COMMENTS & OBSERVATIONS

With the crowds thinned and the weather favourable we headed off to Horseshoe Bay for a dip. The water has warmed up nicely but there is some Trichodesmium around and visibility was not as good as it could be, with it being rather cloudy. We aimed for our usual search area, but rather than following the rocks out, we headed across the reef and followed the eastern edge along in a northerly direction.

We found a Phyllidia coelestis that appeared to have a chunk bitten out of it. We also found the missing chunk so whatever bit the critter had second thoughts about eating it! It was a great surprise to find Cerberilla sp. 03 again, considering the specimens we find are very small at around 3mm. We have now found this species 3 times in roughly the same area, and always only one critter.

We lamented not finding any Elysia only to find the Elysia thompsoni in the first photo taken of the Cerberilla. It never ceases to amaze how you can be looking at one thing and not see another critter literally right next to it (although the Elysia is rather cryptic in colouring and blends in with the algae).

At a total species count of 11, this equals our highest number recorded at this site, which coincidentally was also 11 species, on 26 October 2023, two years ago, almost to the day. We did not dive here in October 2024 so who knows if we would have found 11 species then!

Taxonomic data:
Ten of the eleven species sighted were nudibranchs, six being dorids comprising 2 x porostome (suctorial feeders), 0x phanerobranchs (non-retractile gill), 4 x cryptobranch (retractable gill); and four cladobranchs comprising 3 x aeolids, 1 x arminid and 0 x dendronotinids. A single Sacoglossa species completed the count. A total of 14 specimens were sighted.

Historical Data:
– We have now completed 23 survey dives at this site since our first survey here on 12/06/2018.
– We have recorded 51 species at this site.
– The species we record most often at this site are Gymnodoris citrina (48% of dives), Elysia sp. 30 (26%), Samla bicolor (26%), and Hypselodoris tryoni (22%).
– The most prevalent species we record here are Gymnodoris citrina (1 per dive), Elysia sp. 30 (0.8 per dive), Samla bicolor (0.6 per dive), and Hypselodoris tryoni (0.6 per dive).
– This is the first occasion on which we have recorded Hypselodoris decorata, Mexichromis trilineata or Phyllidia coelestis at this site.
– Our last survey at this site was on 30/09/2025.

Guide to Symbols:
+++ New Species
+ First time sighted in Whitsundays
# Most commonly sighted at this site with %

TOTAL SPECIES SIGHTED: 11

DIVE IMAGES GALLERY

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