Positioning of aquatic animals based on time-of-arrival and random walk models using YAPS (Yet Another Positioning Solver)

Aquatic positional telemetry offers vast opportunities to study in vivo behaviour of wild animals, but there is room for improvement in the data quality provided by current procedures for estimating positions. Here we present a novel positioning method called YAPS (Yet Another Positioning Solver), involving Maximum Likelihood analysis of a state-space model applied directly to time of arrival (TOA) data in combination with a movement model. YAPS avoids the sequential positioning-filteringapproach applied in alternative tools by using all available data in a single model, and offers better accuracy and error control. Feasibility and performance of YAPS was rigorously tested in a simulation study and by applying YAPS to data from an acoustic transmitter towed in a receiver array. Performance was compared to an alternative positioning model and proprietary software. The simulation study and field test revealed that YAPS performance was better and more consistent than alternatives. We conclude that YAPS outperformed the compared alternative methods, and that YAPS constitute a vast improvement to currently available positioning software in acoustic telemetry. Additionally, in contrast to vendor-supplied solutions, YAPS is transparent, flexible and can easily be adapted and extended for further improvements or to meet study specific requirements such as three-dimensional positioning.publishedVersio

Speciation reversal in European whitefish (Coregonus lavaretus (L.)) caused by competitor invasion

Invasion of exotic species has caused the loss of biodiversity and imparts evolutionary and ecological changes in the introduced systems. In northern Fennoscandia, European whitefish (Coregonus lavaretus (L.)) is a highly polymorphic species displaying adaptive radiations into partially reproductively isolated and thus genetically differentiated sympatric morphs utilizing the planktivorous and benthivorous food niche in many lakes. In 1993, Lake Skrukkebukta was invaded by vendace (Coregonus albula (L.)) which is a zooplanktivorous specialist. The vendace displaced the densely rakered whitefish from its preferred pelagic niche to the benthic habitat harbouring the large sparsely rakered whitefish. In this study, we investigate the potential influence of the vendace invasion on the breakdown of reproductive isolation between the two whitefish morphs. We inferred the genotypic and phenotypic differentiation between the two morphs collected at the arrival (1993) and 15 years after (2008) the vendace invasion using 16 microsatellite loci and gill raker numbers, the most distinctive adaptive phenotypic trait between them. The comparison of gill raker number distributions revealed two modes growing closer over 15 years following the invasion. Bayesian analyses of genotypes revealed that the two genetically distinct whitefish morphs that existed in 1993 had collapsed into a single population in 2008. The decline in association between the gill raker numbers and admixture values over 15 years corroborates the findings from the Bayesian analysis. Our study thus suggests an apparent decrease of reproductive isolation in a morph-pair of European whitefish within 15 years (. 3 generations) following the invasion of a superior trophic competitor (vendace) in a subarctic lake, reflecting a situation of ‘‘speciation in reverse’’

Invader population speeds up life history during colonization

We explore the long-term developments in population biology and life history during the invasion and establishment of the fish species vendace Coregonus albula in a subarctic watercourse by comparing life-history traits and molecular genetic estimates between the source and the colonist population. The two populations exhibited highly contrasting life-history strategies. Relative to the source population, the colonist population was characterized by slower somatic growth rates, earlier sexual maturation at smaller individual size, higher mortality rates and a shorter life span. The two populations could also be significantly discriminated by the genetic markers. Limited founder effects were detected from heterozygote deficit and reduced allelic richness in the colonist population, but both populations were associated with relatively high genetic diversity. The study reveals that the invasion into a new environment induced large changes in life-history strategy, with typical r-selected traits being more prominent in the colonist than in the source population. We discuss the mechanisms that may explain the observed life-history differences between the source and the colonist population, and argue that the accelerated life history of the colonist population represents an adaptive pioneer strategy aimed at fast population increase during colonization and establishment

Migration of Atlantic salmon post-smolts in a fjord with high infestation pressure of salmon lice

Understanding Atlantic salmon Salmo salar post-smolt coastal migration behaviour is crucial for predicting their exposure to ecological challenges such as the parasite salmon louse Lepeophtheirus salmonis. We compared the migration of acoustically tagged, hatchery-reared Atlantic salmon post-smolts of wild and domesticated origins from the inner, middle and outer part of a 172 km long aquaculture-intensive fjord in western Norway. Additionally, we examined if the timing of the release or treatment with an anti-parasitic drug (prophylaxis) altered migratory behaviour. We found no significant differences in mean progression rates among the 3 release locations, among genetic groups or between treatments (range: 11.5−16.9 km d−1). However, individual variation in progression rates and migratory routes resulted in large differences in fjord residence times (range: 2−39 d). Ocean-current directions during and after release affected swimming speed, progression rate and route choice, and for most post-smolts, swimming speeds were much higher than their progression rates out of the fjord. The predicted lice loads based on lice intensity growth rates on smolts held in sentinel cages throughout the fjord indicated that individuals taking >10 d to exit the fjord in periods with high infestation pressure are likely to get lethally high sea-lice infestations. We conclude that, as migratory routes of S. salar post-smolts are hard to predict and migration times can stretch up to over a month, it is important to develop aquaculture management that keeps salmon lice levels down along all potential migration routes and during the full potential migratory period. Migratory behaviour · Salmo salar · Lepeophtheirus salmonis · Acoustic telemetry · Management · Fish farming · ParasitepublishedVersio

