Historic catches, abundance, and decline of Atlantic salmon Salmo salar in the River Elbe

Abstract

Fisheries statistics available from the River Elbe catchment since the middle of the 16th century onwards have been compiled and analyzed to assess 1. the spatial distribution and patterns of returning salmon, 2. the total abundance of the salmon stock, as well as 3. local impacts, reasons, and time lags of salmon decline. Catch data and fisheries statistics of up to 117 years from 67 sites have been compiled covering a period from 1552 to 1949. Although often incomplete, the available data revealed strong inter-annual spatial patterns of salmon catches. In particular, last or exceptional salmon records in distant tributaries or headwaters were significantly explained by flood events. In the River Elbe, the historical salmon harvest amounts of about 4,000 salmon annually are well above recent estimates of 300-400 returning salmon. The spatio-temporal patterns of salmon decline in the River Elbe catchment strongly indicate the importance of the historical spawning sites in the upstream river sections for salmon recovery as well as the resilience of large rivers against human disturbances. Both findings underline the need for a catchment approach in salmon rehabilitation including incorporation of and longitudinal connectivity to the upper catchment headwaters.

Managing river fish biodiversity generates substantial economic benefits in four European countries

“…The latter two species either have been declining in recent years, such as eel in Germany, where it is economically still important to local-scale inland fisheries, or are threatened with extinction globally, like the sturgeon species (Freyhof and Brooks 2011). These findings suggest that expensive restoration activities tailored toward eel and sturgeon (e.g., BfN 2010; European Commission 2014) in countries where they were valued in our study are likely to receive considerable public support, whereas efforts to reintroduce, for instance, Atlantic salmon in Germany (e.g., Wolter 2015), the only country where this species was not valued, would not.…”

“…This process describes a long-term inter- and intragenerational extinction of knowledge of, and experience with, the conditions of the biological environments people live in due to a loss of opportunities to interact with nature (Papworth et al 2009; Soga and Gaston 2016), including domestic fish species (Kochalski et al 2018; Liebich et al 2018) and possibly other components of river biodiversity. As a result, people may have become disconnected from (largely) extinct species like Atlantic salmon in countries such as Germany (Wolter 2015; Lenders et al 2016; Kochalski et al 2018; Liebich et al 2018). Such a development would be critical as a loss of memory of past environmental degradation may ultimately lead to a reduction in the public’s engagement with, and notably their willingness-to-pay for, conservation efforts (McClenachan et al 2018).…”

“…While recently hydropower has had its rebirth in an attempt to increase renewable energy production worldwide (Zarfl et al 2015; Winemiller et al 2016; Couto and Olden 2018), in our survey, a river’s utility decreased substantially with increasing fragmentation due to hydropower dams. Given the major negative impact that river fragmentation has had on riverine biodiversity over centuries (Wolter 2015; Lawrence et al 2016; Lenders et al 2016), and is continuing to have globally (Zarfl et al 2015; Winemiller et al 2016; Cooper et al 2017; Couto and Olden 2018), it is vital from an environmental perspective to implement measures (e.g., installing fish ladders for migratory fishes or applying administrative means to adjust a river’s flow regime; Poff and Schmidt 2016) to better balance social and ecological requirements as was done in Norwegian watersheds (Alfredsen et al 2012; Ruud and Fjeldstad 2015; Norwegian Environment Agency 2017). While such regulations are not in place in the small-scale hydropower operations common to, for example, Germany (Zarfl et al 2015), the very low negative MWTP of hydropower in Norway may have resulted from this country’s strong dependence on, and hence from a broad societal acceptance of, hydropower, or from the fact that Norway has protected more watersheds against hydropower development than, for instance, Sweden (Norwegian Environment Agency 2017; Swedish Environment Law 2017).…”

“…Economically important to Norway but extinct in Germany and endangered in France, Atlantic salmon is being restored in the latter two countries. It is also a familiar food product (WWF 2001; Hindar 2003; Wolter 2015), which nutritionists recommend for regular consumption (Dinter et al 2016). We further included two nonnative salmonids (brook trout [ Salvelinusfontinalis ] and rainbow trout [ Oncorhynchus mykiss ]; Table 1) which were both introduced to Europe in the late 19th century (Aas et al in press).…”

“…For example, many riverine fish populations have strongly declined, and selected iconic species, such as Atlantic salmon ( Salmo salar ) and European eel ( Anguilla anguilla ) are threatened, and European sturgeon ( Acipenser spp.) is virtually extinct across Europe (WWF 2001; Hindar 2003; Freyhof and Brooks 2011; Wolter 2015).…”