Search

Start Over Creator Kortan, David

1. Otter, Lutra lutra, freeding pattern in the Kamenice River (Czech Republic) with newly established Atlantic salmon, Salmo salar, population

Creator:
Kortan, David, Adámek, Zdeněk, and Vrána, Pavel
Type:
article and TEXT
Subject:
fish predator, diet composition, and prey fish
Language:
English
Description:
Food composition of otter, Lutra lutra, was studied by the analysis of 349 spraints found during one year period (2003–2004) at the River Kamenice (Czech Republic), where Atlantic salmon, Salmo salar, fry have been stocked regularly since 1998 in a reintroduction programme for the species. Brown trout, Salmo trutta m. fario, dominated otter diet and formed 29% of all prey items and 62% of biomass of all fish eaten. The second most abundant prey (27%) was common sculpin, Cottus gobio, followed by Atlantic salmon, and grayling, Thymallus thymallus. The proportion of salmon in the diet of otters amounted to 14.5% in numerical abundance of all prey items taken and 2% in biomass of fish component of the diet. The majority (71.5%) of fish eaten by otters had a total length between 61 to 200 mm.
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/

2. Winter predation by otter, Lutra lutra on carp pond systems in South Bohemia (Czech Republic)

Creator:
Kortan, David, Adámek, Zdeněk, and Poláková, Simona
Type:
article and TEXT
Subject:
otter diet, spraint analysis, excessive hunting, and fish remains
Language:
English
Description:
Otter (Lutra lutra) diet was studied by analysing of 180 spraints and 29 partly consumed fish remains found in winter around fishponds in South Bohemia (Czech Republic). The proportion of fish found in spraints was 95.6% of all prey items, roach (Rutilus rutilus), topmouth gudgeon (Pseudorasbora parva) and common carp (Cyprinus carpio) being the most numerically abundant species with 37.3, 21.3 and 19.0% respectively. Carp dominated the diet bymass (47.8%), whilst roach and “other commercial fish species” (predatory and herbivorous fish, tench, Tinca tinca) formed 21.8 and 15.3% of total biomass, respectively. Small fish (< 200 mm) predominated in the diet and only 4.0% of all fish found in spraints exceeded 300 mm TL. Large fish remains were very scarce in spraints and were best recorded from uneaten prey remains. The partially eaten remains of carp, pike (Esox lucius) and common bream (Abramis brama) were found on banks or ice, but most (86%) were carp. The original length of carp corpses ranged between 283 and 530 mm TL, and the proportion of body mass consumed varied between 5.0 – 90.1%. The length of pike remains ranged from 386 to 754 mm TL, of which 84.0% of body mass on average was consumed by otters. The otter diet apparently reflects food availability in fishponds and supply channels. Small water basins with a high stock density can be vulnerable to serious damage especially during the winter period and at such places, where no better accessible source of food is available to otters. However, in many such places simple mitigation measures may be able to reduce otter predation.
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/