Erkki Virtanen

Toxicological effects of dehydroabietic acid (DHAA) on the trout, Salmo gairdneri Richardson, in fresh water

Abstract Toxicological and physiological effects of dehydroabietic acid (DHAA), a major poison to fishes in pulp and paper mill effluents, were studied by two experiments with rainbow trout, Salmo gairdneri Richardson: in the first, fish were acutely exposed for 4 days to an average DHAA concentration of 1.2 mg l −1 (Exp. I) and in the second for 30 days to an average of 20 μg DHAA l −1 (Exp. II). Compared to the controls, fish of Exp. I displayed a decreased relative weight of liver, an increased blood haematocrit, and increased haemoglobin as well as plasma protein concentrations. The aspartate aminotransferase activity of heart muscle was significantly elevated, as was also the lactate dehydrogenase (LDH) of white muscle tissue. In the blood plasma, the proportion of muscle type LDH activity was simultaneously increased. UDP-glucuronyl-transferase activities of liver and kidney were strongly decreased. Results suggest an increased and altered use of body energy reserves, decreased plasma volume and impaired liver function. Fish of Exp. II showed an increased relative weight of spleen. In addition, liver and gill LDH shifted towards heart-type. We conclude that 20 μg l −1 is close to the “minimum effective concentration” of DHAA to rainbow trout.

Effect of physiological condition and smoltification status at smolt release on subsequent catches of adult salmon

Abstract In 1981–1986, 48 groups of Baltic salmon smolts were individually tagged and sampled for physiological analysis of their condition and smolt status. Tagging and sampling were carried out prior to release at freshwater rearing units. In mid-May the smolts were transported ca. 200–400 km to the stocking site in the estuary of river Kymi (Gulf of Finland) and released immediately. The catch from each stocking group was estimated on the basis of adult tag recovery rates and average weights of the captured salmon. The catch of adult salmon was affected both by the year of smolt release and smolt size. Therefore, the catch from each smolt group was compared to total mean catch, mean catch of the respective stocking year and mean catch of the respective size category of smolts. Of the measured parameters at release, the ionic and osmotic balance after seawater challenge test (48 h at 30 ppt) and plasma thyroxine were the most predictive for survival in the sea, indicating the importance of the correct migratory status. In addition, such stress indices as blood glucose and lactate showed significant correlation with catch.

Physiological responses to continuous swimming in wild salmon (Salmo salar L.) parr and smolt.

Wild salmon (Salmo salar) parr and smolt were forced to swim against constant flow (50 cm.s−1) for 8 hours. Physiological properties describing the hormonal status, the energy metabolism and the ionic and osmotic balance of fish were measured from the fish prior to and at the end of the swimming test.Plasma cortisol levels were elevated in response to enforced swimming; the response of the smolt was clearly greater than that of the parr. Plasma thyroxine concentration increased in the parr but stayed at the initial level in the smolts. The parr consumed much of their coelomic fat, but the glycogen stores stayed nearly constant. The smolts had very low fat stores, and the glycogen stores were depleted in the test. The ionic and osmotic balance of the parr was stable in the test, but in smolts, the plasma Cl−1 and osmotic concentrations decreased and muscle moisture increased.The results indicate that downstream migration smolts have markedly lower physiological capacity for continuous swimming than parr.

Effects of low acclimation temperature on salinity adaptation in the presmolt salmon, Salmo salar L

Abstract Three-year-old presmolt salmon, Salmo salar, were exposed to seasonal and experimental water temperatures of 1.5 and 10°C, respectively, in February. Thermally preacclimated fish were further exposed to 29‰ salt water (SW) for 9 days. At 10°C fresh water (FW) acclimated fish showed decreased values of the blood haematocrit, haemoglobin, MCHC, liver glycogen content and plasma osmolality. Similarly, plasma Mg2+ concentration decreased significantly, whereas plasma K+and total protein concentrations increased. Hyperglycaemia seen in cold FW was also observed in cold SW. The SW-exposed fish had lower haematocrit values and higher MCHCs than the FW fish. In the kidneys a significant decrease in the Na-K-ATPase was seen in SW. Additionally, plasma osmolality, Na+ Cl−, and Mg2+increased significantly in both SW groups, but the ability to regulate hydromineral balance in SW was clearly better at 10°C than at 1.5°C. In cold water, regulation was obviously very slow to start, thus the weaker regulation capacity in the cold may be a significant reason for the dependence of smolt migration on environmental temperature.

Triploidy decreases the aerobic swimming capacity of rainbow trout (Salmo gairdneri).

