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1.
We investigated juvenile brown trout migration and mortality in a headwater tributary of the Motueka River, New Zealand, by tracking 1000 young‐of‐the‐year passive integrated transponder (PIT) tagged fish over autumn to summer to (i) partition total loss into emigration and mortality and (ii) determine the influence of season and flow on emigration. Fish were tracked using mobile and fixed PIT tag readers. Of the 1000 fish tagged, 173 remained within the Rainy River; emigration contributed 60% and mortality 29% to loss. Only 11% of fish tagged in autumn were predicted to remain in the upper reaches of the stream by early summer, and this agreed with density data collected in a parallel study. We identified a two‐phase downstream migration pattern with early movement of large young‐of‐the‐year fish in autumn (mainly during floods). This was followed by another substantial period of movement in spring (during floods and lower flows) by fish that were initially smaller at the time of PIT tagging. The management implications for damming and fish screening in headwater tributaries are discussed.  相似文献   

2.
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   

3.
In this study, 221 two‐year‐old hatchery‐reared salmon, Salmo salar, smolts were tagged with radio transmitters over a period of three consecutive years and released in the river in groups of 20–21 fish in various dates between late April and early June. Tagged smolts were tracked during their downstream migration in the lower 36‐km stretch of the regulated River Oulujoki, with the focus on the effects of release date, water temperature and river flow on migration behaviour and survival. The results indicate that release timing and river temperature have profound effects on the initiation of migration, swimming speed and survival of released S. salar smolts. Smolts released early in the spring in cold waters ceased migration after brief downstream movement and were vulnerable to predation, whereas the migration speed and survival rates increased markedly for smolts released later in the spring.  相似文献   

4.
Over 3 years, 32,444 age‐0 group Atlantic salmon (Salmo salar) parr tagged with passive integrated transponder tags throughout the River Frome catchment were assigned to one of three groups, nonmigrants, autumn migrants and spring smolts, depending on the detection and the timing of detection at downstream tag readers (situated 8.6 km above the tidal limit). We examined the effect of density at the time of tagging (n·m?2), distance upstream from the tidal limit (km), fish length (mm), Fulton condition index, habitat type (divided into two types, main river and carrier), days after 1 September that each fish was tagged and year (replication) on the proportions of fish in each of the migration groups. Distance upstream from tidal limit was strongly negatively related to the proportion of autumn migrants and positively related to the proportion of spring smolts. Nonmigrants had a lower average body size than migrants, although there were no differences in the sizes of autumn migrants and spring smolts in September prior to migration. Fish density had no effect on migration strategy. A lower proportion of fish migrated as autumn migrants from the smaller carrier habitats than the main river channel. There is some evidence that those parr destined to become autumn migrants underwent a lower mortality rate during September before tagging than those destined to become spring migrants indicating possible physiological or behavioural differences between these two groups of fish at that time. More research into the factors responsible for initiating the autumn migration is required.  相似文献   

5.
Quantifying fish movements in river networks helps identify critical habitat needs and how they change with environmental conditions. Some of the challenges in tracking fish movements can be overcome with the use of passive integrated transponder (PIT) tagging and antennas. We used PIT technology to test predictions of movement behaviour for four fish species at a mainstem–tributary confluence zone in an arid‐land river system. Specifically, we focused on the McElmo Creek tributary confluence with the San Juan River in south‐western Utah, USA. We quantified variation in species occurrences at this confluence zone from May 2012 to December 2015 relative to temporal and environmental conditions. We considered occurrences among species relative to tagging origins (tributary versus mainstem), season and time of day. Generally, fishes tagged in the focal tributary were more likely to be detected compared to fish tagged in the mainstem river or other tributaries. Additionally, adults were most likely to be detected across multiple years compared to subadults. Based on a Random Forests model, the best performing environmental variables for predicting seasonal detections included mainstem discharge during run‐off season (razorback sucker Xyrauchen texanus), tributary discharge during monsoon season (Colorado pikeminnow Ptychocheilus lucius) and mainstem water temperature (flannelmouth sucker Catostomus latipinnis and channel catfish Ictalurus punctatus). The variable responses by endemic and introduced fishes indicate tributary habitats provide several key functions within a fish community including spawning, rearing, foraging and refuge.  相似文献   

