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1.
Abstract The growth and recapture rates of Atlantic salmon, Salmo salar L., smolts that had previously matured as parr were compared with those of immature siblings in a sea‐ranching experiment in western Norway. The smolts were the offspring of three river populations. They were individually tagged, transferred to cages in a small bay where estuarine salinity gradients had been established and released on four dates from mid‐May to early June after either 3 or 7 days of acclimatisation. The previously mature male parr (PMMP) were smaller than their siblings before release, but performed much better during their time in the sea. As grilse, they reached sizes comparable with the formerly immature fish, and their recapture rate was more than four times higher (8.6 vs 2.1%). This difference decreased somewhat during the following years because 0.85% of the immature fish and only 0.1% of PMMP were recaptured as multi‐sea‐winter salmon. The highly successful marine performance of the PMMP demonstrated that this life history strategy may be more flexible than previously believed. 相似文献
2.
The straying rate of ranched Atlantic salmon, Salmo salar L., into rivers in Iceland was estimated on the basis of coded wire tag recoveries. Out of a total of 15 158 recaptured tagged salmon from the releases between 1987 and 1992, 189 fish (1.3%) strayed into 25 out of the 79 salmon rivers observed. Most of the strayers were found in neighbouring rivers to the ranching stations. There were no significant differences in straying rate between different age classes of salmon returning from the same smolt year class. Generally, there was a delay of 26-27 days in running time between strayers in rivers and salmon returning to the ranching station. Higher straying rates were observed for ranching stations using riverine traps than for stations using estuary traps. By close inspection of seven key rivers in Iceland and assuming a 50% exploitation rate (fishing effort) in the rivers, on average, 2.1% of the returning salmon in ranching were estimated to stray to native salmon rivers over the years. A limitation of using these numbers to estimate geneflow between ranching stocks and wild populations is discussed. 相似文献
3.
Jónas P Jónasson Gudrún G Thórarinsdóttir Hrafnkell Eiríksson & Gudrún Marteinsdóttir 《Aquaculture Research》2004,35(15):1405-1414
The effects of temperature on the survival and behaviour of two size classes of Chlamys islandica was investigated in a laboratory study. The scallops were sampled in spring from three localities in Iceland, Breidafjördur (west), Húnaflói (north), and Hvalfjördur (southwest) and again in August from Breidafjördur and Hvalfjördur. Daily observations of mortality and behaviour were made over a 21‐day period at sea temperatures ranging from 7 to 16°C in spring (April–May) and 11 to 14°C in August. During the spring experiment the tolerance of scallops, as expressed by mortality and behaviour, was distinctly reduced at sea temperatures above 12°C among scallops from Breidafjördur and Húnaflói and above 13°C among scallops from Hvalfjördur. During the second set of experiments, conducted in August, scallops were transported into the laboratory from a higher sea temperature than in the spring. As a result, mortality rates were much lower demonstrated by the fact that only scallops reared at sea temperature of 14°C died. This indicates that C. islandica may tolerate somewhat higher temperatures than have been observed in Icelandic waters in recent years. However, the gradual increase in temperature during the last 10 years has brought the mean temperature close to the species' tolerance limit. 相似文献
4.
Per-Olov Larsson 《Aquaculture (Amsterdam, Netherlands)》1984,38(1):83-87
Some 6500 recaptures of salmon tagged as smolts on the Swedish west coast in 1966–1980 were reviewed for remote strayers. Only 27 (0.43%) were found, meaning no risk for the profitability of sea ranching activities. Along the Swedish west coast at least 450 kg salmon per 1000 released smolts can be expected to be caught by Swedish commercial fishermen, which makes public sea ranching highly profitable there. 相似文献
5.
