Dynamics and management of anadromous alewife (Alosa pseudoharengus) populations.
Date
2004
Authors
Gibson, A. Jamie F.
Journal Title
Journal ISSN
Volume Title
Publisher
Dalhousie University
Abstract
Description
The objective of this thesis is to conduct basic research about the population dynamics of anadromous alewife and use the results to develop assessment and management models this species. This objective is met through the development of a population dynamics model based on the life history of anadromous Alosa. The two underlying themes throughout the thesis are the adaptation of the model to individual stocks and management questions, and parameter estimation for the model. I used the model to estimate fishing and natural mortality rates, maturity schedules and spawner-recruit (SR) time series that I used to derive fisheries reference points for alewife populations in the Maritime Provinces, Canada.
The effects of turbine mortality at hydroelectric generating stations on fishery yields and reference points were examined using the model. Based on experiments at the Annapolis Tidal Generating Station, I tested whether a modification to methods used to estimate turbine mortality could improve the resulting estimates and whether modelling of the process governing the rate of fish passage at hydroelectric generating stations could improve assessment of fish diversion systems.
Spawner-recruit relationships for alewife are poorly determined when estimated using population-specific data. I therefore carried out a meta-analysis of the dynamics of eight alewife populations to derive species-level probability distributions for the maximum lifetime reproductive rate and carrying capacity for alewife. I used the resulting distributions as Bayesian priors when estimating fishery reference points.
I evaluated methods of estimating fishery reference points from noisy SR data using simulated data. When the maximum likelihood estimates of the SR parameters are used to estimate the fishing mortality rate that produces maximum sustainable yield, the resulting estimates may lead to substantial under- or over-exploitation of the population. In contrast, the method of maximizing the expectation of the yield is less variable, produces larger yields and substantially reduces the risk of over-exploitation.
Thesis (Ph.D.)--Dalhousie University (Canada), 2004.
The effects of turbine mortality at hydroelectric generating stations on fishery yields and reference points were examined using the model. Based on experiments at the Annapolis Tidal Generating Station, I tested whether a modification to methods used to estimate turbine mortality could improve the resulting estimates and whether modelling of the process governing the rate of fish passage at hydroelectric generating stations could improve assessment of fish diversion systems.
Spawner-recruit relationships for alewife are poorly determined when estimated using population-specific data. I therefore carried out a meta-analysis of the dynamics of eight alewife populations to derive species-level probability distributions for the maximum lifetime reproductive rate and carrying capacity for alewife. I used the resulting distributions as Bayesian priors when estimating fishery reference points.
I evaluated methods of estimating fishery reference points from noisy SR data using simulated data. When the maximum likelihood estimates of the SR parameters are used to estimate the fishing mortality rate that produces maximum sustainable yield, the resulting estimates may lead to substantial under- or over-exploitation of the population. In contrast, the method of maximizing the expectation of the yield is less variable, produces larger yields and substantially reduces the risk of over-exploitation.
Thesis (Ph.D.)--Dalhousie University (Canada), 2004.
Keywords
Agriculture, Fisheries and Aquaculture.