Utility and implications of no-take marine reserves in fishery management strategies
McGilliard, Carey Renee
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This work explores (1) the potential for using marine reserves to manage data-poor fish populations, (2) the potential for marine reserves to influence the performance of commonly used stock assessment approaches relative to alternative approaches that explicitly account for a marine reserve, and (3) hypotheses about the role of older females to population persistence and arguments that marine reserves are needed to maintain this role. In Chapter 1, the potential use of the ratio of the density of fish outside a marine reserve to that inside the reserve in a fishery management control rule (DRCR) is evaluated by Management Strategy Evaluation. The cumulative catch under the optimal DRCR was 90% of the cumulative catch from an optimal constant effort rule (CER). A small range of parameter values for the DRCR produced 75% or more of the cumulative catch produced from optimal CERs for a variety of assumptions about biology and initial stock status. The optimal DRCR was most sensitive to movement patterns of larvae and adults and survey variability. In Chapter 2, a simulation model was used to analyze the ability of several stock assessment approaches to estimate current biomass after the implementation of a marine reserve. Results show that assessing populations as a single stock without accounting for a no-take marine reserve and performing separate assessments for fished and protected areas can lead to severely biased estimates of biomass. An assessment approach which explicitly accounted for fish movement was robust to uncertainty in movement patterns. In Chapter 3, two popular hypotheses are modeled; one assumes that older mothers produce larger offspring capable of surviving longer starvation periods than offspring from younger mothers. The other modeled hypothesis is that mothers of different ages spawned in different times or locations. Recruitment variability was 55-65% lower than for control models in the absence of fishing and increased with increases in fishing mortality rates for both models. A marine reserve policy did not benefit measures of sustainability for either model.
- Fisheries