 Relative to its small size , the onefin electric ray can deliver an extremely powerful electric shock to defend itself against predators , which include the broadnose sevengill shark ( Notorynchus cepedianus ) . It propels itself using its muscular tail rather than its pectoral fins . The diet of this species consists mainly of polychaete worms . The reproductive biology of the onefin electric ray has not been documented ; presumably it is viviparous like other electric rays . Males mature sexually at somewhere between 11 and 17 cm ( 4 @.@ 3 and 6 @.@ 7 in ) long , while females mature at around 16 cm ( 6 @.@ 3 in ) long . 
