Eva Brännäs

DOES RESTORATION OF STRUCTURAL HETEROGENEITY IN STREAMS ENHANCE FISH AND MACROINVERTEBRATE DIVERSITY

Restoration schemes often rely on the assumption that enhancing habitat complexity through addition of in-stream structures such as boulders and woody debris leads to increased biodiversity, but evidence for this assumption is scarce. We compared structural heterogeneity and fish and invertebrate diversity at restored, unrestored, and reference sites on tributaries of the Ume River, northern Sweden, where several kilometers of streams have been restored from channelization through placement of boulders into the channel. Structural heterogeneity at the study sites was assessed using a contour tracer at two spatial resolutions likely to be affected by restoration. These are the patch scale (0.7 m), reflecting substratum characteristics, and the reach scale (50 m), reflecting general channel topography. Fish and invertebrate samples collected via electroshocking were used to assess taxonomic richness, taxonomic density, evenness, and assemblage composition at the study sites. Measures of structural heterogeneity were substantially higher at restored relative to channelized sites; however, components of fish and invertebrate diversity were similar between these treatments. At restored sites, measures of structural heterogeneity and fish and invertebrate diversity were consistent with, or slightly exceeded reference levels. This implies that local (patch to reach) heterogeneity did not structure fish and invertebrate assemblages in the study streams. Our results suggest that restoration might have little beneficial effect on biodiversity if the restoration schemes (and the original impact under amelioration) do not affect structural heterogeneity relevant to the target organisms.

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.

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.

High-resolution 1H magic angle spinning NMR spectroscopy of intact arctic char (Salvelinus alpinus) muscle. Quantitative analysis of n-3 fatty acids, EPA and DHA.

The lipid and small metabolite profiles from intact muscles of Arctic char were investigated using (1)H high-resolution magic angle spinning ((1)H HR-MAS) NMR spectroscopy. Not only the total n-3 fatty acid content but also the eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) contents of the muscle were obtained from the (1)H HR-MAS NMR spectra without pretreatment of the tissue or lipophilic extraction. A number of small metabolites could also be observed, where creatine/phosphocreatine, anserine and taurine were the most abundant. Thus, the use of (1)H HR-MAS NMR led to simplified analysis techniques that can give direct information on the nutritional value of the fish.

The Swedish Arctic charr breeding programme

Results and experiences from a selective breeding programme aiming at improving the performance of an Arctic charr strain in aquaculture are presented. The programme, which has been running since 1985, uses traditional quantitative genetic methods based on relatedness and trait measurements. Traits considered included growth, age at sexual maturity, flesh colour, fat content and other features. Estimates in the early phase of the programme showed promising heritabilities for most traits, e.g. growth heritabilities of 0.34–0.52, and suggested that improvement by selection was feasible. Several traits such as a high rate of early maturation and poor flesh colour that were considered problematic by the Arctic charr farming industry at the programme’s start no longer hamper farming. Considerable improvement of growth by selection, estimated at 8% per generation, has contributed to shortening the production cycle in commercial farming. Results from studies of genotype–environment interactions are presented and discussed. Poor survival of fertilised eggs is a major problem in Swedish Arctic charr farming as indicated by presented survival rates. Efforts have consistently been made to avoid inbreeding in the selected strain, and at the present seventh generation the accumulated increase in inbreeding is estimated from pedigree data to be only approximately 5%.

A test of the individual feeding activity and food size preference in rainbow trout using demand feeders

Feeding activity and food size preferences were investigated in three groups of rainbow trout with initial weights ranging from 200 to 1000 g. Fish were given the option of releasing food from either of two demand feeding devices that contained either 6 mm or 9 mm food pellets. Individual biting activity (to activate release of food) was continuously monitored using specially designed passive integrated transponders (PIT-tags). In each of the groups, biting activity was strongly influenced by three individuals, which accounted for 70–85% of the total. Thus, high bite activity by few individuals indicates the development of social dominance hierarchies. There was no statistically significant correlation between number of bites and growth rate, indicating that the fish that operated the demand feeders did not gain any growth advantage. Trout that dominated the actuation of the feeders were found among both medium- and large-sized fish. There was no evidence of active food size selection, and the fish that most frequently operated the feeders defended one area of the tank rather than preferring the trigger that would have delivered food of the optimal size.

