Developing an index of abundance for gag grouper in North Carolina

dc.contributor.advisorDr. Jeffrey Buckel, Committee Chairen_US
dc.contributor.advisorDr. Joseph Hightower, Committee Memberen_US
dc.contributor.advisorDr. Kenneth Pollock, Committee Memberen_US
dc.contributor.authorAdamski, Kyle Michaelen_US
dc.date.accessioned2010-04-02T18:03:23Z
dc.date.available2010-04-02T18:03:23Z
dc.date.issued2009-08-12en_US
dc.degree.disciplineFisheries and Wildlife Sciencesen_US
dc.degree.levelthesisen_US
dc.degree.nameMSen_US
dc.description.abstractGag grouper (Mycteroperca microlepis) are an economically important fish in the U.S. south Atlantic. Juvenile gag grouper utilize seagrass habitat soon after larval ingress into estuarine environments. The recent stock assessment for gag grouper indicated the need for a fishery-independent index of abundance. The goal of this study was to assess the potential for a post-larval and juvenile abundance index in North Carolina. Data on post-larval gag collected during the NOAA Beaufort Inlet Bridgenet Program (weekly samples from November – May of 1986 to 2008) were examined; additionally, ichthyoplankton were sampled nightly in spring of 2007 and 2008. A 5-m otter trawl was used to sample juvenile gag in seagrass beds at 15 to 20 randomly selected stations every two weeks from June through September in both 2007 and 2008; data on seagrass species and blade densities were determined before each trawl. Age at capture, pelagic larval duration (PLD, determined from transition mark), and fertilization dates were estimated from post-larval and juvenile otolith microstructure. A single cohort was produced each year; estimated fertilization dates ranged from February through April around full and new moons supporting planned January through April fishing closures for adult gag grouper. From 1986 to 2008, weekly concentrations of post-larval gag grouper were highest from late April to mid-May with peak ingress around new moons. Juvenile gag were caught from June through September with highest catch-per-unit-effort (CPUE) in July and August. Time of year, percent seagrass coverage, seagrass species, and sound influenced CPUE of juvenile gag grouper. Growth rates of juveniles were rapid (~1.6 mm/d) during summer months and did not differ between years. The mean PLD was ~ 43 d and did not differ among collection months suggesting no effect of PLD on survival. An annual index of post-larval abundance (adjusted for lunar effects) was developed. The spawning stock biomass (SSB) from the most recent gag grouper assessment was positively correlated with this index; thus, the post-larval index could be used as a fishery-independent index of SSB.en_US
dc.identifier.otheretd-06242009-145255en_US
dc.identifier.urihttp://www.lib.ncsu.edu/resolver/1840.16/1352
dc.rightsI 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, dis sertation, 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.en_US
dc.subjectgrouperen_US
dc.subjectabundanceen_US
dc.subjectindexen_US
dc.subjectgagen_US
dc.titleDeveloping an index of abundance for gag grouper in North Carolinaen_US

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