SEMINAR: MBF 602 Seminar- Mark Fitchett March 5th, 2010 4:00pm MSC 343 PLEASE NOTE LOCATION CHANGE!

[Cary Rios <crios@rsmas.miami.edu>]

The location for this week's student seminar has been moved to MSC 343- only for this week.

Use of Historical Trophy Sizes and Length Frequency Data to Estimate Growth Parameters for Sailfish in the Eastern Pacific

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Reliable growth parameters for sailfish (Istiophorus platypterus) in the Eastern Pacific Ocean (EPO) are lacking. Existing models may underestimate L_â, the average asymptotic growth maxima for sailfish, due to sampling selectivity issues and likely depletion. Additionally, modal progression methods that utilize sequential length-frequency data sets with a likelihood based estimation procedure can estimate growth parameters, but to a limited capacity if executed properly. Historical trophy sizes (annual tournament winning fish recorded by the International Game Fish Association) provide a unique baseline for maximum sized fish. Trophy sizes (weights in kilograms) recorded prior to present-day depletion are converted to lengths through the use of weight-length conversion methods. Through a meta-analysis of weight-length relationships of sailfish and other related istiophorid billfishes, a log-linear weight-length model is bootstrapped to construct a covariance matrix so that weight-length conversions are produced by Monte Carlo simulation. A uniformly distributed series of trophy lengths (in centimeters) is then simulated to generate a series of maximum lengths (L_max) which are compared to length-frequency data for sailfish to estimate a distribution of L_â through the use of extreme value theorem. Growth parameter estimates generated from trophy sizes are then compared to those generated by length-frequency analysis and existing parameter estimates in scientific literature. A growth algorithm following a Bayesian rationale is to be created using an adopted distribution of L_â estimates. Development of reliable growth parameters is imperative such that ontogenetic movement of sailfish throughout the EPO may be modeled effectively and mortality may be better estimated. Age/size structure of sailfish available to catch-and-release sportfisheries will ultimately be modeled in an experimental simulator for my Dissertation.

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Mark Daniel Fitchett

B.S. Zoology

B.S. Natural Resources

North Carolina State University, Raleigh, NC (2004)

Entered MBF: Fall 2004

M.S. Marine Biology and Fisheries

University of Miami, RSMAS, Miami, FL (2007)

Begin PhD: Fall 2007

Advisor: Dr. Nelson M. Ehrhardt

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Cary Rios 
Office of the Dean
University of Miami
Rosenstiel School of Marine & Atmospheric Science

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