As the 29ft Siobhon lies idle at the pier, Mr Macdonald's initial resignation and weariness at the order is now turning to anger: "We have been tied up for three weeks. Yet we have no other income. I and my son make our living on the scallops all year round.
"I have a mortgage to pay like everyone else. While this is said to be just a precaution, it looks very draconian to me," says the fisherman, who works the boat with son Paul, 24.
Summertime is when the pair should be making up for the lean times in winter when Atlantic storms ensure all vessels are in port.
Mr Macdonald, a crab fisherman until he switched to scallops three years ago, is just one of about 50 skippers of boats of varying sizes, working between the Butt of Lewis and Jura.
They have all been ordered to leave the scallops on the seabed in the notified "boxes", the delineated blocks of sea on the government charts. An initial ban on scallop fishing was introduced by the Scottish Executive in waters off the Scottish West Coast, but east of the outer islands' chain, due to a build-up of Amnesic Shellfish Poisoning (ASP) toxins.
The area affected by the original ban lies between the Outer Hebrides and the West Coast of the Scottish mainland as far south as Islay and Jura.
To the complete exasperation of skippers and crews, the ban was extended in the last week to take in the west of the Hebrides following further testing.
Scallops taken from the Atlantic side have also shown that the naturally occurring ASP toxins are at a level which could present a risk to consumers.
The area of water affected by the new ban lies between Griminish Point on North Uist and Gallan Head on the Isle of Lewis.
Greenpeace has suggested that ammonia dumping from processes on the islands' many fish farms could be playing a big part in the toxin's prevalence.
"If Greenpeace is right in claiming that 50,000 tonnes of fish farm waste containing ammonia is dumped every year, then something should be done about that - and now," says Mr Macdonald, 62, who lives in Tong, near Stornoway.
Duncan Macinnes, the secretary of the Western Isles Fishermen's Association yesterday backed calls for urgent research to clarify the cause.
"There should be research into the incidence of the algal blooms which are always more prevalent in the summer months anyway and, if they are caused by pollution, urgent steps should be taken to prevent closures happening every summer," he said.
"And if one high reading closes an area, then surely two consecutive low readings, as currently in the North Minch, should be enough to reopen other areas."
ASP is caused by naturally occurring algal blooms which can extend over considerable areas and move with tidal currents. No other commercially marketed shellfish are affected.Reuse content