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1.
Migratory behaviour of adult wild and escaped farmed Atlantic salmon, Salmo salar L., before, during and after spawning in a Norwegian river 总被引：1，自引：0，他引：1
The migratory behaviour of adult wild and escaped farmed Atlantic salmon, Salmo salar L., before, during after spawning in the River Namsen, Norway, was analysed using radio telemetry. The fish were caught, radio tagged and released into the fjord between 7 and 25 km from the river mouth. A significantly higher proportion of wild (74%) than farmed (43%) salmon was subsequently recorded in the river. Wild salmon (33%) were more frequently captured in the sea and in rivers than farmed salmon (14%). The migration speed from release to passing a data logger 11 km upstream from the river mouth was not significantly different between wild (20.6 km day?1) and farmed (19.8 km day?1) salmon. Wild salmon tagged when water flow in the river was increasing had a significantly higher migration speed than wild salmon tagged when water flow was decreasing. This was not true for farmed salmon. Farmed salmon were distributed significantly higher up the river than wild salmon during spawning, although both types of fish were found together in spawning areas. Thus, there was no geographical isolation to prevent spawning between wild and escaped farmed salmon. Farmed salmon had significantly more and longer up- and downstream movements than wild salmon during the spawning period. Unlike farmed salmon, the number of riverine movements by wild salmon increased significantly when variation in water flow increased. A smaller proportion of wild (9%) than farmed (77%) salmon survived through the winter after spawning. 相似文献
2.
Abstract Variations in the age structure and number of Atlantic salmon, Salmo salar L., running into the River Eo in northern Spain were assessed from catch records of sport fisheries for the period 1949 to 1991. The analysis focused on two periods (1951–1960 and 1981–1991) for which more complete data on fish number, size and age were available. Over the whole period, no evidence for a decline in the total salmon run was found, but the last few years revealed significant changes in both the number and age structure of salmon caught. The catches were mainly composed of multi-sea-winter salmon, and this did not change from the 1950s to the 1980s as the proportion of grilse remained unchanged. However, since 1980, there was a marked decline in both the proportion of 3-sea-winter salmon (versus 2-sea-winter fish) and the frequency of previous spawners among the multi-sea-winter salmon. These changes were probably linked because most of the previous spawners re-entered the river as 3-sea-winter or older salmon. River age of salmon caught in the 1950s was low and constant (about 90% of the catch had smolted at one year) but the mean age of smolting increased in the 1980s. 相似文献
3.
Pål Arne Bjørn Ingebrigt Uglem Sven Kerwath Bjørn-Steinar Sæther Rune Nilsen 《Aquaculture (Amsterdam, Netherlands)》2009,286(1-2):36-44
In several areas along the Norwegian coast local fishermen claim that wild migrating Atlantic cod (Gadus morhua L.) have changed their spawning migratory behaviour following establishment of salmon farms, and no longer enter their natural spawning grounds in the fjords. This has created a heated debate in Norway and, in some areas, passed down a moratorium on establishing new salmon farms. Research has so far not been able to show a causal connection, but it has been suggested that water-soluble odorants from high density salmon stocks in commercial fish farms might be responsible for the avoidance of areas with fish farming and abandonment of nearby traditional spawning grounds. The aim of this study was to test this hypothesis by studying the spatiotemporal distribution of wild migrating cod tagged with acoustic transmitters using an array of automatic listening stations in Øksfjord, a Norwegian fjord with intensive fish farming and traditional spawning grounds for cod. The tagged cod were released either in the outer parts of Øksfjord, i.e. in the area they were caught, or in the inner part of the fjord close to their traditional spawning areas. The olfactory sense was physically blocked for 50% of the fish. Only one cod released in the outer part of the fjord visited the traditional spawning grounds. The majority of the cod that were released in the inner part of the fjord remained in this area for approximately three weeks before they left the fjord. There were no differences in spatiotemporal distribution between cod with intact and cod with blocked olfactory sense. Thus, the results provided no evidence that migrating wild cod avoid areas with fish farming as a response to odorants, but the results do not per se contradict the fishermen's observation that coastal cod have changed their migratory pattern in this fjord. 相似文献
4.
