Tag Return Models for Estimating Fishing Mortality and Natural Mortality:
Application in Fisheries Research and Management Illustrated by Maryland
Striped Bass Tag Return Data

KENNETH H. POLLOCK

Zoology, Biomathematics and Statistics

Abstract

Tag return studies play an important role in providing estimates of
fishing mortality and natural mortality rates needed for management of
many fisheries. I briefly present models that allow age dependent fishing
and natural mortality rates, an important advance, because there is often
substantial variation in age (and size) of fish at tagging. I also present
another extension that allows for some of the fish to be caught and
released rather than harvested as in the traditional models. This is joint
research with various colleagues.

The methodology is illustrated with an application to tagging data from a
Maryland Striped Bass population. We were able to estimate natural
mortality by age and show how those natural mortality rates appear to have
increased since 1999 due to the outbreak of a disease called
mycobacteriosis. At the end of the seminar I will talk about why these
results are so important and how bio mathematical and statistical modeling
are both important and complement each other in fisheries research and
management.