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1.
Incidence of early maturation of female amago salmon was reduced by >32% by feed restriction beginning in May, 5 months prior to spawning. Male early maturation was unaffected by this feed restriction regime. 相似文献
2.
Sigurdur Gudjonsson Ingi Runar Jonsson Thorolfur Antonsson 《Environmental Biology of Fishes》2005,74(3-4):291-296
Synopsis We tagged both wild and hatchery Atlantic salmon, Salmo salar, smolts from River Ellidaar (64 ° 08′ N, 21 ° 50′ W) with ultrasonic tags. We caught the wild smolts in a smolt trap and
selected the largest individuals from the run. We implanted the transmitters in the abdominal cavity of the fish and then
released them in River Ellidaar close to the estuary. We used four ultrasonic receivers; one in the river’s estuary, one outside
the estuary and two further away on both sides of an island in the estuary zone. The receivers recorded all transmitters within
a 600 m radius. The hatchery smolts were larger than the wild smolts. Some of the smolts were lost on the way through the
estuary. Only 4 out of 9 wild smolts and 14 of 17 hatchery smolts were recorded all the way through. The tags and the tagging
likely affected the survival of the smolts especially the smaller fish. There were no differences in the smolt migration between
the 2 years of study and no differences in the migration behavior between the wild and the hatchery smolts. After being released
the smolts stayed on average for 10 h in the river then migrated into the estuary were they stayed for 54 h on average. Then
they migrated straight through the area to the sea at approximately 0.2 fish lengths per second. We recorded large differences
in the migration. 相似文献
3.
I. D. McCarthy 《Journal of fish biology》2000,57(1):224-238
There was a strong correlation between the relative standard metabolic rate (rSMR) values of individual Atlantic salmon Salmo salar L. measured 5 and 22 weeks after first feeding in June and October respectively (Pearson's r =0·68, 26 d.f., P <0·001). However, this is a conservative estimate of repeatability as two separate regressions were used to calculate SMR in October due to the separation of the population into an upper modal group made up of early migrants and a lower modal group comprised of delayed migrants. SMR values in June and October were similar (paired t test, t =-0·85, 27 d.f., P >0·05) when expressed as the percentage deviation from those predicted for a fish of that size based on the body mass/SMR relations in June or October indicating that relative standard metabolic rates were stable over time when food was not limiting. rSMR status was maintained in 19 of the 28 fish (i.e. 68%) between the two measures. rSMR status was correlated with life history strategy: salmon fry with a high SMR in June were more likely to become smolts during the autumn than those with a low SMR. 相似文献
4.
A complex of adaptive changes occurring in the Pacific salmon fry in the process of migration to the sea is described, including behavior, ion content in carcasses, and morphological changes in Stannius bodies, gill epithelium, and nephron tubular epithelium. Participating in experiments with transfer from fresh water into a two-layer aquarium (the lower layer—sea water, the upper layer—fresh water) were smolts of chum salmon and underyearlings of cherry salmon as well as the trachurus and leiurus forms of the three-spined stickleback Casterosteus aculeatus. All fish, regardless of their salt preference, at once after placement into the two-layer aquarium, occupied the sea water zone, at the very bottom of the aquarium. After 1 h, there started brief excursions of cherry salmon and chum salmon to the upper, fresh water layer; however, both forms of the three-spined stickleback did not participate in these excursions. After 12 h, the chum salmon settled down in the lower, sea water layer, while the cherry salmon—in the upper, fresh water layer. Both forms of the three-spined stickleback never left the sea water layer and felt quite comfortably on the aquarium bottom. It seems that the high tolerance of the both stickleback forms to wide salinity limits allows them to choose the convenient position regardless of the water salt composition. By analyzing the material obtained for three years (2001–2003) on structure and functions of the gill epithelium chloride cells (CC), we have come to the conclusion that the fresh water fry of two salmon species, chum and cherry salmons, caught at the same time and practically in the same water reservoirs can be divided into three groups. The underyearlings of the cherry salmon as a rule are characterized by the thickened epithelium of secondary gill lamellae, but by a very small number of CC. In smolts of chum salmon, on the contrary, the epithelium is sufficiently thin, but enriched in the CC that demonstrate an active structure in the very beginning of migration to sea. However, with approaching the sea (and with an increase of terms of migration) the CC activity drops, but their amount does not change. And only after migration to the sea the CC activity rises again, although their amount seems to remain unchanged. The described peculiarities of behavior and of the ion composition regulation in the migrating salmon fry confirm the hypothesis that the salmons evolutionized in fresh water, that the Oncorhynchus genus appeared in large spaces of saltish waters, such as the Japan sea at the period of the early Pleistocene, and that learning of fry of the Oncorhynchus genus (for instance, of O. gorbuscha and O. keta) is the most specialized in the salmons migration to the sea, whereas the fresh water species of chars (Salvelinus) and of trouts (Salmo) are more primitive. 相似文献
5.