E. B. Thorstad F. Økland B. O. Johnsen & T. F. Næsje 《Fisheries Management and Ecology》2003,10(1):13-22
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). 相似文献
5.
Chinook salmon, Oncorhynchus tshawytscha (Walbaum), is an important biological and cultural resource in Alaska, but knowledge about Chinook salmon ecology is limited in many regions. From 2009 to 2012, spawning distribution and abundance of a northern Chinook salmon population on the Togiak River in south‐west Alaska were assessed. Chinook salmon preferred deeper mainstem channel spawning habitat, with 12% (14 of 118 tags in 2009) to 21% (22 of 106 tags in 2012) of radio‐tagged fish spawning in smaller order tributaries. Tributary spawners tended to have earlier run timing than mainstem spawners. Chinook salmon exhibited extended holding and backout (entering freshwater but returning to saltwater before completing anadromous migration) behaviours near the mouth of Togiak River, potentially prolonging their exposure to fishery harvest. Mark–recapture total annual run estimates (2010–2012) ranged from 11 240 (2011) to 18 299 (2012) fish. Exploitation of Chinook salmon ranged from 36% (2012) to 55% (2011) during the study period, with incidental fishery catches near the mouth of the river comprising the largest source of harvest. 相似文献
6.
Abstract A combination of radio and acoustic telemetry was used to monitor the out-migration of hatchery-reared Atlantic salmon, Salmo salar L., in the River Testebo, its estuary and coastal system. As with many other Baltic rivers, the hydropower regulated River Testebo once had a self-sustaining salmon population that is now extinct. Substantial losses of smolts in the river (48–69%) and inner part of the estuary (43–47%) were found, but after leaving the estuary, the success of post-smolts moving out of the Bay was sufficiently high (83–89%) to conclude that habitat within the bay is not a factor limiting initial marine survival. The results suggest that hatchery-based recovery of a wild salmon population in the river will not be successful unless other actions, such as habitat improvement, are included. 相似文献
7.
The migration patterns of wild and released farmed Atlantic salmon, Salmo salar L., were studied by radio-telemetry during migration from entering a river to after spawning. The wild salmon were caught during return migration in bagnets and the farmed salmon were produced in a near by fish farm. Both groups were tagged and released at sea near the river mouth of the River Alta, North Norway. A pronounced individual variation in migration pattern was observed. No significant differences was found between wild and farmed salmon in the distance from entering the river mouth to the place of the first stop (recorded in the same pool for 5 days or longer) and the days from entering the river mouth to arrival at the first stop. For both wild and farmed salmon, mean migration speed was 2.6 km day1, varying from 0.4 to 11.0 km day-1. A larger proportion of farmed salmon distributed to the upper part of the river at spawning; mean distances from the river mouth were 30.1 and 19.1 km. respectively. Farmed salmon spent a significantly longer time from entering the river to reaching the area occupied during spawning. 相似文献
8.
Abstract Isomeric ratios of astaxanthin in eggs and alevins of Atlantic salmon, Salmo salar L., have proven useful in identifying female spawners of farmed origin, but the method underestimates the proportion of fish of farmed origin. The rate of underestimation was studied by analysing astaxanthin content in tissue of 55 farmed Atlantic salmon ascending two Norwegian rivers in the autumn of 1991. The astaxanthin content fell into two distinct classes. Fifty-one per cent of the adult escaped salmon had isomeric ratios similar to salmon fed synthetic astaxanthin, whereas all the remaining fish had ratios similar to wild fish. Discriminant analysis classified 96.4% of the fish with known astaxanthin content into the correct astaxanthin class on basis of tail-fin erosion, length, weight and gill-cover damage. This discriminant function was used to estimate the astaxanthin classification of 1017 farmed salmon caught in nine rivers during 1989–1991. The classification success varied among years from 52 to 64%. Corresponding numbers for females and males were 45–48% and 54–70%, respectively. Thus, estimates of spawning rates of farmed female salmon via astaxanthin content in eggs or alevins from redds should be adjusted accordingly. The observed isomeric ratios of astaxanthin in the escaped farmed salmon and the relationship with morphology indicates that a significant proportion of the escapees ascending rivers have spent more than 1 year in the wild after escape. 相似文献
9.
