ISSN 0003-455X
© Finnish Zoological and Botanical Publishing Board

Contents of Volume 41 Number 1, 2004

Biology and Management of Coregonid Fishes

Proceedings of the Eighth International Symposium on the Biology and Management of Coregonid Fishes, Rovaniemi, Finland, 26–29 August 2002

edited by Outi Heikinheimo, Per-Arne Amundsen, Heikki Auvinen, Drew Bodaly, Randy Eshenroder, Ari Huusko, Ken Mills, Rudolf Müller, Thomas Todd and Ian Winfield


Preface: — Ann. Zool. Fennici 41: 1–2.
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Reshetnikov, Y. S. 2004: Coregonid fishes in Arctic waters. — Ann. Zool. Fennici 41: 3–11.
Abstract
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Politov, D. V., Bickham, J. W. & Patton, J. C. 2004: Molecular phylogeography of Palearctic and Nearctic ciscoes. — Ann. Zool. Fennici 41: 13–23.
Abstract
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Sendek, D. S. 2004: The origin of sympatric forms of European whitefish (Coregonus lavaretus (L.)) in Lake Ladoga based on comparative genetic analysis of populations in North-West Russia. — Ann. Zool. Fennici 41: 25–39.
Abstract
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Sukhanova, L. V., Smirnov, V. V., Smirnova-Zalumi, N. S., Kirilchik, S. V. & Shimizu, I. 2004: Grouping of Baikal omul Coregonus autumnalis migratorius Georgi within the C. lavaretus complex confirmed by using a nuclear DNA marker. — Ann. Zool. Fennici 41: 41–49.
Abstract
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Stott, W., Todd, T. N. & Kallemeyn, L. 2004: Genetic variability among lake whitefish from Isle Royale and the Upper Great Lakes. — Ann. Zool. Fennici 41: 51–59.
Abstract
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Brzuzan, P., Ciesielski, S., Kusznierz, J. & Jurczyk, L. 2004: Identification of whitefish remains by mtDNA analysis. — Ann. Zool. Fennici 41: 61–68.
Abstract
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Huuskonen, H., Haakana, H. & Aho, T. 2004: Stock transfer in vendace: an evaluation using microsatellite markers. — Ann. Zool. Fennici 41: 69–74.
Abstract
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Lahnsteiner, B. & Wanzenböck, J. 2004: Variability in the spatio-temporal distribution of larval European whitefish (Coregonus lavaretus (L.)) in two Austrian lakes. — Ann. Zool. Fennici 41: 75–83.
Abstract
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Albert, A., Vetemaa, M. & Saat, T. 2004: Effects of salinity on the development of Peipsi whitefish Coregonus lavaretus maraenoides Poljakow embryos. — Ann. Zool. Fennici 41: 85–88.
Abstract
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Ylönen, O., Huuskonen, H. & Karjalainen, J. 2004: UV avoidance of coregonid larvae. — Ann. Zool. Fennici 41: 89–98.
Abstract
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Bogdanova, V. A. 2004: Early gametogenesis of the Volkhov whitefish, Coregonus lavaretus baeri. — Ann. Zool. Fennici 41: 99–104.
Abstract
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Wedekind, C. & Müller, R. 2004: Parental characteristics versus egg survival: towards an improved genetic management in the supportive breeding of lake whitefish. — Ann. Zool. Fennici 41: 105–115.
Abstract
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Harrod, C. & Griffiths, D. 2004: Reproduction and fecundity of the Irish pollan (Coregonus autumnalis Pallas 1776), a threatened lake coregonid. — Ann. Zool. Fennici 41: 117–124.
Abstract
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Bøhn, T. & Amundsen, P.-A. 2004: Invasion-mediated changes in the population biology of a dimorphic whitefish Coregonus lavaretus population. — Ann. Zool. Fennici 41: 125–136.
Abstract
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Gjelland, K. Ø., Bøhn, T., Knudsen, F. R. & Amundsen, P.-A. 2004: Influence of light on the swimming speed of coregonids in subarctic lakes. — Ann. Zool. Fennici 41: 137–146.
Abstract
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Hoff, M. H. & Todd, T. N. 2004: Status of the shortjaw cisco (Coregonus zenithicus) in Lake Superior. — Ann. Zool. Fennici 41: 147–154.
Abstract
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Winfield, I. J., Fletcher, J. M. & James, J. B. 2004: Conservation ecology of the vendace (Coregonus albula) in Bassenthwaite Lake and Derwent Water, U.K. — Ann. Zool. Fennici 41: 155–164.
Abstract
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Pelczarski, W. 2004: Mass rearing of juvenile whitefish in brackish water using live zooplankton. — Ann. Zool. Fennici 41: 165–170.
Abstract
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Leskelä, A., Jokikokko, E., Huhmarniemi, A., Siira, A. & Savolainen, H. 2004: Stocking results of spray-marked one-summer old anadromous European whitefish in the Gulf of Bothnia. — Ann. Zool. Fennici 41: 171–179.
Abstract
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Gerdeaux, D. 2004: The recent restoration of the whitefish fisheries in Lake Geneva: the roles of stocking, reoligotrophication, and climate change. — Ann. Zool. Fennici 41: 181–189.
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Ilmast, N. & Sterligova, O. 2004: The results of the introduction of coregonid fishes into Vashozero, a lake in southern Karelia. — Ann. Zool. Fennici 41: 191–194.
Abstract
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Aronsuu, K. & Huhmarniemi, A. 2004: Changes in the European whitefish (Coregonus lavaretus (L.)) population of the Kalajoki — potential consequences of the alterations of fishing patterns in the Gulf of Bothnia. — Ann. Zool. Fennici 41: 195–204.
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Howland, K. L., Gendron, M., Tonn, W. M. & Tallman, R. F. 2004: Age determination of a long-lived coregonid from the Canadian North: comparison of otoliths, fin rays and scales in inconnu (Stenodus leucichthys). — Ann. Zool. Fennici 41: 205–214.
Abstract
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Mills, K. H. & Chalanchuk, S. M. 2004: The fin-ray method of aging lake whitefish. — Ann. Zool. Fennici 41: 215–223.
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Marjomäki, T. J., Auvinen, H., Helminen, H., Huusko, A., Sarvala, J., Valkeajärvi, P., Viljanen, M. & Karjalainen, J. 2004: Spatial synchrony in the inter-annual population variation of vendace (Coregonus albula (L.)) in Finnish lakes. — Ann. Zool. Fennici 41: 225–240.
Abstract
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Viljanen, M., Turunen, T. & Väisänen, P. 2004: Fluctuations in year-class strength and growth of the vendace (Coregonus albula (L.)) in the small, mesohumic, oligotrophic Suomunjärvi, a lake in eastern Finland. — Ann. Zool. Fennici 41: 241–248.
Abstract
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Salonen, E. 2004: Estimation of vendace year-class strength with different methods in the subarctic lake Inari. — Ann. Zool. Fennici 41: 249–254.
Abstract
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Sutela, T., Mutenia, A. & Salonen, E. 2004: Density of 0+ peled (Coregonus peled) and whitefish (C. lavaretus) in late summer trawling as an indicator of their year-class strength in two boreal reservoirs. — Ann. Zool. Fennici 41: 255–262.
Abstract
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Mills, K. H., Gyselman, E. C., Chalanchuk, S. M. & Allan, D. J. 2004: Growth, annual survival, age and length frequencies for unexploited lake whitefish populations. — Ann. Zool. Fennici 41: 263–270.
Abstract
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Schaeffer, J. S. 2004: Population dynamics of bloaters Coregonus hoyi in Lake Huron, 1980–1998. — Ann. Zool. Fennici 41: 271–279.
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Rellstab, C., Bürgi, H. R. & Müller, R. 2004: Population regulation in coregonids: the significance of zooplankton concentration for larval mortality. — Ann. Zool. Fennici 41: 281–290.
Abstract
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Amundsen, P.-A., Bøhn, T. & Våga, G. H. 2004: Gill raker morphology and feeding ecology of two sympatric morphs of European whitefish (Coregonus lavaretus). — Ann. Zool. Fennici 41: 291–300.
Abstract
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Amundsen, P.-A., Knudsen, R., Klemetsen, A. & Kristoffersen, R. 2004: Resource competition and interactive segregation between sympatric whitefish morphs. — Ann. Zool. Fennici 41: 301–307.
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Tolentino, S. A. & Thompson, B. W. 2004: Meristic differences, habitat selectivity and diet separation of Prosopium spilonotus and P. abyssicola. — Ann. Zool. Fennici 41: 309–317.
Abstract
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Jensen, H., Bøhn, T., Amundsen, P.-A. & Aspholm, P. E. 2004: Feeding ecology of piscivorous brown trout (Salmo trutta L.) in a subarctic watercourse. — Ann. Zool. Fennici 41: 319–328.
Abstract
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Valkeajärvi, P. & Marjomäki, T. J. 2004: Perch (Perca fluviatilis) as a factor in recruitment variations of vendace (Coregonus albula) in lake Konnevesi, Finland. — Ann. Zool. Fennici 41: 329–338.
Abstract
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Auvinen, H., Kolari, I., Pesonen, A. & Jurvelius, J. 2004: Mortality of 0+ vendace (Coregonus albula) caused by predation and trawling. — Ann. Zool. Fennici 41: 339–350.
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Salonen, E. & Mutenia, A. 2004: The commercial coregonid fishery in northernmost Finland — a review. — Ann. Zool. Fennici 41: 351–355.
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Heikinheimo, O. & Mikkola, J. 2004: Effect of selective gill-net fishing on the length distribution of European whitefish (Coregonus lavaretus) in the Gulf of Finland. — Ann. Zool. Fennici 41: 357–366.
Abstract
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Gassner, H., Hassan, Y. & Wanzenböck, J. 2004: Adaptive management for a whitefish population exclusively exploited by anglers — first results after a test period of four years. — Ann. Zool. Fennici 41: 367–373.
Abstract
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Muje, K., Lindroos, M., Marjomäki, T. J. & Karjalainen, J. 2004: Interlocked sustainable use of multiple fish stocks — modelling biological and socio-economic conditions in Finnish vendace (Coregonus albula (L.)) fisheries. — Ann. Zool. Fennici 41: 375–390.
Abstract
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Reshetnikov, Y. S. 2004: Coregonid fishes in Arctic waters. — Ann. Zool. Fennici 41: 3–11.

