The scombroid fish are a group of about 100 species that include the mackerel, tuna, marlins and swordfish.
The scombroid fishes are robust, torpedo-shaped, voracious fish. Some have small, inconspicuous scales; others are partly naked. The mouth is large and the color is usually blue or green on top and silvery-white underneath.
Introduction to the Fishery Sciences, by William F Royce, 1972.
It’s a moderately common technical term in zoology, deriving ultimately from the Greek scombros for the mackerel or tunny, which also led via Latin to scomber as an uncommon English word for the mackerel, which is now only used as the formal name for the genus.
It has, extremely rarely (not to say uniquely), been used of somebody of piscine appearance, especially a person who suffers from protruding fishy eyes:
“Here then,” the kindly scombroid face scanning Eventyr, quick as a fire-control dish antenna and even less mercy.
Gravity’s Rainbow, by Thomas Pynchon, 1978.
You are most likely to encounter the word in the phrase scombroid poisoning, which is caused by eating fish that contains histamines produced by bacterial activity as a result of poor storage. As you can get this through eating other spoiled foods such as cheese, perhaps the alternative name of histamine poisoning is more suitable.