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1.
The effect of origin, smolt size and year of release on the sea migration pattern of Atlantic salmon (Salmo salar L.) in the Baltic Sea was examined by tagging experiments conducted in 1991–1993 on wild and reared smolts of the Simojoki river salmon stock. The tag recovery data analysed by log-linear models revealed significant differences in both spatial and temporal sea migrations between the wild and reared salmon; the variation was attributed to the year of release and to the origin of the fish. Grilse accounted for the majority of reared returners (76%) but for a smaller proportion (46%) of the wild fish. The effect of smolt size could be studied only in the smolt groups tagged in 1991. Wild fish were more frequently (71%) caught in the Baltic Main Basin than were reared fish (51%) during their second sea year, and the size variation between wild and reared smolts did not explain the recovery site. No such differences in spatial distribution were found during the third sea year. The tagging place (hatchery/trap) of the reared fish did not affect their later sea migration. The differences in sea migration patterns suggest that the wild salmon are more vulnerable to the intensive salmon fishery in the Baltic Main Basin than are reared fish.  相似文献   

2.
ABSTRACT:   The purpose of the present paper was to reveal the migration pattern of shirauo Salangichthys microdon Bleeker, in the Ishikari River system and its adjacent coastal sea areas. To this end, the strontium–calcium (Sr:Ca) ratios of the otoliths of 98 individuals were examined. Profiles of the Sr:Ca ratios during the life history after hatching in the estuary of the Ishikari River fell into two different patterns. One was characterized by a high (slightly fluctuating) Sr:Ca ratio throughout the life history; the other was characterized by an initial high Sr:Ca ratio followed by a lower value later in life. The former pattern was considered to be that of estuary–sea residents and the latter that of upstream migrants. Most upstream migrants migrated upstream once, although several did it twice. Back-calculated body lengths during the upstream and seaward migrations of the upstream migrants varied widely from 6.4 mm to 39.8 mm and from 13.5 mm to 79.4 mm, respectively. These findings suggest that estuary–sea residents and upstream migrants co-occurred spatiotemporally, and suggest a wide variation in migration patterns in the shirauo's life history.  相似文献   

3.
European sea bass exhibits a feeding rhythm with seasonal phase inversions: nocturnal feeding is predominant in winter, and diurnal feeding during the rest of the year. This explains the increased growth of sea bass fed at night during the winter months, but to fully assess such feeding practices, it is important to monitor food-catching efficiency in the dark. To evaluate the influence of nocturnal feeding on pellet-capture efficiency under laboratory conditions, we developed an infrared pellet detector linked to on-line recording with a microcomputer. Feed waste was recorded for eight groups of four sea bass (54.6±15.8 g body weight) fed either diurnal or nocturnal meals with long (>60 s) or short (<20 s) feed availability times. With short feed availability times, food-catching efficiency in complete darkness (0 lx) was reduced to 78.6%, compared to 93.5% in diurnally fed fish. This was confirmed in a second experiment, performed during winter, involving 4000 sea bass in four sea cages (1000 per cage) provided with self-feeders and pellets detectors. Feed waste amounted to less than 13% of the food distributed, but nocturnal demands (29% of total feed demands) were accompanied by higher levels of uneaten pellets (68% of the total feed waste) than diurnal demand. This suggests that if the aim is to reduce feed waste, nocturnal feeding should be restricted in sea cages.  相似文献   

4.
ABSTRACT:   To compare metabolic activity rhythms between wild and cultured black rockfish Sebastes schlegeli , we measured long-term oxygen consumption rates (OCR) using an automatic intermittent-flow respirometer under constant temperature and darkness. Oxygen consumption rates peaked among wild black rockfish at 12.4 h intervals, which corresponded to a circatidal rhythm. The wild fish were probably exhibiting responses that corresponded to tidal events in their natural environment. However, when captured wild black rockfish were kept under laboratory conditions (12 h light [L] : 12 h dark [D]) for 30 days, the OCR shifted to a circadian rhythm (24.1–24.9 h). The OCR of cultured black rockfish that had been reared in a tank for 9 months peaked at approximately 24 h intervals, corresponding to a circadian rhythm. The results of this study suggest that the differences in OCR patterns between wild and cultured fish were mainly due to differences in the environmental conditions between tidal and non-tidal habitats.  相似文献   

