I have done a follow up study of the restoration of two rivers, Röälven and Grundan, in order to evaluate the effects of the restoration on the endemic population of trout. Both rivers have been used for timber floating during many years throughout the 20th century, and because of this, had all obstacles such as rocks and wood parts removed. In 2004-2005 both rivers were restored, and rocks and wood were put back into the rivers. Spawning grounds were created and boulder dams were constructed to promote the streaming water. The result showed that the trout population of both rivers increased after the restoration, but also that the trout population of Röälven increased more than that of Grundan. My conclusion is that the way the restoration is of a river contributes to the result.

In streams, wood provides protection, food and substrate for benthic macroinvertebrates, which leads a higher density and diversity of the benthic fauna compared to streams without wood. To examine wood and its effect on drift of macroinvertebrates an experiment was done in 18 sections of six semi-natural streams where fine woody debris (Salix sp.) was added to half of the sections (1-2 per stream). The purpose was to investigate possible differences in density and diversity of macroinvertebrates aswell as to investigate if there was any effect of location, upstream or downstream, in the streams. The results showed no significant effect of woody debris on total drift. The lack of an effect is probably related to the high abundance of predators (fish, brown trout) and the time of the day when the samples were taken. There was a significant effect of time on total drift; with more drift in September than in October. An effect of time was also found for the taxon Diptera (Chironomidae not included), with drift decreasing with temperature over the season. / Ved i ett vattendrag ger skydd, föda och substrat åt bentiska makroevertebrater, vilket leder till en högre täthet och diversitet av makroevertebrater än i vattendrag utan ved. För att undersöka vedens inverkan på makroevertebraternas drift utfördes ett experiment i sammanlagt 18 inhägnader i semi-naturliga bäckar där hälften av inhägnaderna behandlades med fin ved (Salix sp.). Syftet var att undersöka eventuella skillnader i täthet och diversitet av makroevertebrater samt om det fanns en skillnad i läge, uppströms och nedströms i bäckarna. Resultatet visade ingen signifikant effekt av ved med avseende på den totala driften. Det fanns heller ingen signifikant effekt av ved på tätheten i enskilda på ved än utan. De bakomliggande faktorerna till varför ingen signifikant effekt av ved visades är troligtvis den höga tätheten av predatorer (öring) och tidpunkten då proverna togs. Det fanns dock en signifikant effekt av tid gällande den totala driften, i september var det mer drift än i oktober. Det fanns även en signifikant effekt av tiden på Diptera (alla Diptera taxa förutom Chironomidae). Detta tros vara på grund av den sjunkande temperaturen mellan månaderna.

