Hans Lundqvist

Forecasting Environmental Responses to Restoration of Rivers Used as Log Floatways: An Interdisciplinary Challenge

Log floating in the 19th to mid 20th centuries has profoundly changed the environmental conditions in many northern river systems of the world. Regulation of flow by dams, straightening and narrowing of channels by various piers and wing dams, and homogenization of bed structure are some of the major impacts. As a result, the conditions for many riverine organisms have been altered. Removing physical constructions and returning boulders to the channels can potentially restore conditions for these organisms. Here we describe the history of log driving, review its impact on physical and biological conditions and processes, and predict the responses to restoration. Reviewing the literature on comparable restoration efforts and building upon this knowledge, using boreal Swedish rivers as an example, we address the last point. We hypothesize that restoration measures will make rivers wider and more sinuous, and provide rougher bottoms, thus improving land-water interactions and increasing the retention capacity of water, sediment, organic matter and nutrients. The geomorphic and hydraulic/hydrologic alterations are supposed to favor production, diversity, migration and reproduction of riparian and aquatic organisms. The response rates are likely to vary according to the types of processes and organisms. Some habitat components, such as beds of very large boulders and bedrock outcrops, and availability of sediment and large woody debris are believed to be extremely difficult to restore. Monitoring and evaluation at several scales are needed to test our predictions.

The effect of time, size and sex on recapture rates and yield after river releases of Salmo salar smolts

Abstract In each of the years 1988 and 1989, about 15 000 individually tagged Baltic salmon juveniles were released into the Umealven (Ume river) in northern Sweden. Two release groups, sexually immature fish and previously mature males, of varying sizes were released at five different times during the natural period for seaward migration for Baltic salmon smolts in this area. Analyses of 1069 adult recoveries caught in the commercial sea fishery from 29 863 releases in 1988 and 1989 were undertaken. An average 7–8 times higher total recapture rate for releases of immature fish than releases of previously mature males was found, suggesting a post-release mortality related to the maturity type of fish after river release. In 1988, the highest recapture rates were obtained for immature fish (18.7%) and previously mature males (3.0%) released in late May. Larger fish had a higher recapture rate at all release dates. Fish released in 1989 showed about the same overall ratio in total recapture rate between immature fish and early mature males although the total number of recoveries was lower in 1989. The two maturity types of released fish had a similar growth pattern in the sea. Average weight at catch for releases of immature smolts and previously mature males was 4.0 kg. There was no relationship between early sexual maturation and grilsing (fish returning after 1 sea-winter). At optimal time of release (27 May), the yields (kg/1000 smolts released) from releases of immature smolts and previously mature males were 748 kg and 120 kg, respectively. This difference in yield between releases of the two maturity types of fish is suggested to be due to a low smolting rate among the previously mature males. If the ultimate goal of river stockings of Baltic salmon is a high survival to adulthood and a maximal yield, the proportion of early mature males in the stocking material has to be controlled. The annual loss in production value by releasing a large proportion of non-migratory previously mature males in Swedish rivers is suggested to be 400 tonnes having a present catch value of c. 16 million Swedish krona (at a salmon price of 40 Kr/kg). Alternative smolt management strategies are discussed.

Use of the Passive Integrated Transponder (PIT) in a Fish Identification and Monitoring System for Fish Behavioral Studies

Abstract Use of the passive integrated transponder (PIT) as a fish identification and monitoring system for behavioral study of Arctic char Salvelinus alpinus was evaluated. The system was developed in order to track individual differences, mainly in rheotactic behavior. In a preliminary experimental setup, Arctic char (N = 20, 9–140 g each) were PIT-tagged and their movements were recorded at regular intervals in a circular stream channel. Two PIT tag loop detectors, placed on a narrow part of the channel, automatically recorded identity and swimming direction of tagged fish. We demonstrate some of the applications in behavioral research, such as individual, general, and diel locomotor activity patterns, rheotactic behavior, and sociograms showing activity relationships among individuals within a group.

Downstream migration of immature salmon (Salmo salar) smolts blocked by implantation of the androgen 11-ketoandrostenedione

Abstract The effect of androgen treatment on individual downstream migratory activity of 2-year-old Baltic salmon ( Salmo salar ) smolts was studied in a circular stream channel during the natural smolt migration period. Fish were tagged with passive integrated transponder (PIT) tags and implanted with silastic capsules containing the androgen 11-ketoandrostenedione or empty capsules. 11-ketoandrostenedione gives increased blood plasma levels of 11-ketotestosterone through peripheral conversion. The migratory activity of individual fish was monitored automatically by means of a PIT-tag system. In androgen-treated fish, the number of downstream passages per day during peak migration was reduced to about 10% of that of control fish. It is concluded that androgens seem to prevent downstream migration, the development of hypo-osmoregulatory ability, silvering, and the decrease in condition factor associated with smolting. Rather, androgens seem to promote retention of freshwater adaptations and increased growth in weight during spring.

