Comparison of three standardised fish sampling methods in 14 alpine lakes in Austria

Abstract

Standardised fishing methods using gillnets (EN 14575), electric fishing (EN 14011) and hydroacoustics (WI 00230244 CEN enquiry) to estimate species composition, abundance, biomass and size distribution were compared in 14 alpine lakes >50 ha. More fish species were detected using benthic gillnets (mean = 72.7%) than electric fishing (mean = 59.5%) and pelagic gillnets (mean = 29.6%). For all but two lakes, additional information from a local fisheries manager was required to obtain a complete list of species. Biomass data generated by standardised gillnetting and hydroacoustic surveys were not fully comparable, but a positive correlation was found. Gill netting and hydroacoustics both indicated a nearly fishless habitat below 75 m, which confirmed the maximum required fishing depth according to the European Standard EN 14757. Size distributions obtained from gillnet and hydroacoustic surveys differed statistically for large fish (>40 cm). Each standardised method reflected typical shortcomings. The European standard (EN 14757) should be amended for pelagic fish habitat in deep alpine lakes to include sampling effort corresponding to water volume, and additional gillnets with larger mesh sizes (e.g. 70 mm). Furthermore, the electric fishing standard (EN 14011) should be extended to incorporate requirements of lake fish sampling.

Efficiency of electrofishing in turbid lowland rivers: implications for measuring temporal change in fish populations

“…Where terms are subscripted by "species" in the text, the term is species-specific. Achleitner et al 2012;Hedger et al 2013), but our nonlethal approach is a more acceptable method, especially for native and threatened species.…”

Comparison of nine different methods to assess fish communities in lentic flood‐plain habitats

“…Despite the assumption that electrofishing is limited in wide and open water bodies without current (Copp & Peňáz, ; Bohlin et al ., ), it was still the least selective method as indicated by the full representation of all species and size classes. This is in contrast with natural lakes or reservoirs, where electrofishing has been observed to be far less effective than in the present study (Achleitner et al ., ; Fischer & Quist, ). This can probably be attributed to the shallow backwater habitats (average water depth per transect 1·16 m, minimum average transect depth 0·50 m, maximum average transect depth 1·62 m) sampled in the present study.…”

“…Consequently, different net‐based (seining, gillnetting, fyke netting, use of baited fish traps, baited lift netting), hook‐and‐line based (angling, longline fishing) and visual fish‐sampling methods (snorkelling) as well as electrofishing were selected for the comparative study. These methods are listed in CEN () or had previously been applied or suggested for the use in lentic flood‐plain water bodies or lakes, but have to the best of the authors' knowledge never been systematically compared for their applicability to fish sampling in typical backwaters of large rivers (electrofishing and point abundance sampling in large rivers, Persat & Copp, ; electrofishing, fyke netting and seining in lakes, Fago, ; fyke netting and electrofishing in small ponds, Basler & Schramm, ; electrofishing, seining, multi‐mesh gillnetting, fyke netting in stagnant flood‐plain water bodies of large flood‐plain rivers, De Leeuw et al ., ; seining and electrofishing in flood‐plain lakes, Jurajda et al ., ; bottom trawls, fyke netting, multi‐mesh gillnetting, longline fishing, drift netting, day and night electrofishing in an impoundment of the River Inn, Schotzko & Gassner, ; fyke netting, gillnetting and electrofishing in flood‐plain lakes, Eggleton et al ., ; gillnetting, seining, trawling and hydroacoustics in lakes, Jurvelius et al ., ; gillnetting, electrofishing and hydroacoustics in alpine lakes, Achleitner et al ., ). Specifically, it was hypothesized that (1) low‐activity methods ( e .…”

Hydroacoustics as a relevant tool to monitor fish dynamics in large estuaries

“…Combined surveys may offer extended complementary information by balancing their particular drawbacks (Emmrich et al, 2010). By defining a standard and robust protocol (Achleitner et al, 2012;Hateley et al, 2013;CEN, 2009), hydroacoustic methods could be extended to finer scales, and may lead to the definition of acoustic-based metrics. These would complement fish-based indicators, such as those laid down in the European Water Framework Directive (e.g., the Estuarine and Lagoon Fish Index already established for assessing the ecological status of French estuaries (Delpech et al, 2010)).…”