Whether time of seaward migration of young Atlantic salmon Salmo salar influences their subsequent survival and growth was investigated in the River Imsa, south‐western Norway. Salmo salar were tagged when moving downstream through a trap near the outlet between 1976 and 2010 and recaptured on their adult return. Most descended as smolts in April and May, but some descended during the other months of the year. Annual variation in timing of the smolt migration was significantly correlated with variation in water temperature during spring. Mean total body length of the descending S. salar varied with month of seaward migration. The sea survival of S. salar emigrating from the River Imsa between January and May was 2·8 times higher than for those descending between June and December. The sea survival of the various cohorts decreased with increasing river temperature in April to May, prior to the smolt migration, and decreasing day number when the smolts moved to sea. The size of smolts descending the river between April and May did not affect the survival at sea as much as it affected the survival of migrants descending in any other month of the year. The majority of the downstream migrating S. salar were 2 years old, but proportionally, more 1 year olds moved downstream in the autumn than in the rest of the year. Mean duration between downstream migration of the young and the return migration of the grilse was shortest (12·7 months) for those descending in July and August and longest for those descending in October (21 months). Mean monthly specific growth rate was highest for those migrating downstream between May and July and lowest for those emigrating in September. Based on the present results, it was hypothesized that S. salar emigrating between April and August migrated directly out into the ocean, while those that emigrated between October and March stayed in the estuary until the subsequent spring. 相似文献
6.
H. Hayano† Y. Miyakoshi M. Nagata K. Sugiwaka‡ J. R. Irvine§ 《Journal of fish biology》2003,62(1):237-241
Smolts of anadromous masu salmon Oncorhynchus masou aged 3+ years were found in a northern Japanese river. This is the first recording of 3+ year smolts in Japan. These fish appeared to originate in the cold upper river where 2+ year parr were found during autumn. 相似文献
7.
A total of 129 sea trout smolts from 10 locations on the west coast of Ireland were examined for metazoan parasites. Of 11 species identified only four had a prevalence >20%. Two species Hysterothylacium aduncum and Hemiuris communis have a confirmed marine origin; Eubothrium crassum has been shown to exist in both the sea and fresh water. The remaining species were fresh water. Overall the parasite community was dominated by autogenic species with only Diphyllobothrium dendriticum having allogenic transmission. Infracommunity values for mean species richness, and Brillouins index of diversity were low, indicating the presence of an impoverished helminth community with little potential for interspecific interaction. The relationship between marine helminths and sea lice was also examined. 相似文献
8.
Hannele M. Honkanen Jessica R. Rodger Alastair Stephen Keith Adams James Freeman Colin E. Adams 《Journal of fish biology》2018,93(1):159-162
What little is known about the seaward migration of Salmo salar smolt migration through standing waters indicates that it is both slow and results in high mortality rates, compared with riverine migration. This may be partly because smolts in lakes need to swim more actively and require more complex directional cues than they do in rivers. In this telemetry study of smolt migration through Loch Lomond, S. salar smolts made repeated movements in directions away from the outflowing river, which considerably increased migration time. 相似文献
9.
Wild, one- and two-summers-old sea-trout parr in a small stream, were tagged with PIT-tags in late autumn and recaptured in a smolt trap during the following spring. One-summer-old smolts migrated later than older ones and were smaller at migration. ANCOVA indicated that migration date was negatively related to body length at tagging, but we found no significant effect of age or condition factor at tagging on this relation. The difference in timing between the age-classes was thus an effect of body size rather than age. 相似文献
10.
Relationships between growth at sea, smolt size and age at sexual maturation of Atlantic salmon Salmo salar were tested. The fish were offspring of brood stocks sampled in eight Norwegian rivers at latitudes between 59° and 70° N, hatchery reared and released at smolting at the mouth of the River Imsa (59° N). Smolt size influenced the subsequent growth rate of Atlantic salmon. The larger the fish were at release, the slower the yearly length increment at sea. Mean sea age at sexual maturity, measured as proportion of the returning adults attaining sexual maturity at sea age 2 years, was significantly correlated with mean growth rate during the first year at sea and mean smolt size ( r 2 = 0·74, P < 0·001). Fish attaining maturity at a relatively high sea age were more fast growing during their first year at sea than those maturing at a younger age. The results indicate that high sea age at sexual maturation is a population-specific characteristic and associated with high early growth rate at sea. 相似文献
11.
