Svein Jakob Saltveit

Electrofishing — Theory and practice with special emphasis on salmonids

This report attempts to establish guide-lines for electrofishing in population studies and is the result of literature studies and experience from electrofishing in Denmark, Finland, Norway and Sweden. Equipment, safety and training, sampling design and precision requirements for various types of investigations, population estimation and fishing practice are discussed. The results are put forward in the form of recommendations. Special attention is paid to the sampling design of surveys in streams of different types and for different purposes. Examples of the computation procedures are also included.

Stream Regulation in Norway

Norway, situated in northern Europe, is characterized by mountainous area in the north and west with relatively short and fast running streams, while in east and northeastern Norway the largest watercourses are found. Watercourses in Norway have been used for various purposes, such as timber transport, mills and sawmills, as well as drinking water. However, the greatest use is connected with the great demand for hydroelectric power, and this paper will consider mainly the effects of such regulation.

Stoneflies and River Regulation — A Review

Stoneflies (Plecoptera) are a widespread and abundant order of benthic freshwater insects, especially in the running waters of temperate regions. They occupy a central role in trophic relationships both in terms of functional feeding groups and as fish food organisms. Although recorded from a range of freshwater habitats, the greatest species diversity is to be found in cool lotic habitats (Hynes 1976; Baumann 1979). They are considered to be good indicators of water quality and environmental change (Gaufin 1973; Baumann 1979).

Survival of eggs of Atlantic salmon (Salmo salar) in a drawdown zone of a regulated river influenced by groundwater

Groundwater may create refuges for Atlantic salmon egg survival during low flows in regulated rivers and thus play an important role for survival during winter. To investigate the links between the survival of salmon embryos and hyporheic hydrological processes during permanent winter drawdown, a 100-m-long and 50-m-wide gravel area in a regulated river, the River Suldalslågen, was used for an experimental study. Surface and subsurface water levels were monitored with 2-min time resolution by means of water pressure sensors placed in pipes. Temperature, conductivity and dissolved oxygen were also measured. Eight cylindrical boxes, each with two compartments (at 10- and 30-cm depth, respectively) containing 50 Atlantic salmon eggs, were placed in the river bed substrate of both the drawdown zone and the permanently wetted area as a reference. They were regularly checked for survival during winter from January to May, coinciding with egg development period for this river. Survival rates in boxes in the dewatered river bed were between 8 and 78% during winter, compared to 80 to 99% in the reference wetted area. The main driver for egg survival in the dewatered area was groundwater with sufficient oxygen levels.

Functional diversity and community assembly of river invertebrates show globally consistent responses to decreasing glacier cover

Global change threatens invertebrate biodiversity and its central role in numerous ecosystem functions and services. Functional trait analyses have been advocated to uncover global mechanisms behind biodiversity responses to environmental change, but the application of this approach for invertebrates is underdeveloped relative to other organism groups. From an evaluation of 363 records comprising >1.23 million invertebrates collected from rivers across nine biogeographic regions on three continents, consistent responses of community trait composition and diversity to replicated gradients of reduced glacier cover are demonstrated. After accounting for a systematic regional effect of latitude, the processes shaping river invertebrate functional diversity are globally consistent. Analyses nested within individual regions identified an increase in functional diversity as glacier cover decreases. Community assembly models demonstrated that dispersal limitation was the dominant process underlying these patterns, although environmental filtering was also evident in highly glacierized basins. These findings indicate that predictable mechanisms govern river invertebrate community responses to decreasing glacier cover globally.Analysing >1 million river invertebrates from nine biogeographic regions, the authors show that functional trait diversity increases consistently as glacier cover decreases.

Rivers of the Boreal Uplands

In Europe, the Boreal forest ecosystem centers around 60°N. The northern limit is roughly along the July 13 °C isotherm and the southern limit along the July 18 °C isotherm. This chapter describes the rivers within this region along the western coast of the Scandinavian Peninsula that drain into the Skagerrak or North Sea. A total of 173 major rivers belong to this region, of which 10 rivers have been selected to illustrate major characteristics. Although a general climate regime for the Boreal Uplands exists, a great variety of micro-climates occurs that significantly affects local vegetation. The south-eastern and northern watersheds are dominated by birch, pine and spruce, whereas western watersheds are dominated by birch. Watersheds in the Boreal Uplands can be divided into three main groups. Most watersheds contain rivers having considerable gradients, intermediate discharge, lakes in the headwaters in mountain regions, and some are even glacier-fed. The second group consists of large watersheds mainly situated in the southeast. These rivers are characterized by relative high discharge and long stretches with low gradients; large, deep lakes are common. The third group comprises of small watersheds in coastal areas. Here, rivers have low discharge, respond quickly to fluctuations in precipitation, and have intermediate gradients. Rivers of the Boreal Uplands have been of significant importance to humans for centuries as reproductive areas for Atlantic salmon, as a transport medium for timber, and for hydropower.