5.
Abstract –  Anthropogenic barriers that may interfere or prevent fish migration are commonly found in streams throughout the distribution of salmonids. Construction of fish passages in streams is a common solution to this problem. However, the goal with fish passages is often, at least in Scandinavia, to allow Atlantic salmon ( Salmo salar L.) and migratory brown trout ( S. trutta L.) to get access to spawning areas above these barriers. Hence, the fish passages may often only be open during the spawning migration of salmonids (late summer to autumn). We present data, on wild brown trout migration, from two trapping systems in two Scandinavian streams showing that intra- and interstream migrations are common throughout the summer and autumn. Moreover, differences in size were found between trap-caught trout and electrofished trout where trapped trout were generally larger than electrofished trout. We suggest that the current regime with fish passages only open parts of the year can have negative effects on populations by depriving trout from the possibility to perform migrations throughout the year.  相似文献   

6.
ABSTRACT:   Post-release movement and diel activity patterns of hatchery-reared and wild black-spot tuskfish were examined using ultrasonic telemetry. Five hatchery-reared and four wild fish were released in the sandy bottom of Urasoko Bay, Ishigaki Island, Okinawa, Japan, and monitored using automated monitoring receivers from November 2005 to February 2006. Both hatchery-reared and wild fish tended to stay near the release site for over two weeks, before leaving the release site. Both hatchery-reared and wild tuskfish showed diurnal rhythm intermittently; signals were recorded more frequently in the daytime and less frequently in the nighttime, suggesting that the fish of both origins were active during the day and inactive during the night. These findings indicate that the one-year-old hatchery-reared tuskfish have some consistent behavioral characteristics with those of the wild.  相似文献   

7.
ABSTRACT:   To determine characteristics which may reflect the behavioral quality of red tilefish Branchiostegus japonicus after release, five wild and four hatchery-reared fish were observed in a laboratory and in the sea. The diel activity of the fish was recorded on video tape for 2 days in a tank, where the light condition was regulated to vary periodically over 24 h. The individuals were then released in Maizuru Bay and tracked using acoustic telemetry. Four wild individuals became most active at dawn during a day in the tank, and settled near the release area to stay for 28–104 days after release in Maizuru Bay. In contrast, one wild and four hatchery-reared individuals were not active at dawn, and then did not settle in Maizuru Bay after release. Among the four settled wild individuals, the more active a fish had been in the tank, the more distant the individual moved from the release point until its settlement. The diel activity pattern should be a factor deciding whether red tilefish would settle nearby after release, and the relative amount of activity during rearing is probably related to the degree of dispersion within the release area.  相似文献   

8.
Abstract –  The real-time diel pattern of Atlantic salmon smolt migration was observed for 8 years using automatic resistivity counters verified by video surveillance. A clear dominant nocturnal migration was demonstrated early in the migration period, later becoming increasingly diurnal, until rates became approximately equal at day and night. Migration patterns were related to water temperature, such that when mean daily temperatures were below 12 °C, hourly rates of migration were significantly lower during the day than at night. When daily mean temperatures exceeded 12 °C, there was no significant difference between diurnal and nocturnal migration rates. Migration patterns showed a distinct suppression of migration at dawn and dusk throughout the migration period. It is hypothesised that this behaviour is an active decision and/or an adaptive strategy either to take advantage of increased food in the form of invertebrate drift or to reduce predation risk from actively feeding piscivores or both.  相似文献   

9.
Atsushi  TAKEKAWA  Koichi  SASAKI  Michio  OMORI 《Fisheries Science》2004,70(6):971-977
ABSTRACT:   Baited traps were used over 24 h to reveal the diel activity and vertical distribution of three dominant lysianassoid amphipods ( Scopelocheirus onagawae , Anonyx omorii , Anonyx abei ) in Onagawa Bay, north-eastern Japan. The three species were the most dominant small crustacean scavengers in the bay. Most individuals were caught by traps deployed 0.3 m above the bottom, showing that they were active in the layers close to the sea bottom. No habitat segregation was found among species or developmental stages, suggesting that these scavengers rely on the food supply from bottom deposits. The three species increased remarkably in numbers of collected individuals at night, showing a rise in feeding activity. The two Anonyx species were collected only during the night, and S. onagawae was collected mostly during the night. The nocturnal activity appears to be an adaptation to reduce predation risks. However, juveniles of S. onagawae appeared even during the day, suggesting that feeding might take precedence over avoiding predation. Baited traps collected ovigerous females of S. onagawae but not of Anonyx species; the reason for the difference could not be determined.  相似文献   

