Sirvi Autor "Tuvikene, Arvo" järgi

Nüüd näidatakse 1 - 20 20

Behavioural responses of invasive (Gmelinoides faciatus) and native (Gammarus lacustris) amphipods to predators on different bottom substrates : [poster]
(Estonian University of Life Sciences, 2023) Teesalu, Paul; Ercoli, Fabio; Tuvikene, Arvo
The amphipod Gmelinoides fasciatus has invaded and established in numerous large lakes in Eurasia and, in the process, has displaced the native amphipod, Gammarus lacustris. In Lake Peipsi, G. fasciatus dominates the shoreline macroinvertebrate fauna, forming up to 99% of macroinvertebrate individuals (Fig. 1). The mechanism behind its invasion success is unclear and remains an important topic for invasion ecology. In order to determine if different bottom substrates and predator avoidance behaviour contribute to the invasion success of G. fasciatus we conducted two laboratory experiments.
Behavioural responses of invasive (Gmelinoides fasciatus) and native (Gammarus lacustris) amphipods to predators on different bottom substrates
(Springer Nature, 2023) Teesalu, Paul; Ercoli, Fabio; Tuvikene, Arvo
The amphipod Gmelinoides fasciatus has invaded and established in numerous large lakes in Eurasia and, in the process, has displaced the native amphipod, Gammarus lacustris. The mechanism behind its invasion success is unclear and remains an important topic for invasion ecology. Three labo- ratory experiments were conducted to determine if superior predator avoidance and different types of bottom substrate could be important factors contrib- uting to the invasion success of G. fasciatus. Our results indicate that, on gravel and sand substrates, G. fasciatus exhibited superior digging behaviour to avoid predation by fishes (perch and common roach), contrary to G. lacustris. On sandy substrate, only 9% of G. fasciatus individuals were consumed, whereas G. lacustris were consumed much more intensively at 74%. In addition, G. fasciatus exhibited a more sub- stantial reduction in activity, where the time spent in motion reduced from 37.6 to 20.8% compared to G. lacustris (from 21.8 to 17.4%) when in the presence of predatory fish kairomones. G. fasciatus movement speed was also reduced in the presence of kairomones (from 57.1 to 39.3 mm/s). However, the presence of kairomones had little effect on digging behaviour of G. fasciatus. G. fasciatus consistently demonstrated superior predator avoidance abilities over G. lacus- tris, suggesting that this mechanism might play an important role in the invasion success of G. fasciatus.
Black and white, day and night – fish diurnal movements in two different Amazonian lakes : [presentation]
(2021) Zingel, Priit; Tuvikene, Arvo; Feldmann, Tõnu; Agasild, Helen
The presentation took place at the 10th International Conference on Shallow Lakes in 2021.
Comparison of larval perch feeding between littoral and open-water sites of the lakes : [presentation]
(Estonian University of Life Sciences, 2021) Karus, Katrit; Žagars, Matiss; Zingel, Priit; Agasild, Helen; Feldmann, Tõnu; Tuvikene, Arvo; Medne-Peipere, Madara; Puncule, Linda
The presentation took place at the 10th International Conference on Shallow Lakes in 2021.
The comparison of the feeding of European perch Perca fluviatilis L. larvae in littoral and pelagic habitats of northern temperate lakes
(Estonian Academy Publishers, 2022) Karus, Katrit; Zagars, Matiss; Agasild, Helen; Feldmann, Tõnu; Tuvikene, Arvo; Puncule, Linda; Zingel, Priit; Chair of Hydrobiology and Fishery; Centre for Limnology
We studied the feeding of European perch Perca fluviatilis L. larvae in littoral and pelagic habitats of four different lakes – one Latvian (Auciema) and three Estonian (Akste, Kaiavere, and Prossa). Altogether, 162 perch larvae (81 from both habitats) were collected to estimate the diet composition of gathered larval specimens in spring (2019) using gut content analysis via epifluorescence microscopy. Attention was paid particularly to the question how does the larval perch food composition differ in pelagic and littoral habitats. We hypothesized that the consumption of zooplankton is higher and the larval condition is better in littoral habitats. We assessed the feeding on both protozoo- (ciliates) and metazooplankton and applied multiple indices (Hurlbert’s standardized niche breadth, Ivlev’s selectivity and relative importance index) to evaluate, respectively, the larval fish prey importance, feeding homogeneity and strategies. The results showed that larval length and weight were slightly higher and body condition was slightly better in the lakes’ littoral habitats. The feeding niche of perch larvae was narrower in the littoral, which can indicate more favourable feeding conditions in littoral than lake pelagic habitats. While the small cladocerans (Bosmina longirostris Müller) were generally the preferred and important food objects, ciliates were avoided and consumed only when their share in the total zooplankton biomass was >40%. However, in shortage of cladocerans, ciliates could be vitally important food objects for perch larvae.
