THE Solitary Islands Marine Park is shaping up as a key player in the effort to get the black cod off the vulnerable species list.
New scientific results from a Northern Rivers Catchment Management Authority (NRCMA) project nearing completion confirm that the Solitary Islands Marine Park and the marine region down to Fish Rock at South West Rocks are the most important areas for black cod abundance, particularly large males, in mainland eastern Australia.
Scientist Hamish Malcolm from the Solitary Island Marine Park, who is conducting the research on behalf of the NRCMA, said this important project aimed to benchmark the abundance and size of black cod within the Northern Rivers Region by targeting 20 sites between Tweed Heads and South West Rocks.
Mr Malcolm said the information gained included accurate measurements of individual fish taken using state-of-the-art underwater stereo video technology was important as it would enable future comparisons to see if black cod numbers are recovering.
He said black cod, which is listed as a vulnerable species, has been protected in NSW waters since 1983.
Black cod used to be targeted by spear and line fishers, however, a noticeable decline in numbers had led those same fishers to seek protected status for it.
Mr Malcolm added that a total of 23 black cod were recently recorded at Fish Rock, with 14 at one site – the highest number recorded at a single site during the research.
Other important sites with similarly high numbers were recorded at the outer islands in the Solitary Islands Marine Park, including North and South Solitary islands and North West Rock. Pimpernel Rock was also identified as important habitat.
“Although overall numbers were low, they exceeded expectations with 75 black cod in total recorded for the 20 sites,” Mr Malcolm said.
“Interestingly, a 1968 spear-fishing guide to NSW indicated that northern NSW and in particular the Solitary Islands were a hotspot for black cod at that time.
“The slow growth rate of this fish, combined with its slow-moving, curious and territorial behaviour made it particularly vulnerable to over-fishing.”
- Black Cod were recorded on 75 per cent of the sites during the survey. A similar study conducted from Port Stephens to Forster in the Port-Stephens Great Lakes Marine Park recorded fewer Black Cod on only 25 per cent of sites.
- A 45-minute survey dive was used to count the number at each site. Each individual fish was accurately measured using stereo video technology www.SEAGis.com.au. A towed surface GPS was used to survey each track and mark individual positions.
- Black Cod are found from southern Queensland to Victoria and eastwards to northern New Zealand and the Kermadec Islands. Black Cod have been reported to reach 1.5m in length in mainland Australia and may reach 2m further east.
- The Black Cod in this study ranged from 41.5cm to 134.4cm, with the largest individuals found at the outer Solitary Islands. Black Cod change sex from female to male at about 1 m, with about 25 per cent of the fish in this study probably being males.