Jostein Skurdal

Nasjonalt villakssenter

How can museums take care of vendace fisheries history, tradition and knowledge? The vendace fishery in the northern part of Lake Mjøsa and lower reaches of river Gudbrandsdalslågen has been the most important inland fishery in Norway. Every autumn large shoals of vendace migrate from Lake Mjøsa and up into the river to spawn. For hundreds of year...

The biology of the noble crayfish Astcus astacus

Occurrence of Psorospermium haeckeli in 28 Norweagian crayfish localities in the years 1989-1993.

Management plans are important tools in environmental management and are well known from the management of protected areas and national parks. In view of the current situation in Erope were most native crayfish species are considered vulnerabel or threatend we wanted to explore the potential of applying the concept of management planning for freswa...

Most of the harvested crayfish populations in Europe are managed through a combination of direct and indirect regulations. Of thes the most importan indirect regualtions is control of catching season. The study descriebes the effect of different catching seasons in Lake Steinsfjorden, Norway.

The article descriebes size and sex composition in the catches of noble crayfish in the heavily exploite Lake Steinsfjorden, Norway.

Noble crayfish management varies considerably between countries, with minimum harvest sizes ranging 70 - 120 mm total length. The use of minimum size is discussed.

An overview of current crayfish management in Norway.

Rearing experiment of anadromous arctic charr to study smolt transfomation.

Quality assurance of data from long time series - Measuring trap effort by field registration and reports from fishermen. Long time series is of crucial importance to assess the long-term changes in the environment, not the least in the context of large-scale ecosystem impacts from eutrophication, acidification and climate change as well as harvest...

1 Norsk institutt for naturforskning 2 Stiftelsen Lillehammer museum Sammendrag Hartvig Huitfeldt-Kaas var en av pionerene innen norsk fiskebiologi, og beskrev fisk og fiskerier i Mjøsa for hundre år siden. Vi ønsker å bruke hundreårsjubileet til å se naermere på hvordan forholdene har endret seg gjennom denne perioden, og sette et søkelys på behov...

Social class challenges faced by Norwegian sport fishing ideals between 1930 and 1960: From the 1920s, there were major changes in working life and society and large groups got regulated work and more leisure time. In addition, transport were improved. Large parts of the population could now participate in various recreational activities that had p...

Construction of artificial overwintering habitats, hibernacula, or newt hotels, is an important mitigation measure for newt populations in urban and agricultural areas. We have monitored the use of four artificial hotels built in September 2011 close to a 6000 m2 breeding pond in Norway. The four hotels ranged from 1.6 to 12.4 m3 and were located f...

Ten years of experience with national salmon rivers – does this management scheme work? Atlantic salmon are found in >600 Norwegian rivers; in a newly introduced national scheme the salmon in 52 rivers and 29 ords have been given particularly strong protection. e scheme includes 75% of the salmon resource, including most of the large and productiv...

«A good sport and a real gentleman?» - a four hundred years history on the development of British sport fishing ideals, the transformation to the Norwegian upper class during the 19th century and the current influence on Norwegian sport fishing. Sport fishing has its modern origins in England more than 400 years ago. It developed as an upper-class...

Brown trout, Salmo trutta Linneaus 1758, occurred worldwide, and is of significant conservation and soci-economic importance. Supplementary stocking of non-native hatchery fish has become increasingly important in the management of brown trout. This is also the case in Norwegian reservoirs, in order to compensate for reduced natural propagation. Th...

To reveal the effects of climate, a generalized linear mixed model was used to explore the variation in onset of spawning migration for the two newt species T. cristatus and L. vulgaris in southern Norway. Amphibians are highly influenced by the physical environment, such as temperature and rainfall. The first migrating newts were observed subseque...

Lange tidsserier er viktig for å kunne vurdere langsiktige endringer i naturen. Nytten av disse er f.eks. vist ved langsomme og storskala økosystempåvirkninger fra overgjødsling, forsuring og klimaendringer. Lange tidsserier kan også være av uvurderlig betydning for å fastslå effekter av fiske, fangst og ulike forvaltningsregimer. Steinsfjorden er...

