Showing papers on "Fish migration published in 1998"
TL;DR: Halupka et al. as discussed by the authors found that millions upon millions of anadromous fish come from the oceans to spawn in freshwater streams, and these fish fall prey not only to marine hunters, such as other fish, whales, and sea lions, but also to numerous terrestrial predators and scavengers.
Abstract: E very year, millions upon millions of anadromous fish come from the oceans to spawn in freshwater streams. In Southeast Alaska alone, these fish spawn in over 5000 streams (Halupka et al. in press). The best-known anadromous fishes on the Pacific coast are the seven species of Pacific salmon of the genus Oncorhynchus (including steelhead, Oncorhynchus mykiss, and sea-run cutthroat trout, Oncorhynchus clarki). Other, less-publicized and less well studied anadromous species include the chars (Salvelinus spp.) and smelt, such as the eulachon (Thaleichthys pacificus). In addition to anadromous species, several species of fully marine "forage fishes" use interand subtidal zones. For example, along the north Pacific coast, Pacific herring (Clupea harengus pallasi) spawn on rocky coastlines, and Pacific sand lance (Ammodytes hexapterus) can be found buried in soft sands, often near the mouths of streams. These teeming hordes of fish fall prey not only to marine hunters, such as other fish, whales, and sea lions, but also to numerous terrestrial predators and scavengers. Historically, the predators were seen as competing with human harvesters of fish, and predator-control programs aimed at reducing the number of
235 citations
TL;DR: It is argued that young fish and crustaceans use the highly turbid Zeeschelde Estuary as a refuge from predators.
Abstract: Fish and crustaceans were sampled for 1 year in the upper reaches of a temperate estuary characterized by high turbidity and a tidal range of up to 5 m. Samples were taken in the cooling-water circuit of the Doel Nuclear Power station (Zeeschelde, Belgium). Between July 1994 and June 1995, 55 fish species, two shrimp species and four crab species were recorded. The fish community was composed of 36 marine species, 16 freshwater species and three diadromous species. Shrimps, Gobiidae and Clupeidae dominated the samples both in numbers and biomass. An exceptionally clear seasonal succession was observed in the species composition. It is argued that young fish and crustaceans use the highly turbid Zeeschelde Estuary as a refuge from predators.
178 citations
Book•
23 Sep 1998
TL;DR: Theoretical background of river corridors and fish migration can be found in this article, where a regional overview of fish passage problems and solutions for upstream and downstream fish passage solutions for downstream migrations are discussed.
Abstract: Part I: Theoretical background of river corridors and fish migration Part II: Regional overviews of fish passage problems Part III: Fish passage solutions for upstream migrations Part IV: Fish passage solutions for downstream migrations Part V: Nature-like bypasses and ramps Part VI: Conclusions.
141 citations
TL;DR: In this article, the influence of the biotransported pollutants was investigated by comparing pollutant levels and compositions in atmospheric deposition as well as in two different populations of arctic grayling (Thymallus arcticus).
Abstract: Persistent organic pollutants such as polychlorinated biphenyls (PCBs) and the pesticide DDT, known to harm wildlife, have been shown to reach pristine Subarctic and Arctic areas by global atmospheric transport. Another transport route for pollutant entry into these ecosystems is provided by migrating salmon. Pollutant transport was studied in a population of sockeye salmon (Oncorhynchus nerka) in the Copper River, Alaska during their 410 km spawning migration. Pollutants accumulated by the salmon during their ocean life stage were not eliminated during migration, but were transported to the spawning lakes and accumulated in the freshwater food web there. The influence of the biotransported pollutants was investigated by comparing pollutant levels and compositions in atmospheric deposition as well as in two different populations of arctic grayling (Thymallus arcticus). One grayling population was in the salmon spawning lake and the other in a nearby lake not hosting anadromous fish, but receiving pollutants only via atmospheric deposition. The grayling in the salmon spawning lake were found to have concentrations of organic pollutants more than two times higher than those of the grayling in the salmon-free lake, and the pollutant composition resembled that found in salmon. Thus, in the studied Alaska river system, biotransport was found to have a far greater influence than atmospheric input on the PCB and DDT levels in lake biota.
