Loher et at: Growth of Paralithodes camtschaticus 
585 
cy toward specific mean size-at-age is not apparent if lon- 
ger time scales are considered. Size-at-age characteristics 
may be different depending on which year class is consid- 
ered, and among crabs >~40 mm CL, mean CLs of iden- 
tifiable cohorts displayed a fairly continuous distribution 
with considerable overlap between adjacent size modes; 
we could not identify specific mean CLs that could be con- 
sistently assigned to various age classes. In addition to 
confounding age estimates, variable MI may cause differ- 
ent year classes to recruit at different ages, over different 
time spans, and increase the number of year classes that 
constitute each year’s new recruitment. These issues have 
been treated elsewhere with respect to variable intermolt 
period (Stevens, 1990); variability in MI will produce the 
same effects. 
We explored the possibility that overlap between size 
modes might be attributable to changes in growth rate 
within the population over time. That is, because bottom 
temperatures in Bristol Bay were colder during the 1970s 
than they have been more recently, growth was expected 
to be slower in the 1970s than later in the time series (Ste- 
vens, 1990). Thus, one might expect size modes to fall clos- 
er together early in the time series and to be spaced farther 
apart later. However, we were unable to resolve a clear tem- 
poral component in the data; even consecutive year classes 
sometimes had different mean size-at-age and growth 
increment characteristics. For example, the 1976 year 
class displayed a mean CL = ~51 mm (range: 44-57 mm) 
and ~63 mm CL (range: 56-71mm) in 1980 and 1981, 
respectively. These represented clear and well-separated 
size modes at ages 3.9 and 4.9, respectively. However, note 
the occurrence of a strong mode in the 1979 data, with 
a mean CL = ~58mm CL (range=50-65 mm); this mode 
probably represents a single year class, settled in 1975, 
which would be expected to have mean size-at-age charac- 
teristics similar to those of the 1976 year class. Yet, this 
mode of the 1975 year class fell almost precisely between, 
and its range encompassed the mean sizes of both age 3.9 
and age 4.9 crabs from the 1976 year class. Such features 
were not uncommon in the length frequencies that were 
presented. For applications requiring accurate size-at-age 
information, the onerous task of year-by-year and year- 
class-by-year-class assessments may be necessary. 
In summary, our results demonstrate that both male 
and female red king crab in Bristol Bay reach maturity 
at least one year later than presently assumed (i.e. at ~7 
years after settlement) due to slower growth from settle- 
ment through age 3. Furthermore, variability in MI in late 
juveniles can result in further reduction in growth rate 
such that reproductive recruitment is delayed by an ad- 
ditional 1-2 years (i.e. reproductive recruitment at ~8-9 
years after settlement). From a management perspective, 
variable MI is a life-history characteristic that should be 
considered in growth- and length-based models of recruit- 
ment. Present models attempt to simulate MI variability 
(Zheng et al., 1995a), but little information exists on the 
magnitude of that variability and its changes over time 
and space. Such information will be valuable to managers 
to calibrate recruitment models with respect to lag times 
between spawning and subsequent recruitment, as well as 
to predict how year classes enter the spawning population 
and the fishery; more research in this area is warranted. 
Inappropriate growth rate and lag-time assumptions have 
resulted in assigning the wrong year’s spawning stock bio- 
mass to subsequent recruitment levels in the Bristol Bay 
stock-recruitment curve; spawning stock abundances are 
presently offset -1-2 years from the recruitment levels 
that they generated. This offset may affect the precise 
shape of the stock-recruitment curve and alter some of the 
models associated with it. Such changes may prove negli- 
gible with respect to actual harvest strategies, but it may 
be prudent to make the appropriate adjustments given 
knowledge of greater age at reproductive recruitment. 
The Bristol Bay red king crab stock has been typified 
by large fluctuations in fishable abundance and by rela- 
tively rare, strong recruitment pulses generating the bulk 
of the fishery. Most recently, relatively strong catches from 
1997-99, yielding a combined landed catch of -35 million 
pounds of crabs with an exvessel value estimated at over 
$137 million (Morrison et al. 7 ), were supported almost en- 
tirely by the 1990 year class (i.e. were spawned by the 1989 
reproductive stock). Former assumptions would have led 
us to assign this pulse to the 1990 spawning stock and 
assume that the planktonic larval phase and settlement 
occurred during 1991. From a management standpoint, 
the ramifications of such an error may be negligible be- 
cause estimated effective spawning biomass was similar 
in both 1989 and 1990 (Zheng and Kruse 1 ). However, as we 
try to elucidate the mechanisms that generated this strong 
year class, it is crucial that we accurately determine when 
those crabs were larvae, early benthic individuals, and 
later stage crabs. Physical forcing, for example, has been 
shown to play a large role in determining recruitment vari- 
ability in a number of commercially important crustacean 
species worldwide (e.g. Polovina and Mitchum, 1992; Po- 
lovina et al., 1993; McConnaughey et al., 1994; Rothlisberg 
et al., 1994; Jones and Epifanio, 1995; McConnaughey and 
Armstrong, 1995; Rozenkranz et al., 1998). Similar correla- 
tions between recruitment and physical parameters have 
been attempted for king crabs (Zheng and Kruse, 2000), 
but our ability to identify causes of recruitment variabil- 
ity relies upon associating the correct life history stages 
with physical forcing events. Even seemingly minor errors 
in growth-rate assumptions can have serious impacts on 
our understanding of population dynamics. 
Acknowledgments 
Funding for preparation of this manuscript was provided 
by the University of Washington, Seattle, through a Victor 
and Tamara Loosanoff Fellowship. We wish to thank Julie 
7 Morrison, R., F. Bowers, R. Gish, E. Wilson, W. Jones, and B. 
Palach. 2000. Annual management report for shellfish fisher- 
ies of the Bering Sea. In Annual management report for shell- 
fish fisheries of the westward region, 1999, p. 147-261 Regional 
Information Report 4KOO-55, Kodiak. Division of Commercial 
Fisheries, Alaska Department of Fish and Game, RO. Box 
25526, Juneau, Alaska, 99801. 
