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Sydney RLS 2021

We’ve really had it all thrown at us the last two years of RLS in Sydney. Last year Covid arrived just as we were getting the URG boat in the water after months of setup and refinement. Along rolls 2021, and we have a 1 in 100-year rain event that smashed water quality for weeks. Aerial maps of chocolate milk-coloured Hawkesbury river water running out to sea, down on the East Australia Current, and into Sydney Harbour (where we had moved our boat for RLS!) said it all.

Compared to some people, who suffered much greater impacts from these events, we have been fortunate. But it did feel like Mother Nature held a bit of a grudge.

We normally aim to get Sydney surveys done before heading down to Jervis Bay for surveys, but this year we were only half finished by then. So, on our return from Jervis Bay we picked up the slate, reel and dive gear and kept going. At the time of writing this report (I say this as we still plan to do a few more) we had completed 56 surveys across 25 Sydney sites, about half before Jervis and half after. You can see the completed sites on this map, flagged in yellow:

One of the most rewarding aspects of this year, for me, was to see the dedication of the RLS volunteer team: Kris O’Keeffe, Josh Moloney, Lou De Beuzeville, newly-certified RLSer Josh Batchelor and visitor (will she come back?) Flora Jennifer. Rain, wind, southerly swells, and cold conditions on some days didn’t deter them… although there were the few days when we couldn’t see our hands in front of our faces underwater, where we had to pull the plug (due to data quality, not motivation!!).

We recorded 129 fish species and 93 cryptic fish and invertebrate species. The most abundant fish was the eastern hulafish Trachinops taeniatus which averaged 320 individuals per transect. The next most abundant was the yellowtail scad Trachurus novaezelandiae followed by mado Atypichthys strigatus. These are all planktivores which may have benefitted from the excess nutrients and ensuing algal growth that flowed from the floods.

The most abundant invertebrate was of course the black long-spine urchin Centrostephanus rodgersii which averaged almost 200 individuals per transect. Noting that the invertebrate transect is one fifth as wide as the fish transect, this is a high density of invertebrate; two urchins per square metre. The next most abundant invertebrate, the tent shell Astralium tentoriiforme, was about one third as abundant. It seems to like bare or algal encrusted rock so may benefit from the urchin barrens created by C. rodgersii

I asked a few of our team what they liked most about the Sydney surveys this year. Here’s what they said:

Josh B: My favourite thing overall was getting certified (author note - it took JB over a year, due to the disruptions noted above). My favourite animal this year was the Rainbow Cale and my favourite site this year was Clifton Gardens wharf with 10 m viz.


Teasing Josh B (just kidding, don’t put that in) (author note – I did!).

Favourite site and animals was Clovelly because of the really super cool and odd hydrozoa creatures feeding on plankton.

Least favourite dive….let’s just say it required me being returned to shore after one dive… (author note: surge + forgetting seasick tablets = unhappy Lou)

Kris: My favourite survey dive was at Shelley Beach where we had the usual large schools of luderick (Girella tricuspidata) , Silver Bat Fish (Monodactylus argenteus) and quite a few Lyretail Dartgoby (Ptereleotris monoptera) in the shallows of North Shelly Beach. My favourite fish was tropical Eviota teresae found on transect at Shelley beach. It will be interesting to see if these persist over/after winter.

Josh M: I enjoyed seeing the tropicals, sunset wrasse Thalassoma lutescens inside North Head and the fine-spotted fairy-wrasse Cirrhilabrus punctatus at Gordon’s Bay. Both my favourite dives and fish this year!

And now my turn… my favourite sites this year were Shiprock, Fairy Bower and Shelly Beach North, which had the highest fish species richness; 39, 35.5 and 33 species per transact against an average for all sites of 21.

Clifton Gardens wharf was pretty good too, coming in just in front of the third site in Cabbage Tree Bay Aquatic Reserve in terms of fish species, and topping the list of species on method 2 (mobile macroinvertebrates and cryptic fish).

Overall it was great to get so many surveys done, and we couldn’t have achieved this without the support of Sydney Institute of Marine Science, which gave us access to their jetty in the Harbour, Ian Potter Foundation, which is supporting the RLS Lap of Australia Project, the RLS mini-grant, Underwater Research Group who provided their dive boat and of course our amazing volunteers!

Report by John Turnbull, June 2021

Images above can be found online on John's flickr account via thees links:


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