<正> 对虾养殖业的迅猛发展,刺激与推动了对虾苗种的生产,沿海各地为数众多的对虾育苗场相继建立,成为苗种供应的基地.在"养虾热"中,上海沿海地区的对虾养殖生产同样得到了长足的发展.养殖面积日益扩大,成为创汇农业的"拳头"产品之一.为满足2万余亩虾池苗种放养的需要,每年向江苏、浙江等省采运数亿尾虾苗,耗费大量的人力、物力、财力.并且对虾苗种生产的丰歉,以及质量的优劣,直接影响对虾养殖的稳产高产和经济效益.地处河口地区的上海沿海海水盐度低,且季节变化幅度大,给对虾育苗技术提出了新的研究课题.上海水产大学、上 相似文献
10.
Endurance of farmed and sea-ranched Atlantic salmon Salmo salar L. males was analysed during spawning time. The fish were endurance tested at different swimming speeds (1.6–2.1 m s?1) in forced swim trials. The sea-ranched males (51-65 cm, n= 20) fatigued significantly earlier than the farmed males(59-72 cm, n= 20),although the sea-ranched males were significantly smaller than the farmed males. When the size difference between the two groups were corrected for, no significant difference in the endurance of the two groups was found. Farmed salmon had a significant higher fat content in white muscle (4.7%) than sea-ranched salmon (1.1%). 相似文献
11.
Sho Kakizawa Toyoji Kaneko Tsuyoshi Ogasawara Tetsuya Hirano 《Fish physiology and biochemistry》1995,14(2):93-101
Plasma somatolactin (SL) concentrations were examined in chum salmon in relation to gonadal maturation; immature salmon in the Bering Sea at various stages of maturation, and mature salmon during upstream migration caught at the ocean, bay and river. Plasma SL concentrations as well as plasma prolactin (PRL) and growth hormone (GH) levels in the immature fish caught in the Bering Sea were maintained essentially at similar levels. Plasma SL in mature salmon increased significantly from the fish in the ocean to the fish in the river in both sexes. Although all the fish had fully developed gonads, females completed ovulation while still in the bay, whereas final spermeation in males was achieved after entry into the river. Thus, no clear correlation was seen between plasma SL levels and final gonadal maturation. On the other hand, plasma PRL concentrations in both male and female fish were higher in the fish in the river than those in the ocean and bay, and plasma GH levels were higher in both sexes in the fish in the bay and river than those in the ocean. Plasma levels of triglycerides, glucose, free fatty acids and ionized sodium and calcium were also examined. Significant-negative correlations were seen between plasma SL and plasma ionized calcium in mature male salmon, and between plasma SL and plasma triglycerides in mature female salmon. Although our findings do not rule out the possibility of the involvement of SL in final maturation, the results indicate that SL seems to be involved at least in energy and/or calcium metabolism during the spawning migration. 相似文献
12.
Immunocytochemical techniques using an antiserum to cod somatolactin (SL) demonstrated the presence of SL cells in the intermediate
lobe of the pituitary in Oncorhynchus tshawytscha. The cells were small in yearling fish. Two groups of maturing fish were studied. In the spring run salmon collected in April
and May during the upstream migration, the SL cells appeared stimulated. In September, during spawning, SL cell stimulation
was maximal with indices of hypertrophy and degranulation often more marked in females than in males. In the other group,
salmon of the fall run collected in the Pacific Ocean in August had well developed gonads, large gonadotropes and abundant
SL cells. In spawning salmon (September) the SL cells were stimulated, mainly in females. However, the final stimulation was
less intense than in spring run spawning fish. The SL cells were smaller, without evident granule release, but still abundant
in spent salmon of the fall run caught at the end of November. Various factors (time spent in rivers before spawning, starvation,
decalcification, stress, hypothalamic influences) were considered which might explain differences between spring and fall
run salmon. These observations suggest that SL may play a role in the control of gonadal maturation in chinook salmon as it
may also do in sockeye and chum salmon previously studied, and that SL cells may be sensitive to the ambient salinity. 相似文献
13.