The diet of Eurasian perch larvae in lakes with different zooplankton assemblages
(2023) Zingel, Priit; Agasild, Helen; Zagars, Matiss; Feldmann, Tõnu; Tuvikene, Arvo; Zingel, Tiina; Puncule, Linda; Karus, Katrit; Centre for Limnology. Institute of Agricultural and Environmental Sciences. Chair of Hydrobiology and Fishery. Estonian University of Life Sciences
Eurasian perch has a great ecological importance in freshwaters as it is often a dominating predatory fish in ecosystems. The knowledge of perch feeding patterns, strategies, and adaptivity to food environment in their early life stages is essential to understand its population development and dynamics. It has been demonstrated that there exists a positive relationships between preferred prey availability and larval feeding success. We examined the diet of larval perch in their natural habitats of different zooplankton assemblages in three small lakes with varying ecological status. In each lake, both pelagial and littoral were studied. We found significant relation between zooplankton biomass in the lake and zooplankton biomass consumed by fish larvae. The most important food objects were crus- taceans (Bosmina longirostris, Chydorus sphaericus). Ciliates were consumed only in one lake. Our results show that perch larvae are flexible in their choice of food and can adapt to different food environments.
Differences on the level of hepatic transcriptome between two flatfish species in response to liver cancer and environmental pollution levels
(Elsevier, 2023) Sepp, Tuul; Baines, Ciara; Kreitsberg, Randel; Scharsack, Jörn Peter; Nogueira, Pedro; Lang, Thomas; Fort, Jérôme; Sild, Elin; Clarke, John T.; Tuvikene, Arvo; Meitern, Richard
Environmental factors can cause cancer in both wild animals and humans. In ecological settings, genetic variation and natural selection can sometimes produce resilience to the negative impacts of environmental change. An increase in oncogenic substances in natural habitats has therefore, unintentionally, created opportunities for using polluted habitats to study cancer defence mechanisms. The Baltic and North Sea are among the most contaminated marine areas, with a long history of pollution. Two flatfish species (flounder, Platichthys flesus and dab, Limanda limanda) are used as ecotoxicological indicator species due to pollution-induced liver cancer. Cancer is more prevalent in dab, suggesting species-specific differences in vulnerability and/or defence mechanisms. We conducted gene expression analyses for 30 flatfishes. We characterize between- and within-species patterns in potential cancer-related mechanisms. By comparing cancerous and healthy fishes, and noncancerous fishes from clean and polluted sites, we suggest also genes and related physiological mechanisms that could contribute to a higher resistance to pollution-induced cancer in flounders. We discovered changes in transcriptome related to elevated pollutant metabolism, alongside greater tumour suppression mechanisms in the liver tissue of flounders compared to dabs. This suggests either hormetic upregulation of tumour suppression or a stronger natural selection pressure for higher cancer resistance for flounders in polluted environment. Based on gene expression patterns seen in cancerous and healthy fish, for liver cancer to develop in flounders, genetic defence mechanisms need to be suppressed, while in dabs, analogous process is weak or absent. We conclude that wild species could offer novel insights and ideas for understanding the nature and evolution of natural cancer defence mechanisms.
Eesti rannikumere reostuse hindamine kalade bioloogiliste kahjustuste kaudu : aruanne
(2016) Tuvikene, Arvo; Kreitsberg, Randel; Raig, Reelika; Tuvikene, Arvo (koostaja); Eesti Maaülikool. Põllumajandus- ja keskkonnainstituut. Limnoloogiakeskus
Töö eesmärkideks oli: 1) testida HELCOMi poolt soovitatud vee reostuse tuumik- biomarkereid: a. polütsükliliste aromaatsete süsivesinike (PAH) laguproduktide kontsentratsiooni ahvena, räime ja lesta sapis/uriinis, b. kalade punaliblede kahjustuste alusel hinnata Eesti rannikumere geno- ja tsütotoksilisust 2) nende biomarkerite alusel selgitada välja reostunumad ja vähemreostunud piirkonnad Soome lahe Eesti rannikumeres.