6.
To determine the efficacy of passive integrated transponder (PIT) tags for marking rohu Labeo rohita (Ham.) in the selective breeding programme, a series of experiments has been carried out at the Central Institute of Freshwater Aquaculture (CIFA) under the Indo–Norwegian project of ‘Selective breeding of rohu’. Six groups of rohu fingerlings with weight ranging from 2 g to 20 g were tagged with PIT tags to determine a suitable size range for tagging. Fingerlings weighing 8–15 g were found to be quite suitable for tagging with a PIT tag. Recovery of the PIT tag depends upon the survival of tagged fish under field conditions. Rejection of the PIT tag by rohu was observed to be only 0.05%. Through effective management practice, the survival of tagged fish increased up to 95%, and thus tag loss was minimized.  相似文献   

7.
Results from an acoustic telemetry study revealed for the first time a northerly migration route for Atlantic salmon (Salmo salar L.) smolts leaving the east coast of Ireland. Atlantic salmon smolts were tagged in spring 2019 in the Castletown and Boyne rivers. Three tagged smolts registered on disparate deep‐water offshore marine receivers as they travelled northwards out of the Irish Sea through the North Channel. One fish had migrated an estimated 250 km in a period of 32 days. The remaining two individuals were detected on receivers located off the Northern Ireland coast, further corroborating the northward migration of salmon smolts through the Irish Sea.  相似文献   

8.
Migration timing, speed, survival and effects of environmental parameters on migration, between wild and hatchery produced Atlantic salmon, Salmo salar L., smolts in the River Lærdalselva were studied. Hatchery‐reared (n = 40) and wild pre‐smolts (n = 40) were tagged with acoustic tags, and an array of receivers along the migration route was deployed. In all, 77 and 85% of the fish from the two groups, respectively, were recorded as migrating smolts, that is, predation rate and/or numbers of fish opting to remain in the river were low. Hatchery‐reared smolts showed a migration pattern, speed and migration route similar to wild smolts, even though the time period between river release and onset of migration was relatively short. Both groups of smolt showed high migration speed through both the river and the fjord compared with other studies.  相似文献   

9.
Abstract –  To address the dearth of information on tagging effects and long-term survivorship of tagged fish in native and introduced species, laboratory and field investigations were undertaken on three non-native fish species (pumpkinseed Lepomis gibbosus ; topmouth gudgeon Pseudorasbora parva ; pikeperch Sander lucioperca ) tagged with coded-wire (CW), passive integrated transponder (PIT), radio (RT) telemetry and/or acoustic tags (AT), with survivorship of native brown trout ( Salmo trutta ) examined in the field. Laboratory results revealed high survivorship following tag attachment/insertion and resumption of feeding within 24–48 h of tagging (all mortalities could be attributed to an unrelated outbreak of fungal infection), with retention rates being high in both pumpkinseed and pikeperch but low in topmouth gudgeon (excluded from field studies). In the field, short-term post-operation survival was high in pikeperch, pumpkinseed and brown trout. In pumpkinseed and trout, 100% of RT fish survived a 24–30 day tracking study, with 60% and 80%, respectively, recaptured alive at least 3 months post-tagging. Of PIT tagged pumpkinseed, 44% were recaptured (after 6–18 months), with small-sized, CW-tagged fish (0.38 g weight) captured up to 1 year after tagging. In pikeperch, all AT fish except one (the smallest specimen) survived their full expected tracking period (i.e. tag life) – the single lost specimen survived at least half of its expected tracking period (i.e. 6 month battery life). Overall, the tagging methods used were highly effective in pumpkinseed and pikeperch, showing good retention and survival, but PIT tagging of topmouth gudgeon was plagued by low survivorship and tag rejection.  相似文献   