135 citations
TL;DR: Epizootics of Ichthyophthirius multifiliis occurred in adult prespawning and spawning sockeye salmon Oncorhynchus nerka during the 1994 and 1995 spawning seasons in the Skeena River watershed in northern British Columbia, Canada.
Abstract: Epizootics of Ichthyophthirius multifiliis occurred in adult prespawning and spawning sockeye salmon Oncorhynchus nerka during the 1994 and 1995 spawning seasons in the Skeena River watershed in northern British Columbia, Canada. Exceedingly high mortalities occurred at Fulton River and in three spawning channels adjacent to Babine Lake. During these 2 years, the infection and subsequent death of prespawning adults resulted in an estimated 153.6 million fewer sockeye salmon fry produced from Fulton River and the three spawning channels adjacent to Babine Lake than the historical average. Resident fish were the most likely source of the parasite in the watershed because several species were found with light infections of I. multifiliis. Transmission of the parasite to anadromous sockeye salmon was enhanced by the high density of fish held below the spawning grounds for days or weeks prior to moving into the spawning channel. This is the first report of an epizootic of ichthyophthiriasis in wild sp...
90 citations
TL;DR: In this paper, a study of fish distributions in rivers of the West Coast of the South Island of New Zealand showed that, in most species, these migrations result in more or less continuous distributions from the lower reaches to the upstream limits of each species' range.
Abstract: 1. Diadromy is a dominating behavioural characteristic of fish faunas in New Zealand rivers, with amphidromy and catadromy being the most common strategies.
2. Juvenile life stages of amphidromous and catadromous species migrate from the sea, through river systems, to find habitats for feeding, growth, maturation and reproduction.
3. Studies of fish distributions in rivers of the West Coast of the South Island of New Zealand show that, in most species, these migrations result in more or less continuous distributions from the lower reaches to the upstream limits of each species’ range.
4. Upstream penetration of rivers varies widely between species and this generates downstream–upstream trajectories of declining species richness.
5. Parallel trajectories of declining downstream–upstream abundance are likely in each species.
6. These patterns demonstrate the presence of downstream–upstream linkages in the community ecology of freshwater fishes in New Zealand rivers.
85 citations
TL;DR: Use of the stable isotope methodology as a tool for proxy analysis of fish behavior in present and future Arctic environmental monitoring studies is suggested from analysis of age-specific isotopic ratio differences in broad whitefish and Arctic cisco.
Abstract: A dichotomy in the natural stable carbon isotope abundance measured in tissues of obligate freshwater and marine fishes from the Alaskan Arctic coastal plain suggested that the methodology can be used to differentiate recent freshwater from marine feeding in migratory fishes. Natural stable carbon isotope ratio of migratory fishes reflected differences of feeding habitat in relation to known life-history patterns. Use of the stable isotope methodology as a tool for proxy analysis of fish behavior in present and future Arctic environmental monitoring studies is suggested from analysis of age-specific isotopic ratio differences in broad whitefish (Coregonus nasus) and Arctic cisco (Coregonus autumnalis).
80 citations
TL;DR: Fish living in the tidal fresh and brackish water reaches of the Zeeschelde Estuary were studied in samples collected from the cooling-water inlets of three power stations and species number as well as fish abundance were correlated significantly with salinity and oxygen concentration.
Abstract: Fish living in the tidal fresh and brackish water reaches of the Zeeschelde Estuary were studied in samples collected from the cooling-water inlets of three power stations. Between July 1994 and June 1995, 42 different species were recorded including 26 marine migrants, 14 freshwater species and two diadromous species. Species number as well as fish abundance were correlated significantly with salinity and oxygen concentration. The community structure was analysed with a correlation biplot based on principal component analysis of the root-root transformed fish abundance. Four separated communities could be distinguished since the first principal component expressed a salinity and the second a temperature gradient. During summer and fall Pomatoschistus microps, P. minutus, P. lozanoi and Syngnathus rostellatus were most abundant in the brackish-water reach. At this time, freshwater species seemed to avoid the freshwater area. During winter, Sprattus sprattus, Clupea harengus and Dicentrarchus labrax were the dominant species of the brackish-water zone while the freshwater reaches were dominated by Gasterosteus aculeatus . Migrating fish such as Pleuronectes flesus, Lampetra fluviatilis, Anguilla anguilla and Osmerus eperlanus were restricted to the brackish environment.