10.
The activity patterns of migrating lampreys (sea lamprey Petromyzon marinus and river lamprey Lampetra fluviatilis) are poorly understood. This study uses extensive screening data from the cooling water intake of a nuclear power plant on the River Rhine, Germany, gathered on 1308 days over 46 consecutive months between 2011 and 2014. More than 34,000 lampreys were retrieved, of which the great majority (99.9%) were outmigrating nonfeeding postmetamorphic individuals. The main factors controlling outmigration were season, water temperature and river discharge. The bulk of downstream migration was observed each year in spring at water temperatures between 9 and 12°C, with earlier migrations during significant discharge peaks between December and February. The migration activity of postmetamorphic individuals declined during summer and autumn, regardless of discharge. Turbidity increased the occurrence of postmetamorphic lampreys and supported diurnal migration, which accounted for nearly 20% of all lamprey records. In winter, outmigrating individuals of both species exhibited significantly longer body lengths than those detected during other seasons. Haematophagus postmetamorphic sea lampreys were also retrieved (n = 28) and represent the most upstream records of parasitically feeding sea lamprey detected thus far. Adult lampreys migrating upstream were found mainly in spring, but in very low numbers, indicating high prespawning mortalities. The study points to a challenging future for the protection of lampreys in this area: the long duration and the round‐the‐clock nature of the observed migration demand flexible solutions to realise safe operational windows for water intake stations and to minimise impacts on juvenile lampreys.  相似文献   

11.
Abstract –  The timing and duration of the estuarine phase during seaward migration were addressed for allis shad and twaite shad, closely related sympatric species in the Gironde system. Otolith Sr:Ca and daily growth increments were used to retrospectively estimate the age at entrance in the estuary, the time spent in estuary and the age at seaward exit from returning adults. The two species exhibited different seaward migration strategies: allis shad entered the estuary at an older age than twaite shad (88 days vs. 59 days), stayed shorter in the estuary (11 days vs. 17 days) and exited to the sea at an older age (99 days vs. 77 days). In the Gironde system, the estuarine phase is very short and occurs within a particular time 'window' for the juveniles that will become future spawners. In this context, it might be suggested that the estuarine phase is a bottleneck for these sympatric shad populations.  相似文献   

12.
Interannual variation in the timing of the return migration to fresh water of adult sockeye salmon, Oncorhynchus nerka, from 46 populations throughout the species North American range was examined in a broad analysis of how timing patterns are affected by marine and freshwater conditions. Migration timing data (measured at various points along the migration, including just prior to freshwater entry, just after freshwater entry, and near the spawning grounds) were examined for correlations with sea‐surface temperatures (SST) prior to migration and to freshwater temperatures and flows during migration. Following a spring–summer period with warm SST, populations from southwestern Alaska tended to return early, Fraser River populations returned late, and populations from other regions showed no consistent patterns. Similarities between interannual timing of both nearby and distant populations indicated the presence of common or coincidental influences on timing. When riverine conditions related to timing, high flows and low temperatures were associated with late migrations, low flows and high temperatures were associated with early migrations. However, even counting stations at upriver locations showed correlations with SST. Notwithstanding some inconsistencies among the many populations examined and the indirect nature of the inferences, the results supported the hypotheses that (i) interannual variations in salmon distributions at sea reflect temperature conditions, and (ii) the date when salmon initiate homeward migration is a population‐specific trait, largely unaffected by the fish's location at sea.  相似文献   

