Enzym-elektrophoretische Untersuchung zur Artunterscheidung von Blaufelchen (Coregonus lavaretus wartmanni Bloch): und Gangfischen (Coregonus lavaretus macrophthalmus Nüsslin) aus dem Bodensee-Obersee, Bundesrepublik Deutschland

Enzym-electrophoretic examination for species identification of wbitefish (Coregonus lavaretus wartmanni Bloch and C.l. macrophthalmus Nüsslin) of the upper pan of Lake Constance, Federal Republic of Germany     

Different growth trends of whitefish (Coregonus lavaretus) forms in the northern Baltic Sea

The sea growth of two whitefish forms, anadromous (Coregonus lavaretus lavaretus) and sea‐spawning (Coregonus lavaretus widegreni), was analysed using samples collected from the commercial sea catch in the Gulf of Bothnia (GoB) in the northern Baltic Sea during 1998–2014. In the GoB area, these two forms are possible to identify because the gill‐raker number and size at maturity vary between forms. The growth rate of the forms is linked to their feeding area. Sea‐spawning whitefish, which has a feeding migration near its home site, was shorter in the northern GoB (66°N–64°N) at the ages of 3–11 than those in the southern GoB (64°N–60°30′N). In the data, most whitefish were caught with gill nets in the GoB. The mesh sizes of gill nets capturing the anadromous form were mostly 35–45 mm, while those capturing the sea‐spawning form were <35 mm in the northern GoB. It is likely that the different growth trends for small and large whitefish were connected with differences in their recruitment for fishing. The length of anadromous females at the age of four sea years increased significantly, but the length of six‐year‐old anadromous female whitefish decreased over the catch years from 1998–2014. In contrast, the length of slow‐growing sea‐spawning whitefish of six years or older increased significantly in relation to the catch year in the gill‐net catch. The increase in the growth of young age groups in both forms was probably associated with the increasing temperature and the low fishing pressure on small fish. The decreasing age at capture for both forms and the depression of the mean size of old anadromous whitefish are signs of high fishing pressure with a high gill‐net effort that selectively removes the largest and oldest individuals of both forms.     

Morphology and mitochondrial DNA variation of the Siberian whitefish <Emphasis Type="Italic">Coregonus lavaretus pidschian</Emphasis> (Gmelin) in the upstream water bodies of the Ob and Yenisei Rivers

Combining morphological, ecological and genetic analyses, we compared patterns of diversification within and among populations of the southern Siberian whitefish species Coregonus lavaretus pidschian (Gmelin) to illuminate their evolutionary history. Using sequencing data from 1,930 bp of NADH dehydrogenase subunit 1 (ND1) mitochondrial DNA regions, we documented phylogeographic relationships among populations and developed a phylogeny of mtDNA haplotypes. We found significant differences in the perforated lateral-line scale numbers within and between some populations. Clear differences in the number of gill rakers on the first branchial arch were only exhibited between populations of C. l. pidschian and Coregonus lavaretus pravdinellus Dulkeit. Concordance between different morphological groups based on two meristic traits and mtDNA patterns was also tested.     

Ultrastructure of the retina of two subspecies of Coregonus lavaretus (Teleostei) from Lake Constance (Germany)

In the two studied subspecies of Coregonus lavaretus , the pollan ( C. l. wartmanni ) (which lives deep in the pelagial) and the gangfish ( C. l. macrophthalmus ) (which lives near the slope, closer to the bottom), duplex retinae containing rod and cone photoreceptors are found. Four morphologically different cone types were observed: unequal double cones, short single cones, long single cones and triple cones. The cones are arranged in a square pattern (four double cones around a central short single cone) in the ventral and ventrotemporal and in a row pattern in the nasal and dorsal areas of the retina. Moreover, intermediate patterns can be observed in several regions indicating that double cone twisting occurs, i.e. double cones twist about their longitudinal axis. The highest cone densities are found in the ventrotemporal area. Conversely, the rod photoreceptor density is the highest in the dorsal retina. While the basic morphology of the retina is the same in both subspecies, the distribution of long single and triple cones differs between the studied animals. While these cone types are very rare in the pollan, they are common in the gangfish, though not exhibiting a regular pattern. The findings are discussed with regard to the photic habitat conditions, the systematic position of coregonids and variation of retinal morphology in the two subspecies.     