Lagesilda i Pasvikvassdraget : langtidseffekter av en biologisk invasjon

Pasvikvassdraget har siden 1991 vært gjenstand for omfattende økologiske studier i regi av Ferskvannsøkologisk faggruppe ved Universitetet i Tromsø. Undersøkelsene har særlig vært rettet mot å undersøke effektene av at lagesilda, en fremmed fiskeart for Nord-Norge, kom inn i vassdraget på slutten av 1980-tallet. For å få en grundig forståelse av økologien i vassdraget har studiene også omfattet andre viktige fiskearter, krepsdyrplankton og bunndyr. Samtidig har vi hatt et nært samarbeid med russiske forskere angående tungmetallforurensing fra de russiske Nikel-smelteverkene, og med finske forskere gjennom sammenlignende studier med fiskebestandene i Enaresjøen og andre innsjøer i den finske delen av vassdraget. Totalt sett har dette resultert i mye ny og interessant kunnskap om Pasvikvassdraget; kunnskap som bl.a. er dokumentert gjennom 36 internasjonale publikasjoner, 22 fagrapporter og populærvitenskapelige publikasjoner, fire doktorgradsavhandlinger og 12 masteroppgaver (se Appendiks 2 for detaljer). I perioden 2008 – 2011 har langtidsstudiene i Pasvikvassdraget vært fulgt opp gjennom et prosjekt finansiert av Norges forskningsråd (Miljø-2015 programmet; prosjektnr. 183984/S30). Denne rapporten er en populærvitenskapelig sammenfatning av kunnskapen som har fremkommet gjennom dette prosjektet, der det særlig har vært lagt vekt på de langsiktige effektene av lagesildas invasjon og viktige forvaltningsmessige implikasjoner

Movement diversity and partial sympatry of coastal and Northeast Arctic cod ecotypes at high latitudes

Movement diversity within species represent an important but often neglected, component of biodiversity that affects ecological and genetic interactions, as well as the productivity of exploited systems. By combining individual tracking data from acoustic telemetry with novel genetic analyses, we describe the movement diversity of two Atlantic cod Gadus morhua ecotypes in two high-latitude fjord systems: the highly migratory Northeast Arctic cod (NEA cod) that supports the largest cod fishery in the world, and the more sedentary Norwegian coastal cod, which is currently in a depleted state. As predicted, coastal cod displayed a higher level of fjord residency than NEA cod. Of the cod tagged during the spawning season, NEA cod left the fjords permanently to a greater extent and earlier compared to coastal cod, which to a greater extent remained resident and left the fjords temporarily. Despite this overall pattern, horizontal movements atypical for the ecotypes were common with some NEA cod remaining within the fjords year-round and some coastal cod displaying a low fjord fidelity. Fjord residency and exit timing also differed with spawning status and body size, with spawning cod and large individuals tagged during the feeding season more prone to leave the fjords and earlier than non-spawning and smaller individuals. While our results confirm a lower fjord dependency for NEA cod, they highlight a movement diversity within each ecotype and sympatric residency between ecotypes, previously undetected by population-level monitoring. This new knowledge is relevant for the management, which should base their fisheries advice for these interacting ecotypes on their habitat use and seasonal movements.publishedVersio

Environmental monitoring of fish in the Paz watercourse

Appendix 7/15 of the publication "State of the environment in the Norwegian, Finnish and Russian border area 2007" (The Finnish Environment 6/2007)

Seasonal habitat use of three predatory fishes in a freshwater ecosystem

To understand the spatiotemporal overlap in the habitat use of sympatric predators, we studied longitudinal activity and reservoir section and depth use of pike (Esox lucius), pikeperch (Sander lucioerca) and catfsh (Silurus glanis) in the Římov Reservoir, using an autonomous telemetry system for 11 months. We found signifcant diferences among these species in studied parameters that varied considerably over tracked period. Pike consistently used the same sections of the reservoir, while pikeperch and catfsh frequently visited a tributary during the warm season (late spring and early autumn), and moved closer to the dam during the cold season (late autumn to early spring). Pike longitudinal activity was highest in the cold season, pikeperch in the warm season, and catfsh activity peaked in both seasons. Overlap in the depth use among species was higher in the warm season, when all species used the upper layer of the water column, and lower in the cold season, when pikeperch and catfsh used deeper areas. These results demonstrated overlay and temporal variation of habitat use among these predators, as well as potential spatiotemporal space for their direct ecological interactions. Acoustic telemetry · Predators · Habitat use · Movement ecology · Winter ecologypublishedVersio

Evaluering av tiltak for å fremme bærekraftig sameksistens mellom fiskeri og havbruksnæring (ProCoEx)

Fiskeri- og havbruksnæringen har felles interesser i kystnære farvann, næringene må i størst mulig grad se nytten i å samarbeide om bruken av områdene uten urimelig forringelse av felles næringsgrunnlag. Økt tilstedeværelse av havbruk vil føre til økte interessekonflikter i kystnære farvann. Mye erfaringsbasert viten ligger til grunn for denne situasjonsbeskrivelsen, og de senere år har området også vært tema for forskningsbaserte tilnærminger. Målsettingen med dette prosjektet er å skaffe til veie kunnskap som kan danne grunnlag for utvikling av tiltak for å bedre sameksistens mellom næringene med tilknytning til kystsonen, hovedsakelig fiskeri- og havbruksnæringene. Vesentlig i denne sammenhengen er å redusere negative og forsterke positive sider ved bruken av felles arealer. Siden erfaringene og kunnskapen er mangelfulle, og sameksistensen i noen grad preges av påstander som ikke er dokumenterte, utgjør en oppsummering av tilgjengelig kunnskap rundt tema en viktig del av prosjektet. Vi har dokumentert at filétkvaliteten på villfisk som har spist laksefôr over noe tid er påvirket negativt, men at denne effekten er begrenset om fangsten håndteres optimalt. Hvilket redskap, og hvordan disse benyttes, har også betydning for kvaliteten. Vi har også belyst mulige effekter på reproduksjon som følge av økt tilgang på laksefôr hos villfisk som beiter ved oppdrettsanlegg