COMMENTS & OBSERVATIONS

Hoping the visibility had improved we headed to Horseshoe Bay for a morning dive. Prior engagements meant we dived a little later than we would like, resulting in a dive on the outgoing tide. This is not really a problem in terms of currents or water depth, but it means there is more beach to trudge up on the return. The water is still cloudy and once again deteriorates the further out you go. We did not let it deter us today though, as the visibility was sufficient to keep each other in sight without bumping into one another.

The recent cyclone seems to have had an impact on the number of nudibranch species as one again we struggled to find much in the way of abundance or diversity. We found the tiny Mnestia on the sand on the way out and it was determined to bury itself in the silt. At around 1-2mm long it made photographing it difficult. We scoured the coral and the algae covered rocks but not a phyllidiid to be found nor any Elysia. It will be interesting to see how long it takes for things to improve.

Taxonomic data:
Four of the five species sighted were nudibranchs, all four being dorids comprising 0 x porostomes (suctorial feeders), 2 x phanerobranchs (non-retractile gill), 2 x cryptobranchs (retractable gill); and zero cladobranchs comprising 0 x aeolid, 0 x armininids and 0 x dendronotinids.  A single bubble-shelled headshield slug completes the count. A total of 7 specimens were sighted. Only two species are spongivores.

Historical Data:
– We have now completed 28 survey dives at Horseshoe Bay since our first survey here on 12/06/2018.
– We have recorded 68 species at this site.
– The species we record most often at this site are Gymnodoris sp. 35 (39% of dives), Samla bicolor (29%), Hypselodoris tryoni (25%) and, Elysia sp. 30 (25%).
– The most prevalent species we record here are Elysia sp. 30 (0.9 per dive), Elysia sp. 31 (0.9), Gymnodoris sp. 35 (0.8), and Samla bicolor (0.7).
– This is the first time we have recorded Mnestia colorata on any of our dives.
– In the Whitsundays, we have recorded Gymnodoris amakusana at both Horseshoe Bay (3 times) and Rose Bay (twice)
– Our last survey at this site was on 26/12/2025.
(Historical data courtesy of Terry Farr, who extracts it from his comprehensive database.)

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

TOTAL SPECIES SIGHTED: 5

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