The River Dalälven Baltic salmon, Salmo salar L., population has been maintained by stocking reared fish since the early 1920s. Initially, all rearing was carried out at one hatchery, but since the late 1980s two have been used. Both hatcheries are situated 9–10 km from the river mouth but some 600 m apart. All broodfish were caught in a single fish trap situated some 700 m upstream of the upper hatchery. The salmon smolts were released just below the water outlets of each hatchery, respectively. About 2% of the released smolts from each hatchery were tagged annually with Carlin tags. Total recapture rates were higher for smolts from the lower hatchery. A higher proportion of recaptured fish was reported from the home river for salmon from the upper hatchery. The migration within the river to the fish trap was more precise for fish from the upper station. Strays were very late in the season and of a higher number from the lower hatchery. Observations of jumping salmon by the outlet from the lower station indicated that salmon returned to that point. The lower recaptures in the trap were considered a result of a shorter river migration of salmon from the lower hatchery. 相似文献
6.
Little is known about the survival rate of wild masu salmon Oncorhynchus masou. To examine the effects of smolt length and migration timing on the recovery rate of wild masu salmon, we reanalyzed past
tagging and recovery data (1993–1994). The tagging study was conducted in the Shokanbetsu River, northern Japan; 863 wild
masu salmon smolts were captured, tagged, and released in a downstream site, and a total of 19 fish were recovered in coastal
fisheries and in the natal river the following year. The data were analyzed by a logistic regression analysis with recapture
as a response variable and tagging date and smolt length as explanatory variables; the tagging date had a significant effect
on the recapture rate, whereas the effect of smolt size was not significant. Despite the small number of recaptures, this
study indicates that migration timing is a factor affecting the marine survival of wild masu salmon smolts, although this
conclusion has been repeatedly documented for other species of Pacific salmon Oncorhynchus spp. 相似文献
7.
Kjell B. Døving Bror Jonsson Lars P. Hansen 《Aquaculture (Amsterdam, Netherlands)》1984,38(4):383-386
Wild and hatchery-reared salmon smolts of the Imsa strain were divided into two groups. One group was made anosmic by cutting the olfactory nerves, the other served as control. The smolts were released at three different sites in the Ims-Lutsi watercourse and recaptured in a fish trap at 100 m above the river estuary. The recapture rates in the trap decreased with increasing migratory distance for the smolts. The experiment indicates that the olfactory sense is not essential for smolt navigation through rivers and lakes. 相似文献
8.
R. A. Cunjak 《Ecology of Freshwater Fish》1992,1(1):26-34
Abstract– The diet composition, movcments and growth of Atlantic salmon parr rearing in the estuary of Western Arm Brook, Newfoundland were compared with those of parr from riverine habitats over 2 years. Estuarine parr consumed a variety of prey, including many freshwater taxa (mainly insects), which indicated a dependence on freshwater drift from the river. Prey of estuarine origin (amphipods and sticklebacks) were increasingly consumed between spring and autumn. Prey volume per fish and number of prey per fish increased significantly for estuarine parr between spring and autumn, suggesting an improvement in food availability. Riverine parr, however, realized a general decrease in both parameters between spring and autumn. The recapture of 16% ( n = 131) of the 829 parr marked in the estuary in 1987 and 1988 indicated a directed movement toward the head of the estuary and river mouth, as also suggested by the diet analysis. Parr from outer estuary sites were very mobile compared with parr from the estuary site closest to the river mouth, which behaved more like parr in the river proper in displaying strong site fidelity. Movement patterns of parr were primarily along the shoreline. Individual growth rates were highly variable in both environments but especially in the estuary. The mean growth of estuarine parr was 0.23 mm. d−1 between May and October with some evidence of fastest growth having occurred in late spring and early summer (approx. 0.4 mm. d−1 ); mean growth rate of riverine parr was slower, at 0.12 mm. d−1 . The results are discussed in the context that estuarine rearing by salmon parr represents an alternative life-history tactic for the species in river systems in eastern Canada. 相似文献
9.
L. J. ROBERTS J. TAYLOR & P. J. GOUGH D. W. FORMAN & C. GARCIA de LEANIZ 《Fisheries Management and Ecology》2009,16(1):10-13
Abstract Hatchery-reared salmon, Salmo salar L., smolts are generally stocked during daylight hours, but the natural migration of smolts tends to occur at night. Recapture rates and timing of migration were compared between Atlantic salmon smolts stocked during the day and during the evening. Timing of release had no significant effect on the number of smolts recaptured, but had a strong effect on nocturnal behaviour. When stocked in the evening (but not during the day) hatchery-reared smolts moved almost exclusively during the night. This study suggests that timing the release to coincide with the natural time of smolt migration may provide valuable acclimatisation and facilitate nocturnal smolt passage. 相似文献
10.