The Arctic ichthyofauna is represented by 460 fish species (2.0% of the world fauna), of which 123 (26.7%) are true Arctic species. The macrostructure of the Arctic ichthyofauna differs significantly from the observed ratio of taxa in the world fauna, and the core elements are salmoniforms, scorpaeniforms, and perciforms. Characteristic features of the Arctic fish fauna are a small number of monotypic genera, a low proportion of endemic genera and species, as well as polymorphism and euryphagy. Polymorphic species of coregonids are represented by forms that have various feeding regimes and different spawning seasons. Coregonids play a major role in transferring energy through trophic chains. A major constraint on the reproductive strategy of Arctic fishes is the need for suitable larval and juvenile rearing conditions during the short polar summer. Among the coregonids, mature individuals generally do not spawn annually, but as a rule spawn every one to three years.

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Politov, D. V., Bickham, J. W. & Patton, J. C. 2004: Molecular phylogeography of Palearctic and Nearctic ciscoes. — Ann. Zool. Fennici 41: 13–23.

We studied mtDNA phylogeography of Palearctic and Nearctic Coregonus, including four species of ciscoes (C. sardinella, C. autumnalis, C. artedi, C. laurettae), Baikal omul (C. migratorius) and related taxa. The C. sardinella complex, which includes C. peled, is distantly related to the other cisco species. Eurasian C. sardinella haplotypes are the most basal in this lineage. C. autumnalis and C. laurettae are well-differentiated species and belong to a clade that also includes C. artedi. This clade likely originated from Baikal omul which is intermediate between the C. autumnalis complex and the rest of the network. Haplotypes from Siberian populations of C. autumnalis occupy the basal positions of the C. autumalis complex. We conclude Siberia is the place of origin for the C. autumnalis and C. sardinella complexes. Two routes of invasion, along the northern and southern coasts of the Pleistocene Bering land bridge, explain the origin of the North American populations of C. sardinella (north), C. autumnalis (north), C. laurettae (south) and C. artedi (probably south).

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Sendek, D. S. 2004: The origin of sympatric forms of European whitefish (Coregonus lavaretus (L.)) in Lake Ladoga based on comparative genetic analysis of populations in North-West Russia. — Ann. Zool. Fennici 41: 25–39.

Four sympatric forms of Lake Ladoga European whitefish (Coregonus lavaretus (L.)) were analyzed at 29 enzyme loci. The genetic distances between these populations were highest when the lake form and the lake-river form from the southern part of the lake (both of them low-density-rakered) were compared with two lake forms ("black" and "white") from the north-western coastal zone of Lake Ladoga (DN = 0.003–0.006). No genetic differences between the low-density-rakered "white" form and the medium-density-rakered "black" European whitefish were found. Analysis of allelic distribution and genetic divergence among European whitefish populations in North-West Russia failed to support the identity of the low-density-rakered forms of Lake Ladoga whitefish with eastern populations of C. lavaretus pidschian. Based on these data, the hypothesis of possible penetration of the White Sea coregonid fauna into Lake Ladoga can be rejected. A more plausible hypothesis is that European whitefish and vendace originated in the Lake Ladoga basin via colonization from a Baltic periglacial lake.

