Management of a multigear fishery exploiting a highly migratory stock: Spanish mackerel, Scomberomorus maculatus, in the eastern Gulf of Mexico

Date of Award




Degree Name

Doctor of Philosophy (Ph.D.)


Marine Biology and Fisheries

First Committee Member

Nelson Ehrhardt, Committee Chair


Three specific problems created by a multigear fishery exploiting a highly migratory population were examined: (1) use of catch per unit effort to reflect population abundance for a migratory stock; (2) seasonal fisheries not adhering to the assumption of a constant annual fishing mortality rate during the year; and (3) the ability to allocate a total quota amongst user groups to achieve a given management goal. The theoretical basis for each problem was examined and simulations incorporating some aspects of uncertainty from the real world were conducted based on the Spanish mackerel, Scomberomorus maculatus, fishery in the eastern Gulf of Mexico.Three catch per unit effort (CPUE) indices were compared in ability to reflect changes in population abundance of a migratory species: whole season, fully available and maximum. An algorithm was developed to correct annual observed catches from seasonal fisheries to meet the assumption of a constant fishing mortality rate during the year. A separate algorithm was developed to allow incorporation of additional constraints to match the allocation scheme when computing a total quota for multiple gears.A migratory age and size based fishery simulation model (MASFISH) was created to examine these problems and potential solutions for the Spanish mackerel fishery in the eastern Gulf of Mexico. Application of the model consisted of six experiments. Two stock assessment experiments examined the ability of the three CPUE indices and two types of catch (observed and corrected) to estimate population abundance when used in tuned virtual population analysis. Four management experiments examined the ability to recover an overexploited stock under the twelve total combinations comprised of three CPUE indices, two types of catch, and two methods of setting quotas (incorporating or independent of quota allocations). The three CPUE indices performed nearly identically, while the corrected catch outperformed observed catch, and the inclusion of quota allocations when setting the quota produced better management than computing the total quota independent of the quota allocation.


Agriculture, Fisheries and Aquaculture

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