A generic recipe for modelling lake food web dynamics ... · Keynote presentation Anna Kuparinen anna.k.kuparinen@jyu.ﬁ University of Jyväskylä, Finland Over the past two decades,

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14th International Coregonid Fishes SymposiumJyväskylä, Finland, 22–26 June 2020

A generic recipe for modelling lake food web dynamics: case studies onlife-history changes, environmental stochasticity, stocking and invasive species

Keynote presentation

Anna [email protected]

University of Jyväskylä, Finland

Over the past two decades, community ecologists have successfully solved many long-standing ques-tions regarding the structure, stability and complexity of food web dynamics using the allometrictrophic network modelling approach (ATN). Later, ATN has also proven successful to describe sea-sonal plankton dynamics in Lake Constance (Bodensee). In my talk, I will describe the fundamentalbiological foundation of the ATN approach and a generic way to parameterize complex feeding inter-actions. The theory will be followed by case studies that illustrate how the modelling tool can be usedto explore ecosystem consequences of fish life-history changes, enhanced whitefish stocking and theways in which environmental noise affect the food web dynamics. I will also demonstrate how thesame modelling approach has been applied to another lake system, to study the ecosystem impacts ofan invasive species.

∗Presenting author

Biology, ecology & population dynamics Oral presentation

Identifying the early-life history survival bottleneck in Lake Erie’s Lake Whitefish (Coregonusclupeaformis) population

∗Zachary Amidon 1, Robin DeBruyne 1, Edward Roseman 2, Christine Mayer 1, Alexis Sakas 3

1University of Toledo, USA2United States Geological Survey Great Lakes Science Center, USA

3The Nature Conservancy, USA

In recent years Lake Erie’s Lake Whitefish commercial landings have declined with few new recruits (age-3)in the fishery. To narrow down the life stage where a survival bottleneck may be occurring, Lake Whitefishwere sampled for abundance at egg, larval, and juvenile stages. In the fall of 2016, 2017, and 2019, eggs weresampled at 35 locations throughout the western basin. Post-hatch pelagic larvae were collected weekly from2017-2019 at 27 locations and abundances compared with similar data from 1995-1998. Fall age-0, age-1, andage-2 juvenile abundances from 1990-2019 were taken from the Ohio Department of Natural Resource fall trawlsurveys. Eggs were collected throughout the western basin, indicating that available spawning habitat is likelynot limited. Larval abundances in 2017-2019 were of the same magnitude as 1995-1998, a time when adultLake Whitefish were recruiting to the fishery, indicating that contemporary Lake Whitefish embryos survivedto the pelagic larval stage with potential to recruit to older age classes. Comparisons of juvenile abundancessuggests that cohort strength may be set by fall age-0. Our results suggest a recruitment bottleneck likely occursduring or after the pelagic larval stage and before fall age-0.


Shift from plankton to benthos in the diet of vendace, Coregonus albula, innorthern regions

∗Nadezhda Berezina 1, Elena Zubova 2, Alexandra Strelnikova 3, Alexey Borovskoy 4

[email protected] Institute of the Russian Academy of Sciences, St. Petersburg, Russia

2Institute of the Industrial Ecology Problems of the North KSC RAS, Apatity, Russia3Papanin Institute for Biology of Inland Waters, Russian Academy of Sciences, Borok, Russia

4Polar Branch of the Federal State Budgetary Institution ”VNIRO”, Arkhangelsk, Russia

The diet of vendace, Coregonus albula (10-25 cm of the total length), was studied in subarctic lakes:small Lake Krivoe and a large Lake Imandra in 2011-19 and compared with its feeding habits in bo-real Lake Pleshcheevo and Rybinsk Reservoir. Vendace from lakes Krivoe and Imandra preferred toconsume benthic macroinvertebrates, but their contribution to the diet varied seasonally and relatedto fish length. In Lake Krivoe, amphipods contributed >50% in the total mass of the stomach contentduring summer, but up to 50% for mollusks and 25% of cladocerans in autumn. In Lake Imandravendace fed on chironomids (75% for >15-cm fish) and bivalve and gastropod mollusks. The dietof another northern form, C. sardinella marisalbi (15-21 cm), from the Pechora River basin based oninsect adults (Simulidae, 73%) and larvae (Trichoptera, 24%). In contrast to the northern areas, plank-tonic crustaceans (Copepoda, Cladocera) were the main food items for C. albula in boreal lakes whilebenthic animals occurred occasionally. In the Rybinsk Reservoir, pelagic vendace fed on planktoniccladocerans, but the coastal part of the fish population consumed also amphipods. Study confirmsa high importance of omnivory in vendace diet with increasing contribution of benthic sources innorthern lakes.



