Life histories of two deep‐water Australian endemic elasmobranchs: Argus skate Dipturus polyommata and eastern spotted gummy shark Mustelus walkeri

Two Australian endemic elasmobranchs, the Argus skate Dipturus polyommata and the eastern spotted gummy shark Mustelus walkeri , were collected from the by‐catch of a prawn Melicertus plebejus trawl fishery off Queensland. Age and growth parameters were estimated from growth band counts in vertebral sections of 220 D. polyommata and 44 M. walkeri . Dipturus polyommata males and females had an observed maximum age of 10 years and reached maximum sizes of 369 and 371 mm total length ( L T ), respectively. Mustelus walkeri lived longer, with the oldest female aged 16 years and measuring 1050 mm stretched total length ( L ST ), and oldest male aged 9 years and 805 mm L ST . Dipturus polyommata grew relatively fast with a von Bertalanffy growth completion parameter of k = 0·208 year −1 with males reaching maturity at 4·0 years ( c. 278 mm L T ) and females at 5·1 years ( c. 305 mm L T ). Mustelus walkeri grew more slowly with k = 0·033 year −1 with males estimated to mature at 7–9 years (670–805 mm L ST ) and females at 10–14 years (833–1012 mm L ST ). Length at birth inferred from neonate D. polyommata was 89–111 mm L T while for M. walkeri it was estimated to be 273 L ST based on the value of L 0 from the von Bertalanffy growth model. Both species appeared to have continuous reproductive cycles and low fecundity with an average ovarian fecundity of eight follicles for D. polyommata and a litter size of five to seven pups for M. walkeri . Based on these life‐history traits, D. polyommata is more resilient to fishing pressure than M. walkeri .