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Diet of Eurasian otter (Lutra lutra) in relation to the stocking of brown trout (Salmo trutta m. fario) and grayling (Thymallus thymallus)
Lyach, Roman ; Čech, Martin (advisor) ; Poledník, Lukáš (referee)
This study aimed to evaluate otter predation on stocked trout and grayling. The diet composition of piscivorous Eurasian otters (Lutra lutra) was studied on the stream Chotýšanka in central Bohemia using spraint (otter faeces) analysis during one winter period (90 days). Stocking took place mostly in the second half of 2005. Around 5000 hatchery-reared brown trouts (Salmo trutta m. fario) of size about 10 cm, 600 graylings (Thymallus thymallus) of the same size and 480 rainbow trouts (Oncorhynchus mykiss) of size about 30 cm were stocked into the stream. Spraints were collected in December 2005 and January 2006. We found and identified 1531 fish in the spraints. The primary food source of otters was fish (almost 85 % of biomass). The main fish prey was small - sized, below 20 g in weight and 13 cm in length. The bulk of otter's diet consisted of less - valued species, especially the gudgeon (Gobio gobio). Other frequently consumed fish species were the European chub (Squalius cephalus), the common carp (Cyprinus carpio), the European perch (Perca fluviatilis), the brown trout and the rainbow trout. Consumption of stocked brown trout was 1,80 %, while cosumption of stocked rainbow trout was 10,90 % of biomass. Otters in this area consumed about 723 - 1446 brown trouts and 72 - 144 rainbow trouts...
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Importance and species composition of non-fish prey in the diet of fish-eating predators
Mach, Jakub ; Čech, Martin (advisor) ; Vejřík, Lukáš (referee)
Piscivorous birds are usually considered to be exclusive fish eaters which are responsible for signifiant numerical and economical losses to fish populations. With a method of literary research the importace and species composition of non-fish prey is determine in the diet of selected fifteen species of piscivorous birds. The aim of this work is to determine the extent of non-fish part of the diet of particular piscivorous predators and categorize them on the grounds of differences between size of this part in their diet. Another goal is to determine any effects which can influence amount and species composition of non-fish part of nourishment, and also factors, which can influence obtained results based on the chosen method of analysis. According to the data found, diet of five bird species was composed almost exclusively with fish. Eight other bird species also showed preference for fish prey, but in most of these cases was present also important part of non-fish prey. Two bird species seems to be very oportunistic in case of composition their diet. As factors that can affect the extent of non-fish part in the diet was established especially the prey availability in environment, used method for diet composition analysis, insufficient attention for parts of prey other than fish, or also less...
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Diet of Eurasian otter (Lutra lutra) in relation to the stocking of brown trout (Salmo trutta m. fario) and grayling (Thymallus thymallus)
Lyach, Roman ; Čech, Martin (advisor) ; Poledník, Lukáš (referee)
This study aimed to evaluate otter predation on stocked trout and grayling. The diet composition of piscivorous Eurasian otters (Lutra lutra) was studied on the stream Chotýšanka in central Bohemia using spraint (otter faeces) analysis during one winter period (90 days). Stocking took place mostly in the second half of 2005. Around 5000 hatchery-reared brown trouts (Salmo trutta m. fario) of size about 10 cm, 600 graylings (Thymallus thymallus) of the same size and 480 rainbow trouts (Oncorhynchus mykiss) of size about 30 cm were stocked into the stream. Spraints were collected in December 2005 and January 2006. We found and identified 1531 fish in the spraints. The primary food source of otters was fish (almost 85 % of biomass). The main fish prey was small - sized, below 20 g in weight and 13 cm in length. The bulk of otter's diet consisted of less - valued species, especially the gudgeon (Gobio gobio). Other frequently consumed fish species were the European chub (Squalius cephalus), the common carp (Cyprinus carpio), the European perch (Perca fluviatilis), the brown trout and the rainbow trout. Consumption of stocked brown trout was 1,80 %, while cosumption of stocked rainbow trout was 10,90 % of biomass. Otters in this area consumed about 723 - 1446 brown trouts and 72 - 144 rainbow trouts...
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Ethological study of river otter (Lutra lutra) with a focus on enrichment in the Zoo Ohrada v Hluboké nad Vltavou.
JARIABKOVÁ, Markéta
The environmental enrichment helps improve mental and physical condition of animals in captivity. It promotes active behavior and seeks to reduce stereotypical behaviors which often carnivores in captivity tend to it. My work was done in Zoo Ohrada in Hluboká nad Vltavou by two individuals of Eurasian otters ( Lutra lutra). The aim was to determine which element of enrichment appeared to be most interested in otters. Submitted enrichment was 7 - olfactory enrichment, ball for food, fixed ball, adapt burrow, eggs, frozen food and live prey. Enriching elements relating to food (ball for food, eggs, frozen food and live prey) activities increased time spent eating, foraging, play and playful eating. Dietary enrichment had an effect on their social behavior. With olfactory enrichment increased movement on the mainland and sniffing of objects. Fixed ball caused playful behavior. Adapt burrow increased time spent adjust bedding and exploring the burrow.
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