We compared the efficiency of active (dip-nets) and passive (fish and funnel traps) methods for sampling smooth (Lissotriton vulgaris) and northern crested (Triturus cristatus) newt. Dip-nets and fish traps were equally effective in detecting presence of L. vulgaris in June and for larvae and adults in August. However, fish traps were the most effe...

Minimum size is a common management regulation in noble crayfish (Astacus astacus) fisheries. The most used catching method baited traps, catch crayfish down to 50 mm total length (TL). In Norway the minimum size is 95 mm TL and this regulation allow female crayfish to spawn a least once before being harvested. To reduce the fraction of non-legal s...

During 1979–1981, a simple and non-expensive monitoring programme for crayfish was developed in Lake Steinsfjorden. From the programme, which includes data on total trapping effort, catch statistics and population composition from test fishing before and after the fishing season, we have estimated yield and monitored population development since 19...

Atlantic salmon, Salmo salar L., stocks are decreasing worldwide, and major efforts are underway to conserve populations that are threatened. In a recent effort to conserve the Norwegian salmon, the Norwegian government implemented in 2007 a scheme called National Atlantic Salmon Watercourses and Fjords (NASW), where 52 rivers were given special pr...

Vi presenterer livssyklus, utbredelse og bestandssituasjon for storsalamander i Norge. Hovedmålet er å etablere et nasjonal overvåkningsprogram for storsalamander.

The EU Water Framework Directive and the monitoring of fish populations in large rivers and lakes: The EU Water Framework Directive is implemented as The Water Regulations in Norway to ensure a more holistic and ecosystem-based water management, and if necessary, initiate preventive or improving environmental measures to ensure environmental condit...

Hemsil renner gjennom Hemsedal og ned til Hallingdalselva ved Gol i Buskerud. Elvas samlede nedbørfelt er 1454 km2 og vassdraget er sterkt preget av reguleringer. Hemsil I kraftverket ble satt i drift i 1960, og utnytter et fall på 540 meter fra Flævann og driftsvannet ledes inn i Hemsil ved Avlaupet ovenfor Eikredammen. Eikredammen er inntaksmagas...

The last of 12 brown trout Salmo trutta stocked in a small pond in south-east Norway in 1979 were caught in July 2011. These fish represent a curiosity regarding longevity and growth pattern, and ageing from otoliths was consistent with the known life history of this specimen. Despite almost total stagnation in growth since the age of 16 years, the...

Norwegian environmental authorities decided to eradicate an introduced signal crayfish, Pacifastacus leniusculus, population using a lethal dose of the pharmaceutical Betamax Vet. Based on the assumption that the Betamax treatment acted as a non-selective sampling method, we conducted a short time experiment investigating selectivity of baited trap...

Large population of fourhorn sculpin (Myoxocephalus quadricornis) on the deep lake-floor in Lake Mjøsa; − should this species be removed from the Norwegian Red List? The fourhorn sculpin is distributed in both brackish water and freshwater in North America and Eurasia. In Norway, the species have only been recorded in the lakes Mjøsa and Store Le....

Native and native-stocked brown trout (Salmo trutta) in Lake Tesse, a regulated hydroelectric reservoir (southern Norway), were spatially segregated according to size: small individuals occurred mainly in the epibenthic habitat and larger individuals mainly in the pelagic habitat. In contrast, all size groups of non-native stocked brown trout were...

The frequency of distinct white fin margins was investigated in four brown trout (Salmo trutta) populations, living in the small stream Austadbekken (anadromous and stream resident) and in Lake Selura (lake and stream spawners). The frequency varied within and among populations. White margins were most common among parr and mature residents from Au...

Abstract  Harvesting regulations for crustacean decapods generally focus on total catch and minimum legal size of individuals. However, there are trade-offs between total catch and minimum size, and possibly also for maximum size. The outcome of various harvesting restrictions was assessed by model iterations for one lake based on a long time serie...

1. The striking variation in fecundity of the noble crayfish (Astacus astacus) was assessed from 1981 to 2009 in the lake Steinsfjorden, Norway. 2. Egg size showed no distinct variation with crayfish size or between years and seems to be a fairly fixed property. Ovarian egg numbers increased linearly with body size, from a mean of 70 eggs at maturi...

