Stochastic Transport Generates Coexistence in a Nearshore
Multi-Species Fishery
Heather Berkley, Satoshi Mitarai, Bruce Kendall, David Siegel,
Robert Warner
NSF Biocomplexity Project - Flow, Fish and Fishing
Multi-species Model
• Stochastic dispersal as a mechanism for coexistence
• What is impact of stochastic dispersal on interactions?
• What factors will influence coexistence?
• Diffusive Dispersal: competitive exclusion
• Stochastic Dispersal: can coexist
Packet Model
• Larval settlement as arrival of N packets
• L = domain size• l = eddy size (50 km)• T = Spawning time• t = eddy turnover rate (14 d)
t
T
l
LN
eddy size (l)
N larval packets
Modeling 2 Species w/ Different Spawning Times
• Considering 2 species with similar life histories (Life span, Fecundity, PLD, etc)
• Differences in when and how long they release larvae will impact where their larvae settle
• Packets released within 14 days will end up in the same location
Spawning Window Overlap
• Specify how many days of overlap between spawning times for both species
• Makes some packets perfectly correlated for both species and others independent
Packets will have same settlement locations
Species A Spawning Window
Species B Spawning Window
TIME
destination
sou
rce
10 20 30 40 50 60
10
20
30
40
50
60
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
destination
sou
rce
10 20 30 40 50 60
10
20
30
40
50
60
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2 2
1 1
Species A Species B
Distribution of Packets
• ~Half of spawning windows overlap
destination
sou
rce
10 20 30 40 50 60
10
20
30
40
50
60
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
destination
sou
rce
10 20 30 40 50 60
10
20
30
40
50
60
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2 2
1 1
Species A Species B
Distribution of Packets
• ~Half of spawning windows overlap
• ~Half of the packets settle in the same locations
Parameters
• spawning time= 30 days for both– Vary amount of overlap
• Fecundity of Sp.A = 0.5• Fecundity of Sp.A = 0.45• Adult Mortality = 0.09• Run time = 500 yrs; • Patch size = 5 km; • Domain size = 500 km; • Larvae on larvae DD (total # of both sp) • Averaged over 10 simulations
Species A Species B
Adult Population• Single run• No overlap in spawning times• Packet transport => patchy distribution • Coexistence
Species A Species B
Mean Adult Abundance
Species A Species B
0 days of overlap
Species A Species B
10 days of overlap
Species A Species B
20 days of overlap
Species A Species B
25 days of overlap
Species A Species B
30 days of overlap
Summary
• Coexistence breaks down as settlement events become more correlated between species
• Increasing the number of independent packets accomplishes the same result– By chance more packets => more concurrent
settlement between species
Future Work
• Quantify how much overlap in spawning time can occur and still get coexistence
• Deal with partial correlation at edges of overlap??
• Statistics from flow simulations on overlapping spawning windows (Satoshi)