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SEX-SPECIFIC GROWTH AND LONGEVITY OF ‘EHU’, Etelis carbunculus (FAMILY LUTJANIDAE), WITHIN THE HAWAIIAN ARCHIPELAGO

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Title:SEX-SPECIFIC GROWTH AND LONGEVITY OF ‘EHU’, Etelis carbunculus (FAMILY LUTJANIDAE), WITHIN THE HAWAIIAN ARCHIPELAGO
Authors:Nichols, Ryan Shane
Contributors:Franklin, Erik C. (advisor)
Marine Biology (department)
Keywords:Zoology
Age
Commercial Bottomfish
Growth
Longevity
show 2 moreRadiocarbon Dating
Sexual Dimorphism
show less
Date Issued:2019
Publisher:University of Hawai'i at Manoa
Abstract:Across their Indo-Pacific distribution, deep-water snapper (Lutjanidae) species have supported valuable commercial, cultural and subsistence fisheries for over a century; however, species-specific information related to demographic variation in life history has been less understood in the deep-water snapper biology and a continuing shortfall. Developing an understanding of the life history of exploited species provides critical information relevant to fisheries conservation and management. In the Hawaiian Islands, the pygmy ruby snapper or ehu (Etelis carbunculus) is a moderately slow growing, long-lived, gonochoristic teleost, that is exploited as part of a deep-water, multi-species complex within the bottomfish fishery. Using collections over a 40-year period (1978-2018) from the main (MHI) and northwestern (NWHI) Hawaiian Islands, this study expands the data on E. carbunculus by examining two important components of the species life history. First, I examined length and age-specific patterns in the demography of E. carbunculus across the subregions of the Hawaiian Archipelago by using an analysis of otolith growth zones and age-validation from bomb-radiocarbon dating. The results indicated females grow larger and live longer than males in the NWHI. In the MHI, maximum sizes were greater in females than males, yet age structure was not different. A conspicuous age truncation, of both sexes, in the MHI compared to the NWHI suggested potential effects from fishing (from greater effort in the MHI), variability in biological traits, or differences in the marine environment between subregions. Second, I investigated sexual dimorphism of this species, using external sex identification of the urogenital region and urogenital distances. The method accurately determined the sex of 96% of 157 specimens ranging between 18.7 – 45.7 cm fork length (FL) for females and 16.7 – 49.7 cm FL for males. Males and females significantly differed in total antero-ventral length of the urogenital region (urogenital distance, UD) and in length of the papilla septum (papilla septum distance, PSD). Although both distances were larger for females, the latter metric (PSD) was the more accruate predictor of sex, based on a logistic regression. The results herein illustrate the general importance that life history traits should not be considered similar between sexes of the deep-water snapper complex, age structure should be considered for exploited species, and the use of external sex determination can facilitate better understanding of sex-specific life history and fisheries data for species of Lutjanid snappers.
Description:M.S. Thesis. Ph.D. Thesis. University of Hawaiʻi at Mānoa 2019
Pages/Duration:137 pages
URI:http://hdl.handle.net/10125/63204
Rights:All UHM dissertations and theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission from the copyright owner.
Appears in Collections: M.S. - Marine Biology


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