Pacific bonito head. The caudal peduncle is slender, and the body entirely scaled. It has no teeth on the vomer. It has a small keel on either side of the median keel on the sides of the caudal peduncle, and six to eight finlets on the dorsal and ventral surfaces of the caudal peduncle. The maximum length is about 40 inches and weight 25 pounds. It is found anywhere from inshore to about 100 miles offshore from northern Vancouver Island to Mexico, though it is not normally found north of Point Conception. It usually travels in schools. Fish and squid are its
Operculum (fish) over time. The fossil record of the threespine stickleback provide the ancestral shapes of the operculum bone. Overall, the operculum bone became more triangular in shape and thicker in size over time. Genes that are essential in the development of the opercular series is the Eda and Pitx1 genes.These genes are known to be a part of the development and loss of armor plates in gnathostomes. The Endothelin1 pathway is thought to be associated with the development of the operculum bone since it regulates dorsal-ventral patterning of the hyomandibular region. Mutations in Edn1-pathway in zebrafish are known to lead to