N. A. Hvidsten O. H. Diserud A. J. Jensen J. G. Jensås B. O. Johnsen O. Ugedal 《Journal of fish biology》2015,86(1):92-104
A model that explains 48% of the annual variation in Atlantic salmon Salmo salar smolt production in the River Orkla, Norway, has been established. This variation could be explained by egg deposition, minimum daily discharge during the previous winter and minimum weekly discharge during the summer 3 years before smolt migration. All coefficients in the model were positive, which indicates that more eggs and higher minimum discharge levels during the winter before smolt migration and the summer after hatching benefit smolt production. Hence, when the spawning target of the river is reached, the minimum levels of river discharge, in both winter and summer, are the main bottlenecks for the parr survival, and hence for smolt production. The River Orkla was developed for hydropower production in the early 1980s by the construction of four reservoirs upstream of the river stretch accessible to S. salar. Although no water has been removed from the catchment, the dynamics of water flow has been altered, mainly by increasing discharges during winter and reducing spring floods. In spite of the higher than natural winter discharges, minimum winter discharge is still a determinant of smolt production. Hence, in regulated rivers, the maintenance of discharges to ensure that they are as high as possible during dry periods is an important means of securing high S. salar smolt production. 相似文献
12.
A bimodal length distribution developed in an Atlantic salmon population planted as start-fed fry in a Norwegian stream. The earliest fish to smolt were from the upper modal group. 相似文献
13.
Páez DJ Brisson-Bonenfant C Rossignol O Guderley HE Bernatchez L Dodson JJ 《Journal of evolutionary biology》2011,24(2):245-255
Migratory behaviour with its associated phenotypic changes is generally viewed as an adaptive strategy because it incurs survival or reproductive advantages to migrants. The development of a migrant phenotype is believed to be controlled by threshold mechanisms, where individuals emigrate only after surpassing a particular body size but delay migration if below. For such a strategy to respond to natural selection, part of the phenotypic variance in the propensity to migrate must be explained by variation in additive genetic effects. Here, we use data gathered in the field and from a common rearing experiment to test for a genetic basis associated with seaward migration in Atlantic salmon (Salmo salar L.). We document a high heritability of the liability trait underlying the propensity to emigrate in juvenile salmon, and significant differences between offspring grouped according to their sires in body-size threshold values above which emigration takes place. The presence of additive genetic variance in both the liability and thresholds makes the onset of migration a process sensitive to selection and may therefore constitute an important explanatory mechanism for the interpopulation differences in the size at seaward migration observed in this species. 相似文献
14.
Analysis of Atlantic salmon Salmo salar scales from the River Dee in Wales between 1937 and 2002 revealed a marked increase in the proportion of 1 + year smolts from c . 5% in the period to 1949, to almost 40% in the decade to 2002. Due to regulation flows post‐1964 over the period of change the Dee became colder during the period April to October, indicating that factors other than climate change are likely to be involved. 相似文献
15.
The downstream migration of Atlantic salmon (Salmo salarL.) and sea trout smolt (S. trutta L.) was investigated using radio telemetry in the spring of 1999 and 2000. Forty wild sea trout smolts, 20 F1 sea trout smolts, 20 hatchery salmon smolts and 20 salmon smolts from river stockings were radio tagged and released in the Danish River Lilleaa. The downstream migration of the different groups of fish was monitored by manual tracking and by three automatic listening stations. The downstream migration of radio tagged smolts of both species occurred concurrently with their untagged counterparts. The diel migration pattern of the radio tagged smolts was predominantly nocturnal in both species. Wild sea trout smolt migrated significantly faster than both the F1 trout and the introduced salmon. There was no correlation between net ground speed, gill Na+,K+-ATPase activity or fish length in any of the different groups. The migration speed of wild sea trout smolts was positively correlated with water discharge in both years. In F1 sea trout smolts, migration speed was positively correlated with temperature in 1999. The migration speed of salmon smolts did not correlate to any of the investigated parameters. 相似文献
16.
