Mrs Burling was a member of Catlins LandSAR.
Information from the GPS unit aboard Mr Kopua's 5.2m Kiwi Kraft boat, Kristala, suggested the pair might have been fishing near White Head on the Catlins Coast.
The boat was spotted overturned about 10am on Thursday, its anchor had snagged southeast of Nugget Point. A fishing rod was recovered that had bait on the hook.
On Friday, a soft drink bottle was found near the two mouths of the Clutha River.
Late on Saturday, a ''bit of a seat'', likely from the boat, was discovered further north on Smails Beach.
Snr Const Hewitson said yesterday that ''lots and lots of stuff'' was picked up along the coastline, but nothing that appeared to be tied to the two missing friends.
He appealed to anyone visiting the coast, fishing or beachcombing, from Dunedin to Long Point, south of Owaka, to report anything that might be of interest to the searchers.
''Anything that's possibly linked to a small boat, or clothing items - I know Lou was one to put her name on things - anything that bore the name Burling or Kopua''.
Rough seas did not allow search boats to launch on Saturday and the forecast was not good for today, he said.
Today's and tomorrow's search would focus on ''beaches of high probability of catchment'' and ''some observations from high points'' unless new information arises.
''And then, after Tuesday, we don't know.''
Snr Const Hewitson said searchers had been ''passionate'' in the search for the two well known residents and he said the support from the community had been appreciated.
Anyone who finds, or may have found, an item of interest in the search should contact Owaka police at (03) 419 1070.