80 citations
TL;DR: The anadromous salmon (Oncorhynchus spp.) of the Pacific Northwest is discussed as an illustration of how important genetic considerations can be as part of an ecosystem approach to resource management.
Abstract: The importance of an ecosystem approach to the management of natural resources—including fisheries—has been widely recognized recently. However, discussions of ecosystem management usually do not provide much detail or emphasis on genetics. Here, we discuss the anadromous salmon (Oncorhynchus spp.) of the Pacific Northwest as an illustration of how important genetic considerations can be as part of an ecosystem approach to resource management. Pacific salmon have a complex genetic and population structure, referred to as a metapopulation structure, that is strongly influenced by the spatial arrangement of the rivers in which they spawn. The many factors that have contributed to the decline of salmon populations in the Pacific Northwest have affected salmon meta-populations as well. As a result, attempts to rehabilitate salmon will need to include a focus on metapopulations as well as on improving habitat and reducing fishing and other sources of mortality.
78 citations
TL;DR: Three sites, two in the tailwater and one upstream of the backwater of a large man-made reservoir in the middle course of the 808 km long lowland Warta River (Oder catchment), were studied.
Abstract: Three sites, two in the tailwater and one upstream of the backwater of a large man-made reservoir in the middle course of the 808 km long lowland Warta River (Oder catchment), were studied. The pre-impoundment study lasted one (1985), the post-impoundment one 10 yr (1986–1995). The dam contributed to the extinction of the anadromous Vimba vimba, and of the rheophilous Chondrostoma nasus, both cyprinids. A number of directly or indirectly negative changes related to the construction of the reservoir were recorded in the tailwater. These changes affected the species number, spawning groups, diversity, density, standing crop, mean body weight, ABC index, and proportional stock density – PSD. Numerous impacts related to engineering, water chemistry and climate were more negative for fish at the tailwater than at the backwater sites. The hydrology of the site upstream of the backwater continued to be dependent on natural factors. Fish populations there suffered only from accidental impacts of the construction of the dam, such as bank revetment or the clearance of trees and shrubs.
77 citations
TL;DR: This work used ultrasonic telemetry to estimate the timing and duration of the upriver spawning migration for the Roanoke River, North Carolina, population and to evaluate whether a short-term fluctuation in temperature or flow would alter the distribution of telemetered fish on the spawning grounds.
Abstract: The spring spawning migration is a key period for effective management of anadromous populations of striped bass Morone saxatilis. Information on migratory behavior is needed in order to develop appropriate harvest regulations and to conduct effective surveys while fish are on the spawning grounds. We used ultrasonic telemetry to estimate the timing and duration of the upriver spawning migration for the Roanoke River, North Carolina, population and to evaluate whether a short-term fluctuation in temperature or flow would alter the distribution of telemetered fish on the spawning grounds. Seventy-eight fish implanted with transmitters were released during 1993 and 1994. Twenty-nine telemetered fish migrated upriver in 1994, and 14 telemetered fish entered the river in 1995. Migration of telemetered fish began in mid- to late April when water temperatures in the lower river reached 17–18°C. Males began their spawning migration significantly earlier than females in 1994; the difference was not signi...
01 Jan 1998
01 Jan 1998
TL;DR: In this article, the authors provide an overview of the functional features and design parameters used in the different types of passage facilities: Denil fish passes, pool fish pass, fish elevators and natural bypass channels.
Abstract: Plans for the restoration or enhancement of anadromous fish stocks were initiated in France more than 15 years ago. A 1984 law concerning freshwater fisheries requires that any obstruction in streams or parts thereof, in the list specified by decree, must include facilities to ensure the passage of migratory fish. As a result, more than 400 fish passes were built or improved, and significant advances in the design of upstream fish passage facilities have occurred during the last 15 years. This chapter provides an overview of the functional features and design parameters used in the different types of passage facilities: Denil fish passes, pool fish passes, fish elevators and natural bypass channels. The relative advantages and drawbacks of each type of fish pass are discussed, with reference to the requirements of specific migratory species and site-specific constraints. Emphasis is placed on the problem of maintenance. The various techniques used in France to evaluate the existing or newly constructed fish passes, as well as the topic of downstream migration at turbine intakes, are reviewed. Recent experiments have tested surface bypasses designed to provide a safe downstream route for smolts at small-scale hydroelectric plants. The efficiency of such bypasses is evaluated by radio telemetry and release-recapture tests. Results from some field studies are outlined. The effect of mercury lights to increase bypass attraction is discussed. The behaviour of fish in relation to the hydraulic flow patterns at the intake should be considered when designing a downstream bypass system. In conclusion, the author presents his view on the priorities for future research on fish passage facilities, insisting on the need for close collaboration between engineers and biologists, in particular fish behaviourists. Some priorities include the use of radio-telemetry to track Atlantic salmon Salmo salar on the migratory rivers, and research aimed at gaining a better understanding of downstream migration of salmon, brown trout S. trutta, and European eel Anguilla anguilla.