Hydrological and thermal effects of hydropeaking on early life stages of salmonids: A modelling approach for implementing mitigation strategies

Alterations in hydrological and thermal regimes can potentially affect salmonid early life stages development and survival. The dewatering of salmon spawning redds due to hydropeaking can lead to mortality in early life stages, with higher impact on the alevins as they have lower tolerance to dewatering than the eggs. Flow-related mitigation measures can reduce early life stage mortality. We present a set of modelling tools to assess impacts and mitigation options to minimise the risk of mortality in early life stages in hydropeaking rivers. We successfully modelled long-term hydrological and thermal alterations and consequences for development rates. We estimated the risk of early life stages mortality and assessed the cost-effectiveness of implementing three release-related mitigation options (A,B,C). The economic cost of mitigation was low and ranged between 0.7% and 2.6% of the annual hydropower production. Options reducing the flow during spawning (B and C) in addition to only release minimum flows during development (A) were considered more effective for egg and alevin survival. Options B and C were however constraint by water availability in the system for certain years, and therefore only option A was always feasible. The set of modelling tools used in this study were satisfactory and their applications can be useful especially in systems where little field data is available. Targeted measures built on well-informed modelling tools can be tested on their effectiveness to mitigate dewatering effects vs. the hydropower system capacity to release or conserve water for power production. Environmental flow releases targeting specific ecological objectives can provide better cost-effective options than conventional operational rules complying with general legislation.

Predicting the Effects of a Possible Temperature Increase Due to Stream Regulation on the Eggs of Whitefish (Coregonus Lav Aretus) — A Laboratory Approach

In the fjord lake Randsfjorden, Norway, the whitefish (Coregonus lavaretus) has four sympatric populations (Enge 1959). One of these spawns in the lower parts of the main inlet River Dokka-Etna, while the others spawn in the lake.

Short-wingedness in the stonefly Diura nanseni (Kempny) (Plecoptera: Perlodidae)

Short-wingedness in adult Diura nanseni is extremely rare and only three short-winged males have been previously recorded. In a population from the Norwegian Jotunheimen Mountains half the males were micropterous in 1976, although normal-winged in subsequent years. The features of this population are described. Several hypotheses, including low temperatures during egg development, are proposed to explain this isolated example of short-wingedness.

Aquatic biodiversity in sedimentation ponds receiving road runoff - What are the key drivers?

Recently, increased attention has been paid to biodiversity conservation provided by blue-green solutions such as engineered ponds that are primarily established for water treatment and flood control. However, little research has been done to analyse the factors that affect biodiversity in such ponds. The purpose of this study was to evaluate the influence of environmental factors on aquatic biodiversity, mainly macroinvertebrate communities, in road sedimentation ponds in order to provide a foundation for recommendations on aquatic biodiversity conservation. Multivariate statistical methods, including unconstrained and constrained analysis, were applied to examine the relationships between organisms and the water quality as well as physical factors (including plant cover). Stepwise multiple regressions indicated that the most important variables governing the variation in the biological community composition were pond size, average annual daily traffic, metals, chloride, distance to the closest pond from study pond, dissolved oxygen, hydrocarbons, and phosphorus. The presence of most taxa was positively correlated with pond size and negatively correlated with metals. Small ponds with high pollutant loadings were associated with a low diversity and dominated by a few pollution tolerant taxa such as oligochaetes. A comprehensive understanding of impacts of various environmental factors on aquatic biodiversity is important to effectively promote and conserve aquatic biodiversity in such sedimentation ponds. Our results indicate that road sedimentation ponds should be designed large enough, because large ponds are likely to provide a more heterogeneous habitat and thus contain a species rich fauna. In addition, larger ponds seem to be less contaminated due to dilution compared to smaller ponds, thereby maintaining a higher biodiversity. Finally, creating some additional ponds in the vicinity of the sedimentation ponds in areas with few water bodies would increase the connectivity that facilitates the movement of invertebrates between ponds.