היומן של shaun-lee

Yesterday Alex Rogers sent me this really interesting report on some multibeam echosounder (MBES) data recorded by NIWA https://storymaps.arcgis.com/stories/7b0c9ab9fd7141abb14884f8a1f3efa4 It includes several interesting features. The most accessible were:

"A cluster of rounded depressions may be indicative of relict or active seabed seepage and potential sites of sensitive ecosystems. Seafloor backscatter reveals the sloping rim of these features may have a harder substrate compared."

They were only 10 m deep, and 1 km off shore. I added some chain to my kayak anchor rope and decided to head out the next morning.

Tue 7 Mar
Sunny
4 knots
HT 8:30AM
Wind N
Wave Hight 0.7

I kayaked from Mairangi Bay to the what I thought was an area of complexity in the middle of the largest depression (-36.736195, 174.767237) and dropped anchor. The sun had just come up but the visibility on the surface was 4-5m. The tide was slack with hardly any current. I descended the anchor line, visibility dropped sharply near the bottom and I had about 70cm vis on the seafloor. It was also very dark due to the low angle of the sun.

I was pleased to see some shells around and noticed interesting nodules protruding from the firm mud. I had decided on a Northern transect and stuck to it for 35 minutes. The substrate changed from firm to very soft mud then a bit more firm towards the end. I saw 10's of dead scallop shells and four cushion stars on the surface. The wandering anemone was by far the highlight of the dive and I wish I had bought my big camera. I was surprised to not see a single Mediterranean fanworm.

Where the mud was soft the visibility dropped to less than half a meter. I dug into the soft mud three times. The first time I could only find a fragment of scallop shell, the second one a scallop shell and a bit of green-lipped mussel shell. The last one had nothing at all. I am used to finding a lot more shell in the mud than this. I did not notice any change in the incline and my depth remained around 12.3m throughout the dive. I wonder if the MBES was detecting and old geological structure that has been since filled with mud.

I ascended with a 100-150m surface swim back to my kayak. On the way back I counted two juvenile southern black-backed gulls and two red-billed gulls on the water. There were also five white-fronted tern feeding close to shore. There were two little penguins feeding near where I dived, I wondered if they fed on the bottom.

Friday 10 Mar
HT 10:20
Wind N, 15 kts
Cloudy rainy
Waves 1m
80 min bottom time
10m max depth

At 9:15 am I walked along the beach from the carpark and disturbed two well camouflaged Reef heron roosting on the stones. I set off east from the end of the predator exclusion fence. I was pleased to find subtidal seagrass at 4m pretty quickly. It was a decent meadow running parallel to the beach. I noted the rhodoliths everywhere which became denser as I headed further east.

I saw a few juvenile goatfish and maybe a juvenile snapper but not much fish life. An octopus had made an impressive home and walled itself in with rocks. I also saw one juvenile octopus in a dead horse mussel.

At 10m I came across a few small boulders with ecklonia growing on them. Under one of the kelp plants a blade stood out to me, mostly because of this video. I had never seen a weedfish before and it was just a magical little fish. I spent the rest of my dive with it until I nearly ran out of air. It would go up into the kelp and then come out and hang out on the seafloor. Here it lay on its side a lot and drifted around just like kelp in an invisible current. It drunkenly walked around on its fins. It was magical to watch. It showed very minimal aversion to me, my bubbles and my giant light. I was able to get very close and it also swam straight at the lens twice. I took about 100 photos :D

15 March 2023
2pm High tide

12:00 pm parked at Kelly Tarltons
Navigated nine fishers along wharf, mostly catching piper but one guy landed a small kingfish. Small mussels growing on steps (new).
12:30 pm Surface swim to breakwater (navigating fishing lines) then along a bit. 20-30 Tara roosting on breakwater. <10 Tara feeding in the bay near, floats (set net?) out from KT's

More wind than predicted, vis at surface not great, I could not see then end of my fins. Descended at breakwater to 5.5m. Nearly 1m vis. Some live oysters on seafloor. A few large dead kūtai shells, not too old, quite thin. Made my way across the mud and kept seeing small fish shoot into holes. I assume they are invasive Bridled Goby. I dont remember seeing them in this bay so tried to photograph them but it's very difficult. My big video light helped them stand out which may be why they seemed new.

