Marine & Environmental Sciences Faculty Proceedings, Presentations, Speeches, Lectures


Age and Growth of Four Mesopelagic Fish Species by Incorporation of Otolith Marginal Increment Analysis

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19th Annual Spring Meeting of the Southern Division of the American Fisheries Society, Tampa, Florida, January 13-16, 2011

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We apply whole and transverse-sectioned otolith ageing techniques to develop indices of somatic growth of four mesopelagic bycatch species in the commercial tuna and swordfish industries by using otolith growth increment widths. The objectives of this study are to i) develop otolith growth chronologies for escolar (Lepidocybium flavobrunneum), oilfish (Ruvettus pretiosus), snake mackerel (Gempylus serpens), and longnose lancetfish (Alepisaurus ferox), and ii) to integrate this information with the von Bertalanffy growth function to determine the rate of growth in length and weight, and iii) to create a methodological tool for other researchers aging deep-sea teleost species. From 2008 to 2010, these mesopelagic fishes were collected as bycatch from pelagic statistical areas in the Gulf of Mexico and the U.S. South Atlantic Bight from commercial pelagic longline vessels. Visual interpretation and UTHSCSA ImageTool measurement software is used in conjunction with a 12.2 megapixel digital camera to identify narrow and wide banding patterns of growth increments. Age assessments will be done via double blind marginal increment analysis. Presence of annual growth patterns was verified by measuring the width of the most distal ring of the sagittal otolith, plotting the width against the month of landing and visualizing the increased width of deposition as distance from the spawning month increases. The harvesting of these individuals has an unknown ecological impact and they currently fall under no protective regulations. Determining growth rates of these mesopelagic fishes give us baseline data for population analysis and future comparisons. Additionally, the processes followed in this research may serve as protocol for future research.





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