Previous studies have shown that ice cover has many positive effects on brown trout (Salmo trutta), including protection from endothermic predators. I tested whether it is the cover provided by the ice itself or the reduction in light that causes behavioral changes in juvenile brown trout. To distinguish between these two effects, behavioural observations were made with and without ice at the same light intensity (500 lux). An additional ice-free, high light (3000 lux) treatment was included to be able to measure brown trout’s response to light reduction. A mink model was used to simulate predation risk to be able to measure the fish’s anti-predator response under these three conditions. I found a significant treatment effect on body and eye coloruration. For eye colouration, I found that fish under ice had a paler eye colouration than fish that experienced high light, which in turn were paler than fish subjected to low light. For body colouration, fish under ice had paler body colouration than fish from the two ice-free treatments, which did not differ from each other. There was no effect of treatment on ventilation rate, time to initiate foraging, time to initiate activity or swimming activity, although both foraging and activity were lowest and swimming activity highest under ice. The changes in body and eye colouration indicate that trout are less stressed under ice, presumably because they perceive ice as a barrier against terrestrial predators. These results suggest that the ongoing climate change, which is leading to shorter periods of sustained ice cover, may have negative consequences for trout populations in the near future. / Tidigare studier har visat att yttäckande is medför många positiva effekter för öring (Salmo trutta), bland annat genom att utgöra skydd mot endoterma predatorer. Jag undersökte om det är den yttäckande isen i sig som medför beteendeförändringar hos juvenila öringar eller om det är det reducerade ljusinsläppet som isen medför. För att separera dessa två effekter gjordes beteendeobservationer med och utan ytis under samma ljusintensitet (500 lux). En ytterligare isfri behandling gjordes, med starkt ljus (3000 lux), för att kunna mäta öringens respons på ljusreduceringen. En uppstoppad mink användes för att simulera predationsrisken, detta för att kunna mäta fiskarnas antipredationsresponser under dessa tre förhållanden. Jag fann en signifikant behandlingseffekt på kropps- och ögonfärg. Under is hade fiskarna en blekare ögonfärg än när de befann sig under starkt ljus, som i sin tur resulterade i blekare färg än när fiskarna utsattes för svagt ljus. När det gäller kroppsfärg uppvisade fiskarna en blekare kroppsfärg under is än när de utsattes för de två isfria behandlingarna, vilka inte skiljde sig från varandra. Behandlingarna gav ingen effekt på gälslagsfrekvens, tid till att initiera födosök, tid till att initiera aktivitet eller simaktivitet, dock var tid till både födosök och aktivitet lägst och simaktivitet störst under is. Förändringarna i kropps- och ögonfärg indikerar att öring är mindre stressad under is, vilket eventuellt kan bero på att de uppfattar isen som en barriär mot terrestra predatorer. Dessa resultat tyder på att den pågående klimatförändringen, som innebär kortare perioder av ihållande yttäckande is, kan medföra negativa konsekvenser för öringpopulationer inom den närmaste framtiden.

Parasiter kan påverka sina värdar på många olika sätt. Flodpärlmusslans (Margaritifera margaritifera L.) glochidielarver lever inkapslade som parasiter på gälarna hos öring (Salmo trutta L.) i flera månader innan de blir frilevande. Genom experiment i ett strömakvarium har denna studie undersökt hypoteserna att öring med inkapslade gälparasiter tar färre byten, och simmar kortare avstånd när de födosöker än öring utan gälparasiter.   Resultaten visade att infekterad öring tog signifikant färre byten/minut än oinfekterad öring både i början och i slutet av en födosöksperiod under vilken individerna konfronterades med tvåhundra poteniella byten. Vilket visar att infekterad öring har en lägre furageringshastighet är oinfekterad öring. Däremot påvisades ingen skillnad mellan öring med och utan parasiter med avseende på antal byten tagna i förhållande till avstånd från bytet.    Den lägre furageringshastigheten som påvisades hos de infekterade öringarna tyder på att infektion av flodpärlmusslans larver kan ha negativa effekter på fiskarnas tillväxt, och därmed överlevnad. Detta kan bero på faktorer som minskad aktivitet, ökad ventilation och förändringar i beteende hos de infekterade fiskarna, som är en effekt av parasitinfektionen. / Parasites can impact their hosts in many different ways. The larval glochida of freshwater pearl mussels (Margaritifera Margaritifera L.) infect the gills of brown trout (Salmo trutta L.), where they spend several months before becoming free-living. Using stream aquarium experiments, this study investigated the hypotheses that infected trout would capture fewer prey, and would swim less distance to capture prey, than would uninfected trout.   The results showed that infected brown trout caught significantly fewer prey/minute both at the beginning and at the end of a foraging period during which individuals were fed two hundred potential prey. This suggests that infected brown trout have a lower foraging rate than uninfected brown trout. However, no significant difference between infected and uninfected fish was found in terms of the number of prey taken in relation to distance to the prey.   The lower foraging rate for infected brown trout suggests that infection of the freshwater pearl mussel’s glochidia may have negative effects on their growth rate, and consequently survival. This may be due to factors such as reduced activity, increased ventilation and changes in behavior, which are effects from the parasite infection.

