Contributes to voltage-gated sodium channel activity. Acts upstream of or within sodium ion transport. Predicted to be located in plasma membrane. Predicted to be part of voltage-gated sodium channel complex. Is expressed in gill; heart; liver; musculature system; and nervous system. Human ortholog(s) of this gene implicated in Brugada syndrome 5; developmental and epileptic encephalopathy 52; familial atrial fibrillation; and generalized epilepsy with febrile seizures plus 1. Orthologous to human SCN1B (sodium voltage-gated channel beta subunit 1).