Comparing dominance relationships and movement of native marble trout (Salmo marmoratus) and introduced rainbow trout (Oncorhynchus mykiss)

Behaviour observations of the endangered native marble trout (Salmo marmoratus,Cuvier, 1829) and introduced rainbow trout (Oncorhynchus mykiss, Walbaum, 1792)in the laboratory and in a tributary to the Idrijca River in Slovenia were combined tostudy the movements and dominance relationships between individuals of the twospecies in an open field test. Under laboratory conditions, no difference between thespecies was detected for neither time spent actively or distance moved. In speciespaired tests, rainbow trout initiated more aggressive behaviours towards marble troutthanvice versa, and rainbow trout were clearly the dominant individuals. After simul-taneous release in the river, marble trout immediately left the release area and spenttwice as long time as rainbow trout until they settled in an area of the river; there-fore, the release site was immediately occupied exclusively by rainbow trout. Thus,the dominant and aggressive behaviour of rainbow trout seen in the laboratorybefore release might have influenced marble trout's subsequent behaviour in theriver, by marble trout leaving the areas occupied by rainbow trout and moving tolocations further away from the release site. In the field, the marble trout occupiedsites individually, whereas rainbow aggregated at a few locations. Rainbow troutshowed higher movement activity in the morning compared to marble trout. Therewas a positive correlation between swimming speed in the laboratory and movementin the field for marble trout but not for rainbow trout. In conclusion, the results in thisstudy support the need to end stocking of rainbow trout in rivers with native marbletrout. To better understand the interaction between the species, and to develop effi-cient management plans to protect the native marble trout, reference behavioursshould first be understood, and future research in sites where the two species do not co-exist is needed. This is especially important for marble trout for which behaviouralresearch and data are lacking.acceptedVersio

An Invited Reply to: A Comment on: Migrating silver eels return from the sea to the river of origin after a false start (2021) by Tambets M et al

publishedVersio

Annual and diel activity cycles of a northern population of the large migratory cyprinid fish asp (Leuciscus aspius)

Little is known about the exact movement parameters of migratory cyprinids listed as conservation priorities. A northern population of predatory asp, listed on the Bern Convention Appendix III, was studied in a near natural lake–river ecosystem by tracking adult fsh tagged with acoustic transmitters for 32 months. Activity levels in terms of swimming speed, swimming distance and movement range were four times higher during the warmer part of the year (water temperatures>12–15 °C, April/May–September), which coincides with their main feeding period, than other times of the year. All fsh had an annual riverine movement range larger than 40 km (max 110 km). Asp activity was afected by light, habitat type and water discharge. For most of the year, activity levels, in terms of number of movements per time unit, were higher during dawn and dusk than during day and night. Under poor light conditions and low temperatures, activity was also relatively high during the day. Fish were more likely to swim upstream around sunrise or during the day than during other diel periods. Knowledge about highactivity periods, which may render the fsh vulnerable to fshing and other impacts, can be used to develop and evaluate fshing regulations. Large annual movement ranges highlight the need for extensive continuous river systems open for migration between essential habitats. This study emphasises the need for region-specifc research on the ecology and behaviour of fsh populations in order to facilitate protection of the populations in the face of negative human impacts.publishedVersio

Kalakasvatusliku taastootmise programm : programm "Riiklikku kaitset vajavate ja ohustatud kalaliikide kaitse ja kalavarude taastootmine (2002-2010)"

