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Adult Atlantic Salmon (adult + atlantic_salmon)
Selected AbstractsAccumulation and distribution of polychlorinated dibenzo- p -dioxin, dibenzofuran, and polychlorinated biphenyl congeners in atlantic salmon (Salmo salar)ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 7 2004Pirjo Isosaari Abstract Adult Atlantic salmon (Salmo salar) were fed on four diets containing polychlorinated dibenzo- p -dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and polychlorinated biphenyls (PCBs) for 30 weeks. Lipid-normalized concentrations showed that all congeners were equally partitioned between whole-fish and fillet samples. Skinned fillet accumulated approximately 30% of the total PCDD/F and PCB content in fish. Accumulation efficiencies in whole fish were 43% for 2,3,7,8-chlorinated dibenzo- p -dioxins and dibenzofurans, 83% for dioxin-like PCBs, and 78% for other PCB congeners. Among PCDD/Fs, tetra- and pentachlorinated congeners were preferentially accumulated in salmon, whereas hepta- and octachlorinated dibenzo- p -dioxins were excreted in the feces. Substitution patterns that were associated with a preferential accumulation of PCBs in salmon included non- ortho substitution and tetrachlorination. Accumulation efficiencies and lipid-normalized biomagnification factors (BMFs) were not influenced by the PCDD/F and PCB concentrations of the diets. Biomagnification (BMF > 1) of tetra- and pentachlorinated dibenzo- p -dioxins and dibenzofurans and of all the PCBs was observed. Differences in the behavior of PCDD/F and PCB congeners resulted in a selective enrichment of the most toxic congeners in salmon. [source] Snorkelling as a method for assessing spawning stock of Atlantic salmon, Salmo salarFISHERIES MANAGEMENT & ECOLOGY, Issue 3 2007P. ORELL Abstract, Reliability of underwater snorkel counts of adult Atlantic salmon, Salmo salar L., was analysed in the tributaries of the River Teno, close to the spawning period. In small (width 5,20 m) rivers, the replicated total counts of salmon were reasonably precise (CV = 5.4,8.5%), while in the medium-sized river (width 20,40 m) the precision of the counting method was considerably lower (CV = 15.3%). Low precision in a medium sized river was also observed in an experiment using marked live fish where the observation efficiency varied between 36.4% and 70.0%. In a small river, the detection efficiency of artificial fish silhouettes (test salmon) was almost perfect in pools (98%), but decreased in rapids (84%). Separate counts of males, females, grilse and large salmon were usually more variable than total counts, indicating that divers were more capable of locating a fish than properly identifying its sex and sea-age. The behaviour of adult salmon was favourable to conduct snorkel counts, as fish normally stayed still, or after hesitating, moved upstream (>95%of the cases) when encountering a diver. The high observation efficiency (>90%) and precision, favourable behaviour of salmon and congruence between snorkel counts and catch statistics in small rivers suggest that reliable data on Atlantic salmon spawning stock can be collected by snorkeling provided that the environmental conditions are suitable and the divers are experienced. [source] Modelling the impacts of removing seal predation from Atlantic salmon, Salmo salar, rivers in Scotland: a tool for targeting conflict resolutionFISHERIES MANAGEMENT & ECOLOGY, Issue 5 2006J. R. A. BUTLER Abstract, Bioenergetics were used to model the potential impacts on adult Atlantic salmon, Salmo salar L., stocks and rod fisheries of removing harbour seals, Phoca vitulina L., from three rivers of different scales in the Moray Firth, Scotland, viz: the Spey (large), Conon (medium) and Moriston (small). Overall, seals had the greatest impact on the Moriston, where removal of a single animal could increase cumulative catch by 17% during the fishing season. On the Conon and Spey the impacts were negligible, and resulted in increased catches of <1% annually. On all rivers eliminating seal predation had the greatest impact during the spring due to the smaller size of spring salmon sub-stocks. A generalised model of seal removal illustrated that stocks and catches increased by >33% in rivers with monthly rod catches ,10 fish, but declined to <10% for rivers with catches >34 fish. The outputs of the models are qualitative, but provide a management tool for targeting action to resolve seal-salmon fishery conflict. Smaller salmon population units, and spring salmon sub-stocks and fisheries in particular, are most vulnerable to predation. The merit of this approach is discussed regarding the management of Special Areas of Conservation for salmon and seals. [source] Upstream migration of Atlantic salmon at a power station on the River Nidelva, Southern NorwayFISHERIES MANAGEMENT & ECOLOGY, Issue 3 2003E. B. Thorstad Abstract The upstream migration of 17 radio-tagged adult Atlantic salmon, Salmo salar L., past hydroelectric developments on the River Nidelva, Southern Norway, was examined. Salmon migrated quickly from the site of release in the lower part of the river up to the tunnel outlet of Rygene power station, but were substantially delayed at the outlet. The salmon stayed in the outlet area for 0,71 days (median = 20), and mainly took up a position inside the dark power station tunnel. Water discharge in the tunnel was 57,176 m3 s,1, while residual flow in the river between the outlet and the dam 2.5 km further upstream was 3 m3 s,1. Ten salmon passed the outlet and entered the residual flow stretch, but none passed the dam. Six of the 10 salmon returned to the tunnel outlet. No major migration barriers were identified in the residual flow stretch, suggesting lack of motivation among the salmon to migrate due to either low water discharge compared with the main river, or several minor migration barriers along the river stretch. [source] Return migration of adult Atlantic salmon, Salmo salar, in relation to water diverted through a power stationFISHERIES MANAGEMENT & ECOLOGY, Issue 1 2003E. B. Thorstad Abstract ,The migration of Atlantic salmon, Salmo salar L., returning to the River Suldalslågen, Norway, was studied in relation to redirection of freshwater flow through a power station. The outlet of the power station is situated in the Hylsfjord, a fjord adjacent to the river mouth. Seventy-two salmon were tagged with acoustic transmitters, released