Waikiki man Ian Gray, 46, was reported missing on Sunday evening after he went fishing off Green Head, three hours north of Perth.
The experienced fisherman's vehicle and trailer remained at the boat ramp.
WA Police on Wednesday said the search would be suspended pending further information, and a report will be prepared for the coroner.
Almost 4000 square nautical miles were scoured by air, land and sea assets during the four-day search, police said in a statement.
The search area stretched to 50 nautical miles offshore.
A crew member from a Chinese bulk carrier was rescued on Monday after spending the night in the water near the Oakajee coast.
The Chinese national, aged in his 30s, was reported missing on Sunday evening from a vessel anchored about 11 kilometres off Geraldton.
He was found in the water some 14 hours later, about 24km northwest of the coastal town.
Police have since revealed the man, who was later assessed in hospital, was wearing a waterproof immersion suit when he was discovered.
"It's unusual for someone to be in the water in an immersion suit unless they deliberately put it on. He was very lucky to be found," Police Commissioner Col Blanch told ABC radio.
"We can all speculate that if you're in an immersion suit, it may have been a deliberate attempt (to get) off the boat. But we don't know that yet, and that's what we are working through."
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