34 
Fishery Bulletin 106(1 ) 
§ Bering See 
Aleutian Islands 
Bathyraja parmlfera 
0 150 300 600 
kilometers 
y 
RUSSIA 
sgfSy 1 
ALASKA 
& 
i Bering Sea SL f 
^ 
jp Gulf of Alaska ^ 
Aleutian Islands 
Bathyraja interrupta 
Fig 
Distribution of (A) Bathyraja parmifera (Alaska skate), (B) B. aleutica (Aleutian skate), (C) B. interrupta 
(Bering skate), and (D) B. trachura (roughtail 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. 
large majority of the hauls, and overall skate num- 
bers have been increasing over the past 20 years (Hoff, 
2006), the mean species richness and skate diversity 
are quite low in this region. In the deeper waters near 
the shelf-slope break, the skate fauna is more diverse, 
and B. aleutica and B. interrupta, two of the most geo- 
graphically and bathymetrically widespread species 
in Alaska, are encountered with greater frequency. In 
addition to widespread distributions in Alaskan waters, 
both of these species are also found farther south along 
the North American west coast and have been collected 
at depths of 20 to over 1000 m. Bathyraja taranetzi and 
B. maculata also begin to appear near the shelf break 
in the eastern Bering Sea, although they are much 
more common on the continental slope. The presence of 
these species near the shelf break accounts for the high 
mean species richness values in the deep depth strata 
in this region. In the southeastern corner of the Bering 
Sea shelf, near the eastern Aleutian Islands, the two 
Alaskan species of Raja are occasionally encountered, 
and their effect on the mean species richness values 
in subregion 1 are offset by the fact that this area 
includes the extensive shallow waters of Bristol Bay, 
where skates are less frequently encountered. 
There were no clear bathymetric or geographic trends 
in skate population density on the eastern Bering Sea 
shelf. Although overall mean density generally increased 
with increasing depth, the middle and deep depth strata 
yielded similar overall means. The low overall mean 
density values for both the shallow depth stratum and 
the southern subregion (subregion 1) appeared to be 
heavily influenced by the relatively low skate densities 
in the shallow waters of Bristol Bay. The mean density 
for the shallow stratum of subregion 3 was probably not 
meaningful because of the relatively low sample size 
and high variability in density data for this stratum. 
The continental slope of the eastern Bering Sea is a 
region of high skate species richness and diversity, and 
skates are encountered in nearly every haul. Several 
species, including B. aleutica, B. interrupta, B. tara- 
netzi, and B. maculata, are encountered from the shelf 
break down to well over 1000 m depth. Another group 
of species, characterized by a dark ventral surface — B. 
lindbergi, B. minispinosa, and B. trachura — -begin to 
