Captive breeding of the critically endangered European weatherfish: A refuge for conservation-sensitive parasites?

Abstract

Despite its large Eurasian range and its global Red List status of Least Concern, in Flanders (Belgium), European weatherfish Misgurnus fossilis (Linnaeus, 1758) (Teleostei, Cobitidae) is a critically endangered freshwater fish. The conservation actions for this species in Flanders include a captive breeding program. In the hatchery, juvenile weatherfish suffered from massive infection by an ectoparasitic flatworm causing mortalities. The helminth was identified as Gyrodactylus fossilis Lupu & Roman, 1956 (Monopisthocotyla, Gyrodactylidae). While this flatworm naturally occurs on this host species, this is its first report in Belgium. At high infection intensities G. fossilis seems a threat to ex situ conservation of M. fossilis. However, adult weatherfish maintained at lower densities in these aquaculture facilities show no visible signs of infection. This observation may make this captive breeding program in fact relevant to the conservation of this host-parasite combination. Indeed, following IUCN criteria, in 1997, the parasite species was proposed to be endangered in the Czech Republic, and critically endangered in Slovakia. Gyrodactylus fossilis is hence of conservation interest as a native parasite of M. fossilis, and it will be interesting to evaluate whether the captive breeding stock of M. fossilis can offer the possibility to sustain a population of G. fossilis with infection levels at which it is not harmful to its host. In case this is found to be practically feasible, we propose conservation efforts to also consider G. fossilis when reintroducing weatherfish in nature; discussion among stakeholders about a policy with regard to parasite conservation is required.