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What’s next for blue crabs? Forecasting blue crab range
expansion into the Gulf of Maine
Tanya Rogers Ph.D. Student
Northeastern University
Marine Science Center
Nahant, MA
Kaneohe Bay, Hawaii
San Francisco Bay, CA
Kaneohe Bay, Hawaii
Kaneohe Bay, Hawaii
Kaneohe Bay, Hawaii
Bodega Bay, CA Bodega Marine Lab
San Juan Islands, WA Friday Harbor Labs
Great Barrier Reef, Australia
Lizard Island Research Station
Panama
Smithsonian Tropical Research Institute
Florida Florida State University Coastal & Marine Lab
New England
Northeastern University Marine Science Center
Species Ranges
Climate Change and Range Expansion
North
South
North
South
Climate Change and Range Expansion
North
South
North
South
Blue Crab Range
Chesapeake Bay
Cape Cod
Blue Crabs (Callinectes sapidus)
“Beautiful savory swimmer” Live in coastal estuaries Omnivorous diet (predators and scavengers) Lifespan: 3-4 years Adult size: 4-9 inches
Blue Crab Range Expansion?
sightings from Johnson (2015)
Historic blue crab range
2012-2014 sightings
Cape Cod
Gulf of Maine
Estuaries Provide Important Sevices • protect shorelines from storms, floods, erosion • filter water (remove pollutants and sediment) • remove and recycle nutrients • sequester carbon • provide habitat for valuable species
Threatened by: • Coastal development • Pollutants and nutrients in run-off • Invasive species • Sea level rise & Climate change
Blue Crabs are Important Predators
+
Blue Crabs are a Major Fishery
8th largest commercial fishery in U.S. 5th largest in value (over $200 million dollar industry)
Over 60,000 metric tons caught annually 75% from North Carolina, Virginia, Maryland, Louisiana
Important recreational fishery in New England Source: NMFS 2010
Green Crab Range
Blue Crab Range
Chesapeake Bay
Cape Cod
Blue Crabs aren’t alone…
• Invasive species from Europe • Similar diet as blue crabs • Similar habitat use • Cause a lot of problems salt marshes seagrass beds softshell clam beds • Large blue crabs can eat green crabs
Research Questions
What limits the northern range of the blue crab?
Will blue crabs expand their range northward as climate warms?
How will salt marshes be affected by blue crabs and directly by temperature increases?
How do blue crabs interact with invasive green crabs?
Blue Crab Life Cycle
hibernation (winter)
spawning (spring)
inner estuary outer estuary open ocean
mating
zoea
megalops juveniles and adults
migration
mated females
growth (summer)
settlement
(early larval stage)
(late larval stage)
What limits the northern range? Physiology
(too cold)
Gulf Stream
Nova Scotia Current
Maine Coastal Currents
Georges Bank
What limits the northern range? Physiology
(too cold)
Recruitment limitation
(crabs can’t get there)
Species interactions
(predator or competitor)
Lack of habitat or food
Gulf Stream
Nova Scotia Current
Maine Coastal Currents
Georges Bank
What limits the northern range? Physiology
(too cold)
Recruitment limitation
(crabs can’t get there)
Species interactions
(predator or competitor)
Lack of habitat or food
Blue Crab Life Cycle
hibernation (winter)
spawning (spring)
inner estuary outer estuary open ocean
mating
zoea
megalops juveniles and adults
migration
mated females
growth (summer)
settlement
(early larval stage)
(late larval stage)
20-25 °C
15-20 °C
0-3 °C
Adults and Late Larval Stages
Wells Bay, ME
Waquoit Bay, MA
Tem
pe
ratu
re (
°C)
Waquoit Bay, MA Wells Bay, ME
Within-estuary water temperature
0-3 °C 15-20 °C
Early Larval Stages
Early larval stages likely limited by cold temperatures in the summer
Cape Cod Bay
Nantucket Sound
Sea surface temperature
Nantucket Sound Cape Cod Bay
Tem
pe
ratu
re (
°C)
20-25 °C
Blue Crabs and Temperature Crab Density Data from Mass DMF Flounder Surveys (1976-2014)
Sea Surface Temperature (°C) (May Average)
2012
Within-Estuary Temperature (°C) (May Average)
Waquoit Bay, MA 2002-2014
Southern Cape Cod 1987-2014
2012
Blu
e C
rab
De
nsi
ty (
Jun
e)
Blue crab densities generally increase with increasing temperature
How will marshes be affected?
