This isn't quite exact, but 1/4 cup of butter (so a half stick if you're in the US) is 57 grams according to the conversion chart from allrecipes below. So use just a slightly heavy 1/4 cup or 1/2 stick.
Yellowtail, including Yellowtail Jack (Seriol landei), are recognized by a yellow stripe across their body and their yellow tail. Range & Habitat: Yellowtail is caught year round, but more commonly during summer in the Pacific Coast and the Sea of Cortez. They are caught primarily with hook and line, and their average weight is 10 to 20 lbs.
Carapace Length (CL) Yellowtail Snapper-Minimum size limit of 12 in (30.5 cm) TL applies year-round for yellowtail snapper. Spiny Lobster-Minimum size limit is 3.5 in (8.9 cm) CL. Seasonal Closures No harvest of the following species in the EEZ during the dates indicated below February 1 - April 30.