Density-dependence and human activities as key drivers of whitefish growth in Lake Geneva

∗Chloé Goulon, Jean Guillard, Orlane AnnevilleUMR CARRTEL INRAE-University of Savoie Mont Blanc, France

Whitefish (Coregonus lavaretus), autochtonous in Lake Geneva, play an important role in the cultural heritage,local economy and in the ecosystem functioning. Eutrophication greatly reduced whitefish catches in the mid-dle of 20th century; with the improvement of water quality, population started to recover in the middle of1990s. Catches reached a record level of over 900 tons in 2014 then dropped significantly. The understandingof population fluctuations is a central goal of population ecology and fish management. Individual growth isa key demographic parameter and variability can be driven throw density-dependent processes and environ-mental conditions, including temperature that increased during the recent decades. The objective of this studyis to analyse long-term whitefish growth dynamics and to identify the main factors involved in the observedchanges. The relative importance of density-dependent (i.e competition) and density-independent processes(water temperature, trophic resources and interspecies interaction) in the observed evolution was analysed.From the beginning of the population recovering to the middle of the 2000s, temperature mainly contributedin growth changes; thereafter, competition became the main driver. Our results indicate that density-dependentprocesses and human activities are important drivers in whitefish growth fluctuation and consequently in white-fish dynamics in Lake Geneva.

Biology, ecology & population dynamics Poster session

Bet-hedging trait of multiple-batch spawning under fishing pressure

∗Sara Hocevar 1, Jeffrey A. Hutchings 2, Anna Kuparinen 1

1University of Jyväskylä, Finland2Dalhousie University, Canada

Under variable environmental conditions, natural selection tends to favour the evolution of risk-managing life-history strategies. These are essential for populations to endure uncertainties and maximize individual fitness.One of these evolved strategies is multiple-batch spawning, a trait common to fishes that ’hedge their bets’,by distributing the risk to their offspring on a temporal and spatial scale. Given that the fitness benefits of thetrait increase with female body size, size-selective fishing pressure could hinder the security that bet-hedging,in the form of multiple-batch spawning provides, and may strip the population of its security mechanism.By applying an empirically and theoretically motivated eco-evolutionary mechanistic model, we simulatedmultiple-batch and single-batch spawning phenotypes and exposed them to varying levels of environmentaland fishing stochasticity. We explored whether fishing mortality alters the life-history traits and fitness of eachspawning strategist and, if so, how these alterations might affect population dynamics. Our findings illustratehow the feedbacks of a bet-hedging strategy illuminate the necessity of accounting for spawning strategy whenmanaging broadcast-spawning fish stocks.


Vendace disperse eggs widely during spawning

∗Juha Karjalainen, Markus Tuloisela, Kristiina Nyholm, Timo J MarjomäkiUniversity of Jyväskylä, Finland

Depending on their reproductive strategy, different fishes aggregate or disperse eggs and larvae in their re-productive habitat. Vendace (Coregonus albula) yolk-sac larvae are known to occur widely around the lakeafter hatching, but it has been unclear, where are exact spawning and egg incubation locations in the boreallakes. Egg and larval densities of vendace were studied in Lake Konnevesi, Finland, to clarify the lake-widespawning strategy of this commercially important species. In October 2019, 1-2 weeks prior to spawning 500egg samplers were installed according to stratified sampling design to the potential spawning areas around thestudy lake. Sampling plots were same as the regular monitoring plots of newly-hatched larvae of coregonids inthe lake. Fertilized vendace eggs were found in 18 of the 20 sampling plots. The mean fertilization rate was84.2% (SD 24.5) and the mean density of eggs 70.8 (SD 110.8) eggs per square metre. The results confirmthe hypothesis that vendace disperse their offspring lake-widely already during spawning. High egg densitiesin autumn have observed in the same areas as the high larval densities in spring. The reproduction strategy ofvendace aim to stabilise the high environmental and temporal fluctuation in their habitats.


