Parturition time for the Blacktip shark, Carcharhinus limbatus (Carcharhiniformes: Carcharhinidae), in Southwestern Atlantic

Abstract

The determination of the period of parturition and identification of nursery areas are fundamental for the management and conservation of a fishing resource. Through combination of monthly abundance, length measurements, and development time of embryos we inferred about parturition time of the Blacktip sharks, Carcharhinus limbatus, from Southwestern Atlantic. Specimens of C. limbatus were caught from 2002 and 2008 by artisanal fleets from three different locations along the Brazilian coast using gillnets (mesh width ranging between 30 and 120 mm between opposite knots and operating from 9 to 120 m in depth), handlines (19 to 140 m depth) and longlines (6 to 90 m depth). Through a comparative analysis of fisheries landing data collected, we have verified neonatal (< 90 cm) catch peaks at specific times of the year in different locations and, matching with birth prediction of embryos, propose that C. limbatuspresents a well-defined parturition time in late spring-early summer in Southwestern Atlantic. Moreover, we indicate supposed nursery grounds for the species along the Brazilian coast. This information will be crucial for stock assessments of the species and may serve as a basis for determining fisheries management measures.

Quantifying changes in umbilicus size to estimate the relative age of neonatal blacktip reef sharks (Carcharhinus melanopterus)

“…However, this method requires intensive monitoring of the adult population via many hours of underwater surveying, and female reappearance may take several weeks. Alternatively, length measurements in combination with embryonic development times and formation of the birth zone in vertebral centra have been used to back calculate the time of parturition ( Hall et al, 2012 ; Santander-Neto et al, 2020 ). Length measurements are, however, not a suitable indicator of age due to the systematic size overlap across age classes ( Weideli et al, 2019a ; this study), and studying vertebral centra is only possible in deceased animals.…”