How is this not totally straightforward?
CAR 7d(IV): the carriage of persons or the carriage of goods without a charge for the carriage being made other than the carriage, for the purposes of trade, of goods being the property of the pilot, the owner or the hirer of the aircraft;
Therefore the carriage of goods, for the purposes of trade, precludes such an operation from being private.
Furthermore...
CAR 206: (viii) carriage, for the purposes of trade, of goods being the property of the pilot, the owner or the hirer of the aircraft (not being a carriage of goods in accordance with fixed schedules to and from fixed terminals);
... clearly states that it's airwork if carrying goods, for the purposes of trade, that are owned by the pilot, owner or hirer. You're carrying the owner's goods (his fish/illegal abalone) for the purposes of trade, therefore it's airwork.