Simulating Larval Dispersal in the Santa Barbara Channel

Three big questions Where do the larvae come from… … where do they go … and how do they do this

The answers are… Source Patch Destination Patch Particle Advection

First things first Velocities….

Thanks Leo…

From Leo I have Velocities every 5 km, every day, from 1992 to the end of This is great as I can look at seasonal, inter-annual variability.

The Domain

The second thing I need to do is define my source/destination patches This is surprisingly complicated!! I am not going to base my patches on Kelp, Fish, Sand, Surfers or anything biotic My patches are ABIOTIC, they are simply areas of the coast

… and here they are, numbered

What do I do with this… I seed my particles uniformly over the entire patch area And then I advect with Leo’s velocities

Advection is simply… Xt+1 = Xt + (Ut * dt) Yt+1 = Yt + (Vt * dt)

Numbers in small print I am working with seeding ~2000 particles every day for 153 days (this is the length of the spawning period of Kelp Bass) ~ 300,000 particles total (takes 30 mins on my mac). I use velocities from May to Sept (the spawning period of Kelp Bass). I linearly interpolate to a 1hr time step. Kelp bass has a PLD of 36 days, this is how long I advect the particles for.

Dispersal Movie See link

COUNTING

Put complicatedly Kelp bass settles within 26 to 36 days of its spawning. So.. I count what patch particles are in within this time window, I also remember which patch they originated from. I can then make source and sink priorities…

Remember the patches

From the White patch, the priority of its sink patches i.e. where particles, that came from it, settled.

From the White patch, the priority of its source patches i.e. where particles that settled in it came from

This patch

Alright, If I put together all this information together I can show you a connectivity matrix. Just remember, particles go from the x-axis to the y-axis.

South Side North Side Mainland North Side South Side Normalized by the area of source and dest patch

South Side North Side Mainland North Side South Side Pure Count

So we can see some patterns in particle settlement. Remember that this isn’t larvae, this is simply where water is in a given time period. Larvae comes later

1997 El Nino 1995 Normal Just out of interest Look at the differences Between 1997 and 1995, Watch this space…

1997 El Nino 1995 Normal

Problems Land is sticky Counting Next steps… Demography? »Validation »Different years »How much physics do we need (how important is flow / how important is habitat)

Bouncing Movie

THANK’S FOR YOUR TIME.