Vol. 53 - Alaska Resources Library and Information Services

4.3 Reproduction and Description of Spawning Stocks
Populations of juvenile and adult Chionoecetes bairdi and C. opilio
in the southeastern Bering Sea are surveyed each year by the National
Marine Fisheries Service for purposes of fishery forecasting. Distribution
and abundance of the spawning stocks are consequently well known.
While both species are found over a wide region of the shelf from depths
of 50-200 m, the majority of the populations of each (see Fig. 4.2b) are
associated with areas which are distinguishable on the basis of average
summer hydrographic conditions.
The bulk of the population of C. opilio
is found in the middle shelf environment betwween 70 and 100 m depths,
where relatively cold bottom water temperatures prevail throughout summer.
[The cold bottom water mass is formed in situ during winter and is
isolated by stratification of the water column in spring.] Most of the
population of C. bairdi is found in the outer shelf environment at
depths of 100-200 m and in the middle shelf environment near the Alaska
Peninsula.
Sexually mature female crabs appear to be patchily distributed
within these regions, but generally are found over wide areas similar
to the rest of the population of each species.
The age at sexual maturity is about five years for females of both
C. bairdi (Donaldson et al. 1980) and C. opilio (from Adams 1979:
Tables 10 and 11; and Watson 1970).
Females undergo a terminal puberty
molt at sexual maturity, but the size (carapace width) at which this
occurs can vary substantially (Ito 1970; Haynes et al. 1976; MacIntosh
et al. 1979; Jewett 1982).
The size at which 50% of C. bairdi females
reach sexual maturity is about 84 mm (post-molt) carapace width (Hilsinger
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