Mussel bed located pretty fast. I took a few photos and checked the bed for anything interesting. It looked very similar to when I last dived it in December, there may well have been more dead shell but it did not look recent (casualties of this summers extreme weather events). If any clumps of mussel had been moved by storm surges they seem to have righted themselves. I tried my luck with laying a few random quadrants and using the GoPro to document them.

While documenting some of the colonial epifauna but began to get depressed by all the eleven-arm sea stars predating the kūtai. The mean size was about the size of my hand (not too big) but there were bigger and smaller ones. I estimated later that there was one every two square meters but I think if I had looked more carefully for smaller ones in a transect I would have found more. Decided to quit early.

Swam NE for 15 minutes, followed the breakwater for a bit and tried to photograph the fish using the crab holes. Dive computer says I was under for 41 minutes. Max depth 6m.

Surface swim back on the out-going tide. Navigated the fishing lines back to the wharf.

Second dive at this spot, first report here https://blog.shaunlee.co.nz/tubeworms/

25 March 2023
1hr before High Tide
Some current
Vis 1.5m
Depth 29.4m

Shane Kelly and I descended closer to the mussel farm this time, near an anchor block. We then headed in the direction of the previous dive at this location. Vis was great on the surface but dropped fast to around 1-1.5 m. Conditions were great, no wind or chop, not much rain recently, perhaps the very high / low tides may have been a factor as well as the summer storms. We only had about 20 minutes on the bottom. We found multiple mounds, some quite large but not as big or dense as the ones we found on the first dive. I was not able to find any obvious Scarlet tubeworms (Galeolaria hystrix), but I did see other tubeworm species. I was particularly pleased to find multiple clumps of bryozoans which I did not find last time. There were a few ascidians I did not recognise.

26 March 2023
Waves 0.5-1m
High Tide 12:30pm
No current
No waves at depth
Vis 6m or so

I didn't get the Kayak into the water until nearly 12pm (many trips carrying stuff from carpark)
Paddled to the eastern arm of Anchor Bay, I could see the bottom to about 8m. Found a spot I thought was safe to anchor, tried to get off the reef but my anchor was in the Ecklonia at 10m.

I descended the anchor line to 10m to find a stunning Ecklonia forest in great condition. No fish on the way down for some reason, but 20 seconds later I saw a small snapper, then a leather jacket, and I was surrounded by jack mackerel (a large school). Medium sized trevally hang back in the distance while a kingfish cruised by. Vis was about 6m.

I looked around the reef a bit, heading North (deeper). I check three crevices and only found one crayfish. I was very pleased to find four Yellow-and-black triplefins in one spot. On the reef I saw many goatfish, a few common triplefins, one masked triplefin, a few variable triplefins, a large school of small juvenile snapper, a school of sweep, a large school of larger juvenile snapper, and a handful of red moki and spotty. I did not see any 'landable' snapper here. By far the most numerous fish were the jack mackerel which came in at least three size classes / schools. It was enjoyable to watch the schools collide in front of me. Still no mediterranean fanworm found.

I followed a valley which turned to rubble and opened up into something between shell hash and sand at around 16m. To warm up I powered out over it, heading North. There were cool mounds in the shell, I'd love to know what made them. I then carried on North for another 30m where there was a dramatic switch to mud / sand. Both substrates were covered in fine algae / biofilm which had an interesting pattern. I enjoyed watching feather duster worms retract into the sediment as I swam by, I stuffed up a photo of a snake eel which I accidentally scared back into it's hole and did not have time to wait for it to come back out.