Feeding behaviour of the Arctic charr in comparison with the rainbow trout

Abstract Appropriate feeding techniques are important in order to optimize feed intake and minimize feed losses in net-pen aquaculture operations. The ability of the Arctic charr to feed in the water column was studied using different techniques of feed pellet release. For comparison, the same study was carried out with rainbow trout. The pellets were all released simultaneously or with a 5-s interval between delivery and with or without dispersal of pellets over the water surface. When the pellets were all delivered simultaneously, the charr only caught 39% (not dispersed) or 65% (dispersed). The charr took more than 94% of the pellets in the water column if they were released at 5-s intervals, irrespective of whether or not the pellets were dispersed over the surface. The rainbow trout, on the other hand, caught nearly 100% of the pellets in the water irrespective of feeding technique. When reared in net-pens, Arctic charr should, therefore, be fed a few pellets at a time, and the pellets should be released at intervals and dispersed over the water surface.

Importance of fatty acids in broodstock diets with emphasis on Arctic char (Salvelinus alpinus) eggs

The importance of long-chain polyunsaturated fatty acids, especially the eicosanoid precursors, is addressed in this paper. It has been generally recognized that eicosapentaenoic (EPA, 20:5n-3) and docosahexaenoic acid (DHA, 22:6n-3) are of significant importance in fish reproduction while arachidonic acid (AA, 20:4n-6) has often been overlooked. The ratio between C20 fatty acids EPA and AA might be important for many physiological functions depending on the species evolution and its requirements. Arctic char (Salvelinus alpinus) has a much more pronounced freshwater history and therefore different fatty acid requirements than the other commonly farmed salmonids such as salmon (Salmo salar), brown trout (Salmo trutta) and rainbow trout (Oncorhynchus mykiss). Therefore there is reason to formulate a feed that is more suitable for farming of this freshwater species. In this study, freshwater wild-origin char eggs were compared to farmed eggs of char. The ratio n-3/n-6 of total phospholipids of eggs was much lower in the wild fish, 3.5 versus 13.5, and the hatching rate of eggs from natural environment was much higher (20–70% vs. >80%). We conclude that feed based on marine raw product does not fulfill the requirements for essential fatty acids for freshwater char and we suggest that AA is supplemented to the broodstock diet and that at least linoleic acid (18:2n-6) is included in the on-growth diet formulas to lower the n-3/n-6 fatty acid ratio.

Thresholds for Survival of Brown Trout during the Spring Flood Acid Pulse in Streams High in Dissolved Organic Carbon

Abstract The survival of brown trout Salmo trutta embryos and first-year juveniles was studied using in situ bioassays during the snowmelt-driven spring flood in 12 streams in northern Sweden. Unlike in most previous studies on the impact of acidity on brown trout, the streams in this study were high in dissolved organic carbon (DOC), and as a result organic acids play a primary role in controlling pH. During the spring flood period DOC concentrations increased strongly in most streams and, in combination with dilution of acid-neutralizing capacity, resulted in a decrease in pH and an increase in total and inorganic monomeric aluminum. High mortality of brown trout juveniles occurred during the spring flood and was best correlated to the high H+ concentration. No toxic effect could be directly attributed to measured inorganic aluminum concentrations. An empirical model to predict juvenile brown trout mortality in DOC-rich streams was developed, and based on these predictions a critical chemical threshold ...

Behavioral Response to Commercial Food of Different Sizes and Self-Initiated Food Size Selection by Arctic Char

Abstract Reaction and handling times for Arctic char Salvelinus alpinus with respect to feed pellets that varied in length or diameter were visually observed. Reaction time decreased and handling time increased with increasing pellet size, responses that were more pronounced with increasing diameter than with increasing length of the food particles. In total, fish missed or failed to respond to nearly 50% of the smallest and largest pellets offered to them. Also, we studied the ability of Arctic char to choose among different sizes of pellets and to locate food of optimal size. Three replicate groups of char each could release three demand feeders, each feeder delivering a different particle size (1.7, 2.5, or 3.6% of fish fork length). After about 2 weeks, the proportion of bites on the feeder that contained pellets close to the optimal size exceeded 70% of the total daily biting activity. This pattern was repeated in a series of experiments with different feeder positions, indicating a strong ability to...