Biennial reproductive cycle in an extensive matrotrophic viviparous batoid : the sandyback stingaree Urolophus bucculentus from south-eastern Australia

<i>Urolophus bucculentus</i>, the largest urolophid species found in southern Australia, exhibits a biennial reproductive cycle. Ovulation occurs during October to January followed by a 15–19 month period of gestation followed by parturition during April to May and a short rest period while the ovarian follicles continue to develop for subsequent ovulation. Male breeding condition peaks during April to June to coincide with the period of parturition. <i>Urolophus bucculentus</i> has the highest matrotrophic contribution reported for any urolophid species, with a mean wet mass gain from egg <i>in utero</i> (4 g) to full-term embryo <i>in utero</i> (250 g) of <i>c.</i> 6250% (maximum c. 7200%), and perhaps explains the biennial female reproductive cycle where 50% of females contribute to each year's recruitment. Litter size (one to five) increases with total length (<i>L_T</i>). Females reach a longer maximum L_T (<i>L</i>_Tmax) than do males (885 v. 660 mm). The <i>L</i>_T at maturity for males and females at 50% mature (<i>L</i>_T50) is c. 414 mm (63% of <i>L</i>_Tmax) for males and c. 502 mm (57% of <i>L</i>_Tmax) for females, length at maternity indicates that recruitment production occurs later in life at <i>c</i>. 632 mm <i>L</i>_T (71% of <i>L</i>_Tmax).<br>