Effects of environmentally relevant concentrations of microplastics on amphipods
(Elsevier, 2022) Rani-Borges, Barbara; Meitern, Richard; Teesalu, Paul; Raudna-Kristoffersen, Merilin; Kreitsberg, Randel; Heinlaan, Margit; Tuvikene, Arvo; Ivask, Angela
Lack of microplastics (MP) toxicity studies involving environmentally relevant concentrations and exposure times is concerning. Here we analyzed the potential adverse effects of low density polyethylene (LDPE) MP at environmentally relevant concentration in sub-chronic exposure to two amphipods Gmelinoides fasciatus and Gammarus lacustris, species that naturally compete with each other for their habitats. 14-day exposure to 2 μg/L (8 particles/L corresponding to low exposure) and 2 mg/L (~8400 particles/L, corresponding to high exposure) of 53–100 μm LDPE MP were used to assess ingestion and egestion of MP, evaluate its effects on amphipod mortality, swimming ability and oxidative stress level. Both amphipod species were effectively ingesting and egesting LDPE MP. On the average, 0.8 and 2.5 MP particles were identified in the intestines of each amphipod exposed to 2 μg/L and 2 mg/L LDPE MP, respectively. Therefore, intestinal MP after 14-day exposure did not fully reflect the differences in LDPE MP exposure concentrations. Increased mortality of both amphipods was observed at 2 mg/L LDPE MP and in case of G. lacustris also at 2 μg/L exposure. The effect of LDPE on swimming activity was observed only in case of G. fasciatus. Oxidative stress marker enzymes SOD, GPx and reduced glutathione GSH varied according to amphipod species and LDPE MP concentration. In general G. lacustris was more sensitive towards LDPE MP induced oxidative stress. Overall, the results suggested that in MP polluted environments, G. lacustris may lose its already naturally low competitiveness and become overcompeted by other more resistant species. The fact that in the sub-chronic foodborne exposure to environmentally relevant and higher LDPE MP concentrations all the observed toxicological endpoints were affected refers to the potential of MP to affect and disrupt aquatic communities in the longer perspective.
Effects of trophic status, water level, and temperature on shallow lake metabolism and metabolic balance: A standardized pan-European mesocosm experiment
(Wiley, 2019) Scharfenberger, Ulrike; Jeppesen, Erik; Beklioğlu, Meryem; Søndergaard, Martin; Angeler, David G.; Çakıroğlu, Ayşe İdil; Drakare, Stina; Hejzlar, Josef; Mahdy, Aldoushy; Papastergiadou, Eva; Šorf, Michal; Stefanidis, Konstantinos; Tuvikene, Arvo; Zingel, Priit; Adrian, Rita; Centre for Limnology. Institute of Agricultural and Environmental Sciences
Important drivers of gross primary production (GPP) and ecosystem respiration (ER) in lakes are temperature, nutrients, and light availability, which are predicted to be affected by climate change. Little is known about how these three factors jointly influence shallow lakes metabolism and metabolic status as net heterotrophic or autotrophic. We conducted a pan-European standardized mesocosm experiment covering a temperature gradi- ent from Sweden to Greece to test the differential temperature sensitivity of GPP and ER at two nutrient levels (mesotrophic or eutrophic) crossed with two water levels (1 m and 2 m) to simulate different light regimes. The findings from our experiment were compared with predictions made according the metabolic theory of ecology (MTE). GPP and ER were significantly higher in eutrophic mesocosms than in mesotrophic ones, and in shallow mesocosms compared to deep ones, while nutrient status and depth did not interact. The estimated temperature gains for ER of ~ 0.62 eV were comparable with those predicted by MTE. Temperature sensitivity for GPP was slightly higher than expected ~ 0.54 eV, but when corrected for daylight length, it was more consistent with predictions from MTE ~ 0.31 eV. The threshold temperature for the switch from autotrophy to heterotrophy was lower under mesotrophic (~ 11 C) than eutrophic conditions (~ 20 C). Therefore, despite a lack of signifi- cant temperature-treatment interactions in driving metabolism, the mesocosm’s nutrient level proved to be cru- cial for how much warming a system can tolerate before it switches from net autotrophy to net heterotrophy.
How long-term water level changes influence the spatial distribution of fish and other functional groups in a large shallow lake
(Elsevier, 2020) Bhele, Upendra; Öğlü, Burak; Tuvikene, Arvo; Bernotas, Priit; Silm, Maidu; Järvalt, Ain; Agasild, Helen; Zingel, Priit; Seller, Siim; Timm, Henn; Nõges, Peeter; Nõges, Tiina; Cremona, Fabien; Chair of Hydrobiology and Fishery. Institute of Agricultural and Environmental Sciences
We numerically explored the effects of long-term water level changes on biotic biomass and spatial distribution of fish in a large shallow lake. We calibrated Ecospace model (Ecopath with Ecosim modelling suite) with data from various functional groups (ranging from phytoplankton to piscivorous fish), and considered 14 different habitats. Two scenarios representing, respectively, a long-term water-level increase and decrease by 1 m were constructed and run for a period of thirty eight years (1979–2016). The results showed a very uneven spatial distribution of fish biomass in the lake, with the highest con- centration in the southern basin. The 1 m decrease scenario caused a diminution in the biomass of all groups but piscivorous fish. The 1 m increase scenario saw a weak decrease in most species biomass. Consequently, in both scenarios, long-term water level changes would be generally detrimental to the lake biota. In the context of more frequent climate-induced hydrological fluctuations, we encourage the use of these simulations as effective tools for future prediction and assessment of ecosystem-based fisheries management and ecological status maintenance of shallow lakes.
