Parasitic copepod, which attaches mainly to the gills of the fish. Can also be found on the body in lesser numbers.
Not fatal if recognized in time and treated.
From Phylogeny of the African genus Ergasilus
by Ruaan Schlebusch
University of the
Very detailed and long
article about 5 species of Ergasilus, including methods for PCR and DNA
extraction ( Chapter 4).