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An Age‐Structured Bioeconomic Simulation of U.S. Silver Hake Fisheries
Author(s) -
Helser Thomas E.,
Thunberg Eric M.,
Mayo Ralph K.
Publication year - 1996
Publication title -
north american journal of fisheries management
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.587
H-Index - 72
eISSN - 1548-8675
pISSN - 0275-5947
DOI - 10.1577/1548-8675(1996)016<0783:aasbso>2.3.co;2
Subject(s) - fishing , fishery , stock (firearms) , yield (engineering) , revenue , population , hake , bioeconomics , economics , environmental science , geography , biology , fish <actinopterygii> , finance , demography , materials science , archaeology , sociology , metallurgy
We present a bioeconomic simulation of the U.S. fisheries for silver hake Merluccius bilinearis , an abundant species distributed over the northwest Atlantic continental shelf and historically important to both U.S. and foreign fishing fleets. The model combines elements of agestructured population and harvest yield models with a two‐equation price response model. The analysis evaluates biological benefits of interest to managers, such as future yields or rebuilding of parental stock, as well as future revenues and net present value of interest to harvesters. In one set of simulations, yield and revenue response surfaces were generated for varying levels of fishing mortality ( F ) and selection at age under constant annual recruitment. In another, a stochastic stock–recruitment function permitted assessment of yield and revenue trajectories over time given variable annual recruitment. Under equilibrium conditions, response surfaces for both total fishery yield and revenue are asymptotic with increasing fishing mortality rates. This result suggests that little yield or revenue would be lost if fishing mortality were reduced to less than 0.5. Maximum revenue occurs at slightly greater F s and with a selection pattern favoring slightly younger fish than is the case for yield maximization. Simulation results, incorporating variable recruitment, indicate that considerable long‐term biological and economic benefits accrue when fishing mortality rates are moderate ( F = 0.35 and F = 0.50 for the northern and southern stocks, respectively) and the age at capture is delayed until age 3 (50% selection at age 3). Over a 10‐year simulation horizon, yield to the fishery increases by 80%, and spawning stock biomass almost doubles, resulting in significant stock rebuilding. Although lower revenues occur in the early years, higher revenue streams are realized later on, producing significant long‐term gains. The net present value of a stock rebuilding strategy was estimated at US$150 million. Other harvesting strategies examined resulted in lower present values.