Takuji Noda Toshihiro Wada Hiromichi Mitamura Manabu Kume Takuhei Komaki Tsuneo Fujita Tatsuma Sato Kaoru Narita Manabu Yamada Akira Matsumoto Tomoya Hori Junichi Takagi Alisa Kutzer Nobuaki Arai Yoh Yamashita 《Journal of fish biology》2021,98(2):507-525
This study monitored post-release movements of 20 wild Japanese eels (Anguilla japonica) [mean ± S.D. 520.8 ± 92.3 mm total length (TL), 217.9 ± 146.3 g body mass (BM)] in a brackish water lagoon in northeastern Japan using acoustic telemetry to elucidate how wild Japanese eels use different river, estuary and marine environments. In addition, 12 cultured Japanese eels (TL = 578.9 ± 18.0 mm, BM = 344.9 ± 25.5 g) were released to understand the comparative behaviours of wild and cultured eels. Both types of eels were simultaneously released in the southern inner part of the lagoon in September 2016 where there are freshwater influences from a river. Following release, eight of the wild eels (40%) were largely sedentary near the released point (river mouth) and stayed at the site for overwinter. Nonetheless, several individuals showed behavioural plasticity of habitat use: three wild eels moved towards the northern part of the lagoon with stronger influence from the sea during May–July 2017. Two wild eels showed clear repeated movements from the lagoon to a river at night and returned to the lagoon by dawn for more than a week every day, and one wild eel migrated upstream for overwintering. Signals from 55% of the wild eels could be detected for more than 6 months, whereas those from all of the cultured eels were lost by December 2016, indicating a short resident time of large cultured eels (BM > 200 g) released in a brackish water area. One wild silver eel migrated to the outer sea during the ebb tide at night in November 2016, probably triggered by the decrease in water temperature (from c. 20°C to c. 13°C), and seven cultured eels similarly moved to the outer sea during October–November 2016. The results revealed the similarities (e.g., nocturnal movements) and differences (e.g., stay period and seasonal movements) in the behavioural characteristics of wild and cultured eels and indicated that habitat connectivity among river, estuary and coastal waters is crucial for enabling eels to efficiently utilise these productive habitats through their behavioural plasticity. 相似文献
17.
The greatest numbers of Atlantic salmon smolts were caught at Uskmouth power station during the day on the flood tide and the least on an ebbing night tide. Catch rates during the day on an ebb tide and at night on a flood tide represented an intermediate state. The results, together with tracking data, suggest that salmon smolts prefer to migrate seaward through the lower Usk estuary during the night Oncc an ebbing tide. 相似文献
18.
Experiments were conducted to estimate the threshold water temperature rise (Δt) for avoidance by smolts of sea trout Salmo trutta . In three out of four experiments, the median avoidance threshold was found to be c . +6° C (+5·4 to +6·4° C). In the fourth experiment, the fish were able to detect and avoid temperature rises of < +1° C. 相似文献
19.
The possibility of using intense sound as an acoustic barrier for downstream migrating smolt of the Atlantic salmon ( Salmo salar ) was studied by observing, the reactions of smolt to 10 and 150 Hz sounds in a small river. At the observation site the river branched into a main course and a minor channel, the latter rejoining the main stream after 30 m. The sound sources were positioned at the lower end of the channel. The number of smolt re-entering the mam stream at the lower end of the channel was recorded during alternating periods with and without sound. Intense 150 Hz sound had no observable effects on the smolt, even at intensities 114 dB above the hearing threshold at this frequency. At intensities above 1.0. 10−2 ms−2 the 10 Hz sound was an effective deterrent for the smolt, which turned and left the channel at the upstream branching point. 相似文献
20.
The effects of size and previous sexual maturity on downstream migration in two-summer-old Baltic salmon were studied during their normal seaward migratory period in spring. We used an automatic PIT (Passive Integrated Transponder) tag monitoring system for individual recognition of tagged fish. Size affected the probability of migration among both previously immature and previously mature males while there was no such relationship among females. Nearly all females and 63.6% of the previously immature males migrated during the smolting period, while only 24.5% of the previously mature males did. In migrating fish the individual activity level increased from almost zero in May to about 450 antenna passages per day in mid June, coinciding with a pronounced increase in ambient water temperature. During the period of increasing activity in early June the fish changed from night activity to day activity and finally activity all day and night. The fish moved downstream in schools but no specific school size dominated. This paper demonstrates the strong effect of body size and previous sexual maturity on the probability of migration. 相似文献