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. 相似文献
14.
ABSTRACT: The aim of the present paper was to provide some information on the distribution pattern and feeding habits of juvenile and young Lutjanus johnii in the Matang mangrove estuary on the west coast of Peninsular Malaysia. Sampling was carried out at five sites using otter trawl nets from October 1998 to January 2000. Ninety-three individuals of juvenile and young L. johnii were collected during the research period. The range in total length varied from 3.4 to 21.1 cm, and the gonads of all fish were at the immature stage. Fish were caught at the river mouth and neighboring sites in Matang at a water depth of 1.6–7.5 m, salinity of 12.4–28.3, and temperature of 27.3–31.6°C. Individuals fed mainly on Natantia and Mysidacea, although the type of food varied with size. Large-sized individuals fed mainly on Natantia, and small-sized individuals on Mysidacea. 相似文献
15.
Alun S. Gee 《Aquaculture Research》1980,11(3):131-138
Salmon catch and effort data for 1977 from ten private fisheries on the River Wye are analysed and discussed. The 555 salmon caught represent 10.7% of the total Wye rod catch and the mean angling success rate of 0.045 ± 0.022 salmon per angler-hour, equivalent to about 22 h per salmon, compares favourably with that for other rivers in Britain and Canada. Over 75% of all salmon caught were 2 sea-winter fish, the age distribution of salmon caught in the sample being similar to those for the whole river. Angling success in the upper reaches during July and August may have been reduced by limited availability affected by water temperatures too high for migration, Flows most suitable for successful angling in each fishery are compared in relation to distance from the estuary and long-term average daily flows. Salmon appeared to be caught nearer the crest of a spate in the upper compared with the lower reaches of the river and this difference is discussed. 相似文献
16.
Life‐history differences of juvenile Chinook salmon Oncorhynchus tshawytscha across rearing locations in the Shasta River,California 
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下载免费PDF全文 Salmon from different locations in a watershed can have different life histories. It is often unclear to what extent this variation is a response to the current environmental conditions an individual experiences as opposed to local‐scale genetic adaptation or the environment experienced early in development. We used a mark–recapture transplant experiment in the Shasta River, CA, to test whether life‐history traits of juvenile Chinook salmon Oncorhynchus tshawytscha varied among locations, and whether individuals could adopt a new life history upon encountering new habitat type. The Shasta River, a Klamath River tributary, has two Chinook salmon spawning and juvenile rearing areas, a lower basin canyon (river km 0–12) and upper basin spring complex (river km 40–56), characterised by dramatically different in‐stream habitats. In 2012 and 2013, we created three experimental groups: (i) fish caught, tagged and released in the upper basin; (ii) fish caught at the river mouth (confluence with the Klamath River, river km 0), tagged and released in the upper basin; and (iii) fish caught at the river mouth, tagged and released in the lower basin. Fish released in the upper basin outmigrated later and at a larger size than those released in the lower basin. The traits of fish transplanted to the upper basin were similar to fish originating in the upper basin. Chinook salmon juvenile life‐history traits reflected habitat conditions fish experienced rather than those where they originated, indicating that habitat modification or transportation to new habitats can rapidly alter the life‐history composition of populations. 相似文献
17.
Abstract – Sixty-five large (>385 mm fork length) bull trout ( Salvelinus confluentus ), a threatened relict charr (Family Salmonidae), were captured in the upper East Fork South Fork Salmon River (EFSFSR), Idaho, USA and implanted with radio tags to investigate their spatial and temporal movements and distribution throughout the South Fork Salmon River (SFSR) basin and beyond. All radio-tagged fish were migratory. Most fish displayed a fluvial migration pattern. They typically overwintered in the larger rivers downriver of the EFSFSR (SFSR and the Salmon River further downstream), migrated upriver to the EFSFSR in June and further upriver into small (<2 m wide) tributaries to spawn in August and September. Both consecutive-year and nonconsecutive-year spawners were found. A typical migration distance between the overwintering habitat and the spawning habitat was 100 km. A minor fraction (<10%) of the fish displayed an adfluvial life history pattern, overwintering in a small (2 ha) 60-year-old flooded mine pit in the EFSFSR upstream of the spawning tributaries. The stock exhibited distinct site fidelity for spawning and overwintering. Similar fluvial and adfluvial migration patterns have been reported for bull trout in the region as well as for other charr species worldwide. Effective management of this and other migratory charr stocks will require protection of a wide range of habitats, from large rivers to the smallest tributaries. 相似文献
18.
