Dive Report

30-08-2021 Canyons & Trench

Aug 30, 2021

DAY/DATE

Monday

30/08/2021

SITE/S

Canyons & Trench

 

PARTICIPANTS

Terry, David

 

TYPE

Subtidal

 

MODE

Boat Dives

 

VESSEL

Rebel II

 

DIVE

1

2

 

SITE/S

Canyons

Trench

 

SPECIES #

16

17

 

DURATION

71 Min

69 Min

 

DEPTH/RANGE

15 – 17 m

15.5 – 18 m

 

TEMP.

21 C

21 C

 

VIS.

7 m

10 m

 

SURGE

Nil

Nil

 

CURRENT

Nil

Nil

 

COMMENTS & OBSERVATIONS

Following the farce of our last attempt at diving Canyons we went back and located some more-promising terrain by sounder. Although a more rewarding experience than last time the dive, at the time, seemed underwhelming so we motored over to the Trench for our second dive. We dropped the pick a little further East than usual. Great terrain to dive on here, with a nice ledge and split boulders but surprisingly our numbers were similar at both sites. Upon reflection we will probably survey Canyons again. Two finds at the Trench are worth comment: Thorunna sp. 04 and Hypselodoris melanesica – are not commonly recorded. The sea butterfly – Diacavolinia longirostris was sighted just below the surface as we ended the second dive. As usual, they were extremely quick at avoiding capture.

Taxonomic Diversity
Combining the two sites:
16 out of the 25 species sighted (almost 2/3 of total) were dorids comprising 3 x phanerobranchs, 4 x porostomes (all belonging to Phyllidiidae) and 9 x cryptobranchs (all belonging to the Chromodorididae Family). The other 9 species comprised: 1 x aeolid, 2 x arminids,1 x dendronotid 1 x sacoglossan, 1 x umbrella shell  2 x side-gilled pleurobranchs, 1 x pelagic pteropodid completing the count. A great cross section of the sea slug groups. If diet is considered 16 of the 25 are spongivores.

Our Historical Data:
Canyons:
– This survey is only the second at this site.
– 22 species have been recorded here

Trench:
– This survey is number 19 at this site since we first recorded information from here on 27/06/2011
– Last surveyed on 20/07/2021
– 105 species have been recorded here
– It is worth noting that all of our dives at this site have been in the months of June to October inclusive – a function of the winds and swell or just happenstance?

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

Total Species Sighted: 25

SPECIES LIST – ALPHABETICAL

Berthella martensi -/1
Bornella anguilla 1/1
Bulbaeolidia alba 1/-
Chromodoris elisabethina 1/3 #95%
Chromodoris kuiteri -/2
Dermatobranchus oculus 2/-
Dermatobranchus rodmani -/1
Diacavolinia longirostris -/3 +
Doriprismatica atromarginata 6/6 #95%
Goniobranchus geometricus 1/-
Goniobranchus splendidus 3/4
Goniodoridella savignyi 1/-
Gymnodoris alba 1/-
Hexabranchus sanguineus -/1
Hypselodoris jacksoni 1/4
Hypselodoris maritima -/2
Hypselodoris melanesica -/1 +
Phyllidia coelestis 1/-
Phyllidia ocellata 2/-
Phyllidia varicosa 1/1
Phyllidiella pustulosa 2/3 #95%
Pleurobranchus peronii 1/-
Thorunna sp. 04 -/1 +
Thuridilla cf. splendens 5/3 #89%
Tylodina corticalis -/2

SPECIES GROUPED BY ORDER

Nudibranchia
Bornella anguilla 1/1
Bulbaeolidia alba 1/-
Chromodoris elisabethina 1/3 
Chromodoris kuiteri -/2
Dermatobranchus oculus 2/-
Dermatobranchus rodmani -/1
Doriprismatica atromarginata 6/6 
Goniobranchus geometricus 1/-
Goniobranchus splendidus 3/4
Goniodoridella savignyi 1/-
Gymnodoris alba 1/-
Hexabranchus sanguineus -/1
Hypselodoris jacksoni 1/4
Hypselodoris maritima -/2
Hypselodoris melanesica -/1 
Phyllidia coelestis 1/-
Phyllidia ocellata 2/-
Phyllidia varicosa 1/1
Phyllidiella pustulosa 2/3 
Thorunna sp. 04 -/1 

Cephalaspidea

Sacoglossa
Thuridilla cf. splendens 5/3

Umbraculoidea
Tylodina corticalis -/2

Pleurobranchoidea
Berthella martensi -/1
Pleurobranchus peronii 1/-

Anaspidea

Pteropoda
Diacavolinia longirostris -/3

DIVE IMAGES GALLERY

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