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Sukhanova, L. V., Smirnov, V. V., Smirnova-Zalumi, N. S., Kirilchik, S. V. & Shimizu, I. 2004: Grouping of Baikal omul Coregonus autumnalis migratorius Georgi within the C. lavaretus complex confirmed by using a nuclear DNA marker. — Ann. Zool. Fennici 41: 41–49.

Previous studies of the mtDNA cytochrome b gene and control region indicated that the Baikal omul was closely related to the Baikal whitefishes, but not to the Arctic cisco, Coregonus autumnalis Pallas, its closest taxonomic relative. Moreover, extremely high mtDNA similarity between Baikal omul and Baikal lacustrine whitefish, C. lavaretus baicalensis (Dyb.), was revealed. Direct sequencing of PCR-amplified DNA of the first internal transcribed spacer of ribosomal DNA (rDNA ITS1) of five taxa was carried out using previously designed primers to determine the position of the species within the Coregonidae: two ciscoes including the Arctic cisco, C. autumnalis Pallas, and the Irish pollan, C. pollan Thompson; and three of Lake Baikal's coregonids including Baikal omul, C. autumnalis migratorius Georgi, Baikal lacustrine whitefish, C. lavaretus baicalensis Dybovsky, and Baikal pidschian, C. lavaretus pidschian Pallas. The study showed again that Baikal omul grouped within the C. lavaretus complex. The trees that were obtained correlated with our previous results based on mtDNA analysis. We conclude that Baikal omul is one of many representatives of the C. lavaretus complex.

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Stott, W., Todd, T. N. & Kallemeyn, L. 2004: Genetic variability among lake whitefish from Isle Royale and the Upper Great Lakes. — Ann. Zool. Fennici 41: 51–59.

The coregonine fishes from Isle Royale National Park represent a unique group that has escaped the successional changes observed elsewhere in North America. Analysis of microsatellite DNA loci revealed significant genetic differences among samples of lake whitefish (Coregonus clupeaformis) from Isle Royale, Lake Superior, and Lake Huron. The amount of genetic variation observed is consistent with that seen in other studies of whitefishes from North America. The lake whitefish from Isle Royale had previously been assigned sub-species status, but no evidence was found to support this. The effects of common ancestry and demographics both play a role in determining the relatedness of the populations. As with other fish species from Isle Royale and the upper Great Lakes, the lake whitefish have their origins in the Mississippi refugium.

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Brzuzan, P., Ciesielski, S., Kusznierz, J. & Jurczyk, L. 2004: Identification of whitefish remains by mtDNA analysis. — Ann. Zool. Fennici 41: 61–68.

Remains of Coregonus sp. were obtained from the collection of archeological materials found in 1991 at the site Wola Grzymalina, Poland. DNA has been extracted from vertebrae that were dated about 500 000 years old. Polymerase chain reactions on extracts from the vertebral remains were succesful only using primers that targeted nucleotide sequences that were not longer than about 100bp. The ancient nucleotide sequence of a 102bp fragment of mitochondrial DNA ND1 gene matched the contemporary sequence of European whitefish (Coregonus lavaretus) and differed from that of vendace (C. albula) by four substitutions. Ambiguous nucleotides were observed at nine positions throughout the 87bp fragment of mtDNA control region (CR), nonetheless the sequence was different from that of vendace by eight additional changes. Phylogenetic analysis utilizing Bayesian inference placed the archival sequence into a clade with European whitefish. The support for this reconstruction was f([tau]|X) = 0.65 after analysis of the ND1 fragment and f([tau]|X) = 0.52 after analysis of the CR fragment. Excellent preservation of the specimen analysed in this study proves the potential for analysing genetic characteristics of species and specimens that are thousands of years old.

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Huuskonen, H., Haakana, H. & Aho, T. 2004: Stock transfer in vendace: an evaluation using microsatellite markers. — Ann. Zool. Fennici 41: 69–74.

Lake Höytiäinen in eastern Finland has suffered from several prolonged vendace (Coregonus albula (L.)) recessions during the last decades. To strengthen the spawning stock, about 2.6 million vendace were transferred from lake Suvasvesi into lake Höytiäinen in late winter 2000. The success of stock transfer was studied with the help of microsatellite genetic markers. Newly hatched larvae were collected in two years preceding and two years after the first reproduction of the transferred fish in lake Höytiäinen. Microsatellite DNA variation of larvae was assessed and the genotypes were compared with the genotypes of the two original populations and known hybrids of these two populations. An assignment test showed that a majority of the sampled larvae originated from the indigenous lake Höytiäinen population, and stock transfer had only minor effects on the population structure of lake Höytiäinen.

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Lahnsteiner, B. & Wanzenböck, J. 2004: Variability in the spatio-temporal distribution of larval European whitefish (Coregonus lavaretus (L.)) in two Austrian lakes. — Ann. Zool. Fennici 41: 75–83.

The spatial and temporal distributions of larval European whitefish (Coregonus lavaretus, species complex) were investigated in the years 1998 and 1999 in two Austrian lakes, Traunsee and Hallstättersee. The fish communities of both lakes are dominated by whitefish, but in addition to a normal-growing form Traunsee is also inhabited by a dwarf phenotype. Larval sampling was done weekly between January and June using a push net system. Whitefish larvae showed a preference for nearshore areas at both lakes. In Traunsee, the mean catch on the first sampling date was higher than those obtained during the following sampling dates in February for both years. A local minimum in temporal occurrence was observed in mid-February (1998) or early February (1999). Catches increased again during March before reaching a maximum in early April of both years. In Hallstättersee, the sampling started at the beginning of February with very few larvae caught. During the subsequent weeks the catches increased steadily until a single peak was reached in mid-March (1998) or late April (1999). This high within-lake variability in maximum larval occurrence between two successive years is the greatest ever reported. The degree of variation in spatial distribution of larvae observed between years was also novel.

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Albert, A., Vetemaa, M. & Saat, T. 2004: Effects of salinity on the development of Peipsi whitefish Coregonus lavaretus maraenoides Poljakow embryos. — Ann. Zool. Fennici 41: 85–88.

Eggs of Peipsi whitefish Coregonus lavaretus maraenoides Poljakow were artificially inseminated and reared in sea water of 0.2–6.2 ppt salinity. Egg fertilisation rate was 97%–99% at 0.2–3.3 ppt but declined to 75%–85% at 4.0–6.2 ppt. Survival until hatching remained high at 0.2–1.3 ppt. Normal embryos hatched at salinity <= 4.8 ppt. Salinity did not affect the timing of development except for hatching, which occurred earlier when salinity increased. The length of free embryos was highest at 2.1 ppt.

