Perth beaches are being progressively closed as a 4m shark travels north about 100m offshore.
Surf Lifesaving WA says the shark is near a whale.
City and Floreat beaches were closed, but are now reopened, and lifesavers also closed Scarborough and Brighton beaches.
All beaches were reopened at 2pm.
Beachgoers in the northern suburbs were warned to take care as the shark may continue to move north along the coast.
The State Government's shark catch-and-kill policy ended yesterday and drum lines 1km off the coast were removed.
A private contractor removed drum lines in the South West.
Although the final cost of the trial is unknown and the Government is yet to release final figures for the number of sharks and other animals caught, it is understood not one great white shark was caught on a line.
The drum lines were set in late January and early February as part of efforts to catch great white, tiger and bull sharks bigger than 3m.
Mr Barnett said "a little over" 100 sharks, mainly tiger sharks, had been caught.
"Of that, about 40 were destroyed or died on the hook," he said.
A poll conducted by ResearchPanel and Painted Dog Research shows a strong anti-shark kill sentiment in WA, with 58 per cent of respondents either strongly or moderately opposed to the policy.
Twenty-two per cent of respondents backed it, including just 8 per cent who were strongly supportive, while 19 per cent were undecided.
An overwhelming 73 per cent of people under 24 opposed the policy, while women were also unlikely to agree with it, with 64 per cent opposed. In comparison, 51 per cent of male respondents opposed it while 29 per cent supported the use of drum lines.