Depth interactions and reproductive ecology of sympatric Sillaginidae: Sillago robusta and S. flindersi

Length- and age-based demographics of exploited populations of stout whiting,Sillago robustaStead, 1908

“…The data presented here and in Gray, Barnes, van der Meulen et al. () provide a base to assess future fishery‐ and climate‐associated changes in the population demographics of east Australian S. robusta .…”

“…Samples of S. robusta were collected from 3 depth ranges: 11–30 m, 31–60 m and 61–90 m (hereafter termed shallow, mid‐ and deep depths, respectively), over inner continental shelf waters adjacent to Yamba (29°26′S, 153°20′E), and Newcastle (32°55′S, 151°45′E) off eastern Australia. A chartered ocean prawn‐trawl vessel from each port made two replicate 60 min tows in each depth strata at night, every 4 weeks (within 1 week of the new moon), between November 2005 and November 2007 at Yamba, and between October 2006 and November 2007 at Newcastle (see Gray, Barnes, van der Meulen et al., for greater operational details).…”

“…All measurements were made along the dorsal edge of the sulcus to the nearest 0.05 mm. Due to the species extended spawning strategy (Gray, Barnes, van der Meulen et al., ), there was no adjustment of counts of opaque zones based on month of capture, but counts were adjusted (+1) for individuals where the first opaque growth zone was obscured in the core growth. Sections were interpreted without the knowledge of the length or sex of the fish, or the date and location of capture; all sections were read twice without the knowledge of the first interpretation.…”

“…The stout whiting Sillago robusta Stead, 1908 is endemic to Australia but consists of two disparate populations extending between approximately 24 and 34°S on the west and east coasts (Gray, Barnes, van der Meulen et al., ; McKay, ). The species has an inshore coastal distribution and is primarily associated with soft sediments <100 m depth (McKay, ).…”

“…Total reported east coast landings have fluctuated between 800 and 1,500 tonnes per annum over the past 10 years, but have been less than 900 tonnes since 2011 (Flood et al., ). Life history information, including growth and reproductive characteristics, are known for western (Hyndes & Potter, ) and eastern (Butcher & Hagedoorn, ; Gray, Barnes, van der Meulen et al., ) populations. However, the age‐based information for the species on both coasts is founded on interpretation of whole otoliths, which can be problematic if not validated correctly and can lead to underestimating the true ages of older individuals (Campana, ).…”