Browsing by Author "Rooker, Jay"

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Life History and Population Structure of Snowy and Warsaw Grouper in US Waters
Marine Biology; TAMUG; https://hdl.handle.net/20.500.14641/522; DOC-NOAA-National Marine Fisheries Services
Important life history and population parameters are currently unavailable for Snowy Grouper (Hyporthodus niveatus) and Warsaw Grouper (H. nigritus), which represent two valuable and vulnerable components of the deepwater grouper assemblage. Since fisheries yields, population dynamics, and rebuilding plans are dependent on life history traits, genetic characteristics, and other population parameters, there is a clear need to close existing data gaps for these two species. Recent assessments indicate these species are overfished (Snowy Grouper) or experiencing overfishing (Warsaw Grouper) in the South Atlantic, while the stock status of both is currently unknown in the Gulf of Mexico. Both species appear on the International Union for the Conservation of Nature (IUCN) Red List of threatened species (2014.2), with Snowy designated “vulnerable” and Warsaw listed as “critically endangered,” indicating that fundamental data on the life history and population structure of each species is needed to reduce the “uncertainty” in stock assessments in the South Atlantic and allow for “initial” stock assessments of each species in the Gulf of Mexico. The goal of this project was to comprehensively investigate the life history and population structure of Snowy Grouper and Warsaw Grouper in U.S. waters by coupling three distinct but complementary research components: 1) age validation (bomb radiocarbon dating) coupled with the development of age-length keys for both species in the South Atlantic and Gulf of Mexico; 2) geochemical and genetic approaches to determine the population structure and connectivity of Snowy Grouper and Warsaw Grouper from four regions (South Atlantic, northwestern [NW], northcentral [NC], and northeastern [NE] Gulf of Mexico); and 3) histological examination to estimate several key reproductive parameters including sex ratios, maturity, the proportion of active spawning adults (i.e., spawning fraction) by age and size class, and spawning seasonality. Data from the project addresses specific research recommendations identified by our NOAA Fisheries colleagues, particularly the need for basic information on the age, growth, and reproductive biology of both Snowy Grouper and Warsaw Grouper.
Origin of yellowfin tuna in the western Atlantic Ocean: importance of outside production to US fisheries
Marine Biology; TAMUG; https://hdl.handle.net/20.500.14641/522; DOC-NOAA-National Marine Fisheries Services
Several novel tools are currently being used to investigate the natal origin and stock structure of Atlantic tunas, including natural chemical markers in hard parts (Rooker et al. 2008, 2014, 2019). Natural markers in otoliths (ear stones) show significant potential for determining origin and quantifying population connectivity. This is due to the fact that otoliths precipitate material (primarily calcium carbonate) as a fish grows, and the chemical composition of each newly accreted layer is often associated with physicochemical conditions of the water mass they inhabit. As a result, material deposited in the otolith during the first year of life serves as a natural marker of the individual’s nursery or place of origin. Previous studies have demonstrated that trace elements and stable isotopes in otoliths can be used to determine the origin of both temperate and tropical tunas (Wells et al. 2012, Kitchens et al. 2018, Rooker et al. 2019). The goal of the SK-funded study was to determine the origin and migratory histories of yellowfin tuna from U.S. fisheries in the Atlantic: 1) Gulf of Mexico [GoM], 2) Mid Atlantic Bight [MAB], and 3) US territories in the Caribbean [CAR]. Our efforts centered on two questions: Q1) Are yellowfin tuna in U.S. fisheries derived from local production or from more distant production zones in the eastern Atlantic Ocean (EAO), and Q2) Are trans-Atlantic movements (E to W) common for yellowfin tuna caught in U.S. waters? Such questions are important to fishery managers because this species is currently managed as a single, panmictic stock, despite the fact that trans-Atlantic movement is well documented. Similar to previous studies, we used natural tracers in otoliths that are linked to ambient physicochemical conditions of the ocean to develop ‘birth certificates’ for individuals from different regions or nurseries in the Atlantic Ocean. Thus, the first step was to develop reliable baseline chemical signatures for young-of-the-year (YOY) tuna from all sources or production areas in the Atlantic Ocean. As demonstrated in Kitchens et al. (2018), classification success to regional nurseries is relatively high, supporting the use of these reference signatures to source yellowfin tuna to their place of origin.