The mussel industry in the Marlborough Sounds is being threatened by an invasive marine pest. About 100 sea squirt Styela clava have been discovered in Picton's inner harbour.
The unwanted pest, also known as the clubbed turnicate, was found as part of the Ministry for Primary Industries' routine surveillance for high-risk marine organisms.
In May, the team, on contract to MPI from NIWA, found four individual sea squirts, but on 12 June 100 were discovered.
The pests can compete with native and aquaculture species for food and space, and are considered a real threat to the mussel industry in the region.