Atlantic croaker are one of the most plentiful inshore, demersal fishes from the Chesapeake Bay to Florida. A coastwide assessment of the stock based on landings, fishery-dependent and fishery-independent length data, and survey abundance information was performed using the stock synthesis model. Landings have generally increased since the 1950s, with most of the catch occurring in North Carolina and Virginia. Major commercial gears are gill net, trawl, haul seine, and pound net. The recreational fishery has become increasingly important over time. Indices of relative abundance generated from fishery-independent surveys show that year-class strength has varied considerably among years. Patterns for year-class strength were consistent within each state, and fairly consistent among states. There is evidence for a potential rebuilding of the stock from both the observed data and model predictions. Coastwide length samples from the recreational fisheries and length samples from NC commercial fisheries demonstrated an increase in the maximum length in recent years. Observed and predicted mean lengths for the gill net, trawl, and recreational fisheries also suggest an increase in the proportion of older and larger fish in recent years. Observed trends in relative abundance and model predictions of recruitment reflect the presence of several recent strong year classes. The model results suggest that the population is highly recruitment-driven and that recruitment is variable. This dynamic is likely reflected in the harvest as variability in catch, which has shown fluctuations for at least the past 50 years. Estimates of fishing mortality have been high, particularly during the late 1980s when abundance was estimated to be low. Evaluation of the uncertainty in model estimates demonstrated that the model was fairly insensitive to changes in source data, but did appear sensitive to changes regarding assumptions about M and assumptions about the error associated with survey abundance indices. The yield-per-recruit analysis results suggested that a significant gain in yield would result if age-at-entry was delayed, which, in turn, would allow for relatively higher Fs. Comparison of age-0 abundance indices between Virginia and North Carolina revealed similar patterns in annual recruitment. Age-0 abundance indices also exhibited significant spatial autocorrelation for both states. In general, sampling stations in close proximity tended to have more similar observations of age-0 abundance. Positive spatial autocorrelation typically occurred at distances less than 30-km, while negative spatial autocorrelation was more often detected at distances of 40-km or greater. Accounting for spatial patterns in recruitment indices should result in a better measure of recruitment for use in future stock assessments.
| Identifer | oai:union.ndltd.org:NCSU/oai:NCSU:etd-11302005-134457 |
| Date | 02 December 2005 |
| Creators | Lee, Laura Maleda |
| Contributors | Kenneth H. Pollock, Peter S. Rand, Joseph E. Hightower |
| Publisher | NCSU |
| Source Sets | North Carolina State University |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://www.lib.ncsu.edu/theses/available/etd-11302005-134457/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to NC State University or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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