USSFN: 1/04/04 - Leave it to us to find the most appetizing articles, huh? Anglers have occasionally reported catching striped bass with what looks like maggots attached to the tongue, gills, and/or the roof of the mouth, according to the Tennessee Wildlife Resources Agency (TWRA). What they are finding is a parasitic copepod in the genus Achtheres. “There is no cause for alarm, however, since these unsightly critters have not been linked to any fish mortality in Tennessee. They are also not harmful to humans since they are destroyed by cooking and are not found in the flesh of fish”, said Jim Negus, TWRA fisheries biologist.

Achtheres is one of several genera of external parasitic copepods that attach to the oral cavity of numerous North American fresh and saltwater fishes. During severe infestations, it appears as if the fishes' mouths are full of maggots; hence the common term, “gill maggots”. Several species of parasitic copepods can inflict great harm and even kill fish, but Achtheres is not considered to be one of them.

“Generally, the adult female copepods attach to various places in the oral cavity of fish and can remain there for extended periods,” continued Negus. “They feed off the soft tissues present and produce eggs which are released into the water after developing into nauplii. The larvae hatch into the first copepodid stage, which is free swimming. A second copepodid stage develops and the females attach to fish by an attachment filament. After mating, the male clings to the body of the female and the second copepodid stage becomes an adult to start the process over again.”

The first known record of Achtheres in Tennessee is from samples taken from largemouth bass from Tellico Reservoir in 1981. While working as a creel clerk, TWRA’s Rick Bivens identified the parasites taken from severely infested largemouth bass. The infestation did not seem to hurt the population and went away quickly.

The critter surfaced again in 2000. This time it was not in largemouth, but in striped bass from Watts Bar and Tim’s Ford Reservoirs. Samples of these parasites were sent to Auburn University and Tennessee Technological University for identification. There was no cause for alarm since they were the “good” copepod, Achtheres, and the striped bass appeared to be in good condition.

Recent outbreaks have occurred in Old Hickory and Norris Reservoirs. Parasites from Old Hickory were sent off in 2002 and were identified as Achtheres. Samples from Norris will be taken in January of 2004, but they also appear to be the “good” copepod. Achtheres should not cause significant harm to healthy fish. One would suspect, however, that heavy infestations could lead to secondary bacterial and fungal infections in fish already compromised by poor water quality or poor condition. These secondary infections could lead to a limited amount of fish mortality. For this reason, they are being intensely studied and monitored by TWRA biologists.