TäistekstKäesolev programm on Eesti Vabariigi keskkonnaministri poolt käskkirjaga nr 352, 06.05.2002 kinnitatud juhend kalakasvatusliku taastootmise riikliku poliitika elluviimiseks Eestis, mis käsitleb kõigi praegu või eeldatavasti lähemas tulevikus Eesti veekogudesse asustatavate kalade taastootmise põhimõtteid ja näitab ära kaitset vajavate (ohustatud) kalade taastootmise riikliku finantseerimise prioriteedid ning kalapüügivõimaluste laiendamiseks vajalike kalade asustamiste toetamise prioriteedid. Programmis toodud asustusmahud ja kohad on soovituslikud ja lähtuvad 2001. aastal prognoositud reaalsetest võimalustest.Taustanalüüs. Kalavarud on tähtis taastuv loodusvara, mille kasutamine peab olema kooskõlas nii rahvusvaheliselt kui Eestis heaks kiidetud säästva arengu põhimõtetega. Eesti säästva arengu seadus sätestab, et loodusvarade säästva kasutamise eesmärgiks on tagada inimest rahuldav elukeskkond ja majanduse arenguks vajalikud ressursid elukeskkonda oluliselt kahjustamata ning looduslikku mitmekesisust säilitades. Kalade arvukuse säilitamise või suurendamise põhimõttelised võimalused on: 1) püügi reguleerimine kalapüügieeskirjas määratud piirangutega (keeluajad ja -piirkonnad, lubatud püünised ja alammõõt jne) ja püüniste arvu või kalakoguse limiteerimisega; 2) elukeskkonna (eeskätt sigimisvõimaluste) kaitse, parandamine või taastamine; 3) kalakasvatuslik taastootmine (kalakasvandustes üleskasvatatud noorkalade asustamine veekogudesse, edaspidi lühendatult taastootmine). Viimane on kulukas tegevus, mis eeldab pikaajalist planeerimist ja otstarbekuse analüüsi. Kalade kaitsemeetmed on sätestatud mitmetes õigusaktides ja dokumentides. Loodusliku mitmekesisuse kaitse huvides on Eestis vastu võetud mitmeid programme, mis puudutavad ka kalu. Igakülgsete kaitsemeetmete väljatöötamine jätkub seoses Eesti ja Euroopa Liidu keskkonnakaitse poliitika harmoniseerimisega. Tehistingimustes peetud loomade loodusesse laskmine (seega ka kalade asustamine kalakasvandustest) toimub loomastiku kaitse ja kasutamise seaduse § 19 järgi keskkonnaministri poolt kinnitatud programmi alusel. Käesolevas programmis on koondatud tähelepanu ohustatud ja majanduslikult kasutatavate kalaliikide arvukuse suurendamisele kalakasvatusliku taastootmise kaudu. Eesti 74 kalaliigist (Saat, 1992) on 8 inimtegevusest ohustatud (neist 4 on looduskaitse all), veel 4 liigi arvukus oleneb tugevasti inimtegevusest. Osa ohustatud liikidest on samal ajal kalanduslikult tähtsad ja neid püütakse pidevalt. Eestis on ka 7 liiki Euroopa Liidus (EL loodusdirektiivi alusel) ohustatuks loetud ja kaitstavaid kalu (sh kolm sõõrsuuliiki), mis on meil kas harva esinevad eksikülalised või pole siin otseselt ohustatud. Kalavarude suurendamiseks ja püügivõimaluste loomiseks taastoodetakse või on toodetud 5 mitteohustatud liiki. Majanduslikult kasutatavate veeorganismide hulka kuulub peale kalade ka inimtegevusest ohustatud jõevähk, mistõttu sellekohaseid probleeme käsitletakse käesolevas dokumendis koos kaladega. Sellise mitmekesisuse tõttu tuleb vaadelda Eestis riiklikku kaitset ja taastootmist vajavaid kalaliike rühmadena, mille suhtes rakendatavad meetmed ja riikliku toetamise vajadus on erinevad. Forelli ja siia liigisiseseid vorme käsitletakse nende ökoloogia erinevuste tõttu eraldi

Ohustatud sh kaitsealuste ja vääriskalaliikide seisundi parandamiseks vajalikud meetmed ja eelistatud tegevused