Abstract 1. 1. Two-summer-old diploid and triploid rainbow trout from an all-female stock were forced to swim for 3 hr at 40 cm/s. At the end of the test the fish were sampled for biochemical analyses. Respective samples were taken from resting controls. 2. 2. Blood haematocrit (Hct) and haemoglobin concentration (Hb), mean corpuscular haemoglobin concentration (MCHC), erythrocytic water content, plasma glucose and lactate concentrations, liver glycogen content, plasma Cl−, Na+, K+, Mg2+ concentration and plasma concentrations of insulin, glucagon and glucagon-like peptide (GLP) were measured. 3. 3. In the triploid trout, the blood Hct value and plasma lactate concentration increased and MCHC decreased in exercise, indicating swelling of the erythrocytes and accumulation of anaerobic metabolites; these changes were less pronounced or not present in the diploid fish, which indicates that triploid trout have a lower aerobic capacity than the diploid ones. 4. 4. Plasma insulin concentration decreased in exercise both in the diploid and triploid fish, but the decrease was more pronounced in the triploids. Plasma glucagon and GLP concentrations of the diploids decreased (GLP not significantly), but those of the triploids increased in exercise.

Effects of a dietary betaine/amino acid additive on growth and seawater adaptation in yearling chinook salmon

Abstract The effect of FinnStim, a betaine/amino acid mixture, on growth and seawater adaptation was studied in yearling chinook salmon Oncorhynchus tshawytscha . The fish were marked with PIT tags and divided into two groups. One group was fed a diet with 1% FinnStim added and the other was fed a control diet with 1% α-cellulose. The diets were fed for 6 weeks in fresh water at a level of 1% body weight per day and for 8 weeks in seawater netpens at 3% body weight per day. Seawater challenge tests were conducted three times during the freshwater phase of the experiment. Growth and mortality in fresh water did not differ significantly between treatments. Seawater challenge tests at days 5, 47 and 70 of freshwater rearing revealed no significant difference in plasma sodium concentration between groups. During the seawater phase of the experiment, the group receiving FinnStim had a significantly higher growth rate and a significantly lower concentration of plasma sodium at the end of the study. The improved growth performance in the group receiving FinnStim was due to a reduction in the number of salmon growing poorly.

Smolting of two populations of Salmo trutta

Abstract Smolting in two hatchery-reared populations of Salmo trutta was compared during their second winter. After a 48-h exposure to 28‰ balanced seawater, the decrease of water content in white muscle was small and mortality negligible in one stock from January till late May. The other stock was able to tolerate seawater exposure only in April–May. In June both stocks showed a decreased seawater tolerance. In spite of the increased seawater tolerance of the first stock in January, the ATP-ase activity of gills peaked first in March and a second time in May, coinciding with the plasma T 4 maximum. The second stock had no peak values in gill ATP-ase activity, but the T 4 surge was bigger than in the first stock. Plasma cortisol of the first stock peaked twice; first in February and then in May, the last peak coinciding with the only one of the second stock. In June the fish of both stocks were totally desmoltified parr.

The quality and condition of reared Salmo salar smolts in relation to their adult recapture rate

Abstract Physiological parameters (haematocrit value (Hct) and haemoglobin (Hb), plasma glucose, lactate and electrolyte concentrations together with tissue energy stores) were used to judge the quality and condition of young Atlantic salmon in several fish farms just prior to release in 1981. Based on the current knowledge of the physiology of parr-smolt transformation and data on natural smolts, we have been able to classify the reared fish from different farms in Finland. The results of this classification have been related to the adult recapture rate.

Desmoltification of heat-accelerated Baltic salmon (Salmo salar) in brackish water

Abstract To produce one-year-old smolts, one-summer-old Baltic salmon were reared in heated brackish water in winter. The development of external smolt indices, salinity tolerance, gill Na,K-ATPase activity and plasma thyroxine concentration were studied. The salmons smoltified in winter, 2–4 months before the normal release time, and desmoltified until the release time, in spite of saline water (5–6 ppt). Both smoltification and desmoltification could be accelerated by increased daylength and delayed by increased fish density in rearing tanks. Transfer to natural temperature before smoltification was completed effectively inhibited desmoltification, whereas later transfer had little effect.

Effects of FinnStim on growth and sea water adaptation of Coho salmon

Abstract The effects of FinnStim (betaine plus 3% protein hydrolysate) on the osmotic balance, metabolism and growth in coho salmon Oncorhynchus kisutch (Walbaum) was studied. The fish were fed at levels of 3.5 to 5% of body weight per day with a commercial-type control diet or diet with 1% of FinnStim. The fish were fed experimental diets for 45 days in fresh water and 40 days in sea water; thereafter both groups were fed the control diet and monitored for additional 50 days. Fish weight, length and concentrations of main plasma ions Na + , Cl − did not differ significantly between treatments. FinnStim supplementation significantly decreased muscle K + load one week after SW transfer, and improved specific growth rate (SGR 1.75%/day vs. 1.66%/day) and FCR (1.27 vs. 1.51) in SW. During the whole trial period the FinnStim group showed lower mortality than the control group (2.78% vs. 4.95%).