TL;DR: It was concluded that FCDI schemes such as the PIRDP negatively affect fish species assemblages and stock values, by reducing the accessibility of impounded floodplains to migrant Fish, and management measures are required to encourage the passage of more species.
Abstract: A mark-recapture programme at the Pabna Irrigation and Rural Development Project (PIRDP) site in NW Bangladesh showed that Catla catla, Channa striata and Wallago attu migrated through the sluice gates, both with and against prevailing currents in different season, while the smaller Anabas testudineus, Glossogobius giuris and Puntius sophore did not. Species assemblages were significantly different inside and outside the flood control, drainage and irrigation (FCDI) schemes, with up to 25 species absent or less abundant inside compared to outside. The majority of these species were large predators or conspicuous members of the highly prized migratory ‘whitefish’ category, including silurid catfish, Indian major carps, mullets and clupeids. In their absence, species inside FCDI schemes were dominated by much smaller resident ‘blackfish’ species. Assemblages inside FCDI schemes thus had both a reduced species richness, and a unit value reduced by up to 25%. It was concluded that FCDI schemes such as the PIRDP negatively affect fish species assemblages and stock values, by reducing the accessibility of impounded floodplains to migrant fish. Though some fish are capable of penetrating existing sluice gates, management measures are required to encourage the passage of more species.
TL;DR: This study demonstrates that it is only by gaining an understanding of how processes operate that the authors will be able to predict the effects of habitat alteration on populations, and found that the mortality of age-0 trout was largely density independent.
Abstract: Populations of stream-dwelling salmonids (e.g., salmon and trout) are gen- erally believed to be regulated by strong density-dependent mortality acting on the age-0 life stage, which produces a dome-shaped stock-recruitment curve. Although this paradigm is based largely on data from anadromous species, it has been widely applied to stream- resident salmonids despite the fact that the processes limiting or regulating stream-resident populations remain poorly understood. The purpose of the present study was to determine whether stream channel morphology affects the availability of spawning habitat for Cali- fornia golden trout, and whether spawning habitat availability influences the production of age-0 trout and recruitment into the adult population. Wide stream reaches contained significantly more spawning habitat and a higher density of nests and age-0 trout than did narrow reaches. In contrast to the idea that salmonid populations are regulated by density-dependent mortality of age-0 fish, we found that the mortality of age-0 trout was largely density independent. In addition, over most of the range of observed fish densities, the density of a particular cohort was positively correlated between years for age-0, age-1, and age-2 trout. Therefore, our golden trout study population was limited by spawning habitat, with spawning habitat availability influencing the pro- duction of age-0 trout as well as recruitment into the adult population. Grazing by cattle has widened the study streams, and our current findings help to explain why stream sections subject to grazing had more spawning habitat and higher golden trout densities than ungrazed sections. Individual growth rates of golden trout are apparently negatively density dependent, and these grazing-related increases in trout density have likely resulted in decreased growth rates. Our study demonstrates that it is only by gaining an understanding of how processes operate that we will be able to predict the effects of habitat alteration on populations.
TL;DR: It is suggested that the problem may originate in freshwater with radiation damage to metabolic machinery that is expressed during stressful periods of smolting and ocean entry and that progressively worse damage may soon appear as reduction in freshwater survivals as well.
Abstract: There have been profound declines in marine survival rates of steelhead trout (Oncorhynchus mykiss), coho salmon (O. kisutch), chinook salmon (O. tschawytscha), and Atlantic salmon (Salmo salar) since the mid-1980s, and these declines have been particularly acute in sunny regions. We suggest that the problem may originate in freshwater with radiation (e.g., UV-B) damage to metabolic machinery that is expressed during stressful periods of smolting and ocean entry and that progressively worse damage may soon appear as reduction in freshwater survivals as well. This hypothesis can be tested quickly by management agencies by comparing survival rates of hatchery-reared fish with and without radiation protection during rearing.
