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)