Victoria Burdett-Coutts* 1 , Richard Wahle 2 , Paul Snelgrove 1 *MSc Candidate

1. Effects of conspecifics on lobster recruitment – Insights from larval behaviour experiments and multi-scale population monitoring. Victoria Burdett-Coutts*1, Richard Wahle2, Paul Snelgrove1 *MSc Candidate 1 Memorial University of Newfoundland, St John’s, Canada 2 Bigelow Laboratory for Ocean Science, West Boothbay Harbor, USA

2. Effects of conspecifics on lobster recruitment • recruitment drivers at different spatial scales • American lobster • patterns: long term recruitment time series • mechanisms: behavioural experiments • conclusions

3. Boundary layer turbulence Ocean gyres Swimming ability Habitat selection Vertical horizontal movement Benthic movements/ migrations - spatial scale + 10-2 104 m Recruitment drivers over different spatial scales Passive Transport Pelagic pre-settlement processes Behaviour Benthic post-settlement processes Inter- and Intra-specific interactions Predation, competition

4. American lobster Homarus americanus

5. Pelagic 9 mm 11 mm 8 mm Stage II Stage III Stage I • What is the relationship between Young-of-Year (YoY) and older conspecific juvenile (OCJ) density at different spatial scales ? • Does this relationship have a behavioural basis? 3-8 weeks Stage IV 11 mm Benthic Reproductive Phase (RP) Early Benthic Phase (EBP) Adolescent Phase (AP) 5-39mm 40-89mm 90+mm

6. REGIONS 100 km SITES 10 km QUADRATS 1 m Nested Sampling Design 2002 - 2008 Evaluate patterns & processes operating at different spatial scales Develop hypotheses for mechanisms

7. 1.8 RI 1.2 0.6 0 3.5 7.0 Regional scale YoY density ( n / m 2 ) OCJ density ( n / m 2 )

8. 3.0 1.5 0 5.0 10.0 Site scale YoY density ( n / m 2 ) OCJ density ( n / m 2 )

9. frequency of quad with/without YoY densities of OCJ Quadrat scale YoY density ( n / m 2 ) OCJ density ( n / m 2 )

10. 0.70 YoY with OCJ observed expected 0.35 0.00 0 1 2 3 4 5+ Quadrat scale proportion of quadrats # of OCJ / quadrat

11. Recruitment drivers over different spatial scales + association between YoY and OCJ at all scales (regional, site, quadrat) • consistent circulation-driven spatial differences in larval supply and settlement • similar habitat requirements, postlarvae select for cobble/boulder habitat • How do stage IV lobsters respond to the presence of older conspecific juveniles during settlement? • Boudreau et al (1993) • + swimming orientation toward conspecifics • Behaviour is cost – benefit • cost • cannibalism, competition • benefit • indicators of suitable habitat • behaviour experiments to identify small scale mechanisms

12. Experimental design • independent – presence/absence of OCJ • dependent – settlement response of individual stage IV postlarvae • sandy bottom, juvenile containers, YoY shelters • short term and long term exp • 4 minutes - immediate • proportion of time on bottom • 24 hour – long term • recorded at 0, 6, 12, 18, 24h • swimming / on bottom

13. present absent Short term – 4 minute Proportion of time on bottom t95 = 1.66 P = 0.02 0.5 0.25 Proportion 0 absent n = 46 present n = 48 OCJ

14. Long term – 24 hour Proportion settled HO≠ HA HO= HA 0.70 proportion 0.35 0 0 6 12 18 24 time (hours)

15. Preference for habitat Regression Analysis Passive ocean processes ? - spatial scale + 10-2 104 m Conclusions Strong YoY – OCJ association at all spatial scales • effect didn’t persist with time ? •  hierarchical cue? •  other cue variables? • i.e. with / without cobble Initial propensity to settle Behaviour experiments

16. Acknowledgements • NSERC, Darling Marine Center, Bonne Bay Marine Station, Stonington Zone C hatchery, NOAA / Sea Grant, DFO, CURRA • Rachel Lasley, Hannah Blossom, Charlene Bergeron, Martina Kluge, Don Saunders, Benoit Bruneau