We use the presence of an umbilical scar as an indication of each shark’s age (as described in my previous blog), and therefore, we are able to guess the approximate sizes of sharks at birth. Additionally, the presence or absence of open umbilical scars helps us to better understand the length of the pupping season for each shark species at a particular location. Numerous studies have demonstrated that gestation in sicklefin lemon sharks and blacktip reef sharks varies from one to five months depending on the study location.
To get even more detailed information about the mating and pupping behaviour of our study species, we also take a small tissue sample from the first dorsal fin of each shark. These samples will later be used for DNA analysis, which will enable us, for example, to determine the relationship between individual juvenile sharks (siblings or half-siblings) and how frequently individual female sharks are giving birth (e.g., annually or every second year).