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.
Depends on the species of grouper. The biggest is the aptly name goliath grouper, with the IGFA world record being 680 pounds (308.44 kg). Yellowfin grouper, one of the most common targets among groupers for anglers, can grow to be over 40 pounds (18 kg).