Evaluation of the use of portable ultrasonography to determine pregnancy status and fecundity in bonnethead shark Sphyrna tiburo

Abstract

This study examined the usefulness of portable ultrasonography in accurately predicting pregnancy and fecundity in the bonnethead shark Sphyrna tiburo by comparing ultrasound‐obtained data with those obtained from animal dissection, the gold standard for elasmobranch reproduction studies. Mature female S. tiburo (n = 66) were collected throughout the period of reproduction and examined via portable ultrasonography using two different ultrasound transducers (8–5 MHz linear array transducer and a 5.0–2.5 MHz curvilinear array transducer) to determine pregnancy status and fecundity. Ultrasound‐derived data were compared with validated assessments of pregnancy and litter size obtained using animal dissection to determine the level of agreement between the two approaches. Overall, there was strong agreement (90.9%) between pregnancy determinations obtained using ultrasonography and dissection. However, the effectiveness of portable ultrasonography in accurately determining specific stages of maturity and pregnancy differed slightly between transducer types (linear = 61.3%; curvilinear = 88.9%). Measurements of fecundity also agreed well between ultrasonography and dissection and there were no significant differences between mean fecundity estimates obtained using the two methods. In general, portable ultrasonography was found to be a good alternative to lethal sampling and animal dissection in obtaining reproductive data critical for the management and conservation of elasmobranchs. Special attention should be given to factors that can influence the reliability of ultrasound‐derived data such as transducer type, embryo size and sound wave interference due to gut contents.

Use of Synthetic Salmon GnRH and Domperidone (Ovaprim®) in Sharks: Preparation for ex situ Conservation

“…Abdominal ultrasonography of the uterus and ovaries was performed on all female sharks to judge sexual maturity and for pregnancy detection using an Aloka ProSound 2 (Hitachi-Aloka Medical Ltd., Tokyo, Japan) with a convex probe set to a frequency of 26 MHz (Madigan et al, 2015;Swider et al, 2017;Anderson et al, 2018). Only F003 among the female T. scyllium displayed an ovarian follicle during ultrasonography and F001 and F002 were confirmed as pregnant.…”

Peer Review #1 of "Steroid hormones and chondrichthyan reproduction: physiological functions, scientific research, and implications for conservation (v0.1)"

“…The holistic science-based approach to the creation of marine protected areas should include the study of the reproductive biology of the species present in these ecosystems. This would benefit from steroid analyses, along with other methods such as ultrasounds and morphometrics for the biological monitoring of protected populations in critical habitats such as nursery areas (Anderson et al 2018;MacKeracher et al 2019).…”

Peer Review #3 of "Steroid hormones and chondrichthyan reproduction: physiological functions, scientific research, and implications for conservation (v0.1)"

“…However, the effect of potent androgens such as DHT, oestrogens like E1 or E3, as well as relevant glucocorticoids such as 1α-hydroxycorticosterone would be greatly beneficial for the characterization of the reproductive cycle in both male and female chondrichthyans (Rasmussen and Gruber 1993;Maruska and Gelsleichter 2011;Iki et al, 2020). As mentioned by several authors such as Anderson et al (2018), there is currently no reliable hormone indicators for the identification of relevant aspects such as maturity, mating seasons, gestation, partum or postpartum in chondrichthyans. In this regard, it is expected that the inclusion of more hormones, whether in sequential or simultaneous analyses, could lead to a better description and greater understanding of reproduction, as some steroids such as 11-KT, A4 or 17-OHP could provide insights about specific conditions in the reproductive cycle of chondrichthyans (Garnier et al 1999;Mull et al 2008;Lyons and Wynne-Edwards 2019).…”

“…To date, there is no general pattern that could describe the specific actions of sex steroids in chondrichthyans, mainly due to the high diversity of species in this group and the few number of comprehensive and detailed research involving specimens in captivity (Anderson et al 2018). The lack of a general pattern is probably due to the variety of embryonic nutrition strategies presented in the group, the overall paucity of species investigated as well as inherent differences between species, localities, and individuals (Compagno et al 2005;Awruch 2013;Nelson et al 2016).…”