13.
Japanese eels (Anguilla japonica) perform large‐scale oceanic migrations between their spawning ground and growth habitats in continental waters during life history. However, between these migrations, they spend most of time in growth habitats such as rivers. To investigate the diel and seasonal activities, homing behaviour and home range of yellow‐phase Japanese eels in the lower reach of the Tone River, we tracked them throughout a year using a fine‐scale positioning system (VPS) based on acoustic telemetry. The tracked eels were generally nocturnal, but not exclusively. They were mainly mobile from spring to autumn, with little or no activity observed during winter. A transport‐release experiment showed that most eels returned to their original capture area within 13 days after release. The eels had very small home ranges (mean ± SD = 0.085 ± 0.068 km2), core areas (0.014 ± 0.014 km2) and linear home ranges (744 ± 268 m). They also tended to be distributed on one particular side of the river (right or left bank) and in one particular shore type (revetment or vegetation), rarely moving from one to the other. This study provides evidence for nocturnal, dormancy, homing behaviours, limited habitat use and small home range size in Japanese eels. The eels clearly showed strong fidelity to a “familiar” site, which contrasts with the long distances travelled during upstream and downstream migration phases in the river, and during spawning migrations in the ocean.  相似文献   

14.
Abstract –  Life history strategies and migratory patterns of 71 adult radio-tagged bull trout, Salvelinus confluentus , were studied in the Secesh River watershed within the South Fork Salmon River (SFSR) sub-basin in west-central Idaho, USA during 2003 and 2004. In both years, upstream migrations occurred during late June and early July, migrations into two spawning tributaries during late July and early August, spawning from mid-August through mid-September, and rapid downstream (postspawning) migrations from late August to mid-September. Primary over-wintering areas were Loon Lake, the lower Secesh River (downstream of Loon Creek), and the lower SFSR (downstream of the confluence with the Secesh River). Loon Lake evidently provides sufficient production to allow the adfluvial life history strategy to persist and predominate in the Secesh River, while the fluvial life history strategy was previously found to predominate in the nearby East Fork SFSR. Adfluvial, nonconsecutive-year migrations were the predominant life history strategy. Only seven fish made consecutive-year migrations to Lake Creek; however, only one of these fish, a female, utilised a spawning tributary in both years and showed spawning tributary fidelity. Three consecutive-year migrants and three in-season migrants showed over-wintering site fidelity by returning to Loon Lake in September, 2004. The life history variations observed for bull trout in the Secesh River watershed are similar to those observed for bull trout throughout their range and to those of other charr species worldwide, yet the development of distinct migration patterns demonstrate the adaptability of the species to a range of available habitats.  相似文献   

15.
ABSTRACT:   In order to investigate the changes in rhodopsin-porphyropsin ratio of chum salmon and pink salmon in relation to the change in their habitat, the ratios were analyzed in individual fish prior to stocking, during the sea run, homing, and upstream migration. The ratio in both the species gradually increased during the sea run. However, the ratio decreased after upstream river migration. Moreover, in the sea, the rhodopsin-porphyropsin ratio of chum salmon was always slightly higher than that of pink salmon. The largest difference in the individual variation was observed in the individuals caught with a set net placed near the mouth of a home river.  相似文献   

16.
Abstract –  The timing of the smolt migration of Atlantic salmon, Salmo salar L., was investigated during 1972–2002 in the Simojoki, a river flowing into the northern Baltic Sea. The onset of the smolt run was positively correlated with the river water temperature; a rise in water temperature above 10 °C being the main proximate environmental triggering factor. There was also a weaker correlation between the decreasing river discharge in the spring and the onset of the smolt migration. The duration of the main run was shorter in the years when the onset of the smolt run was delayed. No differences were found in the onset timing or in the duration of the smolt run between wild smolts and semi-wild smolts released into the river as parr. A polynomial equation fitted to the annual data on the survival of Carlin-tagged wild smolts and the sea surface temperature (SST) in June off the river mouth appeared to follow a dome-shaped pattern. Survival was lower in cold early summers (SST <9 °C) than in those with an average SST (9–11.9 °C), and lower again, although not significantly, in warm early summers (SST ≥12 °C). Too low and probably also too a high water temperature in early summer could thus be one of the underlying reasons for the fluctuations observed in postsmolt survival in the Baltic Sea.  相似文献   

