Table 2). Over 67% of egg cases were identi¬ 
fied as Bathyraja parmifera, and the next most com¬ 
mon taxa were B. aleutica (12%) and B. interrupta 
(7%). The other 7 taxa combined for the remaining 
14% of the identified egg cases. The egg cases of Com¬ 
mander skate and whiteblotched skate are very similar 
and are extremely difficult to distinguish without mag¬ 
nification. Therefore, for the purposes of this study, the 
2 species were combined into a single taxon. 
