212 
Fishery Bulletin 108(2) 
Table 2 
Species composition (% by weight) of observed skate catch by region and by gear type within each region of Alaska for 2004-2008. 
Regions: BS=Bering Sea, AI=Aleutian Islands, GOA=Gulf of Alaska. Gear types: l=Nonpelagic trawl, 2=Pelagic trawl, 3=Long- 
line. * = less than 0.1%. 
Taxon 
BS 
AI 
GOA 
1 
2 
3 
All 
1 
2 
3 
All 
1 
2 
3 
All 
Skate unidentified 
0.6 
1.4 
33.5 
24.2 
3.9 
* 
25.1 
17.6 
2.4 
3.5 
16.7 
9.6 
Bathyraja sp. 
1.9 
1.5 
47.5 
34.5 
4.7 
* 
40.7 
28.0 
2.2 
3.3 
16.5 
9.4 
Bathyraja parmifera 
90.0 
92.8 
14.9 
36.6 
50.9 
* 
18.0 
29.6 
3.6 
9.4 
2.8 
3.2 
Bathyraja aleutica 
3.0 
2.4 
1.2 
1.7 
16.1 
* 
3.7 
8.0 
9.5 
9.8 
13.7 
11.6 
Bathyraja interrupta 
1.3 
1.3 
1.7 
1.6 
1.1 
80.6 
0.4 
0.7 
5.9 
6.3 
3.0 
4.4 
Bathyraja minispinosa 
0.1 
* 
* 
* 
0.1 
* 
0.1 
0.1 
* 
* 
* 
* 
Bathyraja maculata 
0.4 
* 
0.2 
0.2 
17.2 
* 
9.3 
12.1 
* 
* 
0.2 
0.1 
Bathyraja lindbergi 
* 
* 
0.1 
0.1 
0.2 
* 
1.7 
1.1 
* 
* 
0.2 
0.1 
Bathyraja taranetzi 
0.2 
0.1 
* 
0.1 
5.2 
19.4 
0.6 
2.2 
* 
* 
* 
* 
Bathyraja trachura 
* 
* 
* 
* 
0.1 
* 
0.2 
0.2 
* 
* 
1.4 
0.7 
Raja sp. 
* 
* 
* 
* 
* 
* 
* 
* 
0.6 
0.3 
4.6 
2.6 
Raja binoculata 
2.4 
0.4 
0.7 
1.0 
0.4 
* 
0.2 
0.3 
52.3 
24.8 
19.6 
35.7 
Raja rhina 
0.1 
* 
* 
* 
* 
* 
* 
* 
23.4 
42.6 
21.3 
22.4 
Total 
100 
100 
100 
100 
100 
100 
100 
100 
100 
100 
100 
100 
profiles varied more by gear type than in the other two 
regions. All three gear types were dominated by species 
of Raja, but R. binoculata accounted for over 50% of 
OSC from nonpelagic trawl gear, whereas R. rhina was 
the dominant species in pelagic trawl and longline gear. 
As in the other two regions, proportions of unidentified 
skates were much higher on longliners than on vessels 
with other gear types, although a much higher percent- 
age of skates were identified to the species level even 
with longline gear in the Gulf of Alaska. 
Significant amounts of skate bycatch were encoun- 
tered by observers in fisheries targeting a variety of 
commercial groundfish species, including Pacific cod, 
walleye pollock, Atka mackerel, shallow-water flatfishes 
(primarily yellowfin and rock soles), and others. During 
the 1998-2008 study period, nearly 72% of OSC was re- 
ported in longline fisheries, and over 65% was reported 
in longline hauls targeting Pacific cod (Table 3). Non- 
pelagic trawl fisheries accounted for only 22% of OSC, 
most of which was reported in hauls targeting miscel- 
laneous flatfishes. Pelagic trawl fisheries, essentially all 
of which target walleye pollock, accounted for very little 
of OSC (6%). These results reflect the percentages for 
the Bering Sea, a region in which over 90% of OSC was 
reported. In the Aleutian Islands significant numbers 
of skates were also encountered on trawlers targeting 
Atka mackerel, and in the Gulf of Alaska on trawlers 
targeting deepwater flatfishes (arrowtooth flounder and 
Greenland turbot). 
The percentage of OSC retained by commercial fish- 
ermen has increased over the past decade (Fig. 2). In 
1998, overall mean skate retention was just over 12%, 
and that figure steadily increased to a peak of nearly 
40% in 2003. For the most recent 4 years (2005-08) 
overall skate retention has remained relatively consis- 
tent at around 30-35%. Species-level retention data 
were erratic from 1998 through 2003. They have be- 
come more stable since 2004 when observers began 
consistently identifying skates to the species level, but 
the annual mean retention for some of the species, 
particularly the genus Raja, still appears relatively 
inconsistent from year to year. Since 2004, the largest 
species of skates ( Raja binoculata, R. rhina, Bathyraja 
parmifera, B. aleutica, and B. maculata) have generally 
been retained at 30% of OSC or above, and smaller spe- 
cies, such as B. interrupta, B. lindbergi, B. taranetzi, 
and B. minispinosa, have been retained at lower levels 
(5-15%). 
Discussion 
From the inception of the NPGOP through 2003, field 
identification tools for the skates of Alaska were limited, 
and skate bycatch data were collected at a very basic 
level. Almost all skates were reported by observers as 
“skate unidentified.” However, from 2004 through 2008 
this situation changed rapidly. With the development 
and deployment of a field guide and the implementation 
of an observer training protocol (Stevenson, 2004), the 
proportion of skates identified to the species level has 
increased dramatically. For the last year included in this 
study, over 95% of OSC was identified at least to genus, 
and that proportion may continue to rise in future years 