Who’s Who? Identifying three coregonine species at the larval stage

∗Hannah Lachance 1, Amanda Ackiss 2, Wes Larson 3, Verena Lucke 4, Mark Vinson 5, Jason Stockwell 6

1University of Vermont/USGS/NOAA, USA2Wisconsin Cooperative Fishery Research Unit, University of Wisconsin Stevens Point, USA3Wisconsin Cooperative Fishery Research Unit, University of Wisconsin Stevens Point;, USA

4University of Vermont/Woods Hole Oceanographic Institution, USA5USGS, USA

6University of Vermont, USA

Coregonines, including cisco (Coregonus artedi), kiyi (Coregonus kiyi), and bloater (Coregonus hoyi), area focus for prey fish restoration efforts throughout the Great Lakes. However, fundamental questions aboutcoregonine ecology remain. For example, we have limited knowledge about how to identify different speciesfrom one another during the early life stages, which makes coregonine species difficult to study at the eggand larval stage. To increase the probability for success in restoration efforts, current and future research needto integrate traditional and novel approaches to better understand coregonine populations at each life stage.Therefore, we sampled larval coregonines throughout the Apostle Islands of Lake Superior from hatch in Mayuntil late July 2018. We used genomic sequencing to identify 197 larvae as either cisco, bloater, or kiyi. Therewas a temporal difference in estimated hatch dates for each species yet no significant spatial differences in whereeach species was found. The larval demographic characteristics of each species was assessed and revealed thatlength ranges, growth rates, yolk sac condition, and effective population size varied among species. Geneticdiversity within each species appears high. The results from our study help advance our understanding of theimportant early life stages of coregonines.

Biology, ecology & population dynamics Poster session

Tendency for two-year cyclicity (2YC) in Finnish vendace (Coregonus albula) populations: arobust meta-analysis

∗Timo J. Marjomäki 1, et al. 2

1University of Jyväskylä, Finland2JYU, Finland

Significant support for the hypothesis of two-year cyclicity in vendace abundance has been found in in timeseries from certain Finnish vendace abundance indices. Yet, doing correlative analysis for several individualdata sets separately is prone to risk of finding coincidental spurious correlations. To gain further understandingon the veracity of the 2YC hypothesis, a simple meta-analysis was performed by combining the data sets fromdifferent Finnish lakes, developing a robust indicator for 2YC and applying Fisher’s combined probabilitytest fro hypothesis testing. Significant (p < 0.05) support for the tendency for two-year cyclicity in vendaceabundance was found. The potential reasons for this tendency are discussed.


Lifting the vendace (Coregonus albula) on the table: mortality, growth and reproduction indifferent life-stages at low and high population densities

∗Timo J. Marjomäki 1, Pentti Valkeajärvi 2, Juha Karjalainen 1

1University of Jyväskylä, Finland2Not applicable, Finland

The life-cycle of vendace is analysed in life-table context. The level of mortality of immature and mature sub-population as well as growth and reproductive output of females required for population stability are determinedfor both high and low population densities. The capability of real populations for the required compensatorychange in these population parameters at low spawner density is discussed based on the data from populationsthat have experienced long periods of low density. The implications of the results for fisheries managementand risk of extinction due to anthropogenic stressors, such as increased predation due to warming or extensivestocking, are discussed.


Is whitefish (Coregonus wartmanni) seasonal diet resistant to changes, causedby re-oligotrophication and invasive species in Lake Constance?

