Abstract
The eastern shovelnose ray (Aptychotrema rostrata) is a medium-sized coastal batoid endemic to the eastern coast of Australia. It is the most common elasmobranch incidentally caught in the Queensland east coast otter trawl fishery, Australia’s largest penaeid-trawl fishery. Despite this, age and growth studies on this species are lacking. The present study estimated the growth parameters and age-at-maturity for A. rostrata on the basis of sampling conducted in southern Queensland, Australia. This study showed that A. rostrata exhibits slow growth and late maturity, which are common life-history strategies among elasmobranchs. Length-at-age data were analysed within a Bayesian framework and the von Bertalanffy growth function (VBGF) best described these data. The growth parameters were estimated as L0 = 193 mm TL, k = 0.08 year–1 and L∞ = 924 mm TL. Age-at-maturity was found to be 13.3 years and 10.0 years for females and males respectively. The under-sampling of larger, older individuals was overcome by using informative priors, reducing bias in the growth and maturity estimates. As such, the results can be used to derive estimates of natural mortality for this species.
Highlights
The Queensland east coast otter trawl fishery (QECOTF) is the largest penaeid-trawl fishery in Australia
Sample collection on the San Antone II was supplemented by specimens obtained during the post-trawl survival (PTS) experiments conducted by Campbell et al (2018)
214 A. rostrata individuals were collected to assess growth; 142 were collected by the crew of the San Antone II and 72 were collected as part of the PTS experiments conducted by Campbell et al (2018)
Summary
The Queensland east coast otter trawl fishery (QECOTF) is the largest penaeid-trawl fishery in Australia. This fishery targets shrimps (Penaeidae: Melicertus spp., Penaeus spp., Metapenaeus spp.), sea scallops (Pectinidae: Ylistrum balloti), bugs (Scyllaridae: Thenus spp. and Ibacus spp.) and squid (Teuthoidea) with demersal otter trawl gear. Two vessels target stout whiting (Sillago robusta), using Danish seine and fish trawl gear, in southern Queensland and are subject to an annual total allowable catch (TAC) of ,1100 t. Hundreds of species comprise the discarded potion of the QECTOF catch (Courtney et al 2006; Courtney et al 2008), some of which are of conservation concern, such as sea turtles (McGilvray et al 1999)
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