Yuying Zhang

Date of Award

2010

Level of Access Assigned by Author

Campus-Only Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Interdisciplinary Program

Advisor

Yong Chen

Second Committee Member

James A. Wilson

Third Committee Member

Huijie Xue

Abstract

The American lobster (Homarus americanus) supports one of the most valuable commercial fisheries in the United States. Controversy exists in biological reference point (BRP) used in assessing the lobster stock status over the last two decades, and harvest control rule (HCR) is not fully established and evaluated. In this study, using data for the Gulf of Maine from 1982-2007 I developed a seasonal sex-specific size-dependent operating model to evaluate the performance of different HRCs. For each control rule evaluated, different combinations of biomass-based BRPs, fishing mortality-based BRPs and catch-based BRPs had been considered, as well as the management duration (5 and 25 years), recruitment dynamics, and variability in natural mortality. I developed a seasonal sex-specific individual-based per-recruit model to mimic the American lobster life history and fishery in the Gulf of Maine (GOM); Egg-per-recruit, stock spawning biomass-per-recruit, and yield-per-recruit analyses were conducted for estimating F10% and F0.1. I also quantified the relationship between the parental stock and subsequent recruitment; evaluated different time intervals between the spawning stock and recruitment in stock-recruitment modeling; and developed the maximum sustainable yield related biological reference points for the GOM American lobster fishery. In addition, a user-friendly version of stock assessment model was developed to facilitate the easy use of the assessment models by biologists and managers who may not be familiar with modeling and computer programming. This involves interdisciplinary research in the fields of fishery population dynamics, fishery management, statistics and computer programming. It shows that the HCRs with a suitable combination of BRPs can be effective in driving the fishery from the undesired status to an optimal status. The study also suggests that it is important to know the selectivities and pitfalls associated with different stock abundance measures used in the lobster fishery assessment and management. A large uncertainty exists in stock-recruitment relationship for the GOM stock. The study provides a list of HCR and BRPs that can be used as a management target and threshold for the GOM American lobster fishery and develops a series of stock assessment and management tools for the assessment and management of American lobster fishery in the northeast USA.

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