Eesti kalavaru, sh vähivaru kasutamine peab olema kooskõlas nii rahvusvaheliselt kui Eestis heakskiidetud säästva arengu põhimõtetega. Loodusvarade säästva kasutamise eesmärk on inimest rahuldava elukeskkonna ja majanduse arenguks vajalike ressursside tagamine, sealjuures oluliselt kahjustamata elukeskkonda ning säilitades looduslikku mitmekesisust. Kalavaru kaitset ja suurust saab mõjutada püügi reguleerimisega, elukeskkonna kaitse, parandamise või taastamisega ning kalakasvatusliku taastootmise abil. Viimane neist on kulukas tegevus, mis eeldab pikaajalist planeerimist ja otstarbekuse analüüsi. Selleks on vajalik kalavarude taastootmise tegevuskava. Tegevuskava koostamisel on lähtutud Eesti ja rahvusvahelistest valdkondlikest dokumentidest arvestades seejuures hetkeolukorda, kalavarude seisundit ja taastamise vajadust ning olemasolevaid võimalusi. Tegevuskava eesmärk on kalakasvatusliku taastootmise abil parandada ohustatud sh kaitsealuste kalaliikide seisundit ja suurendada nende arvukust, luues avaramad võimalused ka vääriskalaliikide püügiks Eestis. Tegevuskava elluviimist koordineerib ja selle eest vastutab Keskkonnaministeeriumi kalavarude osakond. Vastutav koordinaator koos tegevuskava täitjatega koostab iga nelja aasta tagant tegevuskava täitmise kokkuvõtte. Vastavalt saavutatud tulemustele ja ilmnenud puudustele muudetakse kava, et korrigeerida kalakasvatusliku taastootmise suundasid kalavarude olukorra parandamiseks ja bioloogilise mitmekesisuse hoidmiseks.Programmi koostamist finantseeris Keskonnainvesteeringute Kesku

Effects of a dispersal barrier on freshwater migration of the vimba bream (Vimba vimba)

To study the effects of a dispersal barrier on migration of the semi-anadromous vimba bream in the Pärnu River, Estonia, we tagged thirty fish with acoustic transmitters and released above the barrier. Tagged fish showed variation in behaviour, and 16 different spawning movement patterns were identified. Several fish moved > 25 km upstream. Batch spawning was suggested by stops in up to four different spawning areas. The Fish descended to the sea after spawning in spring; females earlier than males. After spending on average 137 days in the sea, they returned to the river during autumn and stayed in the river on average 174 days until the next spawning. The fish were most active during sunrise and sunset. In conclusion, the study shows that the dam prevents a diversification of migration behaviour and the associated expansion of spawning areas. A more efficient fishway could promote population growth and improve stock status.Effects of a dispersal barrier on freshwater migration of the vimba bream (Vimba vimba)publishedVersio

Session A8: Small Scale Efficiency of Downstream Bypasses and Large Scale Effects of Hydropower Production for Fish Populations: An Advanced Experimental Design Using Radio Telemetry

Abstract: Different technological solutions are currently in use to improve downstream fish passage. However, there is no standardized method of assessing their efficiency. At the same time, negative effects on fish populations caused by river damming are seldom taken into account. Here, an advanced radio telemetry set-up is presented, which provides a standardized method to assess both large scale effects of river damming and small scale efficiency of downstream fish pass solutions. This method divides the river into different sections up- and downstream of the power plant, i.e. i) natural section, ii) reservoir section, iii) power plant section and iv) downstream section. Fixed antenna stations mark the beginning and end of each section, whilst all potential migration corridors at the power plant are also covered by antennas. Antennas are tuned and, if necessary, custom made for each site, providing the ability to adapt the system to most hydropower settings. In addition, manual tracking from the river bank or boat is used to provide higher data resolution and differentiate between live and dead, but drifting fish. Simultaneously to the monitoring of biological data, power production and losses associated with the operation of the bypasses are also documented. Using this design, mortality and migration speed can be compared between natural and impounded river sections. Further, migration route choice can be documented for each fish, thus providing an assessment of bypass efficiency. Using this novel approach, different downstream bypass solutions can be compared, both in terms of their efficiency as well as the system specific large scale effects of river damming, whilst assessing the overall cost to hydropower production

Downstream migration of Atlantic salmon smolts at Unkelmühle power station and Buisdorf dam in 2016