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Ylönen, O., Huuskonen, H. & Karjalainen, J. 2004: UV avoidance of coregonid larvae. — Ann. Zool. Fennici 41: 89–98.

Although several authors have shown that UV radiation can cause damage to fish larvae, the UV avoidance behaviour of larvae has received little attention. Larval coregonids are vulnerable to the recently enhanced UV levels because immediately after hatching in spring they show a distinct positive phototaxis. The behavior of three size groups of vendace (Coregonus albula (L.)) and whitefish (Coregonus lavaretus (L.) s.l.) larvae were studied under enhanced UV-B irradiation in the laboratory. In addition, field data from four coregonid lakes in Finland were analysed. Coregonid larvae avoided UV radiation both in the laboratory and field. The smallest vendace larvae were the most sensitive to changes in UV irradiation in the laboratory experiments. In the field, the avoidance behaviour was more pronounced in lakes with low dissolved organic carbon (DOC) concentrations than in a lake with a high DOC concentration.

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Bogdanova, V. A. 2004: Early gametogenesis of the Volkhov whitefish, Coregonus lavaretus baeri. — Ann. Zool. Fennici 41: 99–104.

The first detailed examination of the gonadal development of Volkhov whitefish juveniles was performed. Morphology and sequence of germ cells and gonad development are presented. Thirty days after hatching in the gonad anlagen, primordial germ cells began to divide. Sex differentiation occurred 82 days after hatching. Gonia in ovaries proliferated rapidly, some of them entered meiotic prophase developing into oocytes. In two weeks, the developing oocytes had reached the `early perinucleolus stage' and began the cytoplasmatical growth. At the same time, in ovaries of some females, cysts with male germ cells appeared. Ten days later, all whitefish females had hermaphroditic features. In male gonads few germ cells were dispersed singly amongst stromal tissue. The reason for the mass hermaphroditism among Volkhov whitefish females may lie in the environmental circumstances such as high temperature during the study period, or the specificity of the early gametogenesis in this whitefish species.

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Wedekind, C. & Müller, R. 2004: Parental characteristics versus egg survival: towards an improved genetic management in the supportive breeding of lake whitefish. — Ann. Zool. Fennici 41: 105–115.

A number of sexual selection models predict that reproductive success in the wild is positively linked to heritable viability (e.g. the "good genes" models). Here we explore whether there is information about heritable viability that could potentially be used in the hatchery management of Alpine lake whitefish (Coregonus sp.). We drew 20 wild-caught individuals out of a breeding program, crossed them in a fully balanced 10 females x 10 males mating design, and incubated each sibship in several replicates until hatching. We then compared egg survival with parental characteristics. Egg number or milt volume were not significantly correlated with egg survival, nor was egg size. However, female size and age, and male quality indicators such as condition factor, breeding ornamentation, and fluctuating asymmetry, were useful predictors of egg survival. We discuss the possibility that a promotion of heritable viability could be carefully balanced with the maintenance of genetic variation in order to maximize the survival prospects of a population.

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Harrod, C. & Griffiths, D. 2004: Reproduction and fecundity of the Irish pollan (Coregonus autumnalis Pallas, 1776), a threatened lake coregonid. — Ann. Zool. Fennici 41: 117–124.

The sex ratio, age at maturation, fecundity, and seasonal development of gonads of pollan (Coregonus autumnalis) in Lough Neagh are described from samples collected between November 1997 and December 1999. Pollan reproductive ecology in the 1990s was similar to that found in the 1970s. Pollan egg size and fecundity differed between years but there were no long-term trends in fecundity despite considerable subsequent eutrophication of the lough and changes in the fish community.

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Bøhn, T. & Amundsen, P.-A. 2004: Invasion-mediated changes in the population biology of a dimorphic whitefish Coregonus lavaretus population. — Ann. Zool. Fennici 41: 125–136.

Population biology changes in native dimorphic whitefish Coregonus lavaretus were studied over a decade in the subarctic Pasvik watercourse, where large biotic changes occurred due to an invasion by vendace C. albula. Although initially recorded in the upstream part of the watercourse, where it is now the dominant pelagic species, the vendace subsequently also colonised the downstream area. We hypothesized that the impact of the invader would affect the population biology (density, habitat choice, growth, size- and age-structure and size and age at maturation) of the native whitefish populations, especially upstream in the watercourse, late in the invasion phase, and in the pelagic whitefish morph. Strong effects from the invading vendace were observed on the native dimorphic whitefish populations. Effects on the densely-rakered whitefish, which are ecologically similar to vendace, ranged from numerical responses (strong density decline in the population), habitat use (shift from pelagic to littoral) and individual growth (significant growth reduction in zooplanktivorous life stages). For the benthic sparsely-rakered whitefish, effects were more restricted and recorded mainly on growth.

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Gjelland, K. Ø., Bøhn, T., Knudsen, F. R. & Amundsen, P.-A. 2004: Influence of light on the swimming speed of coregonids in subarctic lakes. — Ann. Zool. Fennici 41: 137–146.

Swimming speed of pelagic whitefish (Coregonus lavaretus) and vendace (Coregonus albula) was studied in two subarctic lakes at 69°N in northern Norway in June, August and September 2000. At this latitude, the light regime changes strongly during the summer months, from 24 hrs of daylight in June to 14 hrs in September. Swimming fish were monitored by a bottom mounted split-beam echosounder, and the hydroacoustic traces were analysed with software designed for fish track analysis. Fish tracks were smoothed using a locally weighted algorithm before estimating swimming speeds. The swimming speed was strongly influenced by light. Average swimming speed was highest in periods with low incident light or crepuscular light (16–18 cm s–1) and lowest in darkness (8–10 cm s–1). A positive relationship between fish size and swimming speed was observed during daylight, but not during periods of darkness.

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Hoff, M. H. & Todd, T. N. 2004: Status of the shortjaw cisco (Coregonus zenithicus) in Lake Superior. — Ann. Zool. Fennici 41: 147–154.

The shortjaw cisco (Coregonus zenithicus) was historically found in Lakes Huron, Michigan, and Superior, but has been extirpated in Lakes Huron and Michigan apparently as the result of commercial overharvest. During 1999–2001, we conducted an assessment of shortjaw cisco abundance in five areas, spanning the U.S. waters of Lake Superior, and compared our results with the abundance measured at those areas in 1921–1922. The shortjaw cisco was found at four of the five areas sampled, but abundances were so low that they were not significantly different from zero. In the four areas where shortjaw ciscoes were found, abundance declined significantly by 99% from the 1920s to the present. To increase populations of this once economically and ecologically important species in Lake Superior, an interagency rehabilitation effort is needed. Population monitoring is recommended to assess population trends and to evaluate success of rehabilitation efforts.