Improving administrative effectiveness of lake management in the frames of River Basin Management Plans : Implementation Plan
(2014) Tuvikene, Lea; Sammalkorpi, Ilkka; Kreitsberg, Randel; Soo, Kristjan; Tuvikene, Arvo; Estonian University of Life Sciences
Fresh waters make only 3% of the global water resources. Freshwater lakes, including reservoirs and ponds, are important elements for communities and their relevance is increasing. Lake ecosystems and their catchments have provided several societally valuable benefits and ecosystem services like shelter, drinking water, bathing water, food, a means of travel and wealth in a number of ways and allowed whole cultures to develop. Lakes have values associated with well-being and relaxation, their proximity has catalyzed rural development and been important in the regional socio-economic development. Lake districts are often very popular destinations for domestic and foreign tourism and visitors. Eutrophication and its ecological consequences, pollution, over abstraction and invasive species are serious threats and increase the need for restoration and management to prevent the potential adverse economic and social impacts. There is increasing evidence that lakes are affected by climate change. Lake management is for these reasons an important part of sustainable regional development as set by Lisbon and Gothenburg agreements. However, the most significant piece of legislation in response to the increasing threat of pollution and the increasing demand from the public for cleaner lakes, rivers and beaches and freshwater biodiversity, is the EU Water Framework Directive (WFD). This Directive is unique in that it sets out an established framework for the protection of all water bodies (including lakes) and for all EU member states to achieve good water ecological status by December 2015. This objective is likely to be achieved in slightly over half (53 %) of EU waters (A blueprint…, 2013) and, therefore, more effort need to be scheduled for the following 6-year periods of WFD. The economic values of attractive, clean lakes are well established. There is a rising appreciation of good quality lakes across Europe. More intensive lake protection through sharing good practices with European lake managers and the regional influencing bodies is critical if we want to improve the current quality of lakes in Europe and to build long term capacity for sustainable use of lakes.
The influence of macrophyte ecological groups on food web components of temperate freshwater lakes
(Elsevier, 2022) Karus, Katrit; Zagars, Matiss; Agasild, Helen; Tuvikene, Arvo; Zingel, Priit; Puncule, Linda; Medne-Peipere, Madara; Feldmann, Tõnu
Aquatic macrophyte taxonomic composition, species abundance and cover determine the physical structure, complexity and heterogeneity of aquatic habitats – the structuring role of macrophytes. These traits influence richness, distribution, feeding and strength of the relationships between food web communities in lakes. The aim of this study was to determine how lakes with different dominating macrophyte ecological groups affect planktonic food web components, emphasising the influence on young of year (YOY) fish and large (≥1 +) fish community. We hypothesised that different dominating macrophyte ecological groups have different structural effects on food web components and YOY fish growth, abundance and feeding. Studied lakes categorised into three different macrophyte ecological groups – lakes dominated by emergent, floating+floating-leaved or submerged vegetation. We found that all dominating ecological groups had a strong influence on plankton communities (except heterotrophic bacterioplankton and nanoflagellates), YOY fish and large fish. Floating-leaved plant dominance was positively related to planktonic food web structure and YOY fish weight, length, abundance and the consumption of zooplankton as a prey of all major species of YOY fishes. Larger fish tended to favour the presence of emergent vegetation. This conclusion has important implications for local managers and conservationists in respect to the maintenance and protection of littoral habitats and fish resources.
Järvede tervendamine. Kogumik
(2011) Kõiv, Toomas; Ott, Ingmar; Tuvikene, Lea; Sarik, Diana; Panksep, Kristel; Pedusaar, Tiia; Järvalt, Ain; Tuvikene, Arvo; Mäemets, Helle; Timm, Henn; Kisand, Anu; Mugra, Tõnu; Laanetu, Nikolai; Tupits, Ilmar; Laas, Alo; Sammalkorpi, Ilkka; Hamilton, David P.; Eesti Maaülikool. Põllumajandus- ja keskkonnainstituut. Limnoloogiakeskus
