Scottish Shellfish Farm Production Survey 2021

Spat settlement

Following anecdotal industry reports of poor spat settlement and mortality in 2010, Marine Scotland Science developed a questionnaire which was sent to all authorised aquaculture production businesses farming mussels. This 2011 investigation indicated that poor spat settlement and mortality were not widespread in Scottish waters, although they had major impacts on certain individual producers. As a result of talks between the Association of Scottish Shellfish Growers and Marine Scotland a spat collection question was introduced to the 2013 survey. This question focused on mussel spat collection and was presented in two parts: is this a spat collection site; if yes, was spat settlement sufficient for production purposes?

Responses were received from 219 (100%) of the sites authorised for mussel production in 2021. One hundred and twelve (51%) of these were spat collection sites, 58 (52%) of which reported that they had sufficient spat settlement for production purposes. Insufficient spat settlement on sites may require movement of mussels to that site which increases the risk of introduction or spread of diseases.