Population structure and hypothetic pathways of differentiation of whitefishes (<Emphasis Type="Italic">Coregonus lavaretus pidschian</Emphasis>, Coregonidae) in the Dodot lakes (the Khamsara River upstream)

We have studied morphology and ecology of whitefish Coregonus lavaretus pidschian (Gmelin) inhabits the Dodot lakes (Aldy-Deerlig-Khol and Ustyu-Deerlig-Khol) situated in the upstream of the Khamsara River (the Bolshoi Yenisei River basin, Tyva Region). The whitefishes were represented by lacustrine and river populations occupying similar ecological niches. We found significant differences in the perforated lateral-line scale numbers between populations. In conclusion, we suggest that this region is the secondary contact zone.     

Cannibalism in whitefish (Coregonus lavaretus)

Summary Cannibalism in whitefish (Coregonus lavaretus) is studied on the basis of an evolutionary model. The model predicts that individuals may be cannibalistic if they gain sufficiently in terms of fitness relative to the reduction in survival caused by this behaviour. If cannibalistic forms mainly increase survival it is predicted that cannibalism is particularly likely to be an evolutionarily optimal strategy if only a few age classes are being cannibalized and if, simultaneously, many age classes are cannibalistic. The same pattern, although less apparent, emerges on the basis of a model assuming that cannibalistic forms mainly increase fecundity.The whitefish in River Sokna spawn during late October to late November. Males dominate the spawning run numerically. Growth rate in mature stages is low, 1.0 cm·y^-1 for males and 1.3 cm·y^-1 for females. Yearly survival rate in mature stages is 0.574, and survival from egg to mature is 0.000078%. Larger whitefish on the average lay more and larger eggs than do smaller. Females were more cannibalistic than males; in total cannibalism contributed to an egg mortality of at least 8.8%. This is consistent with the derived theoretical predictions.Our theoretical and empirical analyses on whitefish are supported by the observed lack of sexual differences in the cannibalistic behaviour of brown trout (Salmo trutta) and Arctic char (Salvelinus alpinus).     

Fecundity of whitefish (Coregonus lavaretus) during the eu-and oligotrophication of Lake Constance

About 20 ovaries of the whitefish 'Blaufelchen' ( Coregonus lavaretus L.) of Lake Constance (Bodensee) were collected annually from 1964-1991. Absolute and relative fecundity peaked in the early 1980s, lagging about 2 years behind the maximum of total-P in the water (during the circulation period). Out of the biological time-series of Lake Constance, whitefish fecundity is the only one known to follow the phosphorus curve, and this may be the first time-series documented case of parallel trend reversal in the trophic state of a lake and fish biology. It is concluded that fish fecundity serves, at best, as an unspecific monitor of the overall well-being of the fish.     

Genetic-biochemical analysis of hybrids between Arctic cisco Coregonus autumnalis migratorius and lake-river whitefish C. lavaretus pidschian from Lake Baikal

Among the natural hybrids of coregonid fishes in Lake Baikal, the hybrids of the first generation from crossing Arctic cisco Coregonus autumnalis migratorius and lake-river whitefish (pidschian) C. lavaretus pidschian are the most abundant. They are well-identified morphologically. The data of the analysis of allozyme variations confirm the validity of the morphological determination of different Baikal coregonid forms and their hybrids, but do not allow a strict evaluation of its accuracy.     

Tandemly repeated sequences in mtDNA control region of whitefish, Coregonus lavaretus.

Length variation of the mitochondrial DNA control region was observed with PCR amplification of a sample of 138 whitefish (Coregonus lavaretus). Nucleotide sequences of representative PCR products showed that the variation was due to the presence of an approximately 100-bp motif tandemly repeated two, three, or five times in the region between the conserved sequence block-3 (CSB-3) and the gene for phenylalanine tRNA. This is the first report on the tandem array composed of long repeat units in mitochondrial DNA of salmonids.     

