36 
Fishery Bulletin 106(1 ) 
Figure 7 
Distribution of (A) Raja binoculata (big skate) and 
(B) R. rhina (longnose skate) based on data from 
bottom-trawl surveys conducted in the eastern Bering 
Sea, Aleutian Islands, and Gulf of Alaska from 1999 
through 2004. Black circles indicate the presence of the 
species in one or more survey hauls. Depth contour = 
200 m. 
data on overall skate density in enough detail for direct 
comparison with the present work. Similarly, limited 
sampling effort on the continental slope of the Aleutian 
Islands and Gulf of Alaska have precluded us from 
demonstrating a similar pattern in other regions of the 
eastern North Pacific. 
More species of skates have been recorded from the 
Aleutian Islands than from any other survey region, 
and yet the mean species richness figures are relatively 
low for this region. This finding is a result of the low 
encounter rate, because skates were present in only 
about half of the survey hauls completed in the Aleu- 
tian Islands. In areas where skates were encountered in 
the Aleutian Islands, Shannon’s diversity indices were 
relatively high, which may indicate that many species 
have similar habitat preferences. The most commonly 
encountered species of skates in the Aleutian Islands 
were B. maculata, B. taranetzi , and B. parmifera. Bathy- 
raja aleutica was also relatively common throughout 
Figure 8 
Distribution of Amblyraja badia (roughshoulder skate: 
squares), Bathyraja abyssicola (deepsea skate: trian- 
gles), and B. mariposa (butterfly skate: circles) based on 
data from bottom-trawl surveys conducted in the east- 
ern Bering Sea, Aleutian Islands, and Gulf of Alaska 
from 1999 through 2004. Black circles indicate the 
presence of the species in one or more survey hauls. 
Depth contour = 200 m. 
the archipelago. Although the Aleutians Islands survey 
did not explore depths greater than 500 m, some of 
the species commonly found on the Bering Sea slope, 
such as B. lindbergi , B. minispinosa, and B. trachura, 
have occasionally been collected in the archipelago, and 
therefore the skate fauna on the continental slope of 
the Aleutian Islands is probably similar to that of the 
eastern Bering Sea slope. The fact that these species 
were only encountered in the deepest hauls in the Aleu- 
tian Islands survey explains why mean species richness 
increases with increasing depth in this region. 
The skate fauna of the Aleutians also displayed some 
regional variation. Bathyraja interrupta was relatively 
common in the eastern Aleutians but only rarely en- 
countered in the central and western Aleutians, and 
Raja binoculata was not collected west of Unalaska 
Island. Bathyraja mariposa appeared to be endemic 
to the central Aleutian Islands. In the western Aleu- 
tians B. parmifera is apparently replaced by a similar 
undescribed species (Stevenson et ah, 2007), treated 
here as B. parmifera, and the western Pacific species 
B. violacea is known from one specimen collected by 
a groundfish fisheries observer near Buldir Island in 
the western Aleutians. According to Orlov (2005) and 
Orlov et al. (2007), B. maculata, B. aleutica, and B. vio- 
lacea are the most abundant skate species farther west 
in the northern Kuril Islands and along the southern 
Kamchatka Peninsula. At least two of the skate spe- 
cies found in the Aleutian Islands, B. parmifera and 
B. taranetzi, exhibit very different coloration in the 
Aleutian Islands than in other regions where they are 
known. In the eastern Bering Sea, both of these species 
are a relatively uniform brown, often with dark brown 
or black blotches and occasionally pale yellow markings. 