Eessõna järvede tervendamise käsiraamatule Kui veel 1950 – 60-ndatel aastatel võis enamiku Eesti järvede seisundit pidada looduslikuks, siis 21. sajandi alguseks on paljude järvede seisund peamiselt tugeva inimmõju tagajärjel märkimisväärselt halvenenud. Hinnanguliselt 10 – 12% meie järvedest on halvas seisundiklassis ja vajaks kindlasti tervendamist. Lisaks on veel palju järvi , mille seisund ei ole küll päris halb, aga vajab siiski parandamist. Euroopa Liidus 2000. aastal rakendunud veepoliitika raamdirektiiv seab eesmärgiks saavutada aastaks 2015 liikmesriikide kõigi vete, sh pinnavee, põhjavee, reovee ja joogivee, hea seisund. Pinnaveekogudes tuleb lisaks vee heale keemilisele seisundile saavutada ka hea ökoloogiline seisund. Kui veekogu seisund pole hinnatud heaks või väga heaks, tuleb kasutusele võtta meetmed vähemalt hea seisundi saavutamiseks. Selleks võib olla piisav veekogu majandamise ümberkorraldamine, kuid enamasti tähendab see vajadust astuda konkreetseid samme valgalalt saabuva reostuskoormuse vähendamiseks ja ka veekogu enese tervendamiseks. Järvede kui suure loodusväärtuse hea seisund on oluline ka inimese tervise seisukohast. Terved ja kaunid järved pakuvad puhkamiseks ja töövõime taastamiseks mitmekülgseid võimalusi, mille hulgas on kalastamine kindlasti üks märkimisväärsemaid. Keskkonnaministeeriumi korraldatud küsitlusel harrastuspüüdjate seas selgus, et enim häirivad hobikalureid veekogudele ligipääsu puudumine ja väike vääriskalavaru, kuid ka veekogude halb olukord ja üldine kala vähesus. Tervendamine võimaldab lisaks järvede olukorra parandamisele tervikuna taastada või tõsta ka nende kalamajanduslikku väärtust. Nagu igal elualal, on ka järvede tervendamise alases sõnavaras kasutusel palju sama või osaliselt kattuva tähendusega mõisteid. Levinuim vaste järvede tervendamisele on olnud „restaureerimine” , mis on eesti keelde tulnud ingliskeelsest mõistest restoration , otsetõlkena on palju kasutatud ka „taastamist”. Võõrsõna ja selle sisult ebatäpsete eestikeelsete vastete asemel on järveteadlased üsna edukalt suutnud juurutada hoopis kodusema kõlaga ja pehmema sisuga mõistet „tervendamine”. Käsiraamatu esimeses peatükis soovitatakse tervendamise terminoloogiat vastavalt sellele, kui põhjalikku sekkumist on järve seisundi parandamiseks vaja. Seal leiab käsitlemist tervendamise kitsam tähendus. Nii selle käsiraamatu pealkirjas kui tekstis kasutame enamasti seda mõistet laiemas tähenduses, mis hõlmab kõiki järvede olukorra parandamisega seotud tegevusi ja viise olenemata sellest, kui põhjalikke muutusi läbi viiakse. Eestis jõudsalt hoogu koguv järvede tervendamine on seni põhinenud üsna lünklikel ja juhuslikel teadmistel, kuna meil on puudunud seda teemat tervikuna ja põhjalikult käsitlev eestikeelne kirjandus. Heal juhul on järvede tervendajad leidnud üles järveteadlased ja lasknud enne järve kallale asumist teha uuringud, saamaks teada, mis on järve seisundi halvenemise tegelikud põhjused. Keskkonnainvesteeringute Keskuse toel Eesti Maaülikoolis valminud artiklite kogum on „Järvede tervendamise käsiraamatu” käsikiri, mis vajab enne päris raamatuks saamist veel toimetamist. Kuna vajadus sellise juhend- ja õppematerjali järele on suur, siis on käsikirjalised artiklid juba avalikult kättesaadavaks tehtud. Esimene peatükk tutvustab järveteaduse ehk limnoloogia aluseid, mis aitavad mõista järvede tervendamise põhimõtteid. Teises peatükis antakse ülevaade Eesti järvede tervendamisvajadusest. Kolmas peatükk käsitleb kogu tervendamisega kaasnevat protsessi, alates idee tekkimisest ja asja kohasest seadusandlusest ning lõpetades järelseirega. Järgnevad peatükid käsitlevad tervendamise meetodeid: biomanipulatsioon (peatükk 4), vee hapnikuga rikastamine (peatükk 5) , veerežiimi muutmine (peatükk 6) , makrofüüdijärvede tervendamine (peatükk 7), vee ja setete keemilise töötlemise meetodid (peatükk 8) ja setete eemaldamine (peatükk 9). Peatükk 10 tutvustab järve veetaseme tõstmise ja sette eemaldamise ehitusprojektidega seonduvat. Peatükis 11 leiavad käsitlemist keskkonnamõjude hindamine ja järvede hooldus. Kuigi näiteid järvede tervendamisest leidub igas konkreetseid meetodeid käsitlevas peatükis, annab viimane, 12. peatükk veel ülevaate veekogude tervendamise senistest kogemustest Eestis ja mujal Euroopas ning kirjeldab põhjalikumalt mõnd huvitavamat tervendamise näidet nii meilt kui mujalt maa ilmast. Käsikirja autorid loodavad, et kirjapandust on abi järvede tervendamisega seotud inimestele ja lõppkokkuvõttes meie paljude järvede tervisele. Kõik täiendused, parandused ja ettepanekud, mis võiksid kaasa aidata sisuka ja kasuliku käsiraamatu valmimisele, on teretulnud aadressile: Lea Tuvikene, Limnoloogiakeskus, Rannu 61117, Tartumaa , või e - posti aadressile lea.tuvikene@emu.ee
Larval and juvenile perch feeding in some Estonian and Latvian study lakes : [poster]
(Estonian University of Life Sciences, 2021) Karus, Katrit; Agasild, Helen; Feldmann, Tõnu; Tuvikene, Arvo; Medne-Peipere, Madara; Žagars, Matiss; Puncule, Linda; Zingel, Priit
The presentation took place at the Lahti Lakes 2021 Symposium.
