ALBERT — All Library Books, journals and Electronic Records Telegrafenberg

1

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Planktivory and diet-overlap of densely rakered whitefish (Coregonus lavaretus (L.)) in a subarctic lake (2005)

Kahilainen, K. ; Alajärvi, E. ; Lehtonen, H.

Oxford, UK : Munksgaard International Publishers

Ecology of freshwater fish 14 (2005), S. 0

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ISSN: 1600-0633

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition

Notes: Abstract – Three sympatric whitefish (Coregonus lavaretus (L.)) forms, one being pelagic and two benthic, segregate available habitat and food resources in subarctic Lake Muddusjärvi, northern Finland. Zooplankton availability in the lake, food composition, diet-overlap and growth of densely rakered (DR) whitefish were examined during June to September to explore the reasons for the small individual size of the pelagic form. DR whitefish used zooplankton as main food item and prey selection followed zooplankton species density proportions in the lake. Zooplankton density and water temperature was highest in July–August. The average lengths of Bosmina spp., Daphnia spp., Calanoida and Cyclopoida in DR whitefish stomach were higher than in zooplankton sample during June–September, except Calanoida in June. Diet-overlap between DR whitefish age groups was high at all months indicating intercohort resource competition. DR whitefish reached sexual maturity at 3 years of age and at the length of 12 cm, after which somatic growth almost ceased. Reason for the small average size and slow growth of DR whitefish were connected to high diet-overlap between age groups and early sexual maturation.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1111/j.1600-0633.2004.00075.x

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2

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Piscivory and prey selection of four predator species in a whitefish dominated subarctic lake (2003)

Kahilainen, K. ; Lehtonen, H.

Oxford, UK : Blackwell Science Ltd

Journal of fish biology 63 (2003), S. 0

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ISSN: 1095-8649

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Biology

Notes: According to logistic regressions derived for pike Esox lucius and burbot Lota lota, the probability of ingesting fishes in Lake Muddusjärvi, northern Finland, was 50% at 19·3 and 22·1 cm LT, whereas Arctic charr Salvelinus alpinus and brown trout Salmo trutta shifted to piscivory at the lengths of 25·7 and 26·4 cm LT. The specialist piscivores, pike and burbot, consumed more prey species and took a wider range of prey sizes than Arctic charr and brown trout. The prey length for all predators increased in relationship to predator length. Whitefish Coregonus lavaretus was the dominant prey species in the lake and in the diet of all the piscivorous species. The whitefish population was divided into three forms, of which the slow-growing, and the most numerous densely rakered whitefish form (DR), was selected by all predator species. This form also had the smallest average size and widest habitat range, utilizing both pelagic and epibenthic habitats. Two sparsely rakered whitefish forms (LSR and SSR) occupied only epibenthic habitats and had lower relative densities than DR. These forms, LSR and SSR, had a minor importance in the diet of predator species.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1046/j.1095-8649.2003.00179.x

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3

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Diel and seasonal habitat and food segregation of three sympatric Coregonus lavaretus forms in a subarctic lake (2004)

Kahilainen, K. ; Malinen, T. ; Tuomaala, A. ; [et al.]

Oxford, UK : Blackwell Science Ltd

Journal of fish biology 64 (2004), S. 0

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ISSN: 1095-8649

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Biology

Notes: Habitat use of three sympatric whitefish Coregonus lavaretus forms was determined using hydroacoustics, pelagic trawling and epibenthic gillnetting in the subarctic Lake Muddusjärvi during the day and night in June, August and September. Whitefish constituted 97% of the numerical catches and whitefish with high number of gill rakers (DR) were the most abundant whitefish form. Forms with low numbers of gill rakers used only epibenthic habitats during both the day and night in all study periods: large whitefish with low numbers of gill rakers (LSR) dwelled mainly at depths 0–10 m, whereas small whitefish with low numbers of gill rakers (SSR) used deeper (〉10 m) habitats. LSR and SSR whitefish consumed mainly benthic macroinvertebrates during all study occasions. The planktivorous DR whitefish used both epibenthic and pelagic habitats, but vertical habitat selection varied both over time of day and season. In June, when light intensity was continuously high, DR whitefish did not perform diel vertical migrations. In August and September, when dark nights were distinguishable, DR whitefish ascended from the bottom to the pelagic at dusk to feed on zooplankton, and descended at dawn. DR whitefish used pelagic habitats only at the lowest light intensities during the night, which was probably related to the high predation risk from brown trout Salmo trutta.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1111/j.0022-1112.2004.00307.x

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4

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Radioactive strontium (85Sr) in marking newly hatched pike and success of stocking (1998)

Vuorinen, P. J. ; Nyberg, K. ; Lehtonen, H.

Oxford, UK : Blackwell Publishing Ltd

Journal of fish biology 52 (1998), S. 0

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ISSN: 1095-8649

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Biology

Notes: Immersion of newly hatched pike fry in an aqueous solution of 1·85 MBq ml−185Sr did not affect their growth or survival over 3 weeks. Cannibal pike fry retained only l.2–3·3% of the 85Sr from their labelled prey. Newly hatched 85Sr-marked fry stocked into two lakes in 3 years were distinguishable from wild fish 4–6 weeks later. Stocked and wild fry grew equally well, and stocked pike survived best where density of wild pike was highest. There was no evidence of increase in density as a result of Stocking.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1111/j.1095-8649.1998.tb00798.x

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5

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Radioactive strontium (85Sr) in marking whitefish [Coregonus lavaretus (L.)] larvae and the dispersal of larvae from river to sea (1992)

Lehtonen, H. ; Nyberg, K. ; Vuoronen, P. J. ; [et al.]