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Winfield, I. J., Fletcher, J. M. & James, J. B. 2004: Conservation ecology of the vendace (Coregonus albula) in Bassenthwaite Lake and Derwent Water, U.K. — Ann. Zool. Fennici 41: 155–164.

Following extinction of two populations in Scotland, the vendace (Coregonus albula) is now found in only two U.K. lakes, i.e. Bassenthwaite Lake and Derwent Water in north-west England. Although the latter remains mesotrophic, the former has undergone significant eutrophication with associated dissolved oxygen problems and vendace monitoring has shown a declining population status. Additional threats originate from land erosion with subsequent in-lake siltation, and the unconsented introduction of non-native fish species including roach (Rutilus rutilus), ruffe (Gymnocephalus cernuus) and dace (Leuciscus leuciscus). The impact of ruffe as a predator of vendace eggs is considered through diet studies during the spawning period. Climate change may also significantly impact local environmental conditions and these threats to the continued local survival of the vendace are assessed and descriptions given of resulting management measures. The latter include phosphorus-stripping, artificial spawning substratum, egg incubation in captivity, control of further introductions, and establishment of refuge populations.

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Pelczarski, W. 2004: Mass rearing of juvenile whitefish in brackish water using live zooplankton. — Ann. Zool. Fennici 41: 165–170.

The reintroduction of whitefish of Pomeranian Bay origin to Puck Bay (southern Baltic) has been underway since 1993. Stocking has been conducted with juveniles weighing 1–2 g. In 2002, a program was initiated to rear whitefish fry in a manmade brackish water pond located at a sewage treatment plant close to the sea. The fish were fed live zooplankton which was filtered from purified wastewater. Until the current program, this zooplankton was not utilized. The mean weight of the 30 000 fry at the start of rearing on 26 June was 1.2 g. The final mean weight was 21.2 g on 22 October when over 3200 fish were released into Puck Bay as a supplement to the stocking program. The mean growth rate obtained by the fish was 0.82 mm day–1, but the survival rate was only 11% due to heavy losses in July caused by the sudden deterioration of water conditions in the pond.

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Leskelä, A., Jokikokko, E., Huhmarniemi, A., Siira, A. & Savolainen, H. 2004: Stocking results of spray-marked one-summer old anadromous European whitefish in the Gulf of Bothnia. — Ann. Zool. Fennici 41: 171–179.

About 6 million one-summer-old, fluorescent pigment marked whitefish were released in the northern and central parts of the Gulf of Bothnia in 1995–1998. Growth and dispersal of the stocked fish were followed by detecting and recording marked whitefish in samples from the professional fisheries catch during 1999–2002. The yield produced by stocked fish was estimated by assuming that the proportion of the marked fish in the total catch was the same as in the samples. The total yield from the stockings in 1995 was estimated to be 55–90 kg/1000 released fingerlings. A better result from the stockings could be achieved by increasing the recruitment size in the fishery. Even for the 1995 stockings, a few of the released fish were probably still migrating in the sea at the end of the study period, although the main part had already been caught. For fish released in 1996 or later, no exact estimates of total yield can be given, as a considerable part of the catch was still to come. The estimates from the preliminary re-catches, however, suggest that the stockings in northern parts produce lower catches than stockings in central parts of the Gulf of Bothnia.

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Gerdeaux, D. 2004: The recent restoration of the whitefish fisheries in Lake Geneva: the roles of stocking, reoligotrophication, and climate change. — Ann. Zool. Fennici 41: 181–189.

The recent history of the whitefish fishery in Lake Geneva has been very positive. Yields over the last seven years have not been attained for 50 years. Stocking has been increased for 10 years. Stocking was first done with larvae, but now with larvae and also juveniles and fingerlings. Stocking could explain the beginning of the increases in whitefish stocks but cannot completely explain the present level of the stock. Other causes are necessary to explain the situation. Lake Geneva sustained a stage of eutrophication (total phosphorus increasing from 20 µg l–1 to 90 µg l–1) from 1960 to the mid-1970s. Phosphorus levels have been decreasing since then. Improved water quality has contributed to the restoration of the whitefish population. Climate change has also contributed to better recruitment of whitefish. Stocking seems now to be superfluous and will be restricted in the future to fingerlings.

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Ilmast, N. & Sterligova, O. 2004: The results of the introduction of coregonid fishes into Vashozero, a lake in southern Karelia. — Ann. Zool. Fennici 41: 191–194.

Vashozero is a lake located in the southern part of the Republic of Karelia (62°10'N, 34°27'E) in the Lake Onega basin. The fish community had few species before 1933. In 1933–1935, coregonid fishes (1.29 x 106 larvae of Lake Onega whitefish Coregonus lavaretus (L.), 0.94 x 106 larvae of Lake Ladoga ripus — a large form of vendace C. albula (L.), and 0.37 x 106 larvae of Lake Onega vendace C. albula (L.)) were introduced into the lake. The current study, conducted in 2000–2001, provided positive results for the status of European vendace in Vashozero. The vendace population in Vashozero has reached a level at which the biological indices of the species agree with the abiotic and biotic conditions of the environment. The species has reached equilibrium in the lake and a European vendace population has been formed.

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Aronsuu, K. & Huhmarniemi, A. 2004: Changes in the European whitefish (Coregonus lavaretus (L.)) population of the Kalajoki — potential consequences of the alterations of fishing patterns in the Gulf of Bothnia. — Ann. Zool. Fennici 41: 195–204.

The migration and catching areas of Carlin-tagged anadromous European whitefish (Coregonus lavaretus lavaretus) as well as the changes in the mean size, growth and age composition of stocked whitefish migrating to spawn in the Kalajoki, a river in Finland, were studied between the late 1970s and early 2000s. After spawning, whitefish migrate to the south, mostly to the Northern Quark and the Bothnian Sea. The proportion of tagged fish caught during January–June in the southern part of the migration route increased during the study period. At the same time the mean size and growth of whitefish entering the Kalajoki was reduced. In the late 1980s and early 1990s the mean age of whitefish declined rapidly. After that, it has increased gradually. The changes in whitefish growth and age composition were connected to the increased fishing effort and the reduction of the mesh size of gill nets in the Gulf of Bothnia.

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Howland, K. L., Gendron, M., Tonn, W. M. & Tallman, R. F. 2004: Age determination of a long-lived coregonid from the Canadian North: comparison of otoliths, fin rays and scales in inconnu (Stenodus leucichthys). — Ann. Zool. Fennici 41: 205–214.

We examined otoliths, pelvic fin rays and scales of inconnu to determine precision of age estimates within and between readers, and to compare relative accuracy of estimates from different structures. Our main objective was to determine if readability and estimates from fin rays and scales, which can be non-lethally removed, were similar to those of otoliths, which are generally considered the most reliable ageing structure. Among- and within-reader variation was low for both fin rays and otoliths, but higher for scales. Variation tended to increase with fish length for all structures. Scales were most difficult to read and had age estimates that were significantly lower than the other structures at ages of ten years and greater. Age estimates and readability of fin rays and otoliths were similar.

