The Food and Service Workers Union is holding a petition to try to prevent redundancies at a Sealord fish plant at Nelson.
Sealord plans to lay off up to 160 processing workers on the night shift by the start of April, saying the plant is currently not viable.
However, the union says the restructuring is not due to the recession and claims it could be delayed or reconsidered.
The union hopes the petition will help put pressure on Sealord to at least minimise redundancies.