Niche partitioning of invasive Amur sleeper (Perccottus glenii) amongst native fish communities in three different freshwater ecosystems
(Pensoft Publishers, 2024) Ercoli, Fabio; Kiljunen, Mikko; Teesalu, Paul; Tuvikene, Arvo; Tambets, Meelis; Kärgenberg, Einar; Nõges, Tiina
The invasive fish, Amur sleeper, poses a significant and growing threat to Central European freshwater ecosystems. Despite its rapid spread, the ecological implications of its invasion have been poorly explored. Recent findings confirm its presence in various Estonian freshwater systems, raising concerns about its imminent expansion into larger lakes. To better understand its potential ecological impacts, we explored the isotopic niche of the Amur sleeper in comparison with native fish species co-existing in three Estonian freshwater ecosystems. We employed carbon and nitrogen stable isotope analyses alongside gut content analyses. Our findings show that the Amur sleeper’s diet in newly-invaded Estonian water bodies predominantly comprises benthic macroinvertebrates, although it may also include fish, confirming its role as a predator in the local food web. Notably, Amur sleeper populations exhibited clear isotopic niche partitioning in three invaded ecosystems. A logistic regression model, based on stomach content analyses, revealed an ontogenetic diet shift from benthivorous to piscivorous feeding habits from small to large specimens. Amur sleeper exhibits voracious, non-selective feeding habits, which can negatively impact native freshwater communities. The ability to occupy a distinct isotopic niche, with minimal overlap with native fish populations, may reduce interspecific competition, facilitating the spread and establishment of Amur sleeper in newly-invaded habitats. Managing the spread of this invasive species thus becomes even more critical to safeguard the integrity of native aquatic ecosystems.
Prey selection and growth in 0+ Eurasian perch Perca fluviatilis L. in littoral zones of seven temperate lakes
(Wiley, 2022) Karus, Katrit; Zagars, Matiss; Agasild, Helen; Feldmann, Tõnu; Tuvikene, Arvo; Puncule, Linda; Zingel, Priit
We studied the relationships between the planktonic food base and feeding patterns of juvenile mid-summer/ early autumn Eurasian perch Perca fluviatilis L., a common predatory freshwater fish in large parts of Europe and Asia. The feeding of 0+ perch was studied during summer and autumn in littoral habitats of seven lakes with different environmental conditions –four Latvian (Auciema, Riebinu, Vārzgūnes, Laukezers) and three Estonian (Kaiavere, Prossa and Akste) lakes. Simultaneously, the abundance, biomass and structure of zooplankton communities were examined. We focused on the littoral areas because many studies in lakes suggest that littoral habitats are particularly important for 0+ fish growth and survival. We were interested in the question: can the diet and growth of 0+ perch be explained by zooplankton community structure? We also presumed that if the amount of zooplankton is low, more benthic invertebrates will be consumed by 0+ perch. Opposite to expectations, we found that zooplankton always counted for over 90% of diet biomass in perch. There were also clear correlations between the zooplankton biomass in a given lake, the zooplankton biomass in 0+ perch stomachs, and the fish growth rate. The study also suggested that nutrient enrichment can positively impact the 0+ perch feeding conditions in lakes.
