COMMENTS & OBSERVATIONS

Sunday, low winds forecast, everyone saying they are heading out, but still plenty of parking at the boat ramp (unlike the Sunshine Coast) so off we went to Holbourne Island chasing the elusive blue water after the crappy viz at Rose Bay on our last dive. The water stayed green for a very long time and never really got blue. We anchored up in calm conditions at Manta Reef but were disappointed by the limited visibility which was only around 10m. Interestingly there were lots of jellyfish in the water (bigger ones, not the tiny nasty ones).

We scoured the substrate at around 8m and found very little in the way of nudibranch species, with the phyllidiids being dominant. For the second dive we moved around to the Gap, which is on the northern side of the island. The visibility was no better and the reef was in a very sorry state with lots of damage observed to the branching and plate corals, perhaps a result of cyclone Koji. We failed to find any nudibranchs other than phyllidiids on this side but did observe a couple of large Crown of Thorns Starfish and several large Hermit Crabs (Dardanus lagopodes), which we did not see on the other side. So the question remains, have the nudis moved into deeper water or did they get pummelled by the swell in the cyclone? Only time and further dives will tell!

Taxonomic Diversity:
All ten of species sighted were nudibranchs, 8 being dorids comprising 7 x porostome (suctorial feeders), 0 x phanerobranchs (non-retractile gill), 1 x cryptobranch (retractable gill); and two cladobranchs comprising 1 x aeolid, 1 x arminid and 0 x dendronotinids.  A total of 18 specimens were sighted. Eight of the ten species are spongivores.

Our Historical Data:
Manta Reef
– We have now completed 15 surveys at Manta Reef since our first survey here on 13/03/2023.
– We have recorded 70 species at this site.
– Our most frequently recorded species here are Phyllidia varicosa (53%), Elysia marginata (47%), Phyllidiella pustulosa (47%), and Phyllidiella cf. pustulosa (47%).
– The most abundant species recorded by us at this site are Phyllidiella sp. a (1.1 per dive), Elysia marginata (1/ dive), Phyllidiella pustulosa (1/dive), Plakobranchus sp. 04 (1/dive).
  – This is the first occasion on which we have recorded Phyllidiella granulata or Phyllidiella sp. b on any of our dives at this site.
– Our last survey at this site was on 21/12/2025.
The Gap
– We have only completed 7 surveys and recorded 23 species at The Gap since our first on 13/03/2023. Because of the fewer surveys here, more detailed historical data is not presented. Our last survey at this site was on 12/06/2024.

Key to symbols
+++ New Species
+ First time sighted at Whitsundays
# Most commonly sighted at this site with %

TOTAL SPECIES SIGHTED: 10

DIVE IMAGES GALLERY

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