The Atlantic salmon is one of the most prized and exploited species worldwide, being at the centre of a massive sports fishing industry and increasingly as the major farmed species in many countries worldwide. Atlantic Salmon Ecology is a landmark publication, both scientifically important and visually attractive. Comprehensively covering all major...

In this study we explore a rather unique time series (1979–2002) of catch data of the crayfish Astacus astacus in Lake Steinsfjorden (SE Norway) in combination with temperature data and data on Canadian pondweed Elodea canadensis coverage. In 1977, E. canadensis was for the first time observed in the lake. Over the following years, the plant establ...

The effects of density, cover, and individual versus communal holding on brood size and female survival during the breeding period were examined in a large-scale experiment, involving 3591 mature noble crayfish, Astacus astacus L., females. Crayfish density during both mating/spawning and winter incubation had major effects on egg survival. In the...

The noble crayfish, Astacus astacus L., is extensively used for stocking and restocking purposes both in Scandinavia and in other European countries. It also has potential as a farmed species. Thus, it is important to have information about the genetic structuring of the species. Attempts have been made to detect genetic variability in A. astacus a...

In July and August 1980–1987, mark-recapture experiments with noble crayfish, Astacus astacus L., were performed to estimate density in Lake Steinsfjorden, south-east Norway. Recapture rates were examined for variation according to sex, length, sampling method or length of recovery period, i.e. the time between release and recapture. Lake Steinsfjo...

Growth, mortality, moulting rate and cheliped loss were examined in aquaculture experiments with noble crayfish, Astacus astacus L., juveniles from four different Norwegian populations in the period September 1987-June 1988. The juveniles were hatched indoors in May 1987 from parents wild-caught in 1986. The experiments were performed at 18-19°C in...

1. Habitat utilization, as well as inter- and intraspecific relations of different size groups of arctic charr (Salvelinus alpinus (L.)) and brown trout (Salmo trutta L.) in Lake Atnsjø, south-east Norway, were investigated by analysing food and spatial niches from monthly benthic and pelagic gillnet catches during June-October 1985. 2. Small indiv...

During 1981-1986, the mean prevalence of Thelohania contejeani parasitism of the noble crayfish, Astacus astacus L., in Lake Steinsfjorden, S. E. Norway, was 0.29%. The crayfish population is heavily exploited. Thelohania contejeani infection levels increased significantly during the fishing season, and variations between years were more pronounced...

We studied the number of circuli of first year scales in brown trout fry originating from eggs and alevins incubated at 2 °C and 7 °C. During the first 31/2 months the 7 °C fry were reared at a lower temperature than the 2 °C fry whereas temperature was identical during subsequent months. The numbers of circuli increased with body length in both gr...

Patterns of diel food selection in pelagic Arctic charr, Salvelinus alpinus (L.) and brown trout, Salmo trutta L. were investigated in Lake Atnsjo, SE Norway, by gillnet sampling during July-September 1985. Arctic charr feed almost exclusively on zooplankton both day and night, while brown trout had a diurnal shift in diet. For this species zooplan...

Age, growth and density of Siberian sculpin (Cottus poecilopus) and young brown trout (Salmo trutta) within two sections of River Atna; above Lake Atnsjen [Section 1 at altitudes between 739 and 715m] and below Lake Atnsjen [Section 2 at altitudes between 430 and 370m] was studied during a 6-year period (1986–91). The water temperature was consider...

The annual variability in growth and life history traits of brown trout (Salmo trutta L.) and Arctic charr (Salvelinus alpinus (L.)) in Lake Atnsjen, a Norwegian subalpine lake, was studied over a period of 13 years (1985–1997). The extent to which life-history characteristics recorded on one occasion can be regarded as representative for the popul...

The density, diet and habitat use of brown trout (Salmo trutta) and Siberian sculpin (Cottus poecilopus) were studied in the subalpine River Atna in southeastern Norway in the autumn during a six year period (1986–1991). There was an inverse relationship between the density of brown trout and Siberian sculpin. Diet overlap, as indicated by the Scho...

