Distribution and reproductive biology of the sandbar shark, Carcharhinus plumbeus (Nardo), in Western Australian waters
R. B. McAuley A B D , C. A. Simpfendorfer C , G. A. Hyndes B and R. C. J. Lenanton AA WA Fisheries and Marine Research Laboratories, Department of Fisheries, Government of Western Australia, PO Box 20, North Beach, WA 6920, Australia.
B Centre for Ecosystem Management, School of Natural Sciences, Edith Cowan University, 100 Joondalup Drive, Joondalup, WA 6027, Australia.
C Center for Shark Research, Mote Marine Laboratory, 1600 Ken Thompson Parkway, Sarasota, FL 34236, USA.
D Corresponding author. Email: rmcauley@fish.wa.gov.au
Marine and Freshwater Research 58(1) 116-126 https://doi.org/10.1071/MF05234
Submitted: 25 November 2005 Accepted: 26 July 2006 Published: 30 January 2007
Abstract
In total, 7497 sandbar sharks, Carcharhinus plumbeus (Nardo, 1827), were collected between May 2000 and June 2003 from commercial fishers and during fishery-independent research cruises in coastal Western Australian waters. Maximum observed lengths were 165 and 166 cm fork length (FL) for males and females respectively. The lengths at which 50% of sharks were mature were 126.9 and 135.9 cm FL for males and females respectively. Juvenile sharks tended to occur in temperate waters, whereas mature-sized sharks predominantly occurred in tropical waters. Unlike other regions, juveniles were found in offshore continental shelf waters rather than in shallow waters of estuaries and marine embayments. Results indicated a biennial reproductive periodicity. Mating occurred during summer and autumn, and parturition took place after a 12-month gestation. Pups were born at 40 to 45 cm FL throughout most of the species’ Western Australian range. The majority of neonates were caught at temperate latitudes. Litter sizes varied between 4 and 10, with a mean of 6.5. There was a weak but statistically significant increase in litter size with maternal length. Mean embryonic sex ratio of females to males differed significantly from a one-to-one ratio.
Additional keyword: logistic regression analysis.
Acknowledgments
This research was funded by a grant from the Fisheries Research and Development Corporation. Our study would not have been possible without the considerable assistance of the skippers and crews of the Western Australian temperate demersal gillnet and longline and northern shark fisheries, on whose vessels most data were collected. Their help is gratefully acknowledged. We also thank all the staff of the WA Department of Fisheries who contributed to the collection of data, especially Rick Allison, Ryan Ashworth, Justin Chidlow, Dennyse Newbound, Ben Sale and the skipper and crew of RV Flinders and RV Naturaliste. Many thanks to staff at the WA Marine Research Laboratory who provided valuable advice on this manuscript, especially: Jill St. John, Mike Mackie and Jim Penn. All sampling was conducted according to the relevant laws of Australia and the state of Western Australia and with the approval of Edith Cowan University’s Animal Ethics Committee.
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