fish leech stuck to a fish fry

fish leech stuck fry died sucks juices piscicolidae annelida discshaped sucker piscicola geometra bloodsucking discophoran hirudinea bloodsucker caterpillar horseleech sanguisuga parasites hookworm guest sponge sponger bleeder tapeworm deadhead cadger hangeron invader culprit body snatcher host species hostparasite relationships epizoic parasite helminthology scolecology damage fisheries management fishing industry fishfarm juvenile roach