10.
The study examined the effect of PIT tagging and size on the growth, survival, food conversion, tag retention and wound healing in juvenile European whitefish. Three size classes of juvenile whitefish (class S—body weight (b.w.) approx. 4.0 g; class M—b.w. approx. 8.0 g; class L—b.w. approx. 13.6 g) were tagged with PIT implanted intraperitoneally (TROVAN®, United Kingdom). These groups formed S‐P, M‐P and L‐P respectively. Fish from the control groups (groups S‐C, M‐C and L‐C) were not tagged. Whitefish from the tagged and control groups were reared for 28 days in recirculating aquaculture systems. Only in the fish from the smallest group (group S‐P) was tagging confirmed to have a negative impact on growth rate and survival, which, after 28 days, was 70% in comparison with 94.4% in group S‐C. The rate of wound healing in all whitefish groups was similar. After 28 days following PIT implantation, all wounds were healed. Short‐term PIT retention (28 days) for all the groups was > 90%, and no differences were noted among groups. In summary, it is recommended that whitefish be PIT‐tagged using the intraperitoneal method after they have attained a body weight > 8 g. Tagging smaller specimens of this species leads to higher mortality.  相似文献   

11.
In the spring of 1996 and 1997, a prototype 400 kHz flat-plate (pass-by) passive integrated transponder tag interrogation (PIT tag) system was installed at the terminus of the downstream migrant (DSM) channel of the Bonneville Dam First Powerhouse, located on the Columbia River. The system was designed to interrogate previously PIT tagged juvenile salmonids migrating down the Columbia River without interfering with the traditional subsampling of fish passing through the facility. In addition, the design enables fish of virtually any size, and debris, to pass over the system's antennas without the port restrictions imposed by traditional pass-through PIT tag interrogation systems. We describe the fish facility in addition to the flat-plate system and its operation. The system tag reading efficiency was evaluated during 1996 and 1997 using a direct method based on the release of known numbers of tagged test fish and an indirect statistical procedure based on tagged run-at-large fish. The results showed that PIT tag reading efficiency during both years using the direct method averaged 97%, while that using the statistical procedure averaged 99% for the dual multiplexed antenna array. During the 1996 and 1997 field seasons 4371 and 14 733 fish, respectively, were recorded. Daily system functionality was monitored using stick tests (i.e., the passing of PIT tagged sticks across the antenna array).  相似文献   

12.
Abstract –  The round goby ( Neogobius melanostomus Pallas) is an invasive species in North America and Europe. We evaluated the efficacy of passive integrated transponder (PIT) tags for marking round gobies and tracking their movements with a portable underwater antenna in shallow areas (≤1 m) of a lake. Tagging did not markedly decrease growth of fish <105 mm; however, growth decreased unexpectedly for tagged fish ≥105 mm during the final sampling period. Nevertheless, tagging did not increase mortality regardless of size class, and tag retention was 100% for caged fish. Tagged round gobies in a 20 × 20-m2 block net avoided detection by the portable underwater antenna, and a high proportion of fish probably escaped from the net, suggesting that round gobies may be more mobile than previously reported. In conclusion, PIT tags are a viable method for individually marking round gobies, but detecting tagged round gobies with a portable underwater antenna, given current technology, does not appear promising in shallow areas with low habitat complexity.  相似文献   

