Industrial action at TasPorts began at 6am today, with launch masters and vessel traffic services staff walking off the job for four hours before ongoing bans on marine work begin.
The Maritime Union of Australia and Australian Maritime Officers Union have formally notified TasPorts of the action.
TasPorts said it had checked the notices against scheduled vessel movements and did not expect high-frequency Bass Strait freight and passenger services through Burnie and Devonport to be affected.
Other pilot-exempt vessels using those ports should also continue operating, although some could face scheduling issues depending on how the action unfolds.
According to TasPorts, ships that need pilotage and its launch services face tighter limits while the action remains in place.

At Burnie, Devonport and Bell Bay, those movements will be limited to between 6am and 6pm on weekdays.
In Hobart, launch services will stop from 6am Saturday until further notice, affecting pilot launch transfers and bridge transit escorts.
TasPorts said vessel traffic services monitoring and coordination were not currently expected to be affected.
“We have worked through the notified actions in detail and put contingency arrangements in place to maintain services wherever it is safe and practical to do so,” chief executive Allan Gray said.
“Some movements requiring TasPorts’ pilot launch services will be restricted and we are working directly with affected customers and shipping agents to manage scheduled movements.”
Gray said protected industrial action was “a lawful part of enterprise bargaining” and TasPorts respected the rights of eligible employees to take part.
“We remain committed to good faith negotiations and our focus remains on reaching an agreement that fairly recognises our employees, is sustainable for TasPorts and supports the long-term interests of Tasmania,” Gray said.
The unions say the action follows months of unsuccessful bargaining over a replacement agreement.
Members are seeking pay in line with maritime workers interstate, an even-time roster for launch masters and employer superannuation contributions increased from 12.5% to 15%.
In a statement in August, MUA Tasmania branch secretary Alisha Bull said TasPorts “has failed to put forward an offer that recognises the vital role these highly skilled, safety-critical workers perform every day”.
The unions had announced an earlier round of industrial action due to begin on August 8.
TasPorts said it would continue reviewing vessel movements and contact affected customers directly.