Dew on the decks, diesel purring a sweet baritone note at 1800 revs, white prow cleaving a blue-black sea, Marline makes her way up the Northland coast at a stately seven knots. My father is at the helm; I’m on the poop deck with the lines and lures. We’re trolling in the wake of Zane Grey, an American sportsman-writer-adventurer who fished these waters in the 1920s and whose book Tales of the Angler’s Eldorado, New Zealand put the Bay of Islands on the gamefishing map.

We’re trolling in my grandfather’s wake, too, fishing for memories. Leon was a boatbuilder, and Marline was his last boat. Kauri from cabin top to keelson, she was built in 1949 under his sister’s house in St Marys Bay, Auckland, long after he and his brother had closed their Russell boatshed and officially retired.

Leon was not just a builder of boats but one of the pioneer swordfishing skippers of the Bay of Islands, which is how his wake crosses that of Zane Grey. In 1926, Grey chartered Leon and his launch Marlin to help him chase the fighting fish that fired his imagination. There’s a backhanded credit to him and his deckhand in the front of Angler’s Eldorado: “To Leon Warne and Bill Hodgson, who drank gallons of tea and saw millions of imaginary fins.” I never asked my grandfather what he thought of that jibe. Not much, probably.

We’ve journeyed up this coast many times in many weathers, my father and I, making our annual run to El Dorado in the summer and back to Auckland for the rest of the year. We’ve been here on windless days when oily swells sucked at the weed on the Cape Brett rocks and the tide race eddied the dark water. And we’ve felt the teeth of north-east gales, when Marline’s round-bilged hull rolled drunkenly through alarming arcs, tipping charts and rods off their shelves in the saloon and throwing the food out of the fridge. Once we endured the ignominy of being towed in to Russell when the universal joint disintegrated at Whangamumu. Today we have calm seas and an entourage of dolphins and false killer whales leading us through the gap between Brett and Piercy Island.

We travel close to the cliffs, grim battlements that have withstood the battering ram of the sea. I’ve seen these blackened ramparts covered with what looked like snow-flakes—a rabble of roosting gulls. Grizzled pohutukawa cling to the tops, many reduced to staghorn skeletons by possum browsing, but others flushed with fresh growth thanks to a pest-eradication programme. Leon and his fellow skippers used to shoot goats off the cliffs from their launches and pick up the carcasses from the sea.

Cape Brett lighthouse, a dazzling white bastion on a steep grassy slope, has shone here for exactly 100 years—then kerosene, now solar. An early keeper, Robert Wilson, used to go after game fish from a rowboat. On one occasion he was towed a mile to sea by a mako. His gloveless hands were cut to a bloody mess by the wire leader as he attempted to get the thrashing shark into the boat.

We round the cape and enter a broad, cliff-bound bay where Dad brings Marline close to the cliffs and reminisces about the day in 1951 when he was at this same spot, in the same boat, with his father. They’d had a hard, luckless morning trolling in rough seas and they came in here to shelter from the weather while they had a bite of lunch. The lines were left out on the outriggers, the kahawai baits dangling straight down in the water. Father and son were in the saloon, having a cuppa.

“One of the reels went tick, tick, tick, and the line came off the outrigger peg,” Dad recalls. “The old man went out to have a look. He felt the line for a minute, and said, ‘Probably snapper nibbling the bait.’ A few minutes later it happened again. Tick, tick, tick. Then the reel screamed, and I jumped up and went for the rod, belting my head on the door frame and nearly knocking myself out.” The nibbling snapper turned out to be a striped marlin—a pin fish, no less, the heaviest caught in the season. My father still rubs his forehead tenderly at the memory of the splitting headache he had while he fought that fish.

We take a turn around Bird Rock, a guano-frosted slab where gannets occupy the upper storeys and gulls the ground-floor roosts. Between here and the cape was marlin alley. Boats would motor to the cape, drift down to the Bird, then repeat. I can’t begin to calculate how many lines and trolled baits have cut these waters, how many propellers have churned back and forth between here and the Ninepin, the rock that marks the western entrance to the bay.

We pick up a couple of kahawai on lures and head out to the deep. See if we can spot a few “imaginary fins”, eh, Zane?