Reproductive biology and range extension for Mobula kuhlii cf. eregoodootenkee

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 at 29°S -200 km south of their proposed range -off eastern Australia by bather-protection gillnets deployed for 6 mo from December 2016. M. kuhlii cf. eregoodootenkee was the second most abundant netted species (all adults: n = 63), with catches peaking in April. There was no sexual segregation, but females (disc width [DW]: 92.5 to 130.0 cm, mean ± SD 112.8 ± 7.8 cm) were significantly larger than males (99.0 to 123.0 cm, 109.4 ± 6.3 cm). Of those caught, 45 died (71% mortality), of which 20 females and 11 males were assessed for reproduction. Nine females were pre-ovulatory and non-gravid with 7 to 23 oocytes in their left ovary, while 11 had 14 to 40 ovarian oocytes and 1 embryo (DW: 7.0 to 21.2 cm) 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 (DW: 21 cm) suggests parturition occurs well above this size. Males had calcified claspers and exhibited large variation in their testes weights, which might imply seasonal fluctuation in sperm production. In addition to extending the distribution of the species and increasing maximum DW to 130 cm, the data provide further evidence of the low reproductive output of M. kuhlii cf. eregoodootenkee, and a need for their effective management.

Life History, Growth, and Reproductive Biology of Four Mobulid Species in the Bohol Sea, Philippines

“…This suggests that a proportion of females within the population do not reproduce every year and corroborates observations reported in the literature of a potential biennial or triennial reproductive cycle (Notarbartolo-Di-Sciara, 1988;Marshall and Bennett, 2010;Dulvy et al, 2014b;Broadhurst et al, 2018). The length of an inter-pregnancy period could depend on the availability of resources, suggested previously as a driver for reproductive potential.…”

“…Ovarian follicles developed only on the left ovary, supporting previous observations for these species (Notarbartolo-Di-Sciara, 1988;Broadhurst et al, 2018), as well as for many other batoids, such as the cownose rays (Fisher, 2010) and other stingrays (Pierce et al, 2009;Mejía-Falla et al, 2014). One exceptional observation of a female M. birostris with a surprisingly developed follicle in the right ovary suggest that production of a pup in the right uterus could be possible in rare cases.…”

“…Coordinated breeding activity was suggested in Baja California (Notarbartolo-Di-Sciara, 1988), as well as off northern New South Wales for M. kuhlii cf. eregoodootenkee (Broadhurst et al, 2018), although data were sparse in both cases. In Mozambique, M. alfredi seemed to show seasonal peaks (Marshall and Bennett, 2010), while in Hawaii mating trains were observed during 10 months of the year peaking in January and April (Deakos et al, 2011).…”

Mother–embryo isotope fractionation in the pygmy devilray Mobula kuhlii cf. eregoodootenkee

“…eregoodootenkee . The data reiterated the supposition of low reproductive output restricted to a single embryo in the functional left uterus and a non‐annual gestation exceeding 10 months (Broadhurst et al, ).…”

“…Recently, using specimens collected during trials of bather‐protection nets off eastern Australia, Broadhurst et al . () provided a first assessment of reproduction in the pygmy devilray, Mobula kuhlii cf. eregoodootenkee .…”