This is what Okiwi Estuary (Great Barrier Island) used to contain within the main channel close to the estuary entrance. It was the last naturally occurring soft-sediment mussel reef in the Hauraki Gulf.
Aggregations ranged from a few individuals to meters in diameter. Mussels were frequently attached to pipis, partially buried in the sandy substrate. There were an estimated 3.2 million adults. Compared to other sites Okiwi mussels had the poorest condition but highest densities of invertebrates – Ian Mcleod’s 2009 thesis on soft-sediment mussel systems in northeastern New Zealand.
Unfortunately they were nearly completely wiped out by a major storm.
I went for a swim on the outgoing tide (excuse the murky tannin stained water) to investigate 2 years later (April 2017).
Only 50 meters or so upstream I found some small regenerating clumps.
I was really pleased to see juveniles. Note the abundant red (not green) algae. Short video below.
If we left the bed alone, I wonder how many years it might take for it to completely regenerate?
UPDATE January 2018
I was able to visit the site again and was so impressed with it’s growth. The bed is awesome:
- There are still areas with lots of shell including old mussel shell that have not been colonised by green-lipped mussels.
- Most mussels were 4-5cm long but there were much smaller juveniles too.
- The estuary has a lot of cushion stars and sea hares but no eleven armed starfish or octopus which predate mussels. It was quite strange to not see eleven armed starfish there.
- The network pattern was similar to that of both restored and reefs and the one at Marsden Point with a wide range of density. It is most compact in the center where the mussels will run out of space if they grow.
- I was told by a local that there were adults at the mouth of the estuary, they maybe crucial seed stock for the bed.
- Although I saw eagle rays in the estuary I did not see them in the bed. There was no evidence of rays or snapper feeding in the bed but it looked like rays had been digging elsewhere.