13.
This study investigated the cumulative impact of weirs on the downstream migration of wild Atlantic salmon (Salmo salar) smolts in the River Foyle, Northern Ireland. In spring of 2013 fish were released in two tributaries of similar length; one tributary (impacted) had seven low‐head weirs along the migration pathway and the other was devoid of such structures (un‐impacted). Salmon smolts fitted with acoustic transmitters were monitored via a passive acoustic telemetry array during downstream migration. In 2014 the study was repeated only in the impacted tributary. Overall freshwater survival rates were high (>94%). There was no significant difference in mortality, movement pattern, delay or travel speeds between rivers or between years at any phase of migration. Escapement of salmon smolts through Lough Foyle (a marine sea lough) to the open ocean was low, approximately 18% in each year. Escapement did not differ between impacted and un‐impacted rivers. This study showed no postpassage effects of weirs on mortality, migration speed or escapement of downstream migrating smolts. This suggests that the elevated mortality at low‐head obstacles described in other studies is not inevitable in all river systems. Migration through rivers with natural riffle‐pool migration may result in similar effects as those from low‐head weirs. Causes of apparent high mortality in the early part of marine migration in this study, are unknown; however similar studies have highlighted the impact of fish predators on smolts.  相似文献   

14.
Abstract Release strategies of hatchery‐reared Atlantic salmon, Salmo salar L., smolts were compared by studying survival and migration of smolts (n = 99) and their predators (Atlantic cod, Gadus morhua L., n = 8; and saithe, Pollachius virens (L.), n = 2) during the first 37 km of the marine migration using acoustic telemetry. Survivorship was higher in smolts released at the river mouth (30%) compared with smolts released in the river (12%). This was likely due to mortality or reduced migratory behaviour in fresh water. The marine mortality was 37% during the first 2 km after leaving the river (at least 25% mortality because of predation from marine fishes), and total marine mortality over 37 km was 68%. Detection‐depth data were useful for evaluating whether the tagged smolts were alive or predated; mortality during the first 2 km of outward migration would have been underestimated at 26% instead of 37% without the analysis of depth detection. Transmitters from consumed post‐smolts remained in predators for up to 47 days (average 29 days).  相似文献   

15.
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   

16.
The aim of this study was to examine early marine survival and movements of simulated escaped Atlantic salmon Salmo salar L. pre‐smolt and smolt from a commercial smolt farm during autumn. One‐third of the pre‐smolt most likely died in the immediate vicinity of the release location, whereas the corresponding mortality for smolts was lower (8.5%) during the 5‐week study period. The surviving pre‐smolt left the farm area after 2–3 days, predominantly along the shore. In contrast, most of the surviving smolts left the farm area during the first day and 54% seemed to move away from the shore and adopt a more pelagic movement pattern than pre‐smolt. The number of surviving fish recorded in the fjord decreased throughout the study period, possibly due to a combination of fish migrating out of the fjord or undetected mortality. Compared with existing knowledge on migration of released farmed smolts during spring, our results indicate less directional and slower movement rates during autumn. Only two of the tagged fish were detected upstream in the rivers following release. A rapid dispersion of escapees indicates that the potential for recapturing escapees is limited unless recapture efforts are initiated immediately after escape. Hence, there is a need for development of technology that detects and prevents escapees to enter the sea.  相似文献   

17.
The timing of smolt migration is a key phenological trait with profound implications for individual survival during both river descent and the subsequent sea sojourn of anadromous fish. We studied relationships between the time of smolt migration, water temperature and light intensity for Atlantic salmon (Salmo salar) and sea trout (Salmo trutta). During 2006–2012, migrating smolts descending the southern Norway River Storelva were caught in a rotary screw trap located at the river mouth. The date of 50% cumulative smolt descent correlated significantly with the date when the river temperature exceeded 8°C for both Atlantic salmon and sea trout smolts. In 2010, smolts of both species were passive integrated transponder (PIT)‐tagged, and the diel timing of their migration was precisely documented. The degree of night migration decreased in both species as the river temperature rose, and at temperatures above 12–13°C, more smolts migrated during day than during night. A multinomial model was fitted for estimating temperature and species effects on probabilities of migration during night, daytime, dusk and dawn. Atlantic salmon smolts preferred migrating under lower light intensities than sea trout smolts during early, but not late spring when both species migrated during bright daylight. In accordance with the early‐season tendency to migrate at night, Atlantic salmon smolts migrated more during darker hours of the day than sea trout. In both species, smaller smolts migrated under dark conditions than during light conditions. Most of the findings on thermal, light and temporal effects on the observed smolt migration pattern can be explained as adaptations to predation avoidance.  相似文献   

