Search results for "salmonid"
showing 10 items of 82 documents
Mortality of pike-perch (Stizostedion lucioperca), brown trout (Salmo trutta) and landlocked salmon (Salmo salar m. sebago) caught as by-catch in pel…
2000
Altogether 146 pike-perch, 49 brown trout and 19 landlocked salmon were caught in 23 exploratory trawl-hauls in lake Pyhaselka, Finland. Brown trout and salmon were caught only in surface trawling, whereas pike-perch were taken also in mid-water trawling. Most of the fish were smaller than the minimal legal size of 40 cm. To estimate their post-trawling mortality, 129 fish were kept in net cages for 1 week. Less than 15% of the pike-perch and brown trout caught by surface trawl died during 1 week caging, whereas every caged salmon died. Mid-water trawling was far more lethal to pike-perch than surface trawling. We conclude that pike-perch and brown trout can recover from surface trawling. S…
The use of fish bile metabolite analyses as exposure biomarkers to pulp and paper mill effluents
1998
The exposure of caged one-year-old whitefish (Coregonus lavaretus) to wood extractives and chlorophenolics from pulp and paper mill effluents in Lake Saimaa (SE Finland) was investigated. Whitefish were exposed at 17 locations affected by effluents from pulp and paper mills and at 5 reference areas. Resin and fatty acids and chlorophenolics in bile were analysed by GC and GC-MS. Cholesterol concentration in bile was also measured. Results show that despite of process changes to ECF and waste water treatment improvements employed by the pulp and paper industry in the study area, it is still possible to detect elevated concentrations of these substances in the bile of fish exposed in the vici…
Finnish salmon resistant to Gyrodactylus salaris: a long-term study at fish farms.
1996
Abstract The occurrence of Gyrodactylus salaris on Baltic salmon ( Salmo salar ), sea trout ( S. trutta m. trutta ) and brown trout ( S. trutta m. lacustris ) was examined from 1984 to 1993 at 4 fish farms (A, B, C and D) that produce smolts for stocking in northern Finland. No G. salaris was found on the sea or brown trout, but it did occur on salmon for 6–7 years at farms B, C and D, the prevalences of infection being 9.5%, 17.7% and 8.8% for salmon yearlings and smolts during that time, respectively, but less than 1.2% for fingerlings at farms B and C. Only brood stock salmon were infected at farm A in 4 years. The abundances of G. salaris increased during the second winter of each year …
HELMINTH ASSEMBLAGES OF WHITEFISH (COREGONUS LAVARETUS) IN INTERCONNECTED LAKES: SIMILARITY AS A FUNCTION OF SPECIES SPECIFIC PARASITES AND GEOGRAPHI…
2004
This article examined the composition of parasite assemblages of whitefish (Coregonus lavaretus) in 8 interconnected lakes in northeastern Finland and evaluated the role of coregonid specific parasites and the geographical distance between populations in determining the similarity of the assemblages. Parasite assemblages were compared using the Jaccard qualitative similarity index and a quantitative similarity index and by incorporating the allogenic-autogenic species concept and the effects of 2 corresponding measures of geographical distance between the lakes. The majority of the parasite species found (10 of 14) were specific to salmonids. Similarity of assemblages of autogenic parasites…
Effects of weekend starvation and the duration of daily feeding on production parameters of rainbow trout Oncorhynchus mykiss
2021
It would often be practical to starve the cultivated fishes over the weekends, e.g. to save in labour costs. We evaluated the possibility that domesticated juvenile rainbow trout (Oncorhynchus mykiss) could compensate for the lost growth of the 2-day weekend starvation by either hyperphagic response and/or by lower feed conversion ratio, compared to the fish fed every day in an 8-week experiment. Rainbow trout (initial weight c. 30 g, temperature 16 °C) starved during the weekends were able to increase feed intake during the weekdays clearly above the intake of the control fish after the first two weekends, also seen as an increase of the compensation coefficients over the last four weeks o…
Is Aquaponics Beneficial in Terms of Fish and Plant Growth and Water Quality in Comparison to Separate Recirculating Aquaculture and Hydroponic Syste…
2022
Aquaponics is a technique where a recirculating aquaculture system (RAS) and hydroponics are integrated to grow plants and fish in a closed system. We investigated if the growth of rainbow trout (Oncorhynchus mykiss) and baby spinach (Spinacia oleracea) would be affected in a coupled aquaponic system compared to the growth of the fish in RAS or plants in a hydroponic system, all systems as three replicates. We also investigated the possible effects of plants on the onset of nitrification in biofilters and on the concentration of off-flavor-causing agents geosmin (GSM) and 2-methylisoborneol (MIB) in rainbow trout flesh and spinach. For the fish grown in aquaponics, the weight gain and speci…
Adaptive radiation along a thermal gradient: preliminary results of habitat use and respiration rate divergence among whitefish morphs.
2014
Adaptive radiation is considered an important mechanism for the development of new species, but very little is known about the role of thermal adaptation during this process. Such adaptation should be especially important in poikilothermic animals that are often subjected to pronounced seasonal temperature variation that directly affects metabolic function. We conducted a preliminary study of individual lifetime thermal habitat use and respiration rates of four whitefish (Coregonus lavaretus (L.)) morphs (two pelagic, one littoral and one profundal) using stable carbon and oxygen isotope values of otolith carbonate. These morphs, two of which utilized pelagic habitats, one littoral and one …
La remontée du saumon pour le frai dans le fleuve Tornionjoki, suivie au moyen d'un sonar à double faisceau horizontal.
2000
Fixed location split-beam horizontal echosounding was used to assess the size and timing of the Atlantic salmon (Salmo salar) spawning run in the River Tornionjoki. Four transducers, two on each river bank, were mounted across the river at the study site 4 km upstream from the river mouth. Net weirs were used on both shores to direct the passage of fish through the acoustic beams. Hydroacoustic monitoring covered 40-50% of the river cross-sectional area. Also test fishing and yearly catch statistics of salmon were used as an indication of the size of the spawning run in the river. Altogether, 7 700, 5 300 and 4 300 salmon-sized targets (target strength, TS ≥ -29 dB) moving upstream were det…
Attenuated Carbohydrate and Gill Na+ , K+-ATPase Stress Responses in Whitefish Caged near Bleached Kraft Mill Discharges
2002
Exposure to biologically treated bleached kraft mill effluent (BKME) is demonstrated to greatly modify the acute physiological stress response in fish and, accordingly, to lead to inconsistencies in data interpretation due to dissimilar effects of handling procedures on reference and exposed fish. To consider this phenomenon, juvenile whitefish (Coregonus lavaretus) were caged for 30 days in four reference sites and in three areas influenced by different BKME discharges. After exposure, fish were subjected to the impacts of low-level handling by raising the cages to the water surface, serially handnetting the fish, and transferring ( approximately 10 min) the submerged cages to the research…
Nocturnal drift of mayfly nymphs as a post-contact antipredator mechanism
2000
SUMMARY 1. The predominantly nocturnal constrained drift of stream invertebrates is commonly regarded as a behaviour that avoids encounters with visually foraging fish in the water column. The alternative explanation, that drift peaks are caused by bottom-feeding, nocturnal predators, has rarely been tested. 2. We examined these hypotheses by collecting invertebrate drift in five streams in northern Finland: one with brown trout (Salmo trutta, a drift-feeding fish), one with alpine bullhead (Cottus poecilopus, a benthic fish), one with both species, and two fishless streams. 3. Drift by Baetis mayflies was aperiodic or slightly diurnal in both fishless streams on all sampling occasions. In …