Do otters target the same fish species and sizes as anglers? A case study from a lowland trout stream (Czech Republic)

Abstract

Stocking of hatchery-reared fish into streams is a common practice in fisheries industry as it provides catches for recreational anglers and support for native fish populations. The Eurasian otter Lutra lutra is one of the most important freshwater piscivorous predators in Europe. Impact of otters on stocked fish is a source of conflict between fisheries industry and environmental protection. This study aimed to describe differences between otter diet and catches of anglers on a lowland trout stream with salmonid stocking. Otter diet was studied during winter, using spraint analysis. Fish dominated otter diet (85% of biomass). Gudgeon Gobio gobio was the most important otter prey (38% of biomass). Catches of otters and catches of anglers on the stream were significantly different. Otters mostly preyed upon small-growing fish species of medium or no angling value while anglers took large-growing fish species of medium and high angling value. Otters took fish with average weight of 10 g while anglers took fish with average weight of 290 g. Stocked salmonids made up 13% of estimated biomass in otter diet. Otters targeted significantly different fish species of different sizes than anglers did.

Do recreational fisheries metrics vary on differently sized fishing grounds?

“…In addition, smaller streams in the study area were mostly dominated by commercially valuable salmonids (Zavorka, Horký & Slavík, ; Zavorka, Horký, Kohout, Kalous & Slavík, ; Lyach & Čech, ; Matena et al., ; Zavorka et al., ). Previous authors also confirmed dominance of salmonids in smaller streams in Central Europe in general (Klementsen et al., ).…”

Changes in recreational catfish Silurus glanis harvest rates between years 1986–2017 in Central Europe

“…To analyze harvest per hectare, data from 241 fishing grounds over the course of years 1986–2017 (32 years) were used. This database was used for various research questions before (Boukal, Jankovský, Kubečka, & Heino, ; Humpl, Pivnička, & Jankovský, ; Jankovský, Boukal, Pivnička, & Kubečka, ; Lyach & Čech, , , ). Data on average air temperature were provided by the Czech Hydrometeorological Institute.…”

“…The results presented in the tables were derived from models in R while the figures were drawn in MS Excel. The described method was previously used to analyze similar data sets on fish harvest (Boukal et al, ; Humpl et al, ; Jankovský et al, ; Lyach & Čech, , , , Lyach & Remr, ).…”

Fish size selection and diet composition of Eurasian otters (Lutra lutra) in salmonid streams: Picky gourmets rather than opportunists?

“…lowland streams). In those areas, otters rarely consumed species and fish sizes that are also preferred by anglers (Grant and Harrington, 2015;Britton et al, 2017;Lyach and Cech, 2017).…”

“…Recently, this conflict is getting even more severe in riverine habitats especially in the upper regions of salmonid streams, which are crucial refuges and habitats for brown trout (Salmo trutta) (Pletterbauer et al, 2015). These habitats and trout themselves are valued by recreational anglers (Grant and Harrington, 2015;Sittenthaler et al, 2015;Lyach and Cech, 2017). Nevertheless, otter predation on fish relevant for recreational angling and the influence of otters on fisheries yield in running waters are poorly investigated.…”