526 
Fishery Bulletin 96(3), 1998 
erally when a population or stock is modeled, the 
assumption is made that the individuals within the 
population are uniform, but it is important that this 
assumption be verified (Cobb and Caddy, 1989). In 
practice, a stock is often defined as 1) a production 
or management unit about which conclusions can be 
made without regard for differences within the group 
and exchanges with other groups, or as 2) biologi- 
cally, a genetically discrete population (reviewed in 
Cobb and Caddy, 1989). However, stock identity of 
decapod populations has been largely ignored or prob- 
lematic (Cobb and Caddy, 1989; Kruse, 1993). 
Existing shellfish management units in Alaska 
were originally established according to historical 
fishing grounds of red king crab. Current area lines 
for C. bairdi and C. opilio were based on mark-and- 
recapture data, natural geographic barriers, and ar- 
eas of stock abundance grouped by major fishing 
grounds. Although genetic surveys were not con- 
ducted on unexploited Chionoecetes populations in 
Alaska, the establishment of a genetic baseline is 
critical for verifying current fishery management 
units and for monitoring potential fishery-induced 
genetic changes. Additionally, the genetics of C. 
bairdi and C. opilio populations in the Bering Sea is 
complicated by the presence of hybrids of these two 
species. Chionoecetes bairdi and C. opilio appear to 
have many similar morphological, physiological, and 
reproductive features (Watson, 1970; Slizkin, 1990) 
that allow them to hybridize in areas of range over- 
lap (Karinen and Hoopes, 1971; Somerton, 1981; 
Hoopes et al. 1 ). 
Many studies suggest that commercial fishing ac- 
tivities may have significant genetic effects on fish 
stocks without reducing them to near extinction (for 
example, see reviews in Allendorf et al., 1987;Thorpe, 
1993), and genetic selection against fast growth may 
result from intense fishing pressure (Kruse, 1993; 
Stevens et al., 1993); however, these effects can be 
assessed only if there are comparative baseline data. 
In 1990 we began genetic investigations of C. bairdi 
and C. opilio populations in Alaska using allozyme 
electrophoresis. Our objectives were 1) to assess ge- 
netic variation in exploited populations of C. bairdi 
and C. opilio in Alaska and 2) to determine if signifi- 
cant differentiation exists to warrant re-examination 
of current management units. 
Materials and methods 
Population sample collections 
Samples of C. bairdi and C. opilio were obtained be- 
tween 1989 and 1993 from population assessment 
Table 1 
Collection information for Chionoecetes specimens. 
Location 
number 
Location 2 
Date 
n 
Chionoecetes bairdi 
l 2 Bristol Bay 
Jun 90 
50 
Bristol Bay 
Jun 91 
50 
2 2 
Bering Sea and Pribilof 
Islands 
Jul 90 
50 
Bering Sea and Pribilof 
Islands 
Apr 91 
75 
Bering Sea and Pribilof 
Islands 
Jul 92 
30 
Bering Sea and Pribilof 
Islands 
Mar 93 
50 
Bering Sea and Pribilof 
Islands 
Jul 93 
80 
3 
Port Moller 
Jun 90 
42 
4 
Sand Point and Pavlof Bay 
Aug 90 
50 
5 
Kodiak N. Mainland 
Feb 90 
50 
6 
Kodiak S. Sitkalidak Strait 
Feb 90 
50 
7 
Kamishak Bay 
Jun 90 
50 
8 
Montague Strait 
Jul 90 
50 
9 
Kachemak Bay 
Jun 90 
50 
10 
Prince William Sound 
Aug 90 
50 
11 
Sullivan Island 
Jul 93 
100 
12 
Seymour Canal 
Sep 89 
50 
Seymour Canal 
Jul 93 
75 
Chionoecetes opilio 
I 2 Bering Sea 
Apr 91 
75 
Bering Sea 
Mar 93 
50 
II 2 
St. Matthew Island 
Jul 90-Aug 90 
100 
St. Matthew Island 
Jul 92-Aug 92 
100 
III 2 
Pribilof Island 
Jul 90 
44 
Pribilof Island 
Aug 90 
50 
Pribilof Island 
Jul 92 
40 
Pribilof Island 
Jun 93-Jul 93 
80 
Nova Scotia, North Atlantic Sep 91 
97 
1 Latitude and longitude locations available from authors. 
- Collections within geographic location pooled for analyses; C. bairdi 
collection sites in the Bering Sea and Pribilof Islands were overlapping. 
trawl and pot survey catches, test fishery pot catches, 
and dockside commercial pot catches. Crabs caught 
in pots set in adjacent areas were pooled into a single 
collection (Table 1). Chionoecetes bairdi were col- 
lected from sites ranging from Seymour Canal in 
Southeast Alaska to northwest of the Pribilof Islands 
in the Bering Sea (Table 1; Fig. 1). Chionoecetes opilio 
were collected from sites in the Bering Sea. In addi- 
tion, we obtained a collection of C. opilio from the 
North Atlantic for comparison with Bering Sea 
samples. Eighteen collections of C. bairdi and nine 
collections of C. opilio were analyzed in this study. 
1 Hoopes, D. T., J. F. Karinen, and M. J. Pelto. 1970. King and 
Tanner crab research. International North Pacific Fisheries 
Commission Annual Rep. 1970:110-120. 