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Mills, K. H. & Chalanchuk, S. M. 2004: The fin-ray method of aging lake whitefish. — Ann. Zool. Fennici 41: 215–223.

We report the results of a long-term age validation of the fin-ray method of aging lake whitefish (Coregonus clupeaformis). We further compare fin-ray ages with otolith ages and describe a technique to back-calculate lengths of lake whitefish. Using ages determined from individuals when tagged, we correctly predicted the ages determined from fish when they were recaptured one to 28 years later for 1092 (73%) of the 1492 individuals that we examined. When differences occurred between predicted and actual ages at recapture, there was no tendency for the actual ages to be greater or less than the predicted age. We found no significant difference between fin-ray and otolith ages for individual lake whitefish from two other lakes, although the ages agreed for only 49% of the age pairs. We used the upper section of the first pelvic fin ray to back-calculate fork lengths of lake whitefish from one population using the direct proportionality method, and compared these predicted lengths with actual lengths recorded one to three years earlier when fish were tagged to validate the method.

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Marjomäki, T. J., Auvinen, H., Helminen, H., Huusko, A., Sarvala, J., Valkeajärvi, P., Viljanen, M. & Karjalainen, J. 2004: Spatial synchrony in the inter-annual population variation of vendace (Coregonus albula (L.)) in Finnish lakes. — Ann. Zool. Fennici 41: 225–240.

We analysed the spatial scale of synchrony in the inter-annual variation of vendace population indices from time-series of 21 Finnish lake basins. We detected significant positive correlation between lakes in the variation of abundance of young-of-the-year recruits, residuals of a density dependence model for recruitment, newly hatched larvae and spawning stocks. The spatial scale of correlation was typically 100–300 km and anisotropic, being shorter along the north–south vector of distance than along the east–west vector. The outcomes did not change when the data were restricted to rule out cases with a possibility of dispersal between populations. The scale and anisotropy structure of synchrony in mean temperature during the four week period after the local ice break date closely resembled that of the vendace population indices. Regionally correlated exogenous factors synchronise the recruitment variation either directly or perhaps also through environmentally induced synchrony in predator stocks. The effective scale of correlation for these factors, especially along the north–south axis, can be short if a large proportion of the prerecruit mortality occurs during a short period and the timing of this period at different latitudes varies by weeks due to differences in time of ice break and vendace hatching.

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Viljanen, M., Turunen, T. & Väisänen, P. 2004: Fluctuations in year-class strength and growth of the vendace (Coregonus albula (L.)) in the small, mesohumic, oligotrophic Suomunjärvi, a lake in eastern Finland. — Ann. Zool. Fennici 41: 241–248.

Year-class variation and growth of the vendace (Coregonus albula (L.)), the most important commercial freshwater fish species in Finland, was assessed in Suomunjärvi from 1974–2001 seine and gill net catches. We estimated the relative abundances and growth of the individual year-classes. The year-classes 1980, 1985, 1990, and 2000 were strong. There were often oscillations of year-class strengths, although the period of oscillation was not regular. Strong year-classes dominated catches for almost as long as they were present in the lake. The strongest year-class was about 300 times greater in size than the weakest. The growth of the year-classes varied considerably; the difference in growth rate between the strongest and weakest year class was about 2.5-fold. Comparison of the growth of a year-class with its strength showed a marked negative correlation (p < 0.001). The size of the whole stock (CPUE data) also had a negative effect on yearly growth (p < 0.005).

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Salonen, E. 2004: Estimation of vendace year-class strength with different methods in the subarctic lake Inari. — Ann. Zool. Fennici 41: 249–254.

Vendace (Coregonus albula) is a new introduced species in the Paatsjoki river system and lake Inari; it has only got a 30- to 40-year history in the area. The strong vendace year-classes of the 1980s were followed by weak ones until 2000, when a stronger year-class emerged. Data on the vendace catch-at-age were collected from 1987 to 2001 and the year-class strengths (YCS) were estimated by the virtual population analysis (VPA). The YCS was estimated directly by survey trawling conducted annually in early fall aimed at 0+ fish and by seine netting in the following winter. Direct estimates were compared with VPA estimates. The trawl survey and winter seine data show that the YCS of vendace is discernible during the first year of their lifespan. As a practical application in fisheries management, these data can be used in adjusting of e.g. stocking of predatory salmonids.

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Sutela, T., Mutenia, A. & Salonen, E. 2004: Density of 0+ peled (Coregonus peled) and whitefish (C. lavaretus) in late summer trawling as an indicator of their year-class strength in two boreal reservoirs. — Ann. Zool. Fennici 41: 255–262.

Density of young-of-the-year (YOY) peled (Coregonus peled) in late summer trawling was used to estimate their forthcoming year-class strength (YCS) in two northern reservoirs, Lokka and Porttipahta. We applied virtual population analysis (VPA) in estimating year-class strength. A good correlation was found between YOY density and YCS of peled. In contrast, the density of YOY whitefish (C. lavaretus) did not reliably reflect their YCS. Annual number of trawling tows in 1991–2001 averaged 23 per reservoir. Precision (SE [mean]–1) of the annual replicate samples averaged 0.33 and 0.31 for peled and whitefish, respectively. This level of precision was sufficient for detecting the large, often order-of-magnitude differences between annual mean YOY densities. As a practical application in fisheries management, YOY densities in survey trawling can be used in adjusting of stocking density and fishery of peled in the reservoirs studied.

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Mills, K. H., Gyselman, E. C., Chalanchuk, S. M. & Allan, D. J. 2004: Growth, annual survival, age and length frequencies for unexploited lake whitefish populations. — Ann. Zool. Fennici 41: 263–270.

We reviewed growth, annual survival, length distributions, and age distributions for unexploited lake whitefish (Coregonus clupeaformis) populations. We compared Von Bertalanffy growth curves, catch-curve annual survival, and age distributions based on fin-ray and scale ages for 10 populations and found that growth was slower, annual survival higher, and there were many more age groups in the populations when using fin-ray ages than when using scale ages. The average annual survival of populations based on scale ages was 47% yr–1 and 74% yr–1 based on fin rays. Independent mark-recapture estimates of annual survival for two populations were almost identical to those based on fin-ray ages. We believe that growth has been overestimated and annual survival underestimated for many unexploited populations when these have been based on scale ages.

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Schaeffer, J. S. 2004: Population dynamics of bloaters Coregonus hoyi in Lake Huron, 1980–1998. — Ann. Zool. Fennici 41: 271–279.