Ontogenetic changes in habitat use by whitefish,Coregonus lavaretus

Synopsis The whitefish, Coregonus lavaretus, in the lake Mj?sa exhibited two niche changes during their life cycle. Juveniles (< 25 cm body length) were confined to the shallow (0–30 m) epibenthic zone. Medium sized whitefish (25–35 cm body length) expanded their habitat use to include the deep (30–90 m) epibenthic zone as well as the pelagic zone. From a body length of 35 cm, habitat use was restricted to the deep epibenthic zone. Small fish in the shallow epibenthic zone ate small and medium-sized prey (zooplankton, insect larvae and surface insects). Medium-sized fish in this zone were in addition feeding on the larger amphipod, Pallasea quadrispinosa. In the pelagic zone, the diet of medium-sized whitefish was dominated by zooplankton, although some larger prey like surface insects and age-0 smelt, Osmerus eperlanus, were also eaten. In the deep epibenthic zone, the diet of both medium-sized and large (< 35 cm) whitefish consisted mainly of the large prey P. quadrispinosa.     

Relationship between annual variation in reservoir conditions and year-class strength of peled (Coregonus peled) and whitefish (C. lavaretus)

We estimated year-class strength (YCS) of whitefish and peled by VPA in two boreal reservoirs Lokka and Porttipahta with mean regulation of water level amplitudes of 2.34 and 2.49 m, respectively. YCS of peled Coregonus peled(Gmelin) was related to winter drawdown most probably via egg desiccation. In the relatively shallow Lokka dissolved oxygen deficiency in late winter also had a negative impact on survival of eggs and year-class strength. In contrast to peled, whitefish Coregonus lavaretus(L.) indicated no significant relationship with winter drawdown or dissolved oxygen level. The obvious reason for the pattern is that peled spawn on the reservoir bottom, but whitefish spawn in the ascending rivers, which are mainly unaffected by reservoir regulation.     

Seasonal movements and habitat use of river whitefish (Coregonus lavaretus) in the Koitajoki River (Finland), as determined by Carlin tagging and acoustic telemetry

In the Koitajoki River, Eastern Finland, there exists a self-sustaining population of river-spawning densely rakered whitefish (Coregonus lavaretus pallasi). The population has been classified as near-threatened due to overexploitation and possible hybridization with the lake-spawning sparsely rakered whitefish form. Thus, knowledge of habitat use, movements, and migrations is important for threat assessment and management decisions. We employed conventional tagging and acoustic telemetry to provide information on movements and home range of the Koitajoki River whitefish. We tagged mature individuals at their spawning areas and followed fish movements by tag recoveries and continuously recording fixed receiving stations. The maximum movement distances were 40–50?km both upstream and downstream from the releasing site. There were indications of a clear seasonal migration pattern and spawning-site fidelity; riverine habitats were mainly occupied for spawning and overwintering, while feeding and growth mainly took place in lacustrine environments within several lakes of the river system. Due to their migratory nature, whitefish is vulnerable to environmental disturbances and overfishing in a large geographic area.     

Energy allocation in larval and juvenile Coregonus lavaretus: validation of a bioenergetics model

Food consumption and energy allocation of larval and juvenile whitefish Coregonus lavaretus L. were studied by conducting respirometry experiments at 10, 12 and 15° C. Results from these experiments were compared with those predicted by a bioenergetics model that used observed growth as the major input. The data were used to assess the performance of the model, and evaluate its suitability for estimation of food consumption by whitefish. The mean absolute % error (ɛ) between observed and predicted food consumption was 16·3%, and the modelling efficiency (M_E) was 0·90, indicating that the model was reasonably robust. Linear regression analysis of predicted v. observed food consumption values gave a slope slightly above unity, indicating a tendency for the model to overestimate consumption at higher values. ɛ and M e were also calculated for total metabolic rate (RT), and they equalled 13·0% and 0·85, respectively. Despite some deficiencies, it is concluded that the model can be used for prediction of food consumption by highly active, planktivorous fish such as whitefish.     