17.
Sea bass change their feeding rhythms from diurnal to nocturnal in winter, returning to diurnal feeding in spring. Despite behavioral data, the physiological changes that take place during such changes remain unexplored. In this paper, blood glucose rhythms of European sea bass with diurnal/nocturnal self-feeding rhythms were investigated during phase inversions of their feeding behavior (in winter and spring) when both diurnal and nocturnal fish coexist. Blood glucose showed daily variations in both seasons (ANOVA, p < 0.03), fitting a cosine function (COSINOR, p < 0.05) in all cases, except in diurnal fish in spring. The average blood glucose levels of nocturnal fish in winter (2.67 ± 0.09 mmol/l, mean ± SEM) were significantly (t test, p < 0.01) higher than in spring (2.20 ± 0.08 mmol/l), while they were similar (~2.25 mmol/l) in diurnal fish in both seasons. These findings revealed for the first time insights into the seasonal physiological changes that accompany changes in behavioral rhythms in diurnal and nocturnal sea bass.  相似文献   

18.
The sablefish (Anoplopoma fimbria) is a long‐lived species with wide distribution throughout the North Pacific Ocean. While adult sablefish are considered a deep‐water fish, diet analyses suggest that they undergo vertical migrations that could be related to prey movement and feeding. Pop‐up satellite archival tags (PSATs) were used to observe the fine‐scale depth selection behavior of adult sablefish tagged off the Washington coast during the summer from June to August. Tags were physically retrieved after they surfaced using direction‐finding equipment so that complete datasets over the entire deployment were obtained from 14 tags. PSATs that recorded depth and temperature every 4 min during the deployment confirm that sablefish inhabit depths of 750 m or greater. However, a majority of the tagged fish underwent extensive vertical migrations that averaged 254.4 m overall and occurred at a 24 hr periodicity. Variations were observed among individuals in the amount of the deployment during which vertical migrations occurred, ranging from 12.37% to 63.48% of the time. During the vertical migration, fish ascended towards the surface at night and descended prior to daylight (i.e., diel vertical migration). Sablefish generally inhabited temperatures of 5°C but during the vertical migrations were found at temperatures from 6 to 10°C. Sablefish are opportunistic feeders with a large proportion of their diet being fish, euphausiids and cephalopods. Because these prey items also exhibit diel vertical migrations, it is possible that the vertical migratory behavior displayed by the sablefish was in response to the movements or the location of their prey.  相似文献   

19.
An examination of marine growth/marine survival relationships in Atlantic salmon, Salmo salar L., was carried out, based on scale growth measurements in relation to two indices of marine survival in wild fish from the River Bush, Northern Ireland. The survival of cohorts to the Irish/Northern Irish coast (prefishery) and to fresh water was statistically unrelated to variation in growth from smolt migration to the end of the first winter at sea ( P  > 0.1; – P  > 0.7). Marine growth of 1+ smolts decreased significantly during the period of the study ( P  < 0.05), but growth of 2+ smolts did not change ( P  > 0.05). The variability in marine growth was much less than the variation in natural survival at sea, suggesting that factors instead of or in addition to, growth influence natural survival in the marine environment. Survival to fresh water was not related to survival to the coast ( P  > 0.4), although it was inversely correlated with exploitation rate ( P  < 0.01). These results are discussed in relation to the use of freshwater returns to assess marine survival and the potential for the variation in natural marine mortality to influence total life-cycle variation.  相似文献   

20.
Abstract –  Diel vertical migration (DVM) is a widespread behavioural pattern in populations of aquatic animals. Its adaptive value is explained by a trade-off between the protection against visually feeding predators in the dark hypolimnion during daytime, and a higher food uptake in the upper food-rich layers during the night. Whereas vertical migration patterns of entire populations have been frequently described, less is known with respect to individual variability of DVM within fish populations. Here, individual migration patterns of European vendace ( Coregonus albula ) are described, obtained by stationary vertical hydroacoustics in Lake Stechlin (Germany) during the dusk and dawn phases of 2 months in 2004. The variability of speeds of depth change was high, with only a few fish rising or falling faster than 1 cm s−1. Swimming activity was not dependent on fish size. There was some evidence that variability of echo strengths was highest in those fish which showed the greatest three-dimensional swimming distances which might indicate a limited swimbladder compensation during vertical migrations. However, migration seems to be performed mainly in a saltatory mode with vertical swimming always interrupted by phases of constant depth. It is suggested that these phases are used for pressure compensation by fish with the consequence that overall the frequency distribution of target strengths deviates only slightly between the start and the end of the recordings. Stationary hydroacoustics proved to be a useful tool for studying individual fish swimming behaviour.  相似文献   

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