I investigated population dynamics of bloaters Coregonus hoyi in Lake Huron using data collected during 1980–1998 from fixed-site trawl surveys. Bloaters were uncommon in 1980, but abundance increased during 1980–1992 through a series of strong year classes. High adult abundance appeared to suppress recruitment after 1992, and the population subsequently declined. Growth was similar between sexes up to age-5, thereafter females grew faster than males. Both sexes lived to age-9, but females tended to live longer than males. A Ricker least-squares stock–recruitment relationship defined the relationship between adults and age-3 recruits, and may have been due to egg predation by adult bloaters. Higher female survival and shift in age structure toward older ages after 1990 led to female predominance in the population during 1995–1998. Female predominance appeared to be a consequence and not a cause of the observed population cycle.

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Rellstab, C., Bürgi, H. R. & Müller, R. 2004: Population regulation in coregonids: the significance of zooplankton concentration for larval mortality. — Ann. Zool. Fennici 41: 281–290.

Population size and fishing yield of coregonids has considerably diminished in many central European lakes where nutrient concentration, in particular phosphorus, has fallen to oligotrophic levels. In re-oligotrophicated Lake Lucerne, apart from slower growth, reduction in year class strength of the slow growing form of lake whitefish was identified as the major cause for decreasing yield. Stocking of lake whitefish larvae could not counteract this process. It was, therefore, hypothesised that larval mortality of lake whitefish, both from stocking and natural reproduction, had increased during re-oligotrophication because of food shortage during the early larval phase. Feeding experiments in aquaria with newly hatched lake whitefish larvae from Lake Lucerne, and using various concentrations of Artemia salina and zooplankton, showed a clear relationship between food concentration and mortality over the first 34 days. Elevated mortality of 40% or more resulted from food concentration of 20 zooplankton organisms per litre or fewer. Analysis of zooplankton data from Lake Lucerne indicated that concentration of zooplankton organisms usable by the whitefish larvae in late winter and spring was much lower in the years after 1984 than before. This might explain, at least in part, why year class strength and yield of the slow growing form of lake whitefish has decreased during re-oligotrophication of Lake Lucerne.

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Amundsen, P.-A., Bøhn, T. & Våga, G. H. 2004: Gill raker morphology and feeding ecology of two sympatric morphs of European whitefish (Coregonus lavaretus). — Ann. Zool. Fennici 41: 291–300.

European whitefish is a polymorphic species where different morphs often are identified by differences in their gill raker numbers. Gill rakers may play an important role in food-particle retention, particularly with respect to zooplankton feeding. Possible associations between feeding ecology and gill raker number and morphology were studied in European whitefish in the Pasvik watercourse. The numbers of gill rakers exhibited a bimodal distribution pattern, demonstrating the presence of two sympatric forms, including a sparsely-rakered morph with 18–30 and a densely-rakered morph with 28–42 rakers. The morphology of the gill rakers was correlated to the raker number and exhibited distinct differences between the morphs; sparsely-rakered whitefish having shorter, thicker and less densely packed rakers than the densely-rakered morph. Differences in habitat choice and trophic ecology between the two morphs appeared to be correlated to gill raker number and morphology. Densely-rakered whitefish exhibited a diet dominated by zooplankton and other pelagic prey, whereas the sparsely-rakered morph mainly fed on zoobenthos. Within the morphs, however, the feeding ecology of individual fish was not correlated with number and morphology of the gill rakers. Thus, whereas gill raker number and morphology appear to be a reliable marker for identifying ecologically and genetically different European whitefish morphs, the functional role with respect to the feeding performance of individual fish is less obvious.

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Amundsen, P.-A., Knudsen, R., Klemetsen, A. & Kristoffersen, R. 2004: Resource competition and interactive segregation between sympatric whitefish morphs. — Ann. Zool. Fennici 41: 301–307.

Two whitefish morphs have been identified in lakes in northern Norway from a bimodal distribution of gill raker numbers: a sparsely- and a densely-rakered. Habitat choice and feeding ecology of whitefish were studied in five lakes with the two morphs living in sympatry, and in five lakes harbouring only the sparsely-rakered morph. In sympatry, the two whitefish morphs exhibited a strict niche segregation, the sparsely-rakered morph mainly residing in the littoral zone feeding on zoobenthos, whereas the densely-rakered morph predominantly fed on zooplankton and dominated in the pelagic zone. In allopatry, however, the densely-rakered morph exhibited a larger niche width, utilising both the benthic and pelagic habitats and having a diet that included both zoobenthos and zooplankton. Thus, in sympatry with densely-rakered whitefish, the sparsely-rakered morph appears to be relegated from the pelagic zone, resulting in an interactive segregation due to resource competition between the two morphs.

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Tolentino, S. A. & Thompson, B. W. 2004: Meristic differences, habitat selectivity and diet separation of Prosopium spilonotus and P. abyssicola. — Ann. Zool. Fennici 41: 309–317.

Three endemic species of Prosopium inhabit Bear Lake. These are the Bonneville cisco (Prosopium gemmiferum), Bonneville whitefish (P. spilonotus) and Bear Lake whitefish (P. abyssicola). Only P. gemmiferum can easily be distinguished from the other two by simple morphological characteristics. Until recently P. abyssicola and P. spilonotus could only be distinguished from each other because of the temporal differences in their spawning times or at total lengths greater than approximately 280 mm. Samples of the two whitefish were collected during their respective spawning seasons to verify the results of recent research which demonstrated that a combination of lateral line and above lateral line scale counts could be used to separate the species. Results indicated that P. abyssicola and P. spilonotus could be positively separated using scale counts, and we suggest a modification of the recently published method regarding counting scales to determine whitefish identity to species. In 1999–2001, samples of whitefish were collected from standardized gillnetting to determine if any differences in life histories and diets were apparent. Significant differences existed between the diets and depth preferences of the two species. P. abyssicola were found in greater abundance in depths greater than 30 m and fed mainly on ostracods while P. spilonotus preferred depths less than 35 m, were omnivorous in their diets, and became picivorous at total lengths of 350 mm and greater.

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Jensen, H., Bøhn, T., Amundsen, P.-A. & Aspholm, P. E. 2004: Feeding ecology of piscivorous brown trout (Salmo trutta L.) in a subarctic watercourse. — Ann. Zool. Fennici 41: 319–328.