Havn, T.B., Økland, F., Heermann, L., Thorstad, E.B., Teichert, M.A.K., Sæther, S.A., Tam-bets, M. & Borcherding, J. 2018. Downstream migration of Atlantic salmon smolts at Unkelmühle power station and Buisdorf dam in 2016. NINA Report 1412. Norwegian institute for nature research. Background and study aim The aim of this study was to examine migration routes and losses of Atlantic salmon smolts past the Unkelmühle hydropower station in the Sieg. Results from the study in 2016 are the main focus of this report. The results from 2016 are also compared with results from similar studies at Unkelmühle in 2014 and 2015. Technical facilities at Unkelmühle are designed to facilitate safe passage of downstream migrating fish, including ten different bypass routes where fish can pass outside the turbines, and narrowly spaced racks installed in front of the turbine intakes to prevent fish from entering the turbines. The efficiency of these measures are evaluated. Downstream migration past Buisdorf dam was also examined in 2016. This enabled comparison of loss and migration speeds of smolts between the Unkelmühle hydropower station and a weir without a hydropower station at Buisdorf. Methods The study was performed by tagging 227 Atlantic salmon smolts with radio transmitters and recording their migration in the river and past Unkelmühle power station and Buisdorf dam. Their movements were recorded 1) on free-flowing reference stretches upstream of the power station and dam, 2) on impounded stretches upstream of the power station and dam, 3) when they passed the power station and dam, and 4) on downstream river stretches. Migration routes used by tagged fish when they passed the power station and dam were mapped in detail by using networks of automatic, stationary receivers. The loss of downstream migrating smolts due to impoundments and past the power station and dam was calculated by comparing losses in these areas with losses on the reference stretches. This is based on the assumption that the loss per km recorded on the reference stretches (termed “reference loss” in this report) is representative for the developed stretch (stretch affected by hydropower development) if it had been a free-flowing river instead of being impounded by a reservoir and having a power station or dam. To examine if the location of the reference stretches affected the estimated loss caused by hydropower development, we compared two estimates of loss due to Unkelmühle power station based on reference loss on two different reference stretches. Results and conclusions The loss of downstream migrating smolts due to Unkelmühle power station was minimum 2.9% during the study in 2016. This represents the percentage of smolts arriving at the power station area that were lost due to this being a power station area instead of a free-flowing river. The loss estimate represents direct loss at the power station and delayed mortality due to the power station on the stretches downstream (7.5 km). There was no difference in loss between fish using the headrace to pass the power station and those passing over the weir. Loss due to the Buisdorf dam was minimum 3.4 and 5.7% (two different estimates) and not significantly different from the loss at Unkelmühle. The loss estimates are minimum estimates, because fish injured when passing the power station or dam can experience delayed mortality at later stages than recorded in this study, and the total mortality might therefore have been higher. There was no turbine mortality at the power station, because none of the smolts passed through the bar racks in front of the turbines, as expected due to the narrow bar spacing (10 mm) of the racks. Hence, the extra loss of smolts passing the power station was likely related to physical injuries in bypass routes aimed at guiding smolts outside the turbines, and increased predation. Loss due to the hydropower station was lower in 2016 compared to the two previous study years (minimum 9.9% in 2014 and 12.8% in 2015). Although total loss due to the power station was highest in 2015, loss in the bypass route that leads smolts outside the turbines was higher in 2014 than in 2015 and 2016. This was likely caused by smolts becoming trapped in an area of the bypass route where debris and branches piled up in 2014, but not in 2015 and 2016. Water discharge was higher in 2016 compared to the previous study years, and the high water discharge was probably an important factor for reducing loss of smolts passing the power station in 2016. Results showed that the reservoir upstream of the power station can be an area of high mortality for downstream migrating smolts. Of all smolts entering the reservoir upstream of Unkelmühle, 7.2% in 2014, 17.1% in 2015 and 4.4% in 2016 were lost due to this being a reservoir instead of a free-flowing river. The reservoir upstream of Unkelmühle is 2.3 km long, with slow-flowing water, and more resembling a lake than a river. The main reason for the extra loss in the reservoir is likely presence of more fish predators in the slow-flowing reservoir compared to the free-flowing river stretches. These results show that reservoir mortality may vary among years, probably due to variation in the predator community. In contrast to at Unkelmühle, where fish were delayed at the power station, fish moved at the same speed past Buisdorf dam as on unimpounded stretches. This difference in migration speed was also found when comparing only fish that migrated through the spillway gate at Unkelmühle with fish that used the weir at Buisdorf. No fish spent time in the turbine intakes before swimming back upstream and using the spillway gate to pass the power station, so behaviour upstream of the power station did not seem to explain why fish moved slower past the power station compared to the dam. However, smolts seem to follow the main water flow when navigating past power stations, and the observed differences may be caused by a higher proportion of the total water discharge running over the weir at Buisdorf compared to the proportion running through the spillway gate at Unkelmühle, making navigation over the weir and exit of the tailrace faster at Buisdorf compared to Unkelmühle