The population of the crayfish Astacus astacus was recorded in Lake Steinsfjorden (southeast Norway) over the period 1979–1996 by studies of total catch effort (baited traps) and catch per unit effort over the season. Over the years 1979–1987, total population of exploitable crayfish (>9.5 cm) was 194,000 (62,000 SD), and the catches were evenly di...

The effectiveness of different crayfish: predatory (pike, Esox lucius L., perch, Perca fluviatilis L.) and nonpredatory [roach, Rutilus rutilus (L.), and bream, Abramis brama (L.)] fish species as bait for noble crayfish, Astacus astacus L., was tested. Trapping was conducted in two lakes in Norway and Lithuania. Nonpredatory bream and roach were s...

Some of the highest recordings of radioactive fallout from the Chernobyl accident in Norway were found in the south-eastern Oppland and Hedmark counties. Cesium content and decay rates were followed in populations of brown trout and Arctic char in Lake Atnsjen over the years 1986–1995. These results were compared with samples for adjacent lakes to...

Lake Steinsfjorden is the most important noble crayfish locality in Norway. The crayfish population has been monitored annually since 1979 including data on total trapping effort, yield and population composition before and after the catching season. The harvest has ranged from 0.7-4.7 kg.ha-1. The catch per trap night decreased prior to 1991 and...

Wild and non-native hatchery-reared brown trout, Salmo trutta L., released when 2 summers old, were caught in the littoral habitat of Vinstervatna Reservoir, southern Norway. Hatchery-reared brown trout grew more slowly and had a smaller asymptotic length (293 ± 71 mm CL) than native fish (391 ± 56 mm CL). Hatchery-reared brown trout also exhibited...

North America harbors about 390 native species of crayfishes, 75% of the world's total. In this arti- cle, we highlight the threats posed by nonindigenous crayfishes to freshwater ecosystem function, fisheries, and the biodiversity of native crayfishes; draw some lessons for North American freshwa- ter conservation from the experience with nonindig...

1. Models of ecological half‐life may be valuable and cost‐effective predictive tools for authorities setting restrictions on human consumption of freshwater fish after environmental releases of radioactivity. This work aimed to validate such a model for radioactive caesium ( ¹³⁴ Cs and ¹³⁷ Cs) in brown trout Salmo trutta populations. Data were dra...

Increased water discharge during spring floods gives the primary cue for the start of hatching and drift of European vendace (Coregonus albula) and whitefish (Coregonus lavaretus) in the Norwegian River Lâgen. The drift increased with water flow for discharges between 50 and 850 m3∙s−1 (vendace: R2 = 0.91; whitefish: R2 = 0.77). The length of hatch...

A study of post-stocking movements of noble crayfsih was made by SCUBA-diving in River Fosselva i southeastern Norway in September and October 1993 and i July 1994.; furthermore the area was test fished with baited traps in September 1993 before the stocking and in August 1994. The crayfish stocked originated from both river and lake populations an...

Management of noble crayfish fisheries varies considerably between countries. Minimum legal harvest sizes range from 70 to 120 mm TL. National, regional and local crayfish harvesting regulations exist. The variations in regulations are strongly influenced by traditions for crayfish harvest and consumption. The current harvest of noble crayfish in E...

Two-year-old hatchery-reared progeny of inlet- and outlet spawning brown trout from Lake Tytifjorden were released at the mouth of the R. Imsa, south-western Norway. There were significant differences in migratory direction of juveniles between the two populations. After release, juvenile fish from the outlet river population moved against the curr...

This paper describes the crayfish plague situation in Norway as at October 1991 and describes the spread within and between watersheds. Four watersheds are so far affected: the Glomma, the Store Le, the Halden and the Veksa/Vrangselva. The last was affected during 1971–1974 whereas in the others the disease occurred in the period 1987–1989. In the...

Resource utilization and growth of brown trout were studied in four deep (mean depths 16.2–37.5 m) Norwegian hydroelectric reservoirs by benthic and pelagic gillnet sampling. In all the reservoirs supplementary stockings are carried out. The brown trout were spatially segregated according to size as the habitat use of small individuals (< 180–220 m...

