COMMENTS & OBSERVATIONS

Visibility of up to 25 m was reported out on the Gneering Shoals last weekend but with a strong westerly wind predicted to come in before midday we opted to stay close to the mainland by diving off Mudjimba Island. Our site of Bornella Reef is well outside of the no-anchoring zone around the Island so we chose that as our destination for this excursion. 

Upon arrival, visibility did not look too good with a load of heavy particulate matter in the water column but we hoped it was just a layer and did not reach all the way down to the substrate – and so it was, although the substrate itself carried a substantial silt load. We only worked a small area either side of the anchor on each dive but were rewarded with a 17 species count. Finds of note include: Aegires hapsis and Halgerda sp. 03. An unusual looking Dermatobranchus was recorded that we believe is a juvenile of Dermatobranchus rodmani. 

By the time we surfaced from the second dive the westerly wind had arrived in strength. The ugly spectre of insufficient engine cooling raised its head on the return journey necessitating a cautionary slower trip home and a forthcoming trip to the outboard service centre.

Taxonomic Diversity:
Fifteen of the seventeen sighted species were nudibranchs, with 13 being dorids comprising 1 x phanerobranch (non-retractile gill), 5 x porostomes (suctorial feeders – all of the Phyllidiidae family), 7 x cryptobranchs (retractable gill – 5 belonging to the Chromodorididae family) and 2 were cladobranchs comprising 1 x aeolid, 1 x arminid and 0 x dendronotinids. A single sacoglossan (sap-suckers) and 1 x cephalspidean (headshield slugs) complete the species count. If diet is considered then 14 of the 17 species sighted are spongivores. More than 42 specimens in total were recorded.

Our Historical Data:
– This excursion brings the number of survey dives to 38 at Bornella Reef since we commenced fully recording data here on 19/07/2010.
– 149 species have been recorded at this site.
– Our most commonly recorded species at Bornella Reef are Goniobranchus splendidus (97%), Phyllidiella pustulosa (79%)*, Doriprismatica atromarginata (76%), and Hypselodoris jacksoni (71%) – all sighted on this excursion.
– The most abundant species we record at this site are Doriprismatica atromarginata (6.0/dive), Goniobranchus splendidus (5.1/dive), Thuridilla cf. splendidus (3.2/dive), and Phyllidiella pustulosa (2.3/dive)*
– This is the first time we have recorded Aegires hapsis or Halgerda sp. 03 at this site.
– The graph, in the image gallery below, shows that the number of species and organisms recorded in any survey dive has remained relatively constant over the period we have been conducting surveys here.
– Our last survey at Bornella Reef was on 28/10/2024.
* The data for Phyllidiella pustulosa is questionable as Papu et al, 2022 have reclassified some the species, we previously recorded as this species, into a number of separate species (including Phyllidia sp. C recorded on this survey) and we have yet to fully update our records.
(Historical data courtesy of Terry Farr, who extracts it from his comprehensive database.)

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

TOTAL SPECIES SIGHTED: 17

DIVE IMAGES GALLERY

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