ESR prepress abstract  -  DOI: https://doi.org/10.3354/esr00876

Reproductive biology and range extension for Mobula kuhlii cf. eregoodootenkee

Matt K. Broadhurst*, Betty Laglbauer, Katherine B. Burgess, Melinda A. Coleman

*Email: matt.broadhurst@dpi.nsw.gov.au

ABSTRACT: Mobulids have been poorly studied, but most are listed (by the International Union for the Conservation of Nature) as Near Threatened or of greater concern. Here we fill critical knowledge gaps surrounding reproduction for Mobula kuhlii cf. eregoodootenkee caught 200 km south (29oS) of their proposed range off eastern Australia by bather-protection gillnets deployed for 6 months from December 2016. Mobula kuhlii cf. eregoodootenkee was the second most abundant species (all adults; n = 63), with catches peaking in April. There was no sexual segregation, but females (92.5–130.0 cm disc width [DW]; mean ± SD of 112.8 ± 7.8 cm) were significantly larger than males (99.0–123.0; 109.4 ± 6.3 cm DW). Forty-five M. kuhlii cf. eregoodootenkee died (71% mortality), of which 20 females and 11 males were assessed for reproduction. Nine females were pre-ovulatory, non-gravid with 7–23 oocytes in their left ovary, while 11 had 14–40 ovarian oocytes and 1 embryo (7.0–21.2 cm DW) in their left uterus. The diameter of the largest ovarian follicle in gravid females was not correlated with embryo size, indicating ovulation may not occur immediately after parturition. The development of the largest embryo (21 cm DW) suggests parturition occurs well above this size. Males had calcified claspers and large variation in their testes weights, which might imply seasonal fluctuation in sperm production. Beyond extending the distribution and increasing maximum DW to 130 cm, the data reiterate a low reproductive output of M. kuhlii cf. eregoodootenkee, and a need for their effective management.