Defining genetic population structure of snow crab

(Chionoecetes opilio) in the Bering, Chukchi and Beaufort

Seas Greg Albrecht

Dr. Sarah M. HardyDr. Kris Hundertmark

Outline•Species information•Study area•Factors influencing current populations•Purpose of study•Methods •Progress

Distribution(Approximated)

Koryaks.net

Life HistoryPlanktonic zoea – (hatch in

winter – spring, 2 stages, 3-5 months)

Settle as megalopaeMolt through 7-9 instars

Males: 5-10 yearsFemales: 3-7 years

Terminal molt to maturityUp to 7 years post terminal

moltMales: 11-17 yearsFemales: 10-13 years

uwlax.edu

Kruse et al. 2007

Shell condition Index (Not full representation)

1 2

3 4

•Abdominal flap is proportionally larger in mature females

MatingMating in late winterFemales can store sperm in spermathaeca for

later useMales can fertilize several femalesYoung are brooded 12-15 months then

released into water column

Female

Male

Larval Dispersal

Predominantly northward flow

Bering Strait to Pt. Barrow ~6 months

Weingartner et al. 2005

Bering SeaLocal

recruitmentEddiesWeak

currents in central

Southward migration?

Stabeno 2001

Mean circulation of upper 40 m

MigrationAdult females

move from coastal domain towards outer domain (SW)

Male migration not studied as well

Koryaks.net

Ernst et al. 2005

The forces at workCommercial fishing

pressureConcentrating on southern

extent of populationClimate change

Temperatures, ice extent, ocean currents, wind & mixing

Predator preyPacific Cod (Gadus

macrocephalus) and other bottom fish

Resource exploration

Commercial HarvestOne of the largest

crab fisheries in the world2008~ 90 million

dollars1992~ 192 million

Replaced dwindling Tanner (C. bairdi) stocks in 1980s

rcrawford79.wordpress.com

Kruse et al. 2007

Climate changeIce extent determines

cold pool (<2 C)Cold pool trapped by

stratified warm waterCrabs follow cold poolCan crabs re-colonize

south after a warm year?

Cod predation may be too intenseOrensanz et al .

2004

Resource Exploration Areas

Alaska Annual Studies Plan. U.S. Dept. of Interior 2009

Purpose of StudyGain a better understanding of genetic

connectivity Identify genetically distinct subpopulations if

they existGain a better understanding of larval

dispersal distances

Sampling

Sampled

Commercial fishing

Planned sampling

Resource development

MethodsBased on Puebla et al. 2008 (North Atlantic)Extract DNA samples from tissue in ~ 1000

adult female C. opilio samples collected from throughout their range

Amplify DNA using PCR at 8 microsatellite locations

Genotype each individualUse statistical programs to analyze results

and look for distinct populationsMatch larval crabs with upstream

populations

Why Microsatellites?Definition: Molecular markers consisting of

repeat nucleotide units at various locations within nuclear DNA

Previously established for this species by Puebla et al. 2003

Shown to be informative in this speciesHighly polymorphic, yet not under selection

pressuresDeviation from Hardy-Weinberg equilibrium

can be used to detect isolation of a group of individuals

StatisticsA suite of computer programs will be used to

identify genetically isolated populationsF-statistics

Compare pre-established groups in a framework similar to ANOVA

Bayesian methods Assemble populations based on similarity of genetic

signatures

The big picture

8 primers (Identify region for copying)

Taq polymerase(Copies DNA)

Crab DNAPCR(Copying of target DNA) Electrophoresis

Scoring of each individual’s electropherogram

Statistical analysis of genetic signatures

Microsatellite locations are represented by different colors

So how does this work?

100 110

100

110

PCR

Allele “A”

Allele “B”

Heterozygote

Primer region

Population “A”

Population “B”

Electropherogram

Mating

Electrophoresis

100 100

100

100

PCR

Allele “A”

Allele “A”

Homozygote

Primer region

Population “A”

Population “A”

Electropherogram

PCR conditions must be optimized for good amplification

Mating

Electrophoresis

Chukchi

Chukchi

Chukchi

Beaufort

Progress to dateExtracted ~150 samplesTested DNA quality and found donated

Bering samples to be lowMultiplexed all 8 primersTrial and error of PCR conditions (various

annealing temperatures and times, Taq polymerases)

Initial genotyping of individuals

TimelineWinter 2009/10 – begin genotyping (currently

underway)May 2010 – have completed genotyping and

preliminary statistical analysis for 60 individuals

July 2010 – Collect samples from Bering Sea on F&G trawl survey cruise

February 2011 – have completed genotyping and analysis for entire sample collection

September 2011 – have written and defended thesis

Literature Cited• Ernst, B., Orensanz J. M. & Armstrong, D. A. 2005. Spatial dynamics of female snow crab

(Chionoecetes opilio) in the eastern Bering Sea. Canadian Journal of Fisheries and Aquatic Science 62:250-268.

• Kruse, G.H. , Tyler, A.V, Sainte-Marie, B., Pengilly, D. 2007. A workshop on mechanisms affecting year-class strength formation in snow crabs Chionoecetes opilio in the Eastern Bering Sea

• Orensanz, J., B. Ernst, D. A. Armstrong, P. Stabeno, and P. Livingston. 2004. Contraction of the geographic range of distribution of snow crab (Chionoecetes opilio) in the Eastern Bering Sea: An environmental ratchet? Pages 65-79, CalCOFI Report.

• Puebla, O., Parent, E. & Sevigny, J.-M. 2003. New microsatellite markers for the snow crab Chionoecetes opilio (Brachyura: Majidae). Molecular Ecology Notes. 3:644-646.

• Puebla, O., Sevigny, J.-M., Sainte-Marie, B., Brethes, J.-C., Burmeister, A., Dawe, E. G. and Moriyasu. M. 2008. Population genetic structure of the snow crab (Chionoecetes opilio) at the Northwest Atlantic scale. Canadian Journal of Fisheries and Aquatic Sciences 65:425-436.

• Stabeno, P.J., Kachel, N.B., Salo, S.A. & Schumacher, J.D. 2001. On the temporal variability of the physical environment over the south-eastern Bering Sea. Fisheries Oceanography

10(1) 81-98.• Weingartner, T., Aagaard, K., Woodgate, R., Danielson, S., Yasunori, S. & Cavalieri, D. 2005.

Circulation on the north central Chukchi Sea shelf. Deep-Sea Research II 52: 3150-3174.

Questions and Comments?