Visual morphology and feeding behaviour of the daggertooth

Dissection of freshly eaten prey suggests that the North Pacific daggertoot h Anotopterus nikparini sever the spine of small prey with a single slashin g blow. The bite marks indicate that the immobilized prey is manipulated an d swallowed head first. Frequent evidence suggests daggertooth wound prey w hich are too large to consume whole by cutting off strips of flesh. In eith er case the wounds consist of a single prominent slash mark on one side and a series of inconspicuous marks on the opposite side. Retinal morphology p rovides supporting evidence that daggertooths are visual ambush predators t hat attack prey from below, and should be considered as epipelagic rather t han mesopelagic fish. Visual acuity appears to be high, suggesting that fre quent attacks on prey too large to be killed immediately is not error, but a well-defined feeding behaviour. The daggertooth may be a significant sour ce of mortality for economically important fish such as all sizes of salmon .