Black Rocks

Recently a question was posed to me: "What is the cause of the decline of green lipped mussels at the Black Rocks in the Bay of Islands?"

So I went digging. 

According to John Booth, the factors contributing to the decline of green lipped mussels/kūtai are:

1) Overharvesting - likely. The mussel beds are typically highly clumped and very visible, due to being found in the intertidal and subtidal zone.

2) Disease - unlikely. There has been no reports of significant numbers of dead kūtai among living intertidal or subtidal populations, although more evidence is required. 

3) Predation / competition - unlikely. There has been no evidence of an increased population of key predatory fish, starfish or crabs.

4) Lack of food (phytoplankton) - unlikely. There has been no evidence of reduced condition among other filter feeders nearby.

5) Poor water quality - unlikely. No key water-quality indicators failed categorically to meet Australasian guidelines.