Discocotyle sagittata is a species of freshwater monogenean gill ectoparasites of Salmo and Oncorhynchus.

Upon reaching maturity, parasites can remain attached by a posterior opisthaptor with its 8 associated clamps (4 in 2 rows).

Adults are hermaphrodite, and produce 3–14 eggs per day at 13 °C, a process which is temperature dependent.

[1] Once produced, eggs drop to the riverbed surface and at 13 °C take 28 days to develop to hatching larval forms.

Major parasite burden can result in damage to the host gill and anaemia from blood loss.