There are fears Tasmanian farmers could be severely impacted by waterfront protest action that is dogging the Spirit of Tasmania.

About 50 protesters blockaded Melbourne's Station Pier on Friday night over the sacking of a stevedore working for a port contractor.

Freight was left sitting on the dock and the Bass Strait ferry was late departing.

The ship arrived on time in Devonport on Saturday morning and will leave as scheduled on Saturday night.

But it is unclear if protesters will resume action when the ferry docks in Melbourne early on Sunday morning.

The Spirit of Tasmania's executive officer Charles Griplas said he was concerned the dispute could stop Tasmania's primary producers getting their fresh produce to interstate sellers.

Logistics' company Qube has urged the Maritime Union to call off any planned action.

The company is considering legal action.

The union has not responded to calls.