[2021] NZEnvC 131 Wilson v Waikato Regional Council [pdf, 1.4 MB]
...In particular (our emphasis):15 When a mussel larva settles, it attaches itself to the substratum with an anchor thread, and then rearranges its body, including developing gills which are used for filter feeding, and growing a harder shell for protection. At this point the juvenile mussel is less than half a millimetre long. Small mussels from this size, up to around 10 mm in size are commonly referred to as “spat” and are the seed source used in mussel aquaculture. Discussi...