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Dive Report

14-12-2022 North-West Reef

Dec 16, 2022

DAY/DATE

Wednesday

14/12/2022

SITE/S

North-West Reef
Mudjimba Island

 

PARTICIPANTS

David

 

TYPE

Subtidal

 

MODE

Boat Dives

 

VESSEL

Li’l Mischief

 

DIVE

1

2

SITE/S

North-West Reef

North-West Reef

SPECIES #

17

14

DURATION

96 Min

83 Min

DEPTH/RANGE

10-12 m

10-12 m

TEMP.

24 C

24 C

VIS.

10 m

10 m

SURGE

Nil

Nil

CURRENT

Nil

Nil

COMMENTS & OBSERVATIONS

What appeared to be another almost perfect offshore dive day popped out of all the other lousy forecasts. I decided to continue with the Mudjimba Island surveys, if the visibility was suitable. As it happened it was the best it’s been for some time – up to 10 m. North West Reef at Mudjimba Island has usually been a “happy hunting ground” for sea slugs so the pick was dropped there, early morning, in very light drizzle and little breeze. The improvement in diving weather of late has also seen a corresponding improvement in sea slug sightings. A count of 17 species for the first dive was an excellent start. The 24 C water temp was certainly an improvement on last trip’s 21 C. A Berthella martensi with all of its three sacrificial segments autotomised was sighted crawling along the substrate with its side-gill exposed. (View that video under its Species Profile.) Plenty of Chromodorididae species were present with Verconia haliclona being the find of the day. A not so common Thuridilla albopustulosa was also in the mix. Upon surfacing after the second dive I spotted Deb & Ted Aston’s rib on the southern side of the island, anchored on The Wall site. I intended a catch-up on my way back to port, but the divers were down.

Taxonomic Diversity:
20 of the 27 species sighted were nudibranchs, with 18 being dorids comprising 3 x phanerobranch (non-retractile gill), 3 x porostomes (suctorial feeders and all Phyllidiidae family), 12 x cryptobranchs (retractable gill) (all belonging to the Chromodorididae family and 2 x cladobranchs comprising 1 x aeolid and 1 x dendronotid. The balance of sea slugs is made up of 3 x sacoglossan, 2 x pleurobranchid (side-gilled slugs), 1 x cephalspidean (headshield slugs) and 1 x anaspidean (Sea Hares). If diet is considered then 17 of the 27 species sighted are spongivores.

Our Historical Data:
– This excursion brings the number of survey dives to 50 at this site since we commenced fully recording data here on 12/06/2010.
– 166 species have been recorded at this site.
– The most regularly recorded species at this site are Doriprismatica atromarginata (98%), Goniobranchus splendidus (94%), Thuridilla cf. splendens (94%) and Phyllidiella pustulosa (90%).
– This is the first time we have recorded Phyllidiopsis shireenae and Placida kevinleei at this site.
– Two of the species, Goniobranchus decorus and Tenellia sibogae, have only been recorded by us here on two previous occasions.
– There is no obvious pattern to the prevalence of particular species recorded on these surveys.
– Although difficult to draw conclusions based on only 3 subsequent surveys, there has been a slight increase in species and total numbers since the low on 14 June 2022. (See graph below in Image Gallery – Scroll to end.)
– This site last surveyed on 23/10/2022.
(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: 27

 

SPECIES LIST – ALPHABETICAL

Aplysia concava 1/-
Berthella martensi 1/-
Diversidoris crocea 1/-
Diversidoris flava -/2
Doriprismatica atromarginata 1/2 #98%
Glossodoris vespa 1/-
Goniobranchus albonares 1/-
Goniobranchus decorus 1/-
Goniobranchus splendidus 1/11 #94%
Goniodoridella savignyi 1/1
Gymnodoris alba 1/-
Hypselodoris jacksoni 4/3
Hypselodoris obscura 2/-
Miamira magnifica 1/-
Phyllidiella lizae -/1
Phyllidiella pustulosa -/1 #90%
Phyllidiopsis shireenae -/1 +
Placida kevinleei -/1 +
Pleurobranchus peronii 1/-
Roboastra luteolineata -/1
Sagaminopteron ornatum 1/-
Tenellia sibogae 1/-
Thuridilla albopustulosa -/1
Thuridilla cf. splendens -/2 #94%
Tritoniopsis elegans -/1
Verconia haliclona -/1
Verconia simplex 1/-

SPECIES GROUPED BY ORDER

Nudibranchia
Diversidoris crocea 1/-
Diversidoris flava -/2
Doriprismatica atromarginata 1/2
Glossodoris vespa 1/-
Goniobranchus albonares 1/-
Goniobranchus decorus 1/-
Goniobranchus splendidus 1/11
Goniodoridella savignyi 1/1
Gymnodoris alba 1/-
Hypselodoris jacksoni 4/3
Hypselodoris obscura 2/-
Miamira magnifica 1/-
Phyllidiella lizae -/1
Phyllidiella pustulosa -/1
Phyllidiopsis shireenae -/1
Roboastra luteolineata -/1
Tenellia sibogae 1/-
Tritoniopsis elegans -/1
Verconia haliclona -/1
Verconia simplex 1/-

Cephalaspidea
Sagaminopteron ornatum 1/-

Pteropoda

Sacoglossa
Placida kevinleei -/1
Thuridilla albopustulosa -/1
Thuridilla cf. splendens -/2

Umbraculoidea

Pleurobranchoidea
Berthella martensi 1/-
Pleurobranchus peronii 1/-

Anaspidea
Aplysia concava 1/-

DIVE IMAGES GALLERY

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