TL;DR: It is concluded that the artificial environment of hatchery-reared anadromous brown trout can depress the natural parr-smolt transformation, and that this may adversely affect the success of seawater migration and long-term survival of the fish.
TL;DR: In this article, split-beam hydroacoustics were used to describe temporal and spatial patterns of upstream-swimming fall chum salmon Oncorhynchus keta in the Chandalar River, a tributary of the Yukon River, Alaska.
Abstract: Fixed-location, split-beam hydroacoustics was used to describe temporal and spatial patterns of upstream-swimming fall chum salmon Oncorhynchus keta in the Chandalar River, a tributary of the Yukon River, Alaska. Split-beam techniques allow for three-dimensional tracking of fish targets as they pass through the sonar beam. Elliptical-beam transducers were deployed from opposite river banks to optimize acoustic coverage and were aimed perpendicular to the current. Sonar systems were operated continuously from August 8 through September 22, 1996. Acoustic data on positional information of 204,153 upstream-traveling chum salmon were collected. Diel patterns in hourly passage rates differed between banks. On the left bank, chum salmon passage was highest during nighttime hours. On the right bank, fish did not show any consistent trend in diel passage rates. Chum salmon were generally shore oriented and swam near the river bottom. During daylight hours, fish were further offshore and closer to the bot...
TL;DR: A survey of these streams was made to determine whether their communities differed from those in other areas of New Zealand as discussed by the authors, suggesting a biogeographic separation from adjacent eastern and southern areas since the Pliocene or early Pleistocene.
Abstract: New Zealand landscapes were extensively modified after European settlement in the late 1800s. Large areas of native forest were converted to pasture and few large areas of unmodified forest remain. Trout (Salmo trutta and Oncorhynchus mykiss) were introduced into the rivers at the same time, and these two changes are thought to have affected native fish communities. Kahurangi National Park is a large area of unmodified native forest with few introduced trout in smaller rivers draining to the west. A survey of these streams was made to determine whether their communities differed from those in other areas of New Zealand. No non‐diadromous native fish were found, suggesting a biogeographic separation from adjacent eastern and southern areas since the Pliocene or early Pleistocene. Contrary to popular expectation, fish diversity and abundance was often lower than at equivalent elevations in other areas of New Zealand. Lowland fish communities comprised a small stream community dominated by inanga (G...
TL;DR: Putah Creek Council as mentioned in this paper improved the flow regime of a California stream for ecosystem, aesthetic, recreational, educational, and research purposes, which led to a successful court trial in which fish conservation played a key role.
Abstract: Efforts by a citizen's group, Putah Creek Council, to improve the flow regime of a California stream for ecosystem, aesthetic, recreational, educational, and research purposes led to a successful court trial in which fish conservation played a key role A major issue around which the trial revolved was the proper interpretation of a section (5937) of the California Fish and Game Code, which states that fish must be maintained in “good condition” below a dam We defined good condition to mean there had to be healthy individual fish in healthy populations that were part of healthy biotic communities This definition resulted in a conceptual model for instream flows for the creek that favored native resident and anadromous fishes The stream flow recommendations from this model had four components: living space flows for the entire creek, resident native fish spawning and rearing flows, anadromous fish flows, and habitat maintenance flows The trial judge, in attempting to balance competing demands
TL;DR: It was concluded that metalimnetic fertilization could maintain the aesthetic value of these lakes while increasing zooplankton and fish production, and water transparency declined less than 15% compared with controls.
Abstract: Snake River sockeye salmon Oncorhynchus nerka listed under U.S. law as endangered in 1991 in response to a decline in anadromous adult numbers, spend their first 1–2 years in Redfish Lake, Idaho, before migrating to the sea. To determine how nutrient enhancement might influence phytoplankton, zooplankton, and fish production, we performed fertilization experiments in large enclosures in this oligotrophic lake using juvenile kokanee (lacustrine O. nerka) as analogues for endangered sockeye salmon. Fertilization of the metalimnion substantially increased chlorophyll a (150%), phytoplankton biovolume (75%), primary productivity (250%), and zooplankton biomass (200%), and moderately increased fish growth (12%) over our control enclosures. Community composition of phytoplankton and zooplankton changed little, and water transparency declined less than 15% compared with controls. Thus, we concluded that metalimnetic fertilization could maintain the aesthetic value of these lakes while increasing zooplan...