Rändvähi (Gmelinoides fasciatus) kui ohtliku invasiivse liigi levikupotentsiaal ning tähtsus kalade toiduobjektina
(2021) Tuvikene, Arvo; Timm, Henn; Teesalu, Paul; Seller, Siim; Voode, Margus; Timm, Tarmo
Rändvähk siirati Peipsisse 1970. aastate alguses Venemaa kalateadlaste soovitusel, et suurendada kalade toiduvarusid. Paraku muutus ta seal kiiresti invasiivseks ning põhjustab tänapäeval halba bioseisundit Euroopa Veepoliitika Raamdirektiivi (2000) mõttes, sest alandab oluliselt taksonirikkust. Võrtsjärves asustab kohalik liik järve-kirpvähk endiselt sarnaseid elupaiku, mille Peipsis on hõivanud rändvähk. Ta aga ei moodusta kuskil samasugust "monokultuuri". Peipsist on rändvähk seni levinud nii pärivoolu Narva jõkke kui ka suubuvaid jõgesid mööda vastuvoolu, eriti piki Emajõge (Panov et al. 2000, Timm & Tuvikene 2019). Tema kõrge arvukus ning depressiivne mõju teistele liikidele on tõenäoliselt üks põhjus, miks ka Emajõe bioloogilist seisundit mõnedes lõikudes pole hea. Emajões allpool Tartut kuni Peipsini on rändvähk kõikjal levinud. Võrtsjärve elustikule on ta potentsiaalselt väga ohtlik. Loomulikult harvendab rändvähk ka Emajõe enda loomi, kuid et jõepõhi on mitmekesisem ja taimerikkam kui järvepõhi, ei suuda ta seda sama edukalt muudest liikidest puhastada. Keskkonnatingimuste suhtes on rändvähk võrreldes järve-kirpvähiga laiema amplituudiga. Ta talub paremini hüpoksiat ja madalat pH-d. Kalad küll tarvitavad rändvähki toiduks, kuid tabavad teda võrreldes järve-kirpvähiga oluliselt halvemini, sest ta peitub ohu korral liiva või kruusa sisse. Rändvähile meeldib asustada võrkpüüniseid. Katseliselt ulatus nende asustustihedus 5-7 isendini/100 cm2 kohta. Ca 50-60% võrgule kinnitunud vähkidest tuleb võrguga veest väljatõstmisel kaasa. Seega peitub oht rändvähkide sattumiseks Võrtsjärve või mõnda teise veekogusse, kui Peipsist võetud püünised asetatakse kiiresti püügile, ilma et neid oleks vahepeal kuivatatud või kuuma veega töödeldud.
Siseveekogud : õpik kõrgkoolidele
(Kalanduse teabekeskus, 2020) Järvalt, Ain; Järvekülg, Rein; Kisand, Anu; Mäemets, Helle; Ott, Ingmar; Panksep, Kristel; Pedusaar, Tiia; Tammert, Helen; Timm, Henn; Tuvikene, Arvo; Tuvikene, Lea; Tõnno, Ilmar; Vilbaste, Sirje; Ott, Ingmar (koostaja); Timm, Henn (koostaja)
Inimeste kõige tavalisemad seosed siseveekogudega on matkamine, kalapüük, suplemine, janu kustutamine ja taimede kastmine. Et veekogude ääres viibimine mõjub paljudele rahustavalt, on jõgedel-järvedel miljonivaadete kaudu kindel koht ka kinnisvaraäris. Veekogudeta ei saa läbi sportlased (purjetajad, sõudjad ja motohuvilised). Leidub selliseidki indiviide, keda meelitavad mittesöödavad või koguni palja silmaga nähtamatud vee-elanikud. Eesti on väike madal maa, millel on pikk mererand, aga kus leidub ka palju siseveekogusid. Eriline on kahe suure järve – Peipsi ja Võrtsjärve – asumine lähestikku. Seisuvete pindala osakaalu järgi kogu riigi pindalast on Eesti Euroopas pärast Soomet ja Rootsit koos Norraga kolmandal-neljandal kohal. Eesti ja tema ümbrus on puhta veega seni niisiis hästi varustatud, kuid see rikkus ühtlasi kohustab veekogusid heaperemehelikult ja jätkusuutlikult majandama. Ka Eestis on muresid nii veevarude, veekogude kui nende seisundiga. Sisevete uurimine on Eestis kestnud juba üle 100 aasta. Seda on süstemaatiliselt korraldanud nii Looduseuurijate Selts, Tartu Riiklik Ülikool, Teaduste Akadeemia kui Maaülikool. Suurte järvede kõrval pole unustatud väikesi järvi ega vooluveekogusid. Uurida vee ja veekogude omadusi, arendada ja kasvatada nende spetsialiste ongi mõistlik seal, kus on, mida tundma õppida. Üha enam leitakse seoseid looduslike ja inimtekkeliste mõjurite ning ökosüsteemide vastuste vahel. Ühtlasi ühendatakse neid seoseid sotsiaalmajanduslike küsimuste ja looduskaitsega. Eesti siseveekogude kohta on peale arvukate ja enamasti võõrkeelsete teadusartiklite ilmunud ka eestikeelseid raamatuid. Siin neist väike loetelu: väikejärved (Eesti järved, 1968; Mäemets, 1977; Laarmaa jt 2019); Võrtsjärv (1973, 2003); Peipsi (1999, 2008), vooluveed (Järvekülg jt 2001; Timm jt 2019). Kalaraamatuid esindavad Mikelsaar (1984) ning Hunt (2019), veetaimi „Eesti taimede määraja“ (2010). Silmaga nähtavate veeselgrootute ülevaate pakub Timm (2015). Ülevaatlikku eestikeelset õpikut siseveekogude ning nende talitlemise kohta seni polnud. Eesti ülikoolides on kõigil kolmel õppetasandil (bakalaureuse-, magistri- ja doktoriõpe) õppekavasid, kus vajatakse teadmisi siseveekogudest. Võõrkeelseid eeskujusid leidub päris mitu, kuid need käsitlevad enamasti kas ainult hüdrobioloogiat või limnoloogiat. Esimene on elustiku-, teine keskkonna-alase suunitlusega. Uus õpik sisaldab mõlemaid ning sobib loodetavasti paljudele loodusteaduslikele ja looduskaitselistele kursustele, eriti bakalaureusetasemel. Õpik koosneb kolmest suurest alajaotusest: (1) siseveekogude füüsikalis-keemiline iseloomustus, levik ja teke; (2) elupaigad veekogudes, olulised elustikurühmad ning nendevahelised suhted; (3) siseveekogude majandamine, kaitse ja tervendamine. Peamiselt vaadeldakse Eesti siseveekogusid, aga seda kogu maailma taustal. Koostajad loodavad, et raamat annab lugejatele nii vastuseid küsimustele kui ka süvendab huvi sisevete kui kaunite, põnevate ning inimestele eluliselt oluliste loodusobjektide suhtes.
