HISTORICAL EFFECTS OF FISHING ON AGE STRUCTURE AND STOCK MIXING IN NORTHWEST ATLANTIC BLUEFIN TUNA

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dc.contributor.advisorSecor, David Hen_US
dc.contributor.authorSiskey, Matthew Ryanen_US
dc.contributor.departmentMarine-Estuarine-Environmental Sciencesen_US
dc.contributor.publisherDigital Repository at the University of Marylanden_US
dc.contributor.publisherUniversity of Maryland (College Park, Md.)en_US
dc.date.accessioned2015-09-18T06:05:14Z
dc.date.available2015-09-18T06:05:14Z
dc.date.issued2015en_US
dc.description.abstractBluefin tuna support important fisheries in the Northwest Atlantic Ocean, which have declined in yield from intense, size-selective exploitation. Age structure, size-at-age, and stock composition were investigated as principal responses to exploitation, utilizing otolith microstructural and chemical analysis. To evaluate otoliths as ageing structures, annulus formation was compared to temperature-associated oscillations in otolith strontium:calcium. Evaluation of otolith stable isotope measures used in stock composition analyses indicated significant differences in δ18O measurements between laboratories, but not δ13C values. Comparisons of age structure, size-at-age, and stock composition over three periods (1974-1978, 1996-2002, 2009-2014) coinciding with the cycle of exploitation intensity suggest size-selective fishing caused (1) age truncation, where median age declined (14 to 6 years); (2) minor changes in size-at-age; and (3) fluctuating stock composition, with peak mixing in the 1990s (48% eastern stock contribution). Size-specific reductions in fishing mortality could contribute to recovery through more frequent production of strong year-classes.en_US
dc.identifierhttps://doi.org/10.13016/M2X35Z
dc.identifier.urihttp://hdl.handle.net/1903/17126
dc.language.isoenen_US
dc.subject.pqcontrolledAquatic sciencesen_US
dc.subject.pquncontrolledage structureen_US
dc.subject.pquncontrolledAtlantic bluefin tunaen_US
dc.subject.pquncontrolledfisheriesen_US
dc.subject.pquncontrolledsize-selective fishingen_US
dc.subject.pquncontrolledstock mixingen_US
dc.titleHISTORICAL EFFECTS OF FISHING ON AGE STRUCTURE AND STOCK MIXING IN NORTHWEST ATLANTIC BLUEFIN TUNAen_US
dc.typeThesisen_US

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