Growth hormone response to seawater challenge in Atlantic salmon, Salmo salar, during parr-smolt transformation

Abstract The relation between plasma growth hormone (GH) levels and hypo-osmoregulatory ability during parr-smolt transformation was studied in 2-year-old immature parr and previously mature male parr of two different Baltic stocks of Atlantic salmon ( Salmo salar ). At several times between early May and the end of June fish were transferred to seawater (25‰ salinity) and sampled after 24 h. Among freshwater controls plasma GH levels increased only slightly in one stock during the smoltification period, whereas GH levels were significantly elevated in mid-June in the other stock. Seawater adaptability reached an optimum by the end of May to early June in one stock and 2 weeks later in the other one. Plasma GH levels in fish exposed to seawater were similar to those of freshwater fish until mid-May, but increased to significantly higher levels at the time of peak seawater adaptability. Changes in plasma sodium levels during seawater exposure were negatively correlated to plasma GH levels. At the time of peak seawater adaptability two groups were detectable among previously mature males: one group had plasma sodium levels comparable to those of immature fish, while the other had significantly higher sodium levels. In one stock plasma GH showed a similar bimodal distribution, where the group with high GH levels corresponded to low plasma sodium levels and the group with low GH levels had significantly higher sodium levels. The results indicate that some Baltic stocks of Atlantic salmon develop an ability to respond to seawater exposure with a rapid increase in GH levels during the parr-smolt transformation. It is suggested that increasing environmental salinity triggers the final development of hypo-osmoregulatory ability.

A study of the location of the entrance of a fishway in a regulated river with CFD and ADCP

Simulation-driven design with computational fluid dynamics has been used to evaluate the flow downstream of a hydropower plant with regards to upstream migrating fish. Fieldmeasurements with an Acoustic Doppler Current Profiler were performed, and the measurements were used to validate the simulations. The measurements indicate a more unstable flow than the simulations, and the tailrace jet from the turbines is stronger in the simulations. A fishway entrance was included in the simulations, and the subsequent attraction water was evaluated for two positions and two angles of the entrance at different turbine discharges. Results show that both positions are viable and that a position where the flow from the fishway does not have to compete with the flow from the power plant will generate superior attraction water. Simulations were also performed for further downstream where the flow from the turbines meets the old river bed which is the current fish passage for upstream migrating fish. A modification of the old river bed was made in the model as one scenario to generate better attraction water. This considerably increases the attraction water although it cannot compete with the flow from the tailrace tunnel.

Linking genetic assignment tests with telemetry enhances understanding of spawning migration and homing in sea trout Salmo trutta L.

Telemetric and molecular techniques are powerful tools for investigating patterns of species dispersal, habitat use, and reproductive behavior. Yet, these methods are rarely combined when studying spatial structures of migrating animals. This study combines migration data with genetic assignment tests of radio-tagged sea trout, Salmo trutta L., in two Swedish rivers. We investigate how the genetic information enhances the interpretation of the telemetry data. Individual gene frequencies of tagged fish are assigned to baseline samples of brown trout collected in tributaries and the main stems. The genetic assignment tests confirm that individuals returned from the sea to their natal stream, but also suggest that some individuals migrated to other than their native habitat. In total, 82% (R. Piteälven) and 37% (R. Vindelälven) of fish that were successfully assigned to a sample in a baseline migrated to an area in the vicinity of the sample location. The difference between rivers is likely due to low genetic differentiation among baseline samples and effects of stocking of fish in the R. Vindelälven. Combining the two techniques enhances understanding of migration behavior, important for conservation and management.

Monitoring Juvenile Atlantic Salmon and Sea Trout in the River Sävarån, Northern Sweden

Downstream migrations of Atlantic salmon (Salmo salar) and sea trout (S. trutta) smolts were monitored in the in northern Sweden to evaluate the river’s potential as a national index river for salmonid populations in the Baltic region, and to acquire information for stock conservation plans. A rotary screw trap was installed and operated from 2005 to 2008. Recapture rates of tagged smolts were high (from 8% to 31%), which allowed smolt abundances to be estimated. Between 2,600 and 3,900 salmon and 500–1,500 trout emigrated from the river each year. Genetic analyses made it possible to identify the origin of salmon and trout smolts and to determine whether they originated from the Savaran stock or from stocks in neighbouring rivers. In 2005 and 2006, most of the salmon were from the Savaran stock, which previously had been thought to be extinct. By contrast, 58% and 52% of the salmon analysed in 2007 and 2008, respectively, originated from stocks other than Savaran. The density of salmon and trout 0+ parr (i.e. recruitment success) based on electro-fishing was a poor predictor of smolt abundance 2 to 3 years later. The smolt trap data combined with genetic analyses provided valuable information to develop stock conservation plans.