Uudse angerjamõrrasüsteemi katsetamine Võrtsjärvel
(2018) Bernotas, Priit; Silm, Maidu; Järvalt, Ain; Tuvikene, Arvo; Zirk, Jüri; Eist, Andi; Konoplitski, Jüri; Eesti Maaülikool. Limnoloogiakeskus
Euroopa angerjaid (Anguilla anguilla) on Võrtsjärve asustatud 1956. aastast saadik. Kui 50ndatel alguse saanud traditsioon teenis algselt pigem püügivaru pakkumise eesmärki, on asustamisel tänapäeval ka oluline looduskaitseline funktsioon. Olukorras, kus angerjavarud on kogu Euroopas kriitiliselt vähenenud (ICES, 2016), on äärmiselt tähtis tagada võimalikult paljudele angerjatele võimalus merre kuderändele pääsemiseks. Võrtsjärv on angerjale sobiv elupaik, mida tõendavad nii klaas- kui ettekasvatatud angerjate kasvukiirused (vastavalt 6,9 cm/aastas ja 6,5 cm/aastas; Silm et al, 2017). Viimase viie aasta jooksul on Võrtsjärve keskmiselt asustatud 49 klaas- ja 5 ettekasvatatud angerjat järvepinna hektari kohta. Brämick et al (2016) leiavad oma uurimistöös, et asustusmahud alla 50 is./ha kohta, ei mõjuta oluliselt suremust ega ka isaste isendite domineerimist angerjapopulatsioonis. Ka on Võrtsjärve toidubaas angerjat soosiv. Erinevate surusääsklaste arvukus Võrtsjärve põhjaloomastikus moodustab üle 60% kõigist uuritud rühmadest (Kangur et al 2003). Üle kogu järve leidub toiduks sobivat peenkala (särg, kiisk, ahven jne). Ka on Eesti Maaülikooli teadlaste poolt kindlaks tehtud angerja võimalik väljaränne Võrtsjärvest läbi Narva Hüdroelektrijaama turbiinide (Järvalt et al, 2010). Eesti territoorium on jagatud kahte angerjamajandusüksusesse – Narva jõe vesikond (millesse kuulub ka Võrtsjärv) ning Lääne-Eesti vesikond (Joonis 1). Tulenevalt Euroopa Liidu Nõukogu määruse nr 1100/2007 artiklist 9 tuleb angerjavaru olukorrast majandusüksuses anda parim olemasolev hinnang ning võimalikult täpsed andmed. Võrtsjärve angerjavaru hinnati eelnevatel aastatel märgistamise-tagasipüügi meetodil. See tähendab, et populatsioonist eralatakse juhuslikud isendid (keskmiselt 100 isendit aastas), mis märgistatakse Carlin (Carlin, 1955) tüüpi märgisega. Märgistatud isendid lastakse tagasi populatsiooni ning ning mingi osa püütakse tõenäoliselt neist uuesti kinni. Varu arvutamiseks kasutakse järgmist valemit: N=(M+1)*(C+1)*(R+1)-1 kus märgistatud kalad (M) ja populatsiooni suurus (N) on võrdses suhetes märgistatud kaladega, mis olid uuesti kinni püütud (R) ja saagiga (C). Probleem seisneb aga asjaolus, et ametlik püügistatistika on tugevalt allahinnatud ning ka märgistatud kaladest teatamine on sageli väga lünklik. Kuigi metoodika iseenesest on angerjavaru hindamiseks igati sobilik, on see paraku Võrtsjärvel eelmainitud põhjustel liialt ebatäpne. Antud projekti eesmärk oli saada võimalikult täpsed andmed angerja arvukuse kohta Võrtsjärves ning kasutada neid andmeid angerjavaru ning hõbeangerjte väljarände hindamisel.

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