∗Ziga Ogorelec 1, Sarah Gugele 2, Dietmar Straile 1, Alexander Brinker 3

[email protected] Institute, University of Konstanz, Germany

2Fisheries Research Station of Baden-Württemberg, Germany3Fisheries Research Station of Baden-Württemberg, Germany

Whitefish (Coregonus wartmanni) is the most important fish species for the local fishery in LakeConstance and presumably exerts a strong predation pressure on the zooplankton community. Due tore-oligotrophication (phosphorus value dropped from 80µg/L in the 1970s to below 10µg/L nowa-days), there is lower primary production and the whitefish population dropped in its numbers. A quickand massive spread of invasive three-spined stickleback (Gasterosteus aculeatus) in recent years hasquickly outnumbered whitefish population and in a recent study (Alexander & Vonlanthen, 2016) itrepresented 96% of a number and 28% of the biomass of all pelagic fish. Together with zooplanktoncommunity changes towards the domination of smaller species like Daphnia cucullata, the reversibil-ity of whitefish diet and growth in re-oligotrophication period is under question. To achieve theresolution of diet changes, we analyzed the stomach content of adult whitefish monthly from May2017 till May 2018 and compare them with previous studies.



Impact of the invasive three-spined stickleback (Gasterosteus aculeatus) on the native pelagicwhitefish (Coregonus wartmanni) spawners in Upper Lake Constance

∗Roland Roesch, Tyrell DeWeber, Mark Schumann, Jan BaerFisheries Research Station Baden-Württemberg, Germany

A massive increase in the pelagic population of non-endemic three-spined sticklebacks, Gasterosteus aculeatusL. in Lake Constance has coincided with drastic declines in fishery yields. Data from monthly monitoring ofpelagic whitefish (Coregonus wartmanni Bloch, 1784) and the annual spawning fishery were used to compareweight-at-age, abundance, gonadosomatic index, spawner catch and egg mass during spawning season for yearsbefore (< 2013) and after the invasion (2013–2019). In addition, the yearly energy content of spawners after theinvasion was measured. Nearly all parameters showed a negative trend, implying direct effects of sticklebackpresence on pelagic whitefish, including interspecific competition for food leading to reduced growth, energy,survival and egg quality. In conclusion, this study shows that the invasion of sticklebacks had significant effectson the population structure of the economically important whitefish, resulting in reduced yield and a hard futurefor the last remaining fishermen.


Drivers of year-class variation of vendace (Coregonus albula (L.)) revisited: roles ofdensity-dependent and density-independent factors in Lake Pyhäjärvi in 1971-2018

∗Jouko Sarvala 1, Harri Helminen 2

1Department of Biology, University of Turku, Finland2Centre for Economic Development, Transport and the Environment for Southwest Finland, Finland

Wide fluctuations in year-class strength are typical for most populations of the small coregonid vendace (Core-gonus albula). A number of density-dependent and density-independent factors causing this variation havebeen identified. Long-term data (1971-2018) of the vendace population in Lake Pyhäjärvi, southwest Finland,have been useful in evaluating the importance of different factors. In 1971-1986, time series analysis of ven-dace recruitment in Pyhäjärvi showed a two-year cycle of alternating strong and weak year-classes, consistentwith the hypothesis of asymmetric intraspecific competition between age groups, abundant young-of-the-yearleading to inferior egg quality of the adults. Exceptional weather conditions disrupted the two-year cycle,causing recruitment failures, and from 1990 to 1999 year-classes remained small because spawning stock waskept reduced by overfishing. From 2000 onwards the oscillations were re-established, but with different phaseand at lower mean level. Throughout the time series, unpredictable weather conditions caused confoundingvariation through multiple paths, affecting several life stages. During the two-year cycle, vendace recruitmentin Pyhäjärvi was predictable from the abundance of the previous year-class, water temperature in spring, andabundance of predators. Here we compare predictions from this model with observed year-class strength, andexplore which factors and mechanisms might explain the deviations.


Vendace (Coregonus albula) 50 years in Lake Inari – What has changed

∗Erno SalonenLuke Inari, Finland

Lake Inari is a subarctic, oligotrophic, regulated lake in northern Finland, connected via the River Pasvik tothe Arctic Ocean. A new coregonid species, vendace (Coregonus albula), was introduced into the watershedin the 1960’s and gradually established a population in the lake. Hence during the last 50 years the vendacehas been included in the lake ecosystem. The vendace has shown boom and bust development, with the annualcatch reaching 300 tonnes in 1989. Compared to this peak level the vendace catch has declined and stabilizedto a very low level already during the last 25 years’. In this speech, I will review some of the huge changesand impacts happened both independently and dependently of the vendace presence in the lake: i) Climaticand hydrological changes ii) Lake ecosystem changes – due to vendace iii) Fishing culture changes – due tovendace iv) Role of vendace: catch itself and prey for predatory fishes and v) Life history changes of vendaceitself


