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 Candidate1 Memorial University of Newfoundland, St John’s, Canada
2 Bigelow Laboratory for Ocean Science, West Boothbay Harbor, USA
Effects of conspecifics on lobster recruitment
• recruitment drivers at different spatial scales
• American lobster
• patterns: long term recruitment time series
• mechanisms: behavioural experiments
• conclusions
Recruitment drivers over different spatial scales
Behaviour
Inter- and Intra-specific interactions
Benthic movements/migrations
Be
nth
ic
po
st-s
ett
lem
en
t p
roce
ss
es
Pe
lag
ic
pre
-se
ttle
me
nt
pro
ces
ses
Passive Transport
Ocean gyresBoundary layer turbulence
Swimming ability
Habitat selection
Vertical horizontal movement
Predation, competition
spatial scale +- 104 m10-2
American lobsterHomarus americanus
PelagicPelagic
BenthicBenthic
5-39mm
Early Benthic Phase Early Benthic Phase (EBP)(EBP)
Adolescent Phase Adolescent Phase (AP)(AP)
40-89mm40-89mm
Reproductive Phase Reproductive Phase (RP)(RP)
90+mm90+mm
3-8 weeks3-8 weeks
Stage IStage I
8 mm8 mm
9 mm9 mm
11 mm11 mm
11 mm11 mm
Stage IIStage II Stage IIIStage III
Stage IVStage IV
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?
REGIONS100 km
QUADRATS1 m
2002 - 2008
SITES10 km
Nested Sampling Design
Evaluate patterns & processes operating at
different spatial scales
Develop hypotheses for mechanisms
year n R2 p-value
2002 12 0.73 < 0.0001
2003 11 0.89 < 0.0001
2004 11 0.66 < 0.0001
2005 12 0.52 < 0.0001
2006 11 0.69 < 0.0001
2007 12 0.58 < 0.0001
2008 14 0.90 << 0.0001
1.8
1.2
0.6
0 3.5 7.0
Regional scale
OCJ density ( n / m 2 )
Yo
Y d
ensi
ty (
n /
m 2
)
RI
Site scale
OCJ density ( n / m 2 )
Yo
Y d
ensi
ty (
n /
m 2
)
3.0
1.5
0 5.0 10.0
• frequency of quad with/without YoY densities of OCJ
Quadrat scale
# of OCJ
pres abs sumpresprop
0 46 396 442 0.10
1 52 111 163 0.32
2 24 46 70 0.34
3 19 24 43 0.44
4 16 8 24 0.67
<5 10 7 17 0.59
0
1
2
3
4
0 2 4 6 8 10
OCJ density ( n / m 2 )
Yo
Y d
ensi
ty (
n /
m 2
)
0.70
0.35
0.000 1 2 3 4 5+
pro
po
rtio
n o
f q
uad
rats
# of OCJ / quadrat
year χ2 P
2002 103.749 <0.001
2003 156.802 <0.001
2004 107.332 <0.001
2005 113.927 <0.001
2006 59.338 <0.001
2007 12.728 0.026
2008 90.896 <0.001
observed expected
Quadrat scale
YoY with OCJ
• 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
Recruitment drivers over different spatial scales
+ association between YoY and OCJ at all scales (regional, site, quadrat)
behaviour experiments to identify small scale mechanisms
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 - immediateproportion of time on bottom
24 hour – long term recorded at 0, 6, 12, 18, 24h swimming / on bottom
presentn = 48
absentn = 46
0.5
0.25
0
Pro
port
ion
Short term – 4 minute
Proportion of time on bottom
t95 = 1.66P = 0.02
OCJ present absent
HO = HA
Long term – 24 hourProportion settled
HO ≠ HA
pro
po
rtio
n
time (hours)
0.35
0 2418126 0
0.70
Passive ocean processes
Preference for habitat R
eg
ress
ion
A
na
lys
is• effect didn’t persist with time ? hierarchical cue? other cue variables? i.e. with / without cobble
ConclusionsB
eh
avio
ur
exp
eri
me
nts Initial
propensity to settle
Strong YoY – OCJ association at all spatial scales
?
spatial scale +- 104 m10-2
AcknowledgementsAcknowledgements
• NSERC, Darling Marine Center, Bonne Bay Marine NSERC, Darling Marine Center, Bonne Bay Marine Station, Stonington Zone C hatchery, NOAA / Sea Grant, Station, Stonington Zone C hatchery, NOAA / Sea Grant, DFO, CURRADFO, CURRA
• Rachel Lasley, Hannah Blossom, Charlene Bergeron, Rachel Lasley, Hannah Blossom, Charlene Bergeron, Martina Kluge, Don Saunders, Benoit BruneauMartina Kluge, Don Saunders, Benoit Bruneau