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Reproductive Characteristics of Longtailed Red Snapper (Onaga, Etelis coruscans) in the Main Hawaiian Islands
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2021
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[PDF-1.13 MB]
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Description:The reproductive characteristics of the longtail snapper, Etelis coruscans — known locally in Hawaii as “onaga,” — was last assessed in 1989; therefore, updated information is needed for improving its stock assessment and management in the bottomfish fishery of the main Hawaiian Islands (MHI). Specimens were collected during research cruises and either donated by individual fishers or purchased from markets during 2007–2008 and 2012–2017. These samples were supplemented with additional monthly samples beginning in April 2019. In this study we provide a length distribution of samples used for analyses, describe an allometric length-weight relationship (b = 2.81), updated length-at-maturity (L50) estimates using six different combinations of data, and estimated the spawning season in the MHI. Females (N = 285) ranged in size from 21.2 to 96.0 cm fork length (FL) with a mean of 58.0 cm and a median of 60.0 cm FL. Of the six types of length-at-maturity combinations estimated, a functional maturity criterion using fish captured during the spawning season was deemed the most accurate despite having the lowest sample size (N = 107). This resulted in a L50 estimate of 62.2 cm FL (95% CI, 59.3–65.1), compared to previous estimates of 66.3 cm FL in the MHI and 67.1 cm FL in Okinawa. The functional maturity method had the lowest sample size but was the most comparable to published estimates based on histological methodology. Alternatively, our L50 estimate using the physiological maturity method within the spawning season was 54.7 cm FL (95% CI, 51.8–57.6 cm), with a L95 of 68.2 cm FL (95% CI, 65.34–71.06 cm). This L95 value is similar to a previous L50 estimate and may be an appropriate surrogate value in situations when sampling is unable to collect obviously mature females in the spawning–capable phase or at locations where the spawning period is unknown. Data collected to date shows that the E. coruscans progresses in oocyte development during January–April, and clearly spawning–capable females occur during September–December. The largest proportion of regressed females occur in December, most likely indicating the end of the spawning period. The addition of more spawning–capable females during the presumed spawning season in future sampling efforts would help to increase the robustness of our functionally mature length-at-maturity estimates and more accurately define the spawning period.
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Rights Information:Public Domain
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