A weekend of hunting nudibranchs at the Poor Knights Islands (New Zealand) that was so successful it was worth making a list of all the species encountered!

I did 5 scuba dives, including a night dive, for 368 minutes in the water on 16th and 17th November 2019.

Dive sites:
- Northern Arch
- Blue Maomao Arch
- Blue Maomao Arch (night dive)
- Eastern Arch
- Barren Arch

I've put the common name of the nudibranch in brackets because I know some people will find that name more recognisable.

Nudibranchs:

1. Aphelodoris luctuosa (Common nudibranch or Variable nudibranch)
2. Cadlina willani (Willan's cadlina)
3. Caldukia rubiginosa (Ruby caldukia)
4. Ceratosoma amoenum (Clown nudibranch)
5. Chromodoris aureomarginata (Gold-edged chromodoris)
6. Cuthona cf. scintillans
7. Dendrodoris citrina (Lemon dendrodoris)
8. Dendrodoris krusensternii (Gem nudibranch)
9. Eubranchus sp., undescribed
10. Flabellina albomarginata (White-margined flabellina)
11. Janolus ignis (Red janolus)
12. Okenia mija (Speckled okenia)
13. Polycera maddoxi
14. Tambja tenuilineata, including mustard-coloured variant (Fine-lined tambja)
15. Trapania brunnea (Brown trapania)
16. Trapania sp., undescribed - *NEW*
17. Trinchesia sp., undescribed: yellow-tipped cerata with navy/purple highlight and cream speckles, brown rhinophores
18. Trinchesia sp., undescribed: dark green cerata with cream stripes, pale body has cream stripes
19. Cadlina sp., undescribed - seen by Jacqui Robson
20. Jason mirabilis (Jason's nudibranch) - seen by Jacqui Robson
21. Tambja morosa (Morose tambja) - seen by Jacqui Robson
22. Tularia bractea, green variant (Metallic tularia) - seen by Shane Housham

Other sea slugs:
​

1. Elysia sp. (Blue-spotted elysia)

My first ever sighting of Chelidonura inornata - so exciting! A single individual was spotted at Oculina Point at the Poor Knights Islands at a depth of around 10 metres.

Chelidonura inornata is also known as the Ornate swallow-tailed sea slug. It is rarely sighted in New Zealand. It occurs throughout the tropical Indo-West Pacific Ocean. In the southwest Pacific it is recorded from northern New South Wales, Lord Howe Island, Norfolk Island and northeastern New Zealand.*

* Behind the Bubble Curtain, Auckland University Underwater Club 50th Anniversary Book.

I first encountered this species at the Poor Knights Islands on 18 July 2011. I discovered it quite by accident. I was zooming in on a photo I'd taken of a crested blenny and noticed a couple of teensy nudibranch-looking blobs next to the fish - they were blurry. The next day I went hunting in earnest and discovered Landing Bay Pinnacle absolutely covered in these tiny molluscs. They were all over the place, but at about 2mm long, a bit difficult to capture in a photo with my Canon G9 camera.

Years on, these sea slugs have popped up on my radar again. I spotted them in Manta Bay and on Magic Wall at the Poor Knights Islands on 24-25 September 2016. This specimen is from Danger Rock outside of the Bay of Islands (9 October 2016). It was in a depth of about 14-16 metres.

Runcina katipoides is a sea slug but not a nudibranch. It is truly tiny; the slugs I've seen have been about 2-3mm long. It is probably more common than you might believe but its diminutive size makes it difficult to spot unless you're really trying to find micro molluscs.

This photo was taken with my Canon 5D Mark II using a 100mm macro lens. The photograph has been heavily cropped so that you can see the sea slug.