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Fishery Bulletin 106(3) 
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Figure 1 
(A) Map of the eastern Bering Sea, Alaska, and location of 
a nursery site (dark circle) for the Alaska skate ( Bathyraja 
parmifera) at the head of Bering Canyon. (B) Locations at the 
nursery site for all trawls completed. The area in the box was 
designated as the index site and targeted for a 14-month sea- 
sonal study conducted during 2004-05. 
Materials and methods 
Sampling at the nursery site 
The Alaska skate nursery site was sam- 
pled by methods and gear similar to those 
used by the annual Alaska Fisheries Sci- 
ence Center (AFSC) standard eastern 
Bering Sea bottom trawl survey (see 
Lauth and Acuna, 2007). The samples 
were collected with an 83-112 eastern 
otter trawl with a 25. 3 -m headrope and 
34.1-m footrope. The footrope consisted of 
a single firehose-wrapped chain lacking 
bobbins or discs, and bottom contact was 
monitored by using electronic tilt sen- 
sors designed by personnel at the AFSC. 
Towing speed varied from 2 to 3 knots and 
tows were made directly into prevailing 
currents and wind to help control towing 
speed. During each tow, starting and 
ending latitude, longitude, bottom depth, 
time, vessel speed, net height and width, 
and bottom temperatures were recorded 
with NETMIND (vers. 3.0, Northstar 
Technical Inc., St. John’s, Newfoundland, 
Canada) acoustic trawl mensuration gear. 
Area swept was estimated from the aver- 
age net width and distance fished during 
each tow. Egg case, fish, and invertebrate 
densities were estimated from the area 
swept and from the numbers within each 
category (egg case, fish, and invertebrate) 
caught in each trawl haul. 
An initial exploratory trawl was con- 
ducted in June 2004 to locate the skate 
nursery. A subsequent survey to deter- 
mine the spatial coverage of the nursery 
was conducted during July-August 2004. 
The extent of the nursery area was de- 
termined by using an adaptive trawling 
approach, where 1) trawls were conducted 
in each of four directions from 0.5 to 1.5 
km apart and 2) a reduced egg case den- 
sity of <500 eggs/km 2 was used as the 
criterion to indicate the farthest limits of 
the nursery (Fig. 1). The goal was to map 
the egg case distribution and estimate 
the size of the nursery area. 
The Alaska skate nursery site was 
sampled a total of eight times over the 
14-month period in June, July, Septem- 
ber, and November of 2004 and January, 
April, June, and July of 2005. An index 
area was chosen during the July-August 
2004 investigation and was sampled dur- 
ing each of the subsequent six seasonal 
sampling periods (September 2004 to 
July 2005). The index site was defined as 
an area where the skate eggs were pre- 
