River damming drives population fragmentation and habitat loss of the threatened Danube streber (Zingel streber): Implications for conservation

Abstract

1. The Danube streber, Zingel streber, is a threatened and data-deficient percid fish endemic to the Danube catchment. The study provides the first data on distribution, life history, and genetic structure of the species at the upstream limit of its historic distribution (south-western Germany). A 3-year surveyeffort with 143 fishing events identified several small, fragmentary populations covering only 7% of the historical range of the species. Census population sizes (N c ) of these subpopulations were estimated from mark-recapture data at <200 individuals. Effective population sizes (N e ), calculated from genetic data (microsatellite genotyping), were much smaller still, at <15 individuals, resulting in an N c /N e ratio of <0.25, strongly indicating that populations are seriously affected by genetic drift and inbreeding, and are thus facing a severe extinction risk. 3. Life-history parameters recorded during the study indicate a rapid life cycle, with both sexes probably attaining sexual maturity at the age of 1 year or older. Spawning commenced at the beginning of April and fecundity was low (~300-400 eggs per female). 4. Genetic analysis and mark-recapture data indicate that subpopulations of the streber live in effective isolation, separated by impassable weirs that significantly reduce genetic connectivity between subpopulations. 5. The species is rheophilic, and limited to sites with flow velocities of~0.7 m s -1 . Hydropower infrastructure may thus also have diminished the availability of suitable habitat by reducing flow rates. 6. Only 32% of the historical range of the Danube streber is now estimated to be morphologically suitable for the species. Furthermore, relevant parts of this range are located upstream of dams and are therefore not accessible for natural recolonization. 7. The availability and accessibility of suitable habitats seem to be factors limiting the size of the remaining subpopulations. 8. Conservation actions should address the restoration of degraded river habitats and increase the connectivity between isolated subpopulations of the Danube streber.

Environmental drivers of benthic fish assemblages and fish‐habitat associations in offshore areas of a very large river

“…Of the examined species the barbel and the Danube streber showed the highest affinity to pebble and boulder covered, high velocity areas. This finding is consistent with former results about the habitat preference of these species from smaller rivers (Brinker et al, 2018;Er} os, 2007; Gutmann Roberts, Baši c, Britton, Rice, &…”

Habitat mapping of riverine fish by means of hydromorphological tools

“…The Danube streber, on the other hand, is a strictly protected endemic species in Hungary, which is also listed in the Habitat Directive of the European Union (NATURA 2000 species). Although detailed information about the habitat use of the species is limited, the species shows strict preference to medium and large fast‐flowing rivers (Brinker et al, ). In fact, no studies to date examined the offshore habitat use of these species in very large rivers and quantified abundance physical habitat relationships in offshore areas.…”

Dammed river: Short‐ and long‐term consequences for fish species inhabiting a river in a Mediterranean climate in central Chile

“…Examples include Zingel streber in the Danube River (Germany) (Brinker et al, 2017), Salvelinus confluentus in the Clark Fork River (USA) (Neraas & Spruell, 2001), Percina caprodes in the Cuyahoga River (USA) (Haponski, Marth, & Stepien, 2007), Thymallus thymallus in the Skjern River (Denmark) (Meldgaard, Nielsen, & Loeschcke, 2003), Etheostoma blennioides in the Grand, Thames and Sydenham rivers (Canada) (Beneteau, Mandrak, & Heath, 2009) ,and…”

“…Fish population structure driven by the disruptive effect of dams has been described in other species worldwide. Examples include Zingel streber in the Danube River (Germany) (Brinker et al, 2017), Salvelinus confluentus in the Clark Fork River (USA) (Neraas & Spruell, 2001), Percina caprodes in the Cuyahoga River (USA) (Haponski, Marth, & Stepien, 2007), Thymallus thymallus in the Skjern River (Denmark) (Meldgaard, Nielsen, & Loeschcke, 2003), Etheostoma blennioides in the Grand, Thames and Sydenham rivers (Canada) (Beneteau, Mandrak, & Heath, 2009) ,and Salmo trutta in the Nive River (France) (Horreo et al, 2011). Interestingly, Dehais, Eudeline, Berrebi, and Argillier (2010) found a pattern similar to that detected in this study: Squalis cephalus from the Durance River in France also showed low but significant F ST values.…”