Courtship and Reproduction of the Whitetip Reef Shark Triaenodon obesus (Carcharhiniformes: Carcharhinidae) in an Ex Situ Environment, with a Description of the Late Embryonic Developmental Stage

Abstract

Elasmobranchs represent a group of species under considerable anthropic pressure because of the scale of industrial and artisanal fisheries and the loss of essential areas for nursery and feeding, which are causing substantial population losses around the world. Reproduction in an ex situ environment enables a healthy population to be built and maintained in networks of public aquariums, increasing our knowledge of elasmobranch reproductive biology and offering the opportunity for reintroductions in areas where native populations have been removed. The study reports two successful pregnancies of the whitetip reef shark Triaenodon obesus, considered a vulnerable species by the International Union for the Conservation of Nature. Copulation and gestation data are provided, including ultrasound recordings of the late stage of embryo development. Ultrasonography was performed with the GE Logiq and convex transducer and revealed a fetus with defined fins and organogenesis, with definition of eyes, gills, liver, a heart with individualized chambers, partially defined kidneys, and a well-defined spiral intestine. A cartilaginous skeleton forming a posterior acoustic shadow was detailed, as well as a moving fetus with a biparietal diameter of 6.47 cm and a heart rate of 62 Beats Per Minute on spectral Doppler. This is the first successful reproduction of T. obesus in an aquarium in Brazil.

The successful use of a submersible ultrasound to confirm pregnancy on free swimming bull sharks, Carcharhinus leucas, in a provisioned shark site

“…The use of ultrasonography as a non-invasive methodology has proven to be a useful tool for the study of reproductive aspects in both captive and wild caught sharks (Walsh et al, 1993;Daly et al, 2007;Sulikowski et al, 2016;Inoue et al, 2022;Santos et al, 2022;Sulikowski and Hammerschlag, 2023). However, the use of this technology adapted for use underwater on free swimming wild animals is scant, with only one published study to date on whale sharks (Matsumoto et al, 2023).…”