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Dive Report

17-10-2022 North West Reef

Oct 21, 2022

DAY/DATE

Monday

17/10/2022

SITE/S

North West Reef
Mudjimba Island

 

PARTICIPANTS

David

 

TYPE

Subtidal

 

MODE

Boat Dive

 

VESSEL

Li’l Mischief

 

DIVE

1

SITE/S

North West Reef

SPECIES #

13

DURATION

68 Min

DEPTH/RANGE

11 m

TEMP.

22 C

VIS.

8 m

SURGE

Slight

CURRENT

Nil

COMMENTS & OBSERVATIONS

Escape from the Court through the build-up of surfer’s cars was effected not a moment too late. Single-handed set-up and launch of Li’l Mischief went without incident and a short and pleasant 25 knot voyage to Old Woman Island was enjoyed thanks to the almost perfect surface conditions. Gear-up as well as water entry and exit all proceeded as planned. The only hiccup was discovering my first stage o-ring seat was damaged and it would not seal for the second dive, that then had to be abandoned. It is surmised that this was latent damage from a mishap during a recent Bali trip when the regulator was damaged by a careless diving attendant and “repaired”. Although only one dive was conducted by a single surveyor the sea slug population has certainly improved at this site since June of this year when only 8 species were recorded across two dives with two surveyors. This improvement was foreshadowed by the increased Bornella Reef (also at Mudjimba Island) sightings late last month. (Note: A video taken on this excursion of Verconia norba has been placed on its Species Profile page.)

Taxonomic Diversity:
11 of the 13 species sighted were nudibranchs, 8 being dorids comprising 1 x phanerobranch (non-retractile gill), 1 x porostome (suctorial feeder the Phyllidiidae family) and 6 x cryptobranchs (retractable gill) all bar one belonging to the Chromodorididae family. The other three nudibranchs were cladobranchs – one each, aeolid, arminid and dendronotid. The other two non-nudibranch sea slug species were a pleurobranchid (side-gilled slug) and one sacoglossan. If diet is considered then 9 of the 13 species sighted are spongivores.

Our Historical Data:
– This excursion brings the survey number to 48 at this site since we commenced fully recording data here on 12/06/2010.
– 164 species have been recorded at this site.
– Our most common sightings at this site are: Doriprismatica atromarginata (98%), Thuridilla cf. splendens (96%),
Goniobranchus splendidus (94%) and Phyllidiella pustulosa (92%) all of which were recorded on this survey.
– This site last surveyed on 14/06/2022.
– In reviewing the graphical representation (see image gallery below) of both species and total organisms, there seems to have been a gradual decline in the number of both recorded on each survey performed here. The reason for this trend (or the impression of a trend) will need to be examined in relation to other factors.

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

TOTAL SPECIES SIGHTED: 13 

 

SPECIES LIST – ALPHABETICAL

Bulbaeolidia alba -1
Dermatobranchus tuberculatus -1
Doriprismatica atromarginata -3 #98%
Goniobranchus splendidus -10 #94%
Hexabranchus sanguineus -1
Hypselodoris jacksoni -2
Hypselodoris obscura -5
Jorunna sp. 03 -2
Phyllidiella pustulosa -1 #92%
Pleurobranchus peronii -1
Thuridilla cf. splendens -1 #96%
Tritoniopsis elegans -1
Verconia norba -2

SPECIES GROUPED BY ORDER

Nudibranchia
Bulbaeolidia alba -1
Dermatobranchus tuberculatus -1
Doriprismatica atromarginata -3 
Goniobranchus splendidus -10 
Hexabranchus sanguineus -1
Hypselodoris jacksoni -2
Hypselodoris obscura -5
Jorunna sp. 03 -2
Phyllidiella pustulosa -1 
Tritoniopsis elegans -1
Verconia norba -2

Cephalaspidea

Sacoglossa
Thuridilla cf. splendens -1

Umbraculoidea

Pleurobranchoidea
Pleurobranchus peronii -1

Anaspidea

DIVE IMAGES GALLERY

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