Interactions between the European Green Crab and the Asian Shore Crab

Transcription

1 Interactions between the European Green Crab and the Asian Shore Crab Christopher J. Baillie 1 * Jonathan H. Grabowski 1 1 Marine Science Center, Northeastern University Baillie.c@husky.neu.edu

2 Invasion Timeline C. maenas Replacement 1817 Green Crabs introduced to Mid- Atlantic coast of North America 1951 Green crabs present throughout New England fold increases H. sanguineus 40-90% decline C. maenas Green Crab Asian Shore Crab Green Crab populations expand into southern New England 1988 Asian Shore Crabs introduced to Atlantic Coast of North America (New Jersey)

3 Replacement of Carcinus by Hemigrapsus Pattern Proposed Mechanism Hemigrapsus 10-Fold Carcinus 40-90% Lohrer & Whitlatch 2002 Combined effects of Predation and Competition Full Replacement Griffen 2016

4 Invasion Timeline C. maenas Replacement 1817 Green Crabs introduced to Mid- Atlantic coast of North America 1951 Green crabs present throughout New England Early 2000s Asian Shore Crab range: NC to ME Green Crab Asian Shore Crab Green Crab populations expand into southern New England 1988 Asian Shore Crabs introduced to Atlantic Coast of North America (New Jersey) fold increases H. sanguineus 40-90% decline C. maenas

5 Spatial Overlap Native & Early Invasion Air Breathing? Southern New England

6 Field Survey x5-0.5 m MLWL +1.5 m MLWL 0.0 m MLWL Monthly Sampling +1.0 m MLWL

7 High Intertidal Mid Intertidal Low Intertidal Delaney et al. Distribution and Replacement Asian Shore Crab Menge Green Crab Nahant- Swampscott Present Pre-Invasion Post-Invasion Canoe Beach Menge (1983)* Pre-Invasion vs Present H. sanguineus NA C. maenas 89.6% * Reported aggregate low intertidal and shallow subtidal densities Canoe Beach Delaney et al. (2011)* Early postinvasion vs Present H. sanguineus 2300% C. maenas 65.9% * Reported aggregate intertidal and shallow subtidal densities

8 Research Questions Does exclusion of adult H. sanguineus affect densities of C. maenas and H. sanguineus recruits? Are effects of adult H. sanguineus on densities of C. maenas and Asian Shore Crab H. sanguineus recruits density dependent?

9 2015 Exclusion Experiment Closed x m MLWL Open x3 Open x3 Closed x3 Open x3 Closed x3-0.5 m MLWL 0.0 m MLWL Experiment Deployed Cleared Cobble +1.0 m MLWL Monthly Sampling Final Sampling/Breakdown

10 Predator Community Full Cages Open Cages Effectively Excluded Predators 27 H. sanguineus: 1 C.maenas (>10mm CW) >100 H. sanguineus: 1

11 Effect of Caging on Newly Recruited Crabs Treatment P Value Elevation* Cage Treatment P Value Elevation < Cage ns E x C ns

12 Summary: Exclusion Experiment Equal Recruit Density Conspecific Prey Avoidance C. maenas H. sanguineus Anti-Predator Response Efficacy Savaria & O Connor, 2013

13 Research Questions Does exclusion of adult H. sanguineus affect densities of C. Asian Shore Crab maenas and H. sanguineus recruits? Are effects of adult H. sanguineus on densities of C. maenas and H. sanguineus recruits density dependent?

14 2016 Inclusion Experiment Experiment Deployed x 6 Monthly Sampling 0.0 m MLWL Final Sampling/Breakdown Cleared Cobble No Crabs C. maenas 0.25m 2 x 1 Low H. sanguineus Intermediate H. sanguineus x 5 x 10 x 20 High H. sanguineus

15 Density (individuals 0.25m -2 ) Recruit Densities: Control Treatments H. sanguineus C. maenas Newly Recruited

16 H. sanguineus Recruits Effect on H. sanguineus < 10 mm CW H. sanguineus adults C. maenas adult ns C. maenas <10 mm CW ns 40% Decline Intercohort Conspecific Predation/Displacement

17 C. maenas Recruits Effect on C. maenas < 10 mm CW H. sanguineus adults ns C. maenas adult ns H.sanguineus <10 mm CW Intracohort Heterospecific Predation/Displacement

18 Summary: Inclusion Experiment H. sanguineus Dominated Prey Community C. maenas H. sanguineus

19 Conclusions: Juxtaposing Results

20 Acknowledgements Allison Matzelle, Lucy Harrington, Kat O brien, Kelsie Schultz, Rami Maalouf The Grabowski Lab Northeastern University s Marine Science Center Northeastern University College of Science