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ESR prepress abstract   -  DOI:

Preliminary insight into the reproductive traits of the flapper skate (Dipturus intermedius) using in-field ultrasonography and circulating hormone concentrations

James Thorburn*, Georgina Cole, Adam Naylor, Amy Garbett, Kirsten Wilson, Mark James, Jane Dodd, Jonathan D. R. Houghton, Patrick C. Collins

*Corresponding author:

ABSTRACT: Due to global population declines, there is a pressing need for data on the life history traits of many elasmobranch species to support the development of species-specific management plans. A lack of information on the reproductive cycle of the Critically Endangered flapper skate (Dipturus intermedius) was recently identified as a hindrance to its conservation. To address this data gap by combining non-lethal ultrasound and hormone analysis to investigate the size at maturity and reproductive cycle of the flapper skate in the Loch Sunart to the Sound of Jura Marine Protected Area off the west coast of Scotland. In-field ultrasound imagery revealed in-utero encapsulated eggs and was used to determine the presence and size of ovarian follicles. Combining these images with levels of plasma testosterone, progesterone, and oestradiol provided valuable insights into the timing of the reproductive cycle and maturity state of the flapper skate. This preliminary study suggests that male skate start to mature at 165 cm and female skate at 203 cm total length. Oestradiol appears to be the primary hormone controlling the female reproductive cycle and, along with ultrasound images, indicate that females lay pairs of eggs throughout a winter egg-laying season. This study further highlights how non-lethal investigation methods can be used to investigate the life history of oviparous elasmobranchs in the field. This information will support the identification of important life history groups and their associated habitats, helping to develop management strategies for these species.