species (taxonomic group) per site database including environmental information

The dataset contains individual data for almost 8,000 brown trout (Salmo trutta L., 1758) captured during their spawning migration from Lake Mjøsa to the main tributary River Gudbrandsdalslågen in Norway during the period 1966 to 2005. These individuals belong to the large-sized piscivorous population of brown trout named Hunderørret (Hunder brown trout). A majority of these trout spawn upstream the waterfall Hunderfossen. Ascending this large waterfall, the migration length and characteristics of the spawning areas, are probably selection drivers for the large body sizes this population achieves compared to any other populations of piscivorous brown trout spawning in other rivers draining to Lake Mjøsa.

A hydropower dam was established at Hunderfossen between 1961 and 1964, causing a migration barrier for the Hunder brown trout. A fish ladder was also built, making the ascent possible from 1966, but not without negative effects (Aass 1990). The functionality seems to vary due to water temperature and water flow (Jensen & Aass 1995). The body size seems to affect the success of both entering and ascending the ladder. Additionally, the dam reduced survival of both smolt and kelt, due to predation in the dammed area and turbine passage mortality during downstream migration. The damming also reduced the areas of productive fish habitats in the river both upstream and downstream the dam (Aass et al. 1989).

When the fish ladder was opened, allowing the spawners to pass the dam, a capture-mark-recapture program was initiated. Trap capture, individual measurements, tagging, scale sampling and registration of recaptured repeated spawners in the fish ladder, were then implemented in a monitoring program. All spawners caught in the trap were individually measured and tagged with numbered Carlin tags (Carlin 1955).

To abate the reduced natural production of Hunder brown trout in the regulated river, a stocking program was initiated during the mid-1960s. The stocked fish are mainly released as 2-years old both in the river and directly into the lake (15,000-20,000 individuals per year). The stocked fish also returns to the river on spawning runs as mature adults. This long-time data series has been continued more or less unchanged until it was terminated in 2016. All stocked brown trout were tagged by cutting the adipose fin prior to release. To evaluate and optimize the stocking strategy, a large number of stocked smolt individuals were also tagged. Hence more than 30,000 individuals (both wild and stocked, spawners and smolts) have been marked individually with Carlin tags before release both upstream and downstream the Hunderfossen dam during 1966-2015. For a subset of these fish, approximately 8,000 individuals who climbed the fish ladder between 1966 and 2005, information on age, growth, time of migration and spawning history has been obtained from schlerochronological analysis of the sampled scales. This data has also been used to back-calculate yearly growth and to identify important life-history information such as hatching year, growth in river, age and size at smoltification, growth in lake, age and size at sexual maturation, and number of spawning events (e.g. Haugen et al. 2008).

Based on the 1966-2005 data the Hunder brown trout typically spend their first three to five years as parr in the river before migrating downstream to Lake Mjøsa (corresponding to smoltification and seaward migration in anadromous salmon and trout). In the lake they typically prey on fish for two to four years before maturation and migration back to the river to spawn. The Hunder brown trout typically perform biennial spawning runs and average age at first spawning run is ca. 7 years. Average size at first spawning run is ca. 3.5 kg and 65 cm. The Hunder brown trout seem to have a potential maximum life span of 15-20 years and a potential maximum size of 15-20 kg and >100 cm. However, less than 10% of the spawners reach age above 10 years, and less than 1% of the spawners reach weight above 10 kg.

Farming, Biota, Climatology/Meteorology/Atmosphere, Economy, Elevation, Environment, Inland Waters, Location, Society, Structure, Utilities/Communications

lake, brown trout, Salmo trutta, hydropower dam, migration, growth, spawning, capture-mark-recapture, schlerochronology, scales, smoltification, monitoring, fishing, Hunderfossen, Hunder trout, age

Access

all Windows systems

English

restricted access

no

update planned

Per Aass is retired, but affiliated at the Zoological Museum of the University of Oslo.

multiple

The dataset needs to be requested from dataset creator with specific conditions of use.

The Norwegian Institute for Water Research (NIVA) by Jannicke Moe has been given the administrator rights for a period of five years (2016-2020) with option for prolongation.

The dataset needs to be requested from dataset creator with specific conditions of use.

As for data contributor/owner 1.

Life-history data on Hunder brown trout (Salmo trutta) from Lake Mjøsa, Norway. Freshwater Metadata Journal 25: 1-11

Europe: Norway

Group C: temperate/mesothermal climates

Northern Baltic Drainages

Capture, mark and recapture data of Hunder trout (without information on growth and spawning) are available for a larger number of individuals (30,000). These data will be described in a separate metadata paper.

latitude/longitude, format: DD

For most data points a location is reported, but not coordinates.

 

<100

A large number of sites have been reported. In addition to the original site names, the sites are aggregated to larger regions (e.g. "lake", "river above dam" or "river below dam").

Daily meteorological data can be downloaded from eklima.met.no, stations Kise (12550) and Toten (11500).

total P, nitrate, total N, hardness, alkalinity, TOC (total organic carbon), water temperature, pH, conductivity, chlorophyll, colour, Secci disc depth, thermocline depth

Other environmental data are available from NIVA (described by Løvik & Moe 2016). Other parameters (lake data): E. coli (2009-2011), ice cover (1949-2009), primary production, SiO2, turbidity.

per sample

fish

Data on other organism groups from Lake Mjøsa (phytoplankton, zooplankton) and River Gudbrandsdalslågen (phytobenthos, macroinvertebrates) are available from other sources (see Løvik et al. 2016, Løvik & Moe 2016).

no data available

yes

yes

no

The authors have contributed as follows:
Per Aass initiated this important monitoring program when the dam was constructed, and was in charge of the tagging of fish in the fish ladder for several years. Tore Qvenild has supported with computer assistance, digitizing and establishing the first version of the database and early stage analysis of these data. Atle Rustadbakken has been responsible for data cleaning and data compilation. He has also worked closely together with P. Aass on the age and growth analyses of the scales from thousands of trout. Espen Lund has also been involved in the data cleaning process, developing digital documentation, the analysis process and reading growth structures from fish together with A. Rustadbakken. Jannicke Moe has been responsible for constructing a relational database structure in Microsoft Access, importing the data from various Microsoft Excel files, and exporting data for sharing with other researchers.