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