L'article 2 de la tesi enviat a la revista Conservation Biology, finalment va ser publicat a la revistat Conservation Genetics 3:385:400, 2002 / L'estudi de la diversitat i la diferenciació genètiques de les poblacions de truita comuna (Salmo trutta L.) a la Península Ibèrica ha confirmat l'elevada diferenciació observada en treballs previs i la divergència, ja descrita, entre les poblacions de la vessant atlàntica i la mediterrània. El resultats obtinguts, però, ens permeten observar patrons d'estructura poblacional tant en les poblacions atlàntiques com les mediterrànies. A l'Atlàntic s'observa un marcat patró hidrogràfic en la distribució de la diferenciació genètica, que contrasta fortament amb la distribució d'aquesta diferenciació en les poblacions mediterrànies, caracteritzades pels contactes secundaris entre llinatges durant les expansions pleniglacials i una forta divergència local conseqüència de la seva marginalitat i aïllament en els períodes interglacials. El manteniment d'aquesta diferenciació i individualitat descrites en les poblacions de truita de la Península, es veu seriosament compromès per les contínues repoblacions dels rius amb exemplars exògens d'origen nord europeu. La substitució dels genomes autòctons per la introducció de gens al.lòctons provoca una erosió dels patrimonis genètics natius i una homogeneïtzació de les poblacions, destruint els patrons de diferenciació existents. Al mateix temps, els nostres resultats indiquen que les conseqüències de les repoblacions no són sempre les mateixes. Concretament, es constata un fracàs de les repoblacions en rius intensament repoblats i sotmesos a pesca intensiva, que contrasta amb una enorme erosió de les poblacions quan les repoblacions s'efectuen sobre àrees protegides i sense cap mena de pressió pesquera. Això suggereix que múltiples factors com la gestió dels rius posterior a les repoblacions, l'estat de les poblacions o les condicions de l'hàbitat són determinants de la introducció efectiva dels exemplars alliberats; fet que dificulta la predicció sobre actuacions particulars. Malgrat aquesta introgressió de gens exògens que es detecta en moltes de les poblacions analitzades, els gens natius predominen en gairebé tots els rius de la Península. La conservació d'aquesta elevada riquesa genètica que encara resta en les poblacions de truita de la Península Ibèrica ha de ser l'objectiu final de qualsevol programa de gestió. Per això, defensem una gestió basada en el propi riu mitjançant una pesca sostinguda per la reproducció natural de les poblacions salvatges, acompanyada d'una millora i recuperació d'hàbitats adequats per la truita, i evitant, per sobre de tot, la introducció en els rius d'exemplars exògens, degut als efectes nocius i incontrolables que comporta aquest procés. / Our study on the genetic diversity and differentiation of brown trout (Salmo trutta L.) population of the Iberian Peninsula confirmed the high levels of differentiation and the divergence between Atlantic and Mediterranean populations previously described. However, additional substructuring among Atlantic rivers and among Mediterranean ones has been detected. In the Atlantic, genetic diversity is related with the river network, producing a marked hydrographical pattern in sharp contrast with a mosaic distribution of genetic variation among the Mediterranean collections. In this later area, genetic resources distributed as a result of distinct colonization episodes during pleniglacial expansions, secondary contacts, and local divergence due to its marginality and isolation in the interglacial periods. Continuous stocking with hatchery-reared fish of north European origin, seriously compromises the conservation of this differentiation and individuality described in brown trout populations of the Iberian Peninsula. Replacement of the autochthonous genome due to introduction of exogenous genes is leading to an erosion of the native gene pools, a homogenisation of populations, and a destruction of the ancestral patterns of differentiation. At the same time, our results indicated that successful stocking appears to be limited to wild populations subjected to occasional releases in protected or unfished areas. Extensive stocking in fished areas result in a more limited impact on the recipient native population. These results suggest that stocking success is unpredictable and controlled by different factors including habitat and population conditions at the time of stocking, as well as post-release management actuations. Although many of the analysed populations are introgressed with exogenous genes, native gene pools predominate in almost all the Iberian rivers. Conservation of this high genetic richness that still remains in brown trout Iberian populations must be the final goal of any management program. So, our management proposal is based on fisheries sustained by natural reproduction of the respective wild populations, coupled with an improvement and recovery of habitat suitable for brown trout; avoiding stocking with exogenous fish due to the harmful and incontrollable risks that this process involves for the genetic resources of the species.

