SUMMARY

• Main Author: S J Harley
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: Lamna nasus; Northwest Atlantic; Porbeagle
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.581.7153; http://www.iccat.int/Documents/CVSP/CV054_2002/no_4/CV054041314.pdf

A variety of data types are available for the assessment of the Northwest Atlantic porbeagle shark (Lamna nasus) population. I describe an age- and sex-structured population dynamics model that fits to catch-at-length data and catch-per-unit-effort data from the fishery. This model provides an ideal environment for the exploration of the available data as it links the data via a dynamic model. This allows one to look for inconsistencies among data types and may provide insights into both population and fleet dynamics. A model of this general type could also be used in the formal assessment of the stock and has the advantage that by including much of available data into the estimation procedure, it may overcome some confounding from estimating key parameters outside of the model. A number of possible disadvantages of this approach are also discussed. Given the low fecundity of porbeagle sharks it is possible to derive spawner recruitment parameters from biological data, thus overcoming a common problem associated with forward projection models. I show how it is also possible to integrate mark-recapture data into the assessment model to improve the estimation of both annual and age-specific fishing mortalities. Preliminary results from this model were presented