Modeling heterogeneous fishermen behavior Michael Robinson UCSB Geography

Fisherman behavior Fishing is fraught with physical and financial risk and is undertaken in a constantly changing environment. Effort distribution within a fleet appears to be far from homogenous. Successful fishermen exhibit an ability to change their behavior with varying conditions and information. Learning and communication are critical components of fishing activity.

Fisherman behavior Research questions… –How are risk behaviors and decision paradigms set? –How do fishermen learn about their environment? How does this affect their efficiency and success? –How do these factors change over seasons, over years, and as catch is (or is not) accumulated?

Research Heterogeneous effort distribution –Satisficer-maximizer continuum Learning & memory –Bayesian updating Communication –Information exchange

Effort distribution

Effort distribution model Random fishing probabilities (~[0,1]) applied to each fisherman in fleet –Uniform –Exponential –Highly skewed gamma Utility function to decide most attractive patches

Fish block/simulation comparison 2004 DFG urchin block dataUrchin fishing simulation (uniform effort distribution) Memory and learning are missing!

Learning, memory, and communication

Learning & memory Learning: Information received from an individual’s daily fishing effort. Bayesian updating –DeGroot, 1970 –A fisherman updates beliefs about abundance after acquiring signal S a from visiting site a (these signals follow a normal distribution). Good signals (S a >α 0 ) increase expected abundance at site a. Noisy signals (large σ 2 s ) are given less weight.

Communication Communication: Information received from the fleet Information exchange matrix –Allen and McGlade, 1987 –Matrix of “how well” and with whom information is shared No sharing Perfect sharing Imperfect sharing Develop sharing weights –Clubs/code groups –Mean of guy that’s gone 200 times vs. mean of guy that’s only gone once –Variance of signal has an effect on “confidence in the signal”

Fish block/simulation comparison Red = fishing, blue = no fishing 2004 DFG urchin block data Urchin fishing simulation (exponential effort distribution)

Image: Wm. B. Dewey, Questions?Suggestions? THANKS… Dave Siegel, Chris Costello, Kostas Goulias, Kristine Barsky, Chris Miller, Pete Halmay