It came in a day's fishing on family trailer boat Finfinder with dad Hayden Moffitt and family friend Craig Dowling, each of whom has landed striped marlin in the past, but not in the Bay.
Casey, who first started fishing, from the wharf, aged about two years, was at the controls of Finfinder when the marlin was hooked on a 37kg line about 2.30pm.
It was her time on the reel, and the two more experienced anglers aboard decided it was her catch and she would have to do the work, helping only in the last moments as the catch was hauled aboard.
It was an anxious wait for the grandmum, mum and 10-year-old sister Jemma as Finfinder headed home, arriving at the fishing club, near Te Karaka (the point at East Pier) in the entrance to the Napier inner harbour, about 4.30pm.
Renee Moffitt said her daughter fishes whenever possible, but her biggest previous catch was thought to be a kingfish under 20kg.
She has competed in the club's annual February tournament the Megafish, but the family regards that as "dad's tournament", although it was Renee Moffitt who got the biggest catch of all when she won a boat in a lucky draw two years ago.
It was the second striped marlin landed in the Bay in eight days, with long-time club member and Megafish convener Joe Bicknell claiming 112.4kg specimen off Portland Island in the northern reaches of Hawke Bay on January 2.
Several were reported hooked from different boats on Tuesday, but by early afternoon none had been boated, the apparent increase in numbers being attributed to the chase for bait fish in the warmer currents being experienced this summer.