Doctor of Philosophy (Ph.D.)
Virginia Institute of Marine Science
William D. DuPaul
Cooperative research utilizing industry vessels represents a viable approach to acquire the data necessary to meet the increasing needs associated with the modern management of marine resources. This dissertation addresses a variety of topics associated with the integration of commercial vessels into the stock assessment of the sea scallop, Placopecten magellanicus. In this study we evaluate the efficacy of utilizing industry vessels with respect to topics that range from rotational closed area survey design, sampling gear evaluation as well as an experiment that broadens the scale of the traditional use of industry vessels in this fishery and provides data to support the use of commercial vessels for surveying sea scallops resource wide. The first paper presents a methodology to evaluate candidate sampling designs for closed area surveys. We simulated scallop populations within a closed area based upon both empirical data and an analysis of the autocorrelation structure of the scallops in that area. From the simulated realizations of the scallop abundance and distribution, three different sampling designs at three levels of sampling were evaluated with respect to bias and accuracy of both mean abundance and variance of the sample mean. The second and third papers take advantage of the ability of commercial vessels to simultaneously tow two dredges. Based on this ability, in the second paper, we estimate the size selectivity of the currently mandated New Bedford Style sea scallop dredge. In addition to estimating the size selective characteristics of this piece of gear, we also estimate the efficiency of the dredge. Both measures are important with respect to correctly estimating the exploitable biomass of sea scallops in rotational sea scallop closed areas. The third paper again used paired data to evaluate the relative changes in the performance of the NMFS sea scallop survey dredge. We utilize a Generalized Linear Mixed Modeling (GLMM) approach to analyzing these data with the goal of characterizing any structural changes in the performance of the dredge that is used to survey both specifically scallop closed areas as well as the entire resource via the annual NMFS time series since the 1970's. The final paper broadens the scale of the utilization of industry vessels and calibrates two of these platforms to the NMFS annual sea scallop survey. We evaluated four separate vessel gear combinations relative to the R/V Albatross IV, throughout the range of the U.S. sea scallop resource and present information to either utilize these vessels to conduct the survey, or at least form a link to a future platform. The results in this dissertation demonstrate that industry vessels represent a feasible option for the collection of sea scallop stock assessment information and present both methods and current information to facilitate their use. These approaches are especially applicable for sea scallops, where the management for this species embraces the spatial characteristics of the underlying population and crafts appropriate management strategies.
© The Author
Rudders, David B., "Incorporating industry based dredge surveys into the assessment of sea scallops, Placopecten magellanicus" (2010). Dissertations, Theses, and Masters Projects. Paper 1539616833.