As Council and DoC budgets get slashed it’s interesting to see local efforts emulating the success of the Wellingtons Halo project.
The Waitakere Ranges Halo Project
I am hoping this philanthropic partnership ( ZIP ) is a game changer.
Mostly just stuff I am doing to help the planet
As Council and DoC budgets get slashed it’s interesting to see local efforts emulating the success of the Wellingtons Halo project.
The Waitakere Ranges Halo Project
I am hoping this philanthropic partnership ( ZIP ) is a game changer.
An ASAP experiment designed to generate hunches not scientific facts.
This experiment is designed to answer:
Where
Bastion reef is ideal location because divers do not go there. The mussel population does not look to be harvested presumably because it is too close to city runoff. There are blue mussels present but there numbers are relativly low. It is also easily accessed by Kayak so I will not have to scratch anyones nice boat.
Design
Three cages 300x300x900mm (joined for stability) enclose 3 mixed bird netting wrapped bundels of test substrate at two different levels. The top level bundels (above 200mm) should be wire tied to the inside cage lids and should be at least Xmm above the sediment. The 3 mesh sizes test spotty predation the two heights test sediment effects.
“A 40mm spotty could eat a lot of spat”
A cow tag with a note about the experiment with my contact details was attached for curious divers (or if it gets washed up on the beach). Each bundle was clearly labled (cow tags) just incase they get mixed up.
Bricks(2) will be added inside the cages to compensate for the floatation provided by the plywood. Four large concrete block anchors attached by rope to the plywood and 20mm pegs should hold the cage still.
Materials:
Settlement substrates
A. Coconut fibre (a door matt, welded with latex)
B. Cabbage tree leaves (long dead)
C. Manuka (fresh)
D. Gorse (seeding at collection time)
E. Mussel shell (fresh and old)
Substrates to try in the future:
Each bundle was labeled:
BH BL SH SL CH CL
B=big S=small C=control H=high L=low
Deployed: 13 Dec 2014
Just off the edge of the reef, on the southern side.
No holes in my wetsuit! (yet)
When
“Most spawning occurs in late spring to early autumn, but larvae can be present all year. Sexual maturity has been observed in some populations to begin from 27mm shell length, with most individuals sexually mature by 40mm shell length. Sexual maturity is reached in the first year, and females can produce up to 100 million eggs per season. Fertilisation is largely dependent on the proximity of adults.”
– http://fs.fish.govt.nz/Doc/5449/GLM_FINAL%2008.pdf.ashx
Monitoring
Check it once a month (take a brush to clean muck of cage surfaces), after 3 months or before the cage rusts too much the 6 bundels of substrate should be opened up on the beach. Each substrate photographed with a macro lense. Ideally it is then relocated somewhere with no mussels and no reef (for spotty to hide in) to see if transporting spat only to seed locations generates a mussel reef.
The photographs should be shown to marine scientist who can show me how identify spat. I can then count spat and work out spat per square cm or something.
Prediction/ Prevention
UPDATE: 14 Jan 2015
No movement of the cage. Lots of marine growth and sediment, several small spotty (I didn’t see any on installation). Cage cleaned off (a bit). I took this video pre-clean.
UPDATE: 14 Feb 2015
RESULTS: 05 March 2015
Cages opened, substrates well documented with macro lens. Not enough spat settlement for useful substrate observations.
OBSERVATIONS
Coir and cabbage tree leaves had the most suspect spat (I could not confirm without a microscope). Use a microscope to look for spat as you need to look at anything suspect from more than one angle.
The manuaka had the most hydroids (or fine branching structures) growing on it. This is significant as Hydroids are know settlement structures.
Several starfish including 11 arms in the control cage. Shrimps and all sorts of crabs but mostly half crabs and decorator crabs ,all sorts of young shells from whelks to turbans. Lots of other marine growth and invertebrates I could not identify.
Surprising lack of holes in my wetsuit! The hardest thing was lifting the bundles in trash bags back onto the boat by myself.
RECOMENDATIONS
The lack of settlement in all cages suggests spotty are not the main problem at this site. A cage placed higher up in the exposed tidal area would be interesting, as there must be settlement near the existing adult mussels (2 meters above where I had my cages).
UPDATE: Nov 2016
Worth noting nearly 2 years later that parts of the cages are still intact. There are beautiful hyrdroids and finger sponges growing on them and some not so welcome invasive clubbed tunicates. I noticed Mediterranean fanworm nearby and the entire green-lipped mussel reef has been devastated by human harvesting.
July 23 2014
Installed Good Nature A24 trap
August 6 2014
3 strikes recored no dead rats nearby
September 6 2014
5 strikes recorded no dead rats
November 5 2014
Replaced lure in trap
December 3 2014
Still says 5 strikes, replaced gas canister, tested (6 strikes)
December 10 2014
Gas canister says 7 strikes, no dead rat
December 17 2014
Gas canister says 9 strikes, still no dead rats
Early test correlates strikes more closely with canister replacement than lure replacement. Bodies may be removed by other predators, tho disposed bodies from other traps on this line tend to stay around. Strike counter checked weekly.
January 23 2015
Gas canister says 11 strikes, 1 dead rat!
19 September 2015
Reset lure and new canister 3 weeks ago, 3 recorded kills – two rats and one mouse body lying on the ground! So awesome.
13 November 2016
I have had a look at my last two seasons of data and the A24 trap is outperforming my victor rat traps at 4 kills to one just based on the body counts. If I counted strikes (assuming bodies were being removed) then it might be even eight times more effective.
Great product, definitely worth the extra money. Go buy one.
It’s also census year for this species.
Pest meat! Unfortunately there does not seem to be a market for the rats and Possums I catch… fertiliser?
Of course my presence could well have distracted the NNZD but I don’t think she could defend her nest. The whole time I was observing her she was never more than a few meters from her nest. A passing cow would have been a much bigger and very common distraction for her. The Pukeko was moving with two others who stayed nearby but did not seem interested, there were no observable Pukeko chicks (or paternal behaviour from the Pukeko). The Pukeko definitely seemed to be consuming the egg for food not destroying it for territorial reasons.
Egg predation by Pukeko might explain other nest losses I have had this season.
Inspired by some recent conversations, I put together this list (in no particular order).