GRANT
NUMBER:
NA76FD0036
NMFS NUMBER:
96-AKR-025
REPORT
TITLE:
Recruitment Limitation in Alaskan Red King Crab (Paralithodes
camtschaticus): The Importance of Early Life History
Stages
AUTHOR: Timothy
Loher and David A. Armstrong
PUBLISH
DATE:
February 10, 2000
AVAILABLE
FROM:
National Marine Fisheries Service, Alaska Region, P.O.
Box 21668, Juneau, AK 99802-1668. TELEPHONE:
(907) 586-7273
ABSTRACT

The primary
objective of this project was to examine how the unique
habitat requirements of early post-settlement states (or
the "early benthic phase [EBP]) of Alaskan red king
crab (RKC) (Paralithodes camtschaticus) are responsible
for structuring commercial crab stocks by examining the
linkages between larval supply, larval settlement, and
early post-settlement survivorship that govern the distribution,
abundance, and recruitment patterns of juvenile crab.
In order to quantitatively establish the early habitat
needs of the species, the investigators conducted in
situ abundance sampling of EBP crab, settlement experiments,
and simultaneous assessments of larval supply in the shallow
coastal waters of Auke Bay in southeast Alaska. These
studies established that EPB RKC rely heavily, if not
exclusively, upon complex shallow-water habitat for settlement
and early recruitment. Settlement and post-settlement
survivorship were high within rocky nursery habitat and
lower in shell-hash. No settlement or survivorship could
be detected in homogenous muddy-silt habitat despite high
levels of larval supply. These habitat requirements suggest
that recruitment to fishable stocks is likely to be governed
by the spatial structure of the stock in relation to suitable
EBP nursery habitat. In particular, the delivery of larvae
to suitable settlement sites will be critical to ensure
future recruitment, and this process can only be ensured
if larvae are spawned and hatched in areas that are oceanographically
"upstream" of nursery habitats. In order to
assess the likelihood of these events within the Bristol
Bay population, the investigators have begun an oceanographic
modeling effort that will predict larval delivery patterns
given present knowledge of regional oceanography and spatial
stock structure. This model will enhance our ability to
predict the impact of environmental factors on large-scale
recruitment trends and help us to identify spatially explicit
management options for the stock. The investigators also
analyzed historic shifts in centers of adult breeding
distribution to study how subsequent larval dispersion
may affect survival relative to final settlement in nursery
habitat. To fully realize their goals of developing spatially
explicit stock management models, the investigators recommended
that future research should include assessments of local
habitat structure and distribution, as well as field research
examining larval distribution and behavior in relation
to important oceanographic features and conditions.