Optimal escapement in stage-structured fisheries with environmental stochasticity

Holden, Matthew H. and Conrad, Jon M. (2015) Optimal escapement in stage-structured fisheries with environmental stochasticity. Mathematical Biosciences, 269 76-85. doi:10.1016/j.mbs.2015.08.021

Author Holden, Matthew H.
Conrad, Jon M.
Title Optimal escapement in stage-structured fisheries with environmental stochasticity
Journal name Mathematical Biosciences   Check publisher's open access policy
ISSN 1879-3134
Publication date 2015-11-01
Sub-type Article (original research)
DOI 10.1016/j.mbs.2015.08.021
Open Access Status Not Open Access
Volume 269
Start page 76
End page 85
Total pages 10
Place of publication Philadelphia, United States
Publisher Elsevier
Language eng
Formatted abstract
Stage-structured population models are commonly used to understand fish population dynamics and additionally for stock assessment. Unfortunately, there is little theory on the optimal harvest of stage-structured populations, especially in the presence of stochastic fluctuations. In this paper, we find closed form optimal equilibrium escapement policies for a three-dimensional, discrete-time, stage-structured population model with linear growth, post-harvest nonlinear recruitment, and stage-specific pricing and extend the analytic results to structured populations with environmental stochasticity. When only fishing reproductive adults, stochasticity does not affect optimal escapement policies. However, when harvesting immature fish, the addition of stochasticity can increase or decrease optimal escapement depending on the second and third derivative of the recruitment function. For logistic recruitment, stochasticity reduces optimal immature escapement by a multiplicative factor of one over one plus the variance of the environmental noise. Using hard clam, Mercenaria mercenaria, as an example and assuming Beverton–Holt recruitment, we show that optimal fishing of hard clam targets the immature stage class exclusively and that environmental stochasticity increases optimal escapement for low discount rates and decreases optimal escapement for high discount rates.
Keyword Age-structure
Environmental stochasticity
Fisheries management
Mercenaria mercenaria
Optimal harvest
Q-Index Code C1
Q-Index Status Provisional Code
Institutional Status Non-UQ

Document type: Journal Article
Sub-type: Article (original research)
Collections: Faculty of Science Publications
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