We studied vertical distribution, substrate preference and food choice of brown trout, Salmo trutta, from benthic gillnet catches at four littoral sampling locations in a Norwegian hydroelectric reservoir. The sampling locations had different bottom substrates; at one location the bottom substrate consisted of sand, while at the other three, substr...

In Lake Atnsjo, Southeastern Norway, Arctic char Salvelinus alpinus and brown trout Salmo trutta both attained sexual maturity mainly at 6 years of age and older, usually at a body length larger than 26 cm. Both species have been heavily exploited at least since the turn of the century. The annual survival rate was estimated at 0.38 for Arctic char...

La proportion des femelles d'Astacus astacus à maturité (d'après la présence des glandes cémentaires) quand elles étaient soumises à des conditions de culture à l'intérieur à partir du mois d'août, était plus élevée (92,9-96,7%) comparée à celle des femelles dans les conditions naturelles (6,5-74,0%). La mortalité des oeufs variait de façon signifi...

Wild-caught female Astacus astacus were confined in a hatchery at different dates from 7 August throuth 25 September 1987. The proportion that completed ovarian development was high (>70%) amongst those caught during the period 7 August through 15 September. Amongst those females caught on 25 September after the maturation process had been complete...

Two summer old hatchery brown trout were acclimated in a net cage for about two weeks before their release in a subalpine reservoir in southern central Norway in two successive years (1986 and 1987). Fish in the control group were released directly into the reservoir. Gill net fishing in the fall of 1987 resulted in a significantly higher recapture...

Takeable-sized (25-61 cm total length), hatchery-reared brown trout, Salmo trutta L., were released in early July from 1982 to 1984 in the sub-alpine River Sjoa in southern central Norway. Of those recovered during the same season that they were stocked, 67-73% were caught within 10 days. Mean exploitation and survival rates in the same season of r...

Takeable size (age 4+, length 27–67cm), hatchery reared brown trout (Salmo trutta L.) were released into the rivers Lågen and Otta, the Glomma River System, southern Norway, in May-July 1981 and 1983–87. The brown trout released in May gave significantly lower recapture rates compared to those released in June/July, i.e. 22.8 per cent compared to 4...

Surveyed populations of salmonid species from 13 different localities in southern Norway, revealed large differences in gill-raker number, both within and between species. The findings indicate that phenotypic plasticity (expressed as variation in gill-raker number) is more common among the plankti-vores than the benthi-and piscivorous species, due...

In six Norwegian crayfish localities the fracttion of mature females ranged 8.3-74.0% in 1985. Mean size of mature females was significantly different between popuations and varied between 76.3 - 95.6 mm total length. Ovarian egg number increased with female size and mean number of eggs varied significantly between populations (adjusted for length...

Baited traps catch a large fraction of smallsized crayfsih, and in Lake Steinsfjroden SE Norway we have registered an increased mortality of at least 10-20% due to handling stress, consumption and transplantations among non-legalsized crayfsih (i.e. <95 mm totalt lenth). Laboratory experiments with unbaited traps indicated that increased mesh size...

Canadian waterweed invaded Lake Steinsfjorden in 1977, and by 1982 the weed covered some 72% of the lake floor within the 0-6 m depth range. Langth distribution of Astacus astacus in shallow area with dense stands of Elodea outside, were skewed and the fraction of small crayfsih were low compared to areas without Elodea. However, length distributio...

Feeding experiments were performed at different light regimes to reveal consumption of plant and animal food (Shrimp and Elodea) in the nobel crayfish. The shrimps were consumed at a higher rate than Elodea. At summer temperature (17-18 C), daily consumption was respectively 10.5 and 6.5 % of bodyweight on wet weight basis. Turnover rate considered...

Depth distribution, habitat segregation and food choice were examined in the crayfsi in Lake Steinsfjroden, SE Norway, by trapping and SCUBA diving. Temperature was the main determinging factor regulationg depth distribution, while feeding and oxygen conditions seemed to be of minor importance. A significant differende was found between the size di...

Crayfish were collected from Lake Steinsfjorden, Norway, one month before maturation, and transferred to culture conditions. Of the females in culture, 92.8% matured, whereas only 36.3% of females in the lake in the same year (1986) matured. During the preceding 5 years the proportion of mature females in the lake had varied between 6.5 and 62.1%....