Comparative study of bile-acid composition in the bile of the European vendace Coregonus albula L. and whitefish Coregonus lavaretus L. under conditions of technogenic water pollution

Changes of the bile acid composition were studied in bile of the vendace Coregonus albula L. and the whitefish Coregonus lavaretus L. under effect of sewers of an ore mining and processing plant, the main pollutin agents of the sewers being heavy metals. The revealed variability of the bile acid composition indicates different species-related sensitivity to the studied pollutants as well as a lower resistance of males as compared with females to this type of pollution. Mechanisms of effects of industrial sewers on the bile formation processes and a possibility of using parameters of the steroid lipid metabolism at evaluation of the state of water ecosystems are discussed.     

The influence of food competition and host specificity on the transmission of Triaenophorus crassus (Cestoda) and Cystidicola farionis (Nematoda) to Coregonus lavaretus and Coregonus albula (Pisces:Coregonidae) in Finland

As a superior competitor for planktonic food, vendace (Coregonus albula), when abundant, is expected to displace whitefish (Coregonus lavaretus) from feeding on plankton and to force it to rely more on benthic food. The predicted result would be a reduced abundance of the copepod-transmitted cestode Triaenophorus crassus in whitefish, but an increase in the abundance of the nematode Cystidicola farionis transmitted via benthic amphipods. We studied the occurrence of both parasites in whitefish during 1991-1996 in three interconnected areas at Lake Saimaa, Finland, where the densities of the vendace stocks varied due to natural fluctuation in year-class strengths. In accordance with our hypothesis, some indication of the effect of the density of the vendace population on abundance of C. farionis infection in whitefish was found, but not in the case of T. crassus. Only 0.2% of vendace were infected with T. crassus, while up to 100% of the whitefish in the yearly samples harboured the parasite. In further experiments we clarified which copepod species in Lake Saimaa act as first intermediate hosts of T. crassus, and verified from stomach samples the exposure of both whitefish and vendace to those species. Experimental infections indicated that the infectivity of T. crassus is lower for vendace than for whitefish. We suggest that the reason why vendace stock density does not affect T. crassus infection in whitefish is that T. crassus is transmitted in littoral areas during a short period in spring. At that time of the year copepods are abundant and available to both whitefish and vendace, but since the parasite is less infective to vendace. they do not become infected. At other times of the year, dense vendace stocks may force whitefish to shift to benthic food, which includes amphipods transmitting C. farionis. During vendace stock decline, whitefish may, however, continue to feed on plankton and avoid exposure to C. farionis.     

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

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 .     

Food selection of Coregonus lavaretus in a brackish water ecosystem

This study examined how variability in the abundance and biomass structure of benthic invertebrates affected the feeding choice of the whitefish Coregonus lavaretus on a hard bottom habitat of the brackish Baltic Sea. In general, crustaceans such as Idotea balthica and Gammarus spp. were preferred over molluscs. Although being the most numerous taxon in the invertebrate samples, Mytilus trossulus was the lowest ranking in C. lavaretus food preference. The availability of benthic invertebrate prey set the dietary range of fish but the selectivity largely described fish feeding within this range. There was no clear link between fish predation and the dominance structure of benthic invertebrate communities, suggesting that species composition, abundance and biomass of invertebrate species had no impact on the feeding selectivity of the fish. Thus, while fish predation may not affect the dominant species within a benthic community, due to strong selectivity fish may impose strong pressure on some rarer but highly preferred invertebrate prey species.     

Adaptive changes in fatty acid compositions of whitefish Coregonus lavaretus L. tissue lipids induced by anthropogenic factors]

Adaptive processes in the body of whitefish (Coregonus lavaretus L.) caused by anthropogenic effects on aquatic systems were studied. It was demonstrated that the content of fatty acid acyls correlated with the water pollution level. The role of a decrease in the content of arachidonic acid in fish reproduction under adverse conditions is discussed. It is underlined that the quantitative alterations in the gonad and liver fatty acid patterns are unidirectional. A compensatory character of the changes discovered is hypothesized.     

A hermaphrodite specimen of Coregonus lavaretus (L.) (Salmoniformes, Salmonidae) from Loch Lomond, Scotland

A single hermaphrodite specimen of Coregonus lavaretus (L.) was caught mid-January in Loch Lomond, Scotland.