Abstract. To assess the merits of rearing coho salmon, Oncorhynchus kisutch (Walbaum), smolts semi-naturally, trials were made in which 17 groups of tagged smolts, from 4 brood years, were raised on a partially natural diet in a semi-natural habitat. Their subsequent survival, as determined from catch and escapement, was compared with that of four groups of smolts, from the same brood years, raised by a conventional hatchery method. The returns of the semi-natural fish proved lower than or similar to those of the hatchery fish, which attained a maximum survival to catch and escapement of 26%. The survival of the semi-natural fish showed no relation to their location in their linear rearing facility, nor to size of smolt (within a narrow range). Further trials showed that a month's delay in release of the semi-natural fish did not increase returns, contrary to a current predictive model. The distribution of the catches of both kinds of fish was broadly similar in the troll and sport fisheries. It is concludedthat semi-natural rearing of coho smolts is not superior to that of standard hatchery procedures, although it may be favoured for specific locations that lend themselves to this approach. 相似文献
11.
Reared salmon smolts have been released into the Burrishoole river system since 1957. From 1970 it has been possible to record all adult returns. Survival of reared smolts to adult, as measured by numbers of fish returning to fresh water, has averaged 2.1% cf. 8.4% for wild smolts. A number of factors contributing to the comparatively poor returns of reared smolts are outlined. The behaviour of reared adults on return to fresh water is described and it is concluded that once past their homing point, their contribution to the rod and line fishery diminishes. Thus, the exploitation rate of reared grilse below their homing point (L. Furnace) exceeds that above (L. Feeagh). In confirmation, whilst a positive correlation exists between total stock and total catch of reared grilse on L. Furnace, no significant correlation exists between stock and catch on L. Feeagh. In the Burrishoole system, the exploitation rate of wild grilse usually exceeds that of reared and it is only in L. Furnace that reared grilse make a significant contribution to the total rod catch. The mean exploitation rate obtained for Burrishoole reared grilse is low (10.8%) when compared with those recorded for salmon in other systems. The comparable exploitation rate of Burrishoole wild grilse is 14.3%. 相似文献
12.
RANDALL M. PETERMAN SILVIO G. MARINONE KEITH A. THOMSON IAN D. JARDINE ROBERT N. CRITTENDEN PAUL H. LEBLOND CARL J. WALTERS 《Fisheries Oceanography》1994,3(4):221-235
Previous research has documented two main migratory routes of juvenile sockeye salmon (Oncorhynchus nerka) through the Strait of Georgia, British Columbia, Canada, and large interannual variability in marine survival rates of the Chilko Lake stock. Simulation models were used to explore the influence of surface currents on the migratory route of juvenile sockeye salmon (smolts) through the Strait of Georgia. We used a model of downstream migration to generate daily numbers of Chilko Lake sockeye salmon smolts entering the Strait of Georgia, based on daily counts of smolts leaving the rearing lake. A numerical hydrodynamic model (driven by surface wind, tide, and Fraser River discharge) hindcasted surface currents in the Strait of Georgia on a 2 km × 2 km grid. A smolt migration model simulated fish moving through the Strait with different compass-oriented migratory behaviours (i.e. swimming speed and directional orientation) within the time-varying surface advection field. Results showed that surface currents within the Strait of Georgia can affect the migratory route of sockeye salmon smolts in spite of their large size (8 cm). Wind is the forcing mechanism primarily responsible for determining which migratory route would be used. Under prevailing wind conditions (i.e. toward the north-west), most sockeye salmon smolts would use the eastern migratory route; however, relatively brief south-eastward wind events (lasting about 2 days) would force most smolts into the western migratory route. Given the heterogeneity of food for salmon within the Strait, we hypothesize that wind-driven variability in the annual proportion of smolts that use the western and eastern migratory routes in the Strait of Georgia affects early marine survival rates of Fraser River sockeye salmon. 相似文献
13.
