Reproductive biology of the tiger shark (Galeocerdo cuvier) in Hawaii |
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Authors: | Nicholas M Whitney Gerald L Crow |
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Institution: | (1) Zoology Department, University of Hawaii, 2538 The Mall, Honolulu, HI 96822, USA;(2) Waikiki Aquarium, University of Hawaii, 2777 Kalakaua Ave, Honolulu, HI 96815, USA |
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Abstract: | The tiger shark (Galeocerdo cuvier) is the largest shark in the family Carcharhinidae and the only carcharhinid with aplacental viviparous (ovoviviparous) reproduction.
Despite its size and prevalence, many details of tiger shark reproductive biology are unknown. Size at maturity and litter
size have been reported by several authors, but a lack of large numbers of pregnant females has made it difficult to determine
gestation period, seasonality, and timing of the female reproductive cycle. Here we analyze data from shark control program
fishing and incidental catches in Hawaii (n = 318) to construct the most complete picture of tiger shark reproduction to date. Males reached maturity at approximately
292 cm total length (TL) based on clasper calcification, whereas females matured between 330 and 345 cm TL based on oviducal
gland and uterus widths. Litter sizes ranged from 3 to 57 with a mean of 32.6 embryos per litter. Data from 23 litters from
various months of the year indicate that tiger sharks are usually 80–90 cm TL at birth, and that the gestation period is 15–16
months. Mating scars were observed in January–February and sperm is presumably stored for 4–5 months until ovulation takes
place in May–July. Gestation begins in June–July and pups are born in September–October of the following year. Our data suggest
that female tiger sharks in Hawaii give birth only once every three years. This could have major implications for conservation
and management of this species, as it suggests that tiger shark fecundity is 33% lower than previously thought. This could
greatly reduce the ability of this species to rebound from fishing pressure.
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