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Reproductive biology of the milk shark Rhizoprionodon acutus and the bigeye houndshark Iago omanensis in the coastal waters of Oman

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Abstract:

Female Rhizoprionodon acutus were found to mature between 62 and 74 cm total length (LT) whereas males matured between 63 and 71 cm LT. The LT at 50% maturity was 64·3 cm for females and 64·7 cm for males. Litter size varied from one to six embryos, and was positively correlated with maternal LT. Female embryos outnumbered males by a ratio of 2·3:1. The size at birth was c. 37 cm LT. Full‐term embryos and post‐partum females were observed during all seasons although their occurrence was highest in spring. Spermatozoa were rarely recorded in the oviducal gland, indicating that this species does not store sperm. It was not possible to generate maturity curves for Iago omanensis but it was evident that females matured by the time they reached 35 cm and males were mature by 31 cm LT. This species displayed a clearly defined reproductive cycle with parturition occurring primarily in spring, after a gestation period of c. 1 year. Maximal embryo size was 19 cm LT while maximal litter size was 24 embryos. The oviducal gland appeared to act as a seminal receptacle and it appeared that females may utilize these stores by not mating every year.

Keywords: Iago omanensis; Oman; Rhizoprionodon acutus; oviducal gland; reproduction; shark

Document Type: Regular Paper

DOI: https://doi.org/10.1111/j.0022-1112.2006.01011.x

Affiliations: Department of Marine Science & Fisheries, College of Agricultural & Marine Sciences, Sultan Qaboos University, P.O. Box 34, Al-Khod 123, Sultanate of Oman

Publication date: 2006-06-01

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