In Iceland the rearing temperature of salmonid fish, mostly Atlantic salmon, is generally below 10°C. Infections most often characterized by shallow skin lesions that may cause considerable mortality have been endemic in the country since rearing in salt water started. A variety of Vibrio spp. has been isolated from the diseased fish. In the present study, a total of 58 strains isolated from salmonid fish and 21 reference strains were subjected to a numerical taxonomy study. The results show that two phena are most common in the diseased fish; one of them includes V. marinus, whereas the other does not include a reference strain but has similarities to V. logei. Challenge tests showed that a representative strain of the phenon that included V. marinus is pathogenic for Atlantic salmon with an LD50 lower than 3.5 × 103. 相似文献
14.
Magnus Hulbak Erlend M. Hanssen Robert J. Lennox Anne Gro Vea Salvanes Bjørn Barlaup Naouel Gharbi Tom Ole Nilsen Knut Wiik Vollset 《Fisheries Management and Ecology》2021,28(5):428-436
Telemetry tags are increasingly used in management to monitor the migration timing of Atlantic salmon smolts (Salmo salar L.). It has been postulated that (1) effects from tagging and handling may alter migration behaviour, and (2) that the selection of fish during sampling is not representative of all migrating smolts, yielding bias in migration timing estimates. In the River Dale (Vestland, Norway), five groups of wild Atlantic salmon smolts (N = 385) were tagged in April–May and recaptured in a wolf trap. Migration timing was then compared to the untagged population. Migration timing differed between tagged (12 mm PIT) and untagged fish for 4/5 groups. Only fish tagged at the first time point did not have significantly different timing of migration from untagged counterparts. The relationship between length and the timing of migration was different for initial length and length at recapture; initial length suggested earlier migration of longer fish, but the extra time spent in the river prior to migrating for smolts that were initially smaller compensated for the size difference. The tagging protocol is crucial to obtaining representative migration timing results. Smolts should be tagged as early as possible and include the entire size distribution. 相似文献
15.
Abstract. This paper describes tests which were made to determine if smolt age at release influences the migratory pattern of three different stocks of salmon, Salmo salar L. The fish were hatchery-reared and released in two different rivers, the River Imsa and the River Akerselv. Based on the tag returns we found that Baltic salmon from the River Neva, USSR differed in migratory pattern from two Norwegian stocks from the River Lone and the River Imsa. A large proportion of the 2+ River Neva smolts stayed in the fjord during the summer and autumn after release. On the other hand, 2+ smolts of the Norwegian stocks left the fjord and migrated to the feeding areas in the Norwegian Sea within a short time after release. The 1+ smolts of all stocks showed the same migratory pattern as the 2+ smolts of Norwegian origin. We propose that the observed differences in migratory pattern are influenced by the developmental rate of the smolts. The effect of developmental rate on the migration may differ among stocks. Our results show that it is possible to develop a fjord fishery by releases of 2+ smolts of Neva salmon. However, such releases must be carried out with the utmost caution, preferably in fjords with no salmon rivers, so that the possibility of gene flow between populations is minimized. 相似文献
16.
L. G. de Mestral P. T. O'Reilly R. Jones J. Flanagan C. M. Herbinger 《Fisheries Management and Ecology》2013,20(1):75-89
The selective and environmental effects of captivity on several fitness‐correlated traits were assessed in smolts of endangered Atlantic salmon, Salmo salar L., from the inner Bay of Fundy, produced via artificial spawning and released into the wild as juveniles. Smolts were sampled as they migrated downstream and identified through microsatellite‐based parentage analysis as offspring of either wild‐spawning adults or adults that were spawned in captivity. Overall, captive‐origin smolts exhibited a significantly later run timing and smaller body size than wild smolts. Significant differences in run timing and body size were also found between captive‐origin smolts that had experienced rearing environments that differed in duration of captivity and thermal regime. Significant differences in run timing, fork length and weight were found between first and second generation captive‐origin smolts, although the expression of these differences depended on the rearing environment experienced, suggesting a possible genotype by environment effect. The ratio of effective‐to‐census number of breeders that produced the captive‐origin smolts was higher than that of the wild‐origin smolts due to successful captive breeding management practices. These results have direct implications for captive breeding and rearing programmes for salmonids and wider implications for understanding the rates of evolutionary and environmentally induced change that can occur in captivity. 相似文献
17.
