Enables carnitine transmembrane transporter activity. Acts upstream of or within carnitine transport and heme biosynthetic process. Predicted to be located in apical plasma membrane. Is expressed in several structures, including gill; head; liver; pleuroperitoneal region; and skeletal muscle. Human ortholog(s) of this gene implicated in Crohn's disease; cardiomyopathy; inherited metabolic disorder; and systemic primary carnitine deficiency disease. Orthologous to human SLC22A5 (solute carrier family 22 member 5).