The Cod Grounds Australian Marine Park is in Commonwealth waters approximately four nautical miles (7 kms) off the coast of North Haven, New South Wales, Australia. It includes three underwater pinnacles that rise to about 18 m at the shallowest point from 40 m depth.
The Cod Grounds AMP was established primarily due to its value as habitat for grey nurse sharks (Carcharias taurus) and black cod (Epinephelus daemelii), which are protected under both NSW State and Commonwealth environmental legislation. The complex benthic terrain within the park forms a variety of distinctive habitats including steep outcrops, shallow gutters, boulder/cobble slopes, and expanses of sand which together support a wide variety of sessile invertebrates and provide habitat for large numbers of grey nurse sharks and itinerant pelagics.
We had already cancelled the trip earlier in May due to 7.5 m swell and 48kt winds so anticipation was high, and as the team began to trickle in to Port Macquarie, each new arrival was met with excitement and bewilderment that we were actually here - this was actually happening!
Toni and Liz arrived from Tasmania, and made a quick pit stop at Sydney International Airport to pick up German who thankfully was available to come over from New Caledonia! With Scott also travelling up from Tas, and Yanir making the long drive down from Brisbane, it was a solid team but we were still a diver down - we needed 6 divers to get all the sites done… After a couple of quick phone calls which came with the promise of perfect weather and unimaginable visibility, we managed to convince Rick at RLS HQ to get on a last-minute flight and join us!
We met with local dive guru, Pete Heuttner from Scuba Haven and headed out from North Haven – from memory his words were, “hmmm… it’s the clearest I’ve ever seen the river which means we’ll have good vis out there, but that usually means one thing – current…”. Now, there aren’t many people who know the area like Pete and he is usually on the money with these things – but gee, I had everything crossed that, this time, he was wrong! As we travelled over the sand bar and headed out to the Cod Grounds Marine Park, the winds became lighter and seas became glassier, things were looking very, very good! Pete dropped the shot line at the Pinnacles, and we watched on with excitement as the rope hung loosely in the water column – no current!
These sites are deeper than our standard RLS sites. The transect lines sit between 25-30m so a fair bit of planning needs to go into the diving and logistics. We use a mix of nitrox 30-32% to get the dives done safely while maximising our bottom times. Having been to the Cod Grounds twice before and having pushed through current combined with below average visibility both times, we couldn’t believe what we were seeing. As we descended down towards the main pinnacle, we were greeted with a sharknado of approximately 60 grey nurse sharks (Carcharias taurus) surrounding the rock structure, schools of huge yellowtail kingfish (Seriola lalandi), clouds of yellowtail scad (Trachurus novaezelandiae), and silver trevally (Pseudocaranx georgianus) as far as the eye could see. Yep, not only was there zero current or swell - we also had 30+ metres visibility! There was certainly a buzz in the air after that first dive which was topped off by inquisitive humpback whales breaching next to the boat on multiple occasions. By some miracle, the conditions held for our remaining dives over the following days.
The remaining dives were a mixture of steep outcrops, shallow gutters and boulder/cobble slopes covered with either crustose coralline algae or beds of complex sessile invertebrates. The shallower sites saw benthic communities typical of urchin barrens found throughout NSW, with a high abundance of the barrens-forming long-spine urchin Centrostephanus rodgersii, while deeper areas (29m +) hosted colourful swaths of sponges, ascidians, soft corals and hard corals. A total of 98 grey nurse sharks (Carcharias taurus) were counted across 9 sites (18 transects), and three were seen with retained fishing gear.
Some fun facts from the trip include:
- Grey nurse sharks were recorded at 4 of the 9 sites surveyed.
- We witnessed a large spawning aggregation of hundreds and hundreds of red morwong (Morwong fuscus)
- Observations of black coral at unexpectedly shallow depths
- Recorded 18 species of fish we hadn’t encountered on previous Cod Grounds surveys
- The sites around the Pinnacles had the highest biomass (average biomass between 1600 and 3000kg) – these sites are now the highest biomass sites in our Australian surveys ( and 4th highest, globally).
Thanks to all the team members, Liz, Scott, German, Yanir and Rick, for being flexible and for making the long trip to Port Macquarie – it was a mission, but there has been unanimous agreement that it was well worth it! Thanks to Kevin at Southwest Rocks and huge thanks to Peter and Grant from Scuba Haven for providing exceptional boat handling and surface support. These surveys will feed into important reporting to Parks Australia to describe patterns of reef biodiversity within the Cod Grounds AMP.