Features of hearing in Baikal coregonid fishes

∗Yulia Sapozhnikova 1, Polikarp Gasarov 1, Mikhail Makarov 1, Viktor Kulikov 2, TuyanaSidorova 1, Anastasia Koroleva 1, Vera Yakhnenko 1, Olga Glyzina 1, Marina Tyagun 1, Lyubov

Sukhanova 1

[email protected] Institute SB RAS, Russia

2Skolkovo Institute of Science and Technology, Institute of Automation and Electrometry SB RAS,Russia

The main goal of this study is the comparative auditory structure and function in different habitats ofcoregonid fishes to test correlations between habitat and hearing. We have determined and examinedthe different ciliary bundle types, their distribution in the macula sacculi, ranges of maximum audi-tory sensitivity of fish, as well as their auditory threshold. Our work demonstrates that the hearingfeatures are more constrained by the phylogeny of these fish. Nevertheless, inside these fish groups,there is a place to be insignificant ecological heterogeneity at the comparative studies of the audi-tory system adaptations. The presence of these different specifications can be critically important fortheir behavioral response and activity. Particularly, there are correlations between the ultrastructureof macula sacculi, fish acoustic behavior and the environment, which implies some ecological andmorphological plasticity in coregonid fishes of Lake Baikal. This work was performed at the LIN SBRAS Collective Instrumental Center using the unique scientific installation Experimental FreshwaterAquarium Complex for Baikal Hydrobionts at LIN SB RAS supported by RFBR and the Governmentof Irkutsk Region, projects Nos. 17-44-388081 r-a and 17-44-388106 r-a, and within the frameworkof the State Task No. 0345-2019-0002 (AAAA-A16-116122110066-1).



Spawning behavior of whitefish

∗Sergey Semenchenko, Natalya SmeshlivayaTyumen Branch of VNIRO, Russia

Coregonus migratorius, C.peled, C.tugun, C.pidschian, C.muksun have been used for visual observation, pho-tography, video and audiorecording of spawning in facilities for gathering eggs by ecological method. Spawn-ing of each species takes place in autumn for 2-3 weeks every day in nighttime. The following phases can bedistinguished in the spawning process: courtship, an act of spawning and rest, which are frequently repeatedduring night. Spawning is an act for a couple, in combination male-female or male-male, taking place eitherin water depth or on surface. Males are initiators. Spawning act is a rhythmic impingement of fish bodieswith parallel movement and synchronous excretion of reproductive products. Vertical, horizontal and com-bined types of spawning can be distinguished in terms of prevailing couple motion. Frequency of such types isspecies-specific. Once the act of spawning is over, fish can swim up and topple over on the surface. A male inthe pair is shifted ahead of a female for one head length. Male hits its tail stalk in the back of female abdomen.Depending on fish size, spawning act continues for 0.3-3sec with a path of 0.3-2m. One female participates in20-80 spawning acts for 1-3 nights. Eggs cannibalism has been noticed.


Recovering Inconnu, Stenodus leucichthys, on Great Slave Lake: The effectiveness of marineprotected areas, harvest control rules, habitat management and non- quota limitations in the

rehabilitation of depleted resources.

∗Ross Tallman, M. Yamin Janjua, Melanie Van Gerwen Toyne, Lauren WiensFisheries and Oceans Canada, Canada

Inconnu, Stenodus leucichthys, stocks have been subject to commercial and subsistence fishing on Great SlaveLake, Canada from the late 1940s to the present. They are part of larger multispecies fishery principallyfocussed on Lake Whitefish, Coregonus clupeaformis and Lake Trout, Salvelinus namaycush. Inconnu areconsidered the most valuable Coregonid per kilogram harvested and conservation is an important concern.Some stocks have been extirpated while others such as the Buffalo River stock hover close to collapse. Toconserve Inconnu a variety of measures have been implemented including mesh size changes, marine protectedareas, and formal and informal quota regulations. Recently, genetic techniques such as micro-satellite mixedstock analysis and environmental DNA have been applied to determine the status of stocks. We review theeffectiveness of the management measures and note directions for the future. In general, closed areas havebeen moderately effective in recovering Inconnu stocks but it also appears that market forces may overwhelmnon-quota restrictions applied to the fishery.