18.
Partial migration is a common phenomenon in many fish species. Trout (Salmo trutta) is a partially migratory species where some part of the population migrate to the marine environment, while another remains in freshwater. In the years 2008 and 2009, a total of 159 wild sea trout smolts were tagged with acoustic and PIT‐tags in the river Villestrup (Denmark) to study the initial postsmolt marine behaviour within a fjord system. We found that the strategies of the sea migrants vary: some stay in the fjord, while others migrate to the sea, suggesting that partial migration occurs even in the marine environments. Overall, a total of 53% of the tagged smolts migrated from the fjord to the sea, and 47% stayed (or potentially died) in the fjord. The ratios of fjord‐resident versus sea‐migrating postsmolts were consistent at the study times, and no differences between the early and late migration periods of the smolts were observed. The individual's size or body condition at the time of tagging did not affect survival or the migratory decisions in the fjord. High overall initial survival (74%) was found 30 days after the fjord entry. We suggest that within a continuum of migration to sea, there is a migratory decision point when sea trout postsmolts encounter a fjord system. At this point, postsmolts will assess the possibility of migration versus the alternative of fjord residency.  相似文献   

19.
Electronic tags have become a common tool in fish research, enhancing our understanding of how fish interact with their environment and move among different habitats, for estimating mortality and recording internal physiological states. An often‐untested assumption of electronic tagging studies is that tagged fish are representative of untagged conspecifics and thus show ‘normal’ behaviour (e.g. movement rates, swimming activity, feeding). Here, we use a unique data set for potamadromous walleye (Sander vitreus) in Lake Huron and Lake Erie tributaries to assess whether the lack of appropriate controls in electronic tagging could seriously affect behavioural data. We used fish tagged in previous years and compared their migratory behaviour during the spawning season to fish tagged in a current year at the same location. The objective of the study was to determine whether intracoelomic acoustic tag implantation altered downstream movement of walleye after spawning. Fish tagged in a given season travelled slower downstream from two river spawning sites than fish tagged in previous years. Fish tagged one or two years earlier showed no differences between each other in downstream travel time, in contrast to fish tagged in a given year. Our results support notions that standard collection and intracoelomic tagging procedures can alter short‐term behaviour (i.e. days, weeks, months), and as such, researchers should use caution when interpreting data collected over such time periods. Further, whenever possible, researchers should also explicitly evaluate post‐tagging effects on behaviour as part of their experimental objectives.  相似文献   

20.
The effect of two physical tagging systems, Visible Implant Elastomer (VIE) and Passive Integrated Transponder (PIT), was evaluated in red porgy (Pagrus pagrus) fingerlings, at different sizes. For VIE tagging, the weight classes were <1 and 1?C5?g and no tag effect was detected on fish growth. There was a significant difference in mortality between tagged and untagged <1?g fish, but not for the 1?C5?g fish. The tag loss rate was null for all sizes, however, tags showed fragmentation. This partial tag loss was evaluated and quantified. Seven VIE colours were compared and arranged from best to worst visibility: green, red, pink, orange, yellow, white and blue. For PIT tagging, 2?C6?g, 5?C10?g and 10?C20?g weight classes were analysed. There was no significant tag effect on fish growth, for any size, nor on mortality from 10?g. Tag loss rate ranged from 2.9 to 5.9%. These results demonstrate that, in red porgy, VIE is a successful tagging system from 2?g onwards whereas PIT system is successful from 10?g onwards. The combination of both systems allows traceability of fish from a very small size on, which is necessary for the implementation of genetic breeding programmes.  相似文献   

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