TranslocatedEsox luciusL. (PISCES) trigger aTriaenophorus crassusForel (CESTODA) epidemic in a population ofSalvelinus umbla(L.) (PISCES)

Abstract

In 2005, an epidemic of the pike tapeworm Triaenophorus crassus Forel, 1868 broke out in the Arctic charr (Salvelinus umbla (L. 1758)) stock of Lake Grundlsee, Austria. Besides the definitive host Northern pike (Esox lucius L. 1758), which was introduced into the lake in the 1960s, the cestode requires copepods as first and salmonid fish as second intermediate hosts. Within 2 years, the prevalence of the cestode in medium sized Arctic charr increased to almost 100% and the abundance reached a maximum of 55 cysts per fish, leading to the closure of the fishery. Such a massive infection of Arctic charr has never been reported. High pike abundance and the occurrence of a suitable copepod host facilitated the outbreak. The only first intermediate host Cyclops abyssorum praealpinus Kiefer, 1933 predominated the zooplankton community during May, when cestode coracidia hatch from eggs. Only during this infectious period, C. abyssorum praealpinus was eaten by Arctic charr (2–50% of prey organisms). Low fishing pressure on pike enabled the development of a large population that served as reservoir for T. crassus with up to 687 cestodes per fish. To contain the epidemic, 1671 pike were removed between 2008 and 2013. Infection of Arctic charr decreased to 60% and a maximum number of 16 cysts in 2013.

Infestation of zooplankton with Triaenophorus and Proteocephalus procercoids (Cestoda) in a deep oligotrophic lake

“…Although all C. lavaretus and ~16% of S. umbla investigated in Lake Achensee were infested with T. crassus (Schähle et al, 2014), the prevalence of the parasites was low (0.38%; maximum infection rate, 3.7%; Fig. 2), but comparable to studies from several lakes in Austria (Lahnsteiner et al, 2009;Sichrowsky et al, 2013;Schaufler et al, 2014), France (Hanzelova and Gerdeaux, 2003) or Canada (Watson and Lawler, 1965). In Lake Fuschlsee, for example, up to ~2% (mean 0.4%) of the C. abyssorum population were infested with Triaenophorus procercoids (Sichrowsky et al, 2013).…”

“…2). This is relatively late in the year compared to the first procercoid occurrence in other Austrian lakes (from mid-May to beginning of June; Lahnsteiner et al, 2009;Sichrowsky et al, 2013;Schaufler et al, 2014), but corresponds with the lower water temperature found in our study system. In Lake Achensee, highest infection rates of Triaenophorus spp.…”

“…In Lake Achensee, water level fluctuations might affect the feeding behaviour of whitefish and subsequent parasite infestation at least to some extent. Changes in physical processes, but also biological factors such as high abundances of the final host, pike, may have led to the increased occurrence of tapeworm infections as observed in Lake Achensee and other Austrian pre-alpine lakes (Achleitner et al, 2009;Schaufler et al, 2014) over the last years. …”

“…Occurrences of the whitefish tapeworm Triaenophorus Rudolphi, 1793 (Cestoda: Pseudophyllidea) have been observed in Central and Western European (Brinker and Hamers, 2007), Scandinavian (Pasternak et al, 1999;Pulkkinen et al, 2000), as well as North American lakes (Ekbaum, 1935;Miller, 1952;Watson and Lawler, 1965;Hursky and Pietrock, 2012). Recently, these parasites have also been reported in some Austrian lakes (Lahnsteiner et al, 2009;Sichrowsky et al, 2013) where they caused epidemics in the Arctic charr (Salvelinus umbla) population (Achleitner et al, 2009;Schaufler et al, 2014). Members of the genus Triaenophorus have a complex three-host life cycle, with copepods as their first, planktivorous fish like coregonids as their second intermediate host, and pike (Esox lucius) as their definitive host (Kuperman, 1981).…”

How to contain a tapeworm epidemic-testing the efficiency of different catch methods to reduce the translocated final hostEsox luciusin an alpine lake

“…The costs for the 54 gill nets (70.0 EUR n −1 ), 54 fykes (190.0 EUR n −1 ) and the harpoon (100.0 EUR) bought for this study were divided by the respective numbers and weights of pike caught. Infection rates of T. crassus in Arctic charr were monitored concurrently to assess the impact of intensive pike removal (see Schaufler et al, ).…”