FISHING TRIGGERS TROPHIC CASCADE IN TERMS OF VARIATION, NOTABUNDANCE

∗Silva Uusi-Heikkilä, Tommi Perälä, Anna KuparinenUniversity of Jyväskylä, Finland

Trophic cascade studies that rely on linear food chains may not realistically represent complex food webs.Further, trophic cascades are almost exclusively measured as biomass averages whereas measures of biomassvariation have remained unexplored. We adopt a multi-dimensional view on trophic cascades by modeling thempropagating across a complex food web and include a measure of biomass variation in addition to a measure ofbiomass average. We examined whether two different fishing strategies removing different predatory speciesfrom the ecosystem induce trophic cascades and whether the cascades differ from each other. The two differentfishing strategies did not trigger a traditional trophic cascade propagating across the food web, as measured inbiomass averages. Instead, both fishing strategies triggered a variation cascade that propagated across the foodweb including fish, zooplankton and phytoplankton. In fisheries that removed a large amount of top-predatoryand cannibalistic fish, the biomass oscillations started to decrease shortly after fishing was started while infisheries that mainly targeted large planktivorous whitefish, the biomass oscillations did not show any sign ofstabilizing. Predicting under what fishing strategy and at what rate trophic cascades might occur could help usto anticipate, and potentially prevent, the cascading effects of fishing.


Drift of whitefish (Coregonus lavaretus L.) larvae in a tributary river of the Hallstättersee

∗Josef Wanzenböck, Tobias GrossgasteigerResearch Department for Limnology Mondsee, University of Innsbruck, Austria

The fish community of Hallstättersee is dominated by European whitefish (Coregonus lavaretus). Besides thecommonly used spawning habitats within lakes, mostly in shallow littoral areas, potamodromous spawningmigrations are also known in several (sub-) populations of whitefish, e.g. in Hallstättersee. We investigated thedrift of newly hatched larvae of whitefish in the major tributary of Hallstättersee during seven weeks in spring2019 using drift nets. We used known numbers of larvae marked with alizarin red to spike larval fish drift and toimprove quantitative assessments. Furthermore, the distribution of larvae within the lake was investigated usingan established push net method. Driftnet catches of larval whitefish were generally lower compared to similarcatches done in 1999. The diel and seasonal (February, March, April) patterns of larval drift were analyzed.


Whitefish Coregonus lavaretus in the upper reaches of the Pasvik River (Murmansk Region,Russia)

∗Zubova Elena, Kashulin Nikolay, Terentjev PetrInstitute of the Industrial Ecology Problems of the North of the Kola Scienсe Center of the Russian

Academy of Sciences, Russia

The ichthyofauna in the upstream of the Pasvik River was investigated. Whitefish dominated in catches andwas represented by individuals with the number of gill rakers from 19 to 34. It is known that the whitefish ofthe Inari-Pasvik system has from 16 to 40 gill rakers with a pronounced bimodal distribution according to thisfeature, which makes it possible to distinguish sparsely- and densely-rakered morphs. However, whitefish inthe upstream of the Pasvik have no bimodal distribution. In appearance the rakers on the first branchial arch aredifficult to attribute to an individual in some form. The relative length of the largest gill raker in the whitefishdid not depend on the number of rakers on the branchial arch and varied from 8.9 to 18.8%. Research in theagricultural district of Rayakoski in 2002-2004 showed a wider range of the number of whitefish rakers withoutbimodality in their distribution. Perhaps the convergence of the trait is associated with the hybridization ofwhitefish in the upper reaches of the Pasvik River. The hybridization reasons are: migration restriction due todam construction; reduction of whitefish habitats, due to the vendace introduction, which actively displaces thedensely-rakered whitefish from the pelagial.

Documents

A generic recipe for modelling lake food web dynamics ... · Keynote presentation Anna Kuparinen anna.k.kuparinen@jyu.ﬁ University of Jyväskylä, Finland Over the past two decades,