Abstract Upstream migrating Atlantic salmon, Salmo salar L., were trapped annually between 1990 and 2003 at the mouth of the River Simojoki in the northern part of the Gulf of Bothnia, the Baltic Sea, to collect hatchery brood fish. They were also collected between 1996 and 1998 in the river to estimate the number of ascending salmon. These data on spawners were used to study the effect of changing fishing regulations in the Finnish coastal fishery in the mid-1990s on the structure of the spawning stock. In total, 1.9% of 2290 multi-sea-winter adults had previously spawned. The average annual proportion of repeat spawners was 0.5% between 1990 and 1996, but significantly higher (2.8%) between 1997 and 2003. The age distribution also changed significantly, as 4SW and 5SW salmon appeared in the population in the latter years. These changes were most probably due to the application of stricter fishing regulations. The potential of salmon to spawn repeatedly was thus preserved, despite a severe decline in natural production in the 1980s and early 1990s. 相似文献
19.
Gonad development of an anadromous fish <Emphasis Type="Italic">Coilia ectenes</Emphasis> (Engraulidae) in lower reach of Yangtze River,China 总被引：1，自引：0，他引：1
ABSTRACT: Anadromous Coilia ectenes was sampled from the Yangtze estuary at Chongming and two of the primary upstream spawning grounds at Jingjiang and Anqing in April, May, June and August 2006. Gonad development was analyzed for females. In April, fish were collected in the estuary and at Jingjiang, but not at Anqing. No female was mature (gonad at stages IV or V) at either location. In May, 45% of the females were mature in the estuary, 9% at Jingjiang and 5% at Anqing. In June, 86% were mature in the estuary, 83% at Jingjiang and 7% at Anqing. In August, C. ectenes was absent at Jingjiang. No female was mature in the estuary, and all females were mature at Anqing. Absolute fecundity ( AF ) increased significantly with standard length ( SL ) by a power function AF = 2.27 × 10−6 × SL 2.67 ( r 2 = 0.57, n = 48, P < 0.05). Mature females in the estuary were smaller than those at Jingjiang and Anqing. Conservation of spawners in the upstream spawning grounds is important because they have a size-related fecundity advantage over the smaller spawners in the estuary. 相似文献
20.
Behavioural transition during the estuarine migration of wild Atlantic salmon (Salmo salar L.) smolt
F. Martin R. D. Hedger J. J. Dodson L. Fernandes D. Hatin F. Caron F. G. Whoriskey 《Ecology of Freshwater Fish》2009,18(3):406-417
Abstract – Ultrasonic telemetry and hydrodynamic modelling were used to study the migratory behaviour of 54 wild Atlantic salmon ( Salmo salar ) smolt captured in freshwater during their downstream migration and tracked in 2 years through a shallow estuary system. A high-density, fixed array of receivers provided detailed spatial and temporal resolution of behaviour in the second year of study. Smolt migration in the river occurred mostly at night and downstream migration was slower during the day. In the estuary, smolt moved seaward on ebbing tides and landward on flooding tides. The effect of current velocity was greater during the night than during the day. We documented for the first time that current velocity and diurnal period only accounted for approximately one-third of the variation in smolt ground speeds in the estuary, indicating that smolt movements were far less passive than previously reported. Smolt energetic status had no effect on smolt swimming behaviour or migratory performance. With an increase in salinity, smolt seaward movements during flooding tides were more frequent, and overall seaward ground velocity increased. The increase in salinity experienced by the smolt during their migration through the leading edge of saltwater intrusion thus induced a behavioural transition from a more passive, fluvial migration to a more active- and seaward-oriented migration. 相似文献