The effects of year, size, sexual maturity and release date on the probability of recapture of tagged Atlantic salmon, Salmo salar L., released from a Swedish hatchery in the Baltic Sea were examined. The probability of recapture varied among years for individuals which were juvenile when released (1988, 13.5%; 1989, 4.4%; 1990, 1.2%) or previously mature males (1988, 1.9%; 1989, 0.5%; 1990, 0.4%). Body size was positively associated with the probability of recapture in each release year for both life-history types. Inter-annual changes in recapture rates were similar for both large and small smolts. There was a significant effect of life-history type on recapture rates in 1988 and 1989, but not in 1990. There was a significant effect of release date on recapture rates in 1988 and 1990, but not in 1989. The maximum recapture rates were associated with different release dates in each year, i.e. 27 May 1988, 6 June 1989 and 21 June 1990. 相似文献
18.
Abstract. Estimates of Atlantic salmon, Salmo salar L., smolt density were conducted in the river Orkla, central Norway, in spring 1983 by tagging 2671 smolts. The fish were captured in three sections of the river and marked by cutting the fins. Smolts larger than 110 mm were separated from fish between 100 and 110 mm, resulting in four series of markings. During the smolt run, 1285 smolts were captured in two traps lowered from a bridge, situated downstream of the area of the river where the fish were tagged. The recapture of tagged smolts was 27 specimens (1%). varying between 0·8% and 1·2% for the different series of markings. The estimated smolt densities varied between 2·8 and 4·4 smolts per 100 m2 from the four markings, with 4·1 smolts per 100 m2 (95% confidence interval 2·8–6·1) based on the total number of recaptures. 相似文献
19.
D. MILLS 《Aquaculture Research》1994,25(Z2):3-8
Over a period of 4 years a total of 10482 Atlantic salmon, Salmo salar L., smolts were transported from the River Bran, one of the tributaries of the Conon River system in Ross-shire, Scotland and released at a point below all the dams on this river system. The percentages of smolts recaptured as adult fish from the 4 years of the experiments were 2.8, 2.2, 2.2 and 4.0. Ninety per cent of the fish were recaptured within the Conon River system by anglers and at trapping sites or in neighbouring coastal nets, while the remaining 10% were taken in Greenland waters. The recapture of tagged fish in other tributaries of the river system indicated that there was a certain amount of straying, with a straying rate of 18.9%, although it was only appreciable in the tributary nearest to the Bran. The results are compared with those obtained from smolt transportation experiments in northern England where no adult trapping facilities were available. Discussion covers the probability of straying as a result of hydroelectric and water abstraction schemes involving inter-river transfer. 相似文献
20.
Experimental evidence suggests that olfactory imprinting by salmon occurs during a sensitive period associated with surges in plasma thyroxine (T4) levels during smolting. Life-history studies, however, suggest that imprinting may occur prior to smolting. A possible resolution of this paradox may lie in the finding that exposure of coho salmon, Oncorhynchus kisutch (Walbaum) smolts to novel water sources induced transient increases in plasma T4 levels. If novel water-induced T4 surges occur prior to smolting and T4 surges are required for olfactory imprinting, juvenile salmon experiencing novel water sources as they move through their watershed may learn olfactory waypoints (e.g. stream confluences). To test this hypothesis, we exposed subyearling coho salmon, Oncorhynchus kisutch (Walbaum), to novel odours or water sources at distinct developmental stages. Subyearlings did not demonstrate dramatic increases in plasma T4 levels during smolting and exposure to novel water sources also had no effect on basal T4 levels. Previous studies have indicated that such coho smolts successfully imprint to similar exposure paradigms and home accurately. These results suggest that surges in plasma T4 levels during smolting may not be necessary for olfactory imprinting and accurate homing. 相似文献