Reproductive parameters of rhinobatid and urolophid batoids taken as by‐catch in the Queensland (Australia) east coast otter‐trawl fishery

Abstract

Reproductive variables are provided for batoids regularly taken as by-catch in the east coast otter-trawl fishery on the inner-mid continental shelf off the south-east and central coasts of Queensland, Australia. Total length at maturity (LT50 and 95% c.i.) for the eastern shovelnose ray Aptychotrema rostrata was 639·5 mm (617·6-663·4 mm) for females and 597·3 mm (551·4-648·6 mm) for males. Litter size (n = 9) ranged from nine to 20 (mean ± s.e. = 15·1 ± 1·2). This species exhibited a positive litter size-maternal size relationship. Disc width at maturity (WD50 and 95% c.i.) for the common stingaree Trygonoptera testacea was 162·7 mm (155·8-168·5 mm) for females and 145·9 mm (140·2-150·2 mm) for males. Gravid T. testacea (n = 6) each carried a single egg in the one functional (left) uterus. Disc width at maturity (WD50 and 95% c.i.) for the Kapala stingaree Urolophus kapalensis was 153·7 mm (145·1-160·4 mm) for females and 155·2 mm (149·1-159·1 mm) for males. Gravid U. kapalensis (n = 16) each carried a single egg or embryo in the one functional (left) uterus. A single female yellowback stingaree Urolophus sufflavus carried an embryo in each uterus. A global review of the litter sizes of shovelnose rays (Rhinobatidae) and stingarees (Urolophidae) is provided.

Life-history characteristics of the eastern shovelnose ray,

“…Kyne and Bennett (2002b) collected A. rostrata individuals from Moreton Bay, adjacent to the grounds in the current study, and reported that 41 of 48 (,85%) females sampled were mature. These authors used rodand-reel in water depths of 3-10 m and reported a female L 50 similar to that in Kyne et al (2016). The number of mature females was higher than from the current study; only 9 of the 102 females caught aboard the San Antone II were mature and no mature animals were collected during the PTS experiments conducted by Campbell et al (2018).…”

“…This under-sampling may have been due to the selectivity of the sampling gears used in the respective studies. Kyne et al (2016) conducted sampling using shrimp (Melicertus plebejus) trawls in water depths to 100 m. In contrast, samples in the present study were predominantly (67%) collected on the San Antone II, which deploys Danish seine gear to target S. robusta in water of ,50 m. The Danish seine used in this fishery is characterised by slow haul speeds and short haul times (Rowsell and Davies 2012), which may allow larger A. rostrata to escape capture.…”

“…In accord with other elasmobranchs, the published estimates of L N for the trygonorrhinids were higher for females; Cortés (2000) found that the maximum size of males was, on average, ,10% smaller than that of females in 164 shark species. Kyne et al (2016) reported an L 50 for male A. rostrata of 597.3 mm. This is comparable to the present study: however, their L 50 for females (639.5 mm) is lower than the L 50 reported here.…”

“…The maturity of each individual was assessed according to Kyne et al (2016). Maturity in males depended on the calcification of the claspers, categorised as immature (possessing short, flexible, uncalcified claspers) or mature (rigid, calcified and elongated claspers).…”

“…Diet (Kyne and Bennett 2002a), dentition (Gutteridge and Bennett 2014), sensory characteristics (Hart et al 2004;Wueringer et al 2009) and post-trawl survival (Campbell et al 2018) have been the subject of recent research. Although reproductive strategies were described in two studies (Kyne and Bennett 2002b;Kyne et al 2016), no previous study has quantified growth and ageat-maturity.…”