Feeding ecology of piscivorous brown trout was studied in the Pasvik watercourse, Norway and Russia. The watercourse is heavily regulated for hydroelectric purposes, and 5000 brown trout > 25 cm are stocked annually to compensate the negative impacts of the impoundments. Stocked and wild trout had almost identical diets consisting mainly of vendace Coregonus albula and partly of whitefish Coregonus lavaretus. Vendace has recently invaded the watercourse, and totally dominated the brown trout diet in the upstream part, where it has become the dominant species in the pelagic habitat. In the downstream part, where vendace were less prevalent, whitefish contributed to a larger extent to the trout diet. No correlation between predator (brown trout) and prey (vendace) lengths was found in the upstream part, and only a weak positive correlation was found in the downstream part. The length of whitefish eaten by brown trout, in contrast, showed a positive correlation with predator length in both the upstream and downstream part. The prey selection of brown trout was, to a large extent, explained by the differences in density and size-structure of coregonids in the two sampling areas.

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Valkeajärvi, P. & Marjomäki, T. J. 2004: Perch (Perca fluviatilis) as a factor in recruitment variations of vendace (Coregonus albula) in lake Konnevesi, Finland. — Ann. Zool. Fennici 41: 329–338.

The population dynamics, especially recruitment, of vendace (Coregonus albula) in lake Konnevesi were analysed from a time series of three decades from 1971 onwards. Recruitment success was highly variable, with no clear relationship between spawning stock and recruitment. Furthermore, no regular recruitment failure from large spawning stocks that would imply over-compensation was detected. Since 1982, an 11-year period of very poor year classes occurred despite the spawning stock and larval density being at high enough levels to produce abundant year-classes in the beginning of this period. A comprehensive recession appeared at the same time in other vendace stocks in southern Finland. In lake Konnevesi, perch (Perca fluviatilis) stock increased rapidly during the vendace recession. High summer temperatures were revealed to strengthen the perch stock, especially in the 1980s, as indicated by CPUE data with a lag of two years. Perch probably delayed the recovery of vendace and it is also likely that its predation affected the dynamics of the vendace stock even in the beginning of the recession. We suggest that predation pressure as a whole was an important factor for the onset and duration of the vendace recession.

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Auvinen, H., Kolari, I., Pesonen, A. & Jurvelius, J. 2004: Mortality of 0+ vendace (Coregonus albula) caused by predation and trawling. — Ann. Zool. Fennici 41: 339–350.

Vendace (Coregonus albula) is the main fish caught in commercial lake fishery in Finland. It is also important in the diet of landlocked salmon (Salmo salar m. sebago). The vendace stock in lake Paasivesi has not recovered from a 10-year recession, and the number of stocked salmon has risen to a level where predation can contribute to the mortality of vendace. We constructed a model of the influence of salmon predation and commercial trawling on the mortality of 0+ vendace in this lake. Our analysis revealed that predation by salmon alone could cause a year-class failure with the present low level of vendace larvae in spring. With a high spring density, only a high trawling effort could thin the year-class to a low level. We recommended that in order to guarantee a high number of larvae in spring, the spawning stock biomass of vendace should be raised.

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Salonen, E. & Mutenia, A. 2004: The commercial coregonid fishery in northernmost Finland — a review. — Ann. Zool. Fennici 41: 351–355.

In northernmost Finland, in lake Inari (1100 km2) and the reservoirs, Lokka and Porttipahta (total 630 km2), commercial fishing is significant for its economical and social aspects. Local European whitefish (Coregonus lavaretus) is the most important catch species. Two new coregonids were introduced: vendace (Coregonus albula) in the Inari area in the 1950s, and peled (Coregonus peled) into the reservoirs in the 1970s. Later these species have naturally succeeded in reproduction. In lake Inari, the commercial fishery originated in the 1930s and in the reservoirs in the 1980s. Essential for the development of the commercial fishery was the modern infrastructure, established in the 1980s, when the stocks of vendace and peled became dense. The commercial fishery took up trap netting and trawling, in addition to gillnetting. The number of commercial fishermen increased and the commercial coregonid catches peaked at 350 tonnes in both areas. After the collapse of the vendace and peled stocks, European whitefish has maintained the commercial fishery. Today, in all about 50 commercial fishermen supply the market with high-quality coregonids.

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Heikinheimo, O. & Mikkola, J. 2004: Effect of selective gill-net fishing on the length distribution of European whitefish (Coregonus lavaretus) in the Gulf of Finland. — Ann. Zool. Fennici 41: 357–366.

The Finnish sea area is inhabited by migratory and sea-spawning forms of the European whitefish (Coregonus lavaretus (L.)). In the Gulf of Finland, these forms have overlapping gill-raker counts but differing growth rates. The whitefish are heavily exploited with gill nets, so an age-and-length structured model was constructed to study the effects of fishing effort and alternative mesh size restrictions. The results show that the gill-net fishing effectively removes the largest individuals from the four- and five-year-old whitefish and thus strongly affects the length distribution, decreasing the mean length of the surviving population. Consequently, the share of slowly-growing individuals increases in mature age groups. In naturally-reproducing whitefish, this might be reflected in the genetic characteristics of the population. The strength of the selective effect on different age groups depends on the fishing effort and the mesh sizes used.

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Gassner, H., Hassan, Y. & Wanzenböck, J. 2004: Adaptive management for a whitefish population exclusively exploited by anglers — first results after a test period of four years. — Ann. Zool. Fennici 41: 367–373.

The whitefish population of Irrsee, a typical Austrian prealpine lake, is exploited exclusively by anglers, which is an unusual situation for many lakes dominated by Coregonids. Because of a significant decrease in the whitefish harvest, fishery regulations were changed between 1996 and 2002. The object of this study was to investigate whether the changed harvest regulations influence the proportion of catchable whitefish, to test the effectiveness of the size limit in force, and to investigate whether the practice of releasing undersized and hooked whitefish affected condition factors. The results from our study show a significant effect of changed harvest regulations on the number of catchable whitefish, on the proportion of hooked whitefish with typical injuries, and on the population size structure. Until now the effect of intensive angling on a whitefish population was largely underestimated in the Austrian lakes, but more attention should be paid to these effects in the future.

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Muje, K., Lindroos, M., Marjomäki, T. J. & Karjalainen, J. 2004: Interlocked sustainable use of multiple fish stocks — modelling biological and socio-economic conditions in Finnish vendace (Coregonus albula (L.)) fisheries. — Ann. Zool. Fennici 41: 375–390.

Using economic and historical yield data models in this paper we outline the socio-economic and ecological conditions for sustainable use of fish resources in commercial lake fisheries in Finland, in the context of fragmented private ownership and owner-based management. Interlocked use refers to area greater than the typical current area on one or two lakes, and that could be used as a joint resource by the fishers in the area. The results of the economic model show that the management of the interlocked fishery, in particular by encouraging mobility of fishers, can produce higher sustainable economic benefits from the fishery. The yield data analysis shows that an interlocked resource may considerably decrease fluctuations of yield in commercial vendace fisheries. This implies that the interlocked use approach would increase the cost-effectiveness and decrease the interannual variability in income to the fishers, thus promoting sustainability in the fishery and making it potentially a more viable livelihood in rural areas.

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