1) Where are the crabs and what do the marshes look like? Surveys to describe patterns in crabs, invertebrates, and plants north and south of Cape Cod (2014-2015) 2) How will crab introduction and temperature increase
(alone and together) affect marshes? Lab and/or field experiment based on surveys, using
existing environmental gradient (2016-2017)
2014 Summer Survey Sites
Within-Estuary Surveying
mid
inner
outer
5 meters back from creek bank
Crab Trapping
creek bank creek channel
• Crab species • Crab abundance • Crab size • Crab sex
Vegetation & Invertebrate Surveying
• Vegetation cover • Vegetation height • Invertebrate abundances crab burrows mussels snails other crustaceans
Green Crabs
Blue Crabs
Cra
bs
pe
r Tr
ap
Cra
bs
pe
r Tr
ap
Creek
North South
North South
Mussels
Crab Burrows
Mu
sse
ls o
n C
ree
k Ed
ge
(# p
er
Qu
adra
t)
Cra
b B
urr
ow
s
(# p
er
Qu
adra
t)
Creek
North South
North South
2015 Summer Survey Sites
outer creek
inner creek
main channel
200 m inlet
9 traps
trap placement
2015 Sampling
12 hours
Blue Crabs – Green Crab Interactions
green crabs small blue crabs
big blue crabs
shared prey
Asymmetric Size-dependent Temperature-dependent
only at higher temperature does growth rate depend
on temperature?
does competitiveness depend on temperature?
Intraguild Predation
Green Crab Range
Blue Crab Range
Chesapeake Bay
Cape Cod
Blue Crabs – Green Crab Interactions
Can temperature – dependent interactions explain where crabs coexist and don’t coexist?
Blue Crabs – Green Crab Interactions
Blue Crabs – Green Crab Interactions
Who gets the food?
ha ha!
Blue Crabs – Green Crab Interactions
Who gets the food? Did a predation event occur?
nom nom nom!
Blue Crabs – Green Crab Interactions
10 C 20 C 30 C
Who gets the food? Did a predation event occur?
Green Crab Range
Blue Crab Range
Chesapeake Bay
Cape Cod
Blue Crabs – Green Crab Interactions
Can temperature – dependent interactions explain where crabs coexist and don’t coexist?
Why Crab Zonation? Negative interactions between species, or different environmental preferences?
Does this partitioning of habitat allow for their coexistence? Will have undergrad working on this summer
Implications
Environmental and biotic (predatory) controls of disruptive, invasive green crabs
- Possible biotic control by native predator?
Whether blue crabs are coming to an estuary near (or just north of) you
How crabs and climate change impact marsh ecosystem services
How you can help me: Let me know if you see (or have ever seen)
any blue crabs north of Cape Cod
Alive, dead, or shells (molts)? When and where?
How big? [email protected]
Acknowledgments Advisor: Dr. David Kimbro Committee members: Dr. Brian Helmuth Dr. Jonathan Grabowski Dr. Tarik Gouhier Dr. Amy Freestone Partners: Waquoit Bay NERR Narragansett Bay NERR Great Bay NERR Wells Bay NERR Steward B. McKinney NWR Parker River NWR New Partners (2015): Orleans Conservation Trust Conservation Commissions of Duxbury, Sandwich, Brewster, Harwich, and Chatham Cape Cod National Seashore
Field Help: Joe Gladstone & Forest Schenck Funding: Northeastern University MSC NSF Graduate Research Fellowship Data: Massachusetts Division of Marine Fisheries U. Maine Satellite Oceanography Data Lab National Estuarine Research Reserve System Crab Drawings: Myself Contact info: Email: [email protected] Lab website: kimbrolab.weebly.com