in the outer part of the fjord system and automatically recorded when entering the Hylsfjord or the river. Data were collected during one period when the power station was running and two periods when the power station was closed. The release of water from the power station did not greatly attract the salmon during their return migration. Proportions of salmon entering the river or time from release to entering the river did not differ among salmon tagged in the different periods. The salmon were recorded in the Hylsfjord both when the power station was running and closed and there were no differences in number of times, number of days or hours recorded in the Hylsfjord among salmon tagged in the three periods. The only significant difference found among periods was duration of continuous stays in the inner part of the Hylsfjord. This may indicate a slight attraction to the freshwater release, but the difference seems small (1.8 vs. 0.7 h) compared with the time the fish stayed in the fjord system before entering the river (16,85 days). [source] Synchrony in the downstream migration of smolts and upstream migration of adult Atlantic salmon in the subarctic River UtsjokiJOURNAL OF FISH BIOLOGY, Issue 6 2007P. Orell Seasonal and diel migration timing of wild Atlantic salmon Salmo salar smolts and adults were investigated annually (2001,2004) in the subarctic River Utsjoki, a tributary of the large River Teno (70° N), using underwater video monitoring. Submerged video cameras provided information on the exact timing and intensity of both migrations in a natural river channel, without disturbing the fish. In contrast to the mainly nocturnal migration pattern described from temperate rivers, the River Utsjoki smolts and adults migrated throughout the day. Smolts migrated most intensively during hours of rising (0300,0900 hours) and high sun (0900,1500 hours), while adults favoured the period of low sun (2100,0300 hours). Smolt migrations started in June and lasted on average 42 days. Adults usually ascended the site 2,3 weeks before the first descending smolts were observed and the adult migrations extended to the end of August. Seasonal synchrony was observed between smolt and adult migrations in years of slowly warming water, whereas in a year of exceptionally warm early summer (2002), smolts migrated earlier than adults. Thus, water temperature seemed to be an important environmental factor triggering the smolt migration, while the migration of adults was probably more fixed to a certain season. Weak positive correlations between fish counts and water temperature were observed, indicating that increasing water temperature may have promoted both smolt and adult migrations. The influence of discharge was negligible, although increasing discharge late in the season may have activated the remaining individuals in both groups. [source] Factors affecting river entry of adult Atlantic salmon in a small riverJOURNAL OF FISH BIOLOGY, Issue 4 2007B. Jonsson In this study, effects of stock origin, fish size, water flow and temperature on time of river ascent of adult Atlantic salmon Salmo salar were tested. Brood stocks were collected in eight Norwegian rivers situated between 59 and 69° N. The fish were reared to smolts, individually tagged and released in the River Imsa, south-west Norway (59° N). Adults from all stocks approached the Norwegian coast concurrently, but Atlantic salmon ,70 cm in natural tip length entered coastal water slightly earlier during summer than smaller fish. Atlantic salmon <70 cm, however, ascended the river significantly earlier and at lower water flow and higher water temperature than larger fish. Although largest in size, the fish from the northern populations (62,69° N) ascended the River Imsa almost 1 month earlier than those from the south (59,60° N). They seemed less restricted by the environmental factors than the fish originating from the more southern rivers. There was no apparent trend among years in time of river ascent. Maximum ascent per day occurred at water discharges between 12·5 and 15 m3 s,1 and at water temperatures between 10 and 12·5° C. There was a significant positive correlation between water flow and river ascent during the first part of the upstream run from July to September with best correlation for September, when multiple regression analysis indicated that water temperature had an additional positive effect. Stock origin, fish size and water discharge were important variables influencing the upstream migration of Atlantic salmon in small rivers. [source] A comparison of muscle- and scale-derived ,13C and ,15N across three life-history stages of Atlantic salmon, Salmo salarRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 18 2008R. Niloshini Sinnatamby Stable isotope signatures were obtained from paired scale and muscle tissue samples from smolt, post-smolt and one-sea-winter adult Atlantic salmon (Salmo salar). Post-smolt and adult scales were separated into central and outer (marine) portions with analyses carried out on the marine growth section of both life-history stages and the central portion for the adult scales. Muscle and scale ,13C and ,15N signatures were assessed (1) to determine whether a linear relationship exists between tissue types, (2) to determine if a constant offset exists between tissue signatures across all life-history stages, and (3) to evaluate whether underplating imparts a significant bias to life-history scale segments that would preclude their use in retrospective analyses of any ontogenetic dietary changes between life-history stages. Significant correlations were found to exist between muscle and scale stable isotope signatures obtained from smolts (,13C and ,15N) and adults (,15N). Both the muscle and the scale signatures captured the dietary shift associated with the transition from freshwater to the marine environment. Post-smolt and adult scales were depleted relative to muscle tissue, which may be attributed to isotopic differences in amino acid composition between muscle and scale tissues. The results suggest that scales may better represent dietary carbon sources because they are not influenced by lipid dynamics. The scale, however, appears less responsive to short-term shifts in diet relative to muscle and, therefore, must be used only to infer seasonally integrated dietary patterns for slow-growing life-history stages. Copyright © 2008 John Wiley & Sons, Ltd. [source] | ||||||||||