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Dive Reports

12-06-2024 Holbourne Island

DAY/DATE

Wednesday

12/06/2024

SITE/S

Holbourne Island
Bowen 

 

PARTICIPANTS

Terry & Julie

 

TYPE

Subtidal

 

MODE

Boat Dives

 

VESSEL

Rebel II

 

DIVE

1

2

SITE/S

The Gap

Manta Reef

SPECIES #

6

21

DURATION

72 Min

109 Min

DEPTH/RANGE

18 m

7.3 m

TEMP.

24 C

24 C

VIS.

15 m

20 m

SURGE

Nil

Nil

CURRENT

Nil

Nil

COMMENTS & OBSERVATIONS

With a forecast of < 10 knots variable we headed off in the boat after surviving the inefficiencies of people fluffing around at the boat ramp. The seas became a little lumpy about the half-way mark but we pressed on hoping the forecast was correct. For our first dive we chose the more protected site of The Gap on the northern side of the island. Visibility was lovely and we were able to cruise around the reef without the need for a reel. We did not find many sea slugs nor did we see any complete Crown of Thorns starfish that we usually see at this site.

After a welcome warm up coffee break we noticed that the seas had settled so we moved back around to Manta Reef where conditions were indeed calm. We anchored over the rubble, slightly shallower than normal, with the intent to head to deeper water. However as we dropped down onto slugs, we simply scoured the rubble patches finding a nice diversity of species including some that we had not recorded here before. We did observe one phyllidiid being checked out by a gymnodorid and when reviewing our photos on the big screen we found another phyllidiid with an aeolid hitchhiker (we did not see it at the time). After surfacing to glassy conditions, we cruised home at high speed in much nicer conditions than the trip out.

Taxonomic Diversity:
18 of the 23 species sighted were nudibranchs, of which 14 were dorids comprising 10 x porostome, (suctorial feeders – all of the Phyllidiidae family), 2 x phanerobranchs (non-retractile gill), 2 x cryptobranch, (retractable gill) and 4 were cladobranchs comprising 2 x aeolids, 2 x arminids and 0 x dendronotinids. A single cephalaspidean (headshield slug) and 4 x sacoglossans complete the species count. If diet is considered 12, of the total of 23 species, were spongivores dominated by the phyllidiids. 51 specimens in total were recorded.

Our Historical Data:
– We have now completed 7 surveys and recorded 26 species at The Gap.
– At Manta Reef we have completed 6 surveys and have recorded 48 species.
– Both sites were first surveyed on 13/03/2023.
Excluding the undescribed phyllidiids, which we still have under review:
– This is the first occasion on which we have recorded Plakobranchus sp. 04 in Australia.
– This is the first occasion on which we have recorded Dermatobranchus fortunatus, Dermatobranchus tuberculatus, Goniobranchus sinensis, Philinopsis gardineri or Phyllodesmium sp. 2 in the Whitsundays;
– This is the first time we recorded Phyllidia varicosa at The Gap, and
– This is the first time we have recorded Elysia marginata, Elysia sp. 30, Elysia sp. 31, Gymnodoris sp. 26, or Hypselodoris whitei at Manta Reef.
– We last surveyed The Gap on 21/09/2023 and Manta Reef on 14/08/2023.

The large number of phyllidiid species in the lists below reflects the work that has identified taxonomic-cryptic species delineated in the paper: Papu, A., Bogdanov, A., Bara, R., Kehraus, S., Konig, G., Yonow, N. & Wagele, H. (2022). Phyllidiidae (Nudibranchia, Heterobranchia, Gastropoda): an integrative taxonomic approach including chemical analyses. Organisms Diversity & Evolution. https://doi.org/10.1007/s13127-021-00535-7 At the time of publishing this report we are in the process of reviewing all of our Phyllidiella records to align them with the findings of the above paper.

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

TOTAL SPECIES SIGHTED: 23

 

SPECIES LIST – ALPHABETICAL

Dermatobranchus fortunatus -/1 +
Dermatobranchus tuberculatus -/1 +
Elysia marginata -/8
Elysia sp. 30 -/2
Elysia sp. 31 -/1
Goniobranchus sinensis -/1 +
Gymnodoris sp. 26 -/5
Gymnodoris sp. 31 1/-
Hypselodoris whitei -/1
Philinopsis gardineri -/1 +
Phyllidia coelestis 1/-
Phyllidia picta -/1
Phyllidia varicosa 1/1
Phyllidiella cf. pustulosa 1/2
Phyllidiella lizae 1/1
Phyllidiella sp. a (Papu et al. 2022) -/2
Phyllidiella sp. c2 (Papu et al. 2022) 1/1
Phyllidiella sp. d (Papu et al. 2022) -/1
Phyllidiella zeylanica -/2
Phyllidiopsis burni -/1
Phyllodesmium sp. 02 -/1 +
Plakobranchus sp. 04 -/10 +++
Tenellia sp. 33 -/1

SPECIES GROUPED BY ORDER

Nudibranchia
Dorids
Phanerobranchs
Gymnodoris sp. 26 -/5
Gymnodoris sp. 31 1/-

Cryptobranchs
Goniobranchus sinensis -/1
Hypselodoris whitei -/1

Porostomes
Philinopsis gardineri -/1
Phyllidia coelestis 1/-
Phyllidia picta -/1
Phyllidia varicosa 1/1
Phyllidiella cf. pustulosa 1/2
Phyllidiella lizae 1/1
Phyllidiella sp. a (Papu et al. 2022) -/2
Phyllidiella sp. c2 (Papu et al. 2022) 1/1
Phyllidiella sp. d (Papu et al. 2022) -/1
Phyllidiella zeylanica -/2
Phyllidiopsis burni -/1
Cladobranchs
Aeolids
Phyllodesmium sp. 02 -/1
Tenellia sp. 33 -/1​
Arminids
Dermatobranchus fortunatus -/1
Dermatobranchus tuberculatus -/1
Dendronotinids
– 

Cephalaspidea

Pteropoda

Sacoglossa
Elysia marginata -/8
Elysia sp. 30 -/2
Elysia sp. 31 -/1
Plakobranchus sp. 04 -/10

Umbraculoidea

Pleurobranchoidea

Anaspidea

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