Mr Marsh (67) hauled in the 94cm male brown trout, known as a ''jack'', during a fly fishing expedition at Lake Aviemore on April 16.
He was standing knee-deep in water when he spotted what at first appeared to be a log, which then flashed a fin and disappeared.
He eventually coaxed it on to a hook and spent 20 minutes reeling in the trout, which appeared to be old and in poor condition.
''I've never seen a fish that big up there.
''My net wasn't big enough ... I sort of got his head in it and dragged him back on to the beach.''
Mr Marsh's catch was now stored in his freezer, but would be mounted and taken to his crib at Otematata.
''It's something I can brag about.''