Thesis (M. Sc.)--University of Canterbury, 2007. / Typescript (photocopy). Includes bibliographical references (leaves 65-75). Also available via the World Wide Web.

Thesis (M.S.)--West Virginia University, 2005. / Title from document title page. Document formatted into pages; contains xi, 155 : ill., maps (some col.). Includes abstract. Includes bibliographical references (p. 80-91).

The aim of the work will be based on the diet composition monitoring of the introduced rainbow trout and wild brown trout and grayling in defined time intervals, and assessing the degree of the food competition among the monitored species. The experiment was held in the second half of September 2010 in the river Blanice in the protected fish areas close to the village Těšovice, where several dozens of rainbow trout were stocked. In a predefined several - day interval of were caught 30 pieces of the rainbow trout (SL = 266 ? 14 mm, m = 347 ? 54 g), 33 brown trout (SL = 244 ? 19 mm, m = 219 ? 51 g), 14 graylings (SL = 256 ? 27 mm, m = 240 ? 91 g) and 12 resident rainbow trout (SL = 255 ? 13 mm, m = 280 ? 47 g) originated from the last plant. Within these groups a fish stomach content and consequently food selectivity was examined by using of the Ivlev's selectivity index (1961), a food competition was examined by using of the Schoener's index food overlap (1970) and the importance of various food components was examined by using of the index of preponderance according to Natarajan (1961). Rainbow trout began to ingest food immediately after the stocking into the stream and its occurrence was seen in all fish crop caught during the period. The insect (Insecta) was given as a preferential food of the rainbow trout and according to the index of preponderance (IP), it formed 54%, Trichoptera (IP) 24% and Ephemeroptera (IP) 19% orders belonged to the most preferable kinds of the food. According to the index of preponderance, gastropod (Gastropoda) formed (IP) 25% of a secondary food. The rainbow trout was accepting the same dietary components as well as the original sorts of salmonoid fish within the river. According to the index of a food overlap (S), the food competition between rainbow trout and brown trout was equal to the value of (S = 0.566) during the whole monitored period and the grayling was equal to (S = 0.520). Even though both of these values are slightly below the significant food overlap (S = 0.6), we can still say that the food competition is relatively high among these kinds.

The work deals with the rearing of brown trout (Salmo trutta m farion) under controlled conditions. For this study was use intensive hatching metods. We observed and recorded stocking density and her influences an growth, survival in controlled conditions in fish hatchery in Kaplice Ltd

Central parts of the Šumava national park has specific nature conditions which we must respect when fish farming is carry out . In 1998 fish {--} hatchery near Borová Lada was established. The fish hatchery exists more than 10 years and we still have no professional report about exploitation this object. (using assorted technologies of rearing, rearing under controlled conditions). The aim of this graduation thesis is evaluation results of trout culture and make proposition new improved technologic process in fish farming on this site. The thesis also includes experiments with initial feeding of fry of brown trout (Salmo trutta morpha fario) carryed out during the spring 2008. The main observed values were survivance, specific growth rate (SGR) and feed conversion ratio (FCR). After 17 weeks of initial feeding fry of brown trout the observed values were achieved: survival of fish 38,2 % , average length SL = 69,0 mm, average weight 4,9 g. Experiments showed that initial feeding of fry of brown trout (Salmo trutta morpha fario) with using feeding mixtures in the Borová Lada fish {--} hatchery is possible and effective.