mtank 的鑑定

Depth 28m on medium relief high energy reef v scuba.
Sorry about very vague date of image .I do have record of exact date, in dive log and on slide mount, but for now, suffice to say I was volunteer medico on an annual abalone stocks survey (guest medical clinician on SA Govt's and PIRSA-SARDI's marine research vessel MV Ngerin ).
*The location where image was taken is an extensive and quite deep ( by abalone diver standards of the time) submerged rock reef benthos notable for its big sponges, variety and density of bryozoans, echinoderms et al, and some very large stalked ascidians, interspersed with smaller areas of sand and rubble, and occasionally very small seagrass patches.
This extensive area of fully submerged reef was known to the local professional abalone divers as *'Abalone Hotspot' .It supported (and presumably still supports ) a very large biomass of greenlip abs.
It is( or was?) also a highly productive area for commercial rock lobster fishers and I remember being impressed at the sight of so many pot surface marker buoys scattered over such a remote offshore region, with even the larger of the Investigator Groups islands being low on horizon.
*as I'm not sure exactly where Abalone Hotspot is on Google Maps, I've defaulted to Flinders Island for location marker.

[NB: I saw far fewer lobster (Jasus edwardsii) adults on the 1-2 dives there than I expected. That was a surprise to me then, but is a meaningless anecdote given I've only ever dived Abalone Hotspot on that one single day.]