Oxford, UK : Blackwell Publishing Ltd

Journal of fish biology 41 (1992), S. 0

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ISSN: 1095-8649

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Biology

Notes: Anadromous whitefish [Coregonus lavaretus (L.)] yolk-sac larvae were marked with a radioactive strontium isotope, 85Sr. Before marking the method was tested in accumulation-elimination tests using various strontium concentrations. The first-phase effective half-life of 85Sr in yolk-sac larvae was 4 days. The mean 85Sr radioactivity was 81 Bq per larva at the day of release and the half-life of the slow component was 51 days, so the strontium label was easily detected up to 60 days after marking. The larvae were released into the River Simojoki about 12 km upstream from the river mouth and recaptured from early May to the end of July. Marked larvae were found at the river mouth 12–13 days after release, while the last marked fish in the river were found at 16 days. It is likely that all leave the river within 2 to 3 weeks post-hatching. Two months after marking some larvae had attained a distance of 10 km from the river mouth.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1111/j.1095-8649.1992.tb02670.x

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6

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Consequence of habitat segregation to growth rate of two sparsely rakered whitefish (Coregonus lavaretus (L.)) forms in a subarctic lake (2003)

Kahilainen, K. ; Lehtonen, H. ; Könönen, K.

Oxford, UK : Blackwell Science, Ltd

Ecology of freshwater fish 12 (2003), S. 0

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ISSN: 1600-0633

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition

Notes: Abstract – The aim of this study was to explain the growth differences of the two sympatric sparsely rakered whitefish (Coregonus lavaretus (L.)) forms in the subarctic Lake Muddusjärvi by comparing their habitat and food selection to available benthic food resources. The average number of gillrakers was 22.9 for large sparsely rakered whitefish (LSR) and 16.8 for small sparsely rakered whitefish (SSR). LSR dwelled primarily in the littoral zone at depths 〈 10 m, whereas SSR used mostly profundal habitats in depths 〉 10 m. LSR and SSR consumed mainly benthic macroinvertebrates, their abundance, biomass and diversity was highest in the littoral, decreasing towards the profundal. As the individual size of fish increased, LSR was able to shift to larger food items, which were available in the littoral. Possibility of SSR to ontogenetic food shift was scarce in the profundal, where availability of larger benthic macroinvertebrates was low. Because of abundant food resources in the littoral, growth rate of LSR was faster than that of SSR.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1046/j.1600-0633.2003.00029.x

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7

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Brown trout (Salmo trutta L.) and Arctic charr (Salvelinus alpinus (L.)) as predators on three sympatric whitefish (Coregonus lavaretus (L.)) forms in the subarctic Lake Muddusjärvi (2002)

Kahilainen, K. ; Lehtonen, H.

Oxford, UK : Munksgaard International Publishers

Ecology of freshwater fish 11 (2002), S. 0

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ISSN: 1600-0633

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition

Notes: Abstract – Brown trout (Salmo trutta L.) and Arctic charr (Salvelinus alpinus (L.)) use whitefish (Coregonus lavaretus (L.)) as their main prey in the subarctic Lake Muddusjärvi. Brown trout dwelled in littoral and pelagic habitat, whereas Arctic charr lived only in epibenthic habitat. Both species shifted to whitefish predation at a length of 20–30 cm. At this size, brown trout fed on larger whitefish than Arctic charr. Whitefish occur in three sympatric forms, differing in their habitat, ecology and morphology. Both the predators preyed primarily upon the small-sized, densely rakered whitefish form (DR), which was the most numerous whitefish form in the lake. DR used both epibenthic and pelagic habitat, whereas two sparsely rakered whitefish forms dwelled (LSR and SSR) only in epibenthic habitat: LSR in littoral and SSR in profundal areas. Sparsely rakered whitefish forms had minor importance in predator diet.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1034/j.1600-0633.2002.t01-2-00001.x

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Modelling pig sector dynamic adjustment to livestock epidemics with stochastic-duration trade disruptions (2011)

Niemi, J. K., Lehtonen, H.

Oxford University Press

In: European Review of Agricultural Economics

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Publication Date: 2011-11-24

Description: We use a stochastic dynamic programming model to simulate the market implications of alternative foot and mouth disease scenarios in the Finnish pig sector. The model considers the dynamics of animal stock adjustment and price movements when the duration of export disruptions is unknown. Explicit treatment of these issues is crucial in the economic analysis of livestock epidemics, especially if there is a risk of a prolonged export ban. Results suggest that the risk of a prolonged ban increases disease losses considerably. It also increases economic benefits from production adjustments.

Keywords: C61 - Optimization Techniques ; Programming Models ; Dynamic Analysis, Q13 - Agricultural Markets and Marketing ; Cooperatives ; Agribusiness, Q18 - Agricultural Policy ; Food Policy

Print ISSN: 0165-1587

Electronic ISSN: 1464-3618

Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Economics