TL;DR: The catchment areas of Icelandic rivers are mostly barren or with little vegetation cover in the highlands, but with heathland and mire vegetation in the lowlands Chemical composition and nutrient availability in Icelandic rivers were influenced by geology, topography and vegetation cover as mentioned in this paper.
Abstract: Catchment areas of Icelandic rivers are mostly barren or with little vegetation cover in the highlands, but with heathland and mire vegetation in the lowlands Chemical composition and nutrient availability in Icelandic rivers are influenced by geology, topography and vegetation cover in the river basins This seems to determine the density and diversity of benthic invertebrates, species composition of anadromous fish and catch of salmon in Icelandic rivers Species composition of benthic communities is determined by particulate organic matter drifting downstream from river head-waters Filter feeding blackfly larvae dominate lake outlets, while algal grazing chironomid larvae dominate rivers not influenced by lakes In well vegetated catchment basins, lake-fed rivers have higher catches of salmon than non-lake fed rivers Only a few of the rivers flowing from poorly vegetated areas sustain salmon Glacial rivers have the lowest density and diversity of benthic invertebrates of all river groups and do not sustain fish populations
TL;DR: A simulation model was constructed for Redfish Lake, Idaho, to predict the dependence of lake production on nutrients from the watershed, precipitation, lake fertilization, and marine-derived nutrients from sockeye salmon Oncorhynchus nerka which historically have reared in the lake.
Abstract: We constructed a simulation model for Redfish Lake, Idaho, using water budget and nutrient loading measurements, to predict the dependence of lake production on nutrients from the watershed, precipitation, lake fertilization, and marine-derived nutrients from sockeye salmon Oncorhynchus nerka which historically have reared in the lake. We also used the model to simulate different management scenarios to help restore the endangered Snake River sockeye salmon. The model and other empirical evidence indicated that even before hydropower dams were present in the migration corridor, marine-derived nutrients were not of major importance to lake production, contributing only about 3% of the annual phosphorus load of the lake. This contribution was partially removed by the quick flushing rate (3 years) of the lake and phosphorus export by smolts. The model predicted annual adult sockeye salmon returns to be 3,800 fish under predam conditions, 370 fish under modern conditions, 780 fish when watershed nutr...
TL;DR: It is suggested that spring smolt emigration of trout, whether or not they belong to anadromous or freshwater resident stock, is principally by passive displacement.
Journal Article•
TL;DR: Maintaining this developmental diversity in rehabilitation of depleted populations depends on breeding programs designed to maintain genetic continuity, creation of the appropriate range of environmental opportunities during early rearing, and conservation of a sufficiently diverse freshwater habitat.
Abstract: Salmonid stocks have been depleted quantitatively and qualitatively, and much of their freshwater habitat has been destroyed. Extensive enhancement programs through hatchery rearing have not restored these stocks, largely because their evolutionary heritage and the discrete stock structure that it has engendered are poorly understood. Salmonids show a wide range of life-styles and high phenotypic plasticity. The simplest are those of pink salmon, Oncorhynchus gorbuscha, of which some populations spawn in brackish tidal waters and never use fresh water, and the most complex those of steelhead trout O. mykiss, which exhibits more than 30 life-history types, from anadromous to landlocked. Between these two extremes, life-styles range from those with some elements emancipated from the sea through some that complete their life cycles wholly within fresh water. Successful enhancement of salmonid stocks requires an understanding of the nature of this flexibility and of the controls over maturation that determine the life-cycle pattern that individuals will adopt. Hence, understanding fish life histories depends on understanding the control of fish reproduction. Maintaining this developmental diversity in rehabilitation of depleted populations depends on breeding programs designed to maintain genetic continuity, creation of the appropriate range of environmental opportunities during early rearing, and conservation of a sufficiently diverse freshwater habitat.
TL;DR: In 1989, a project was conceived to address the man-made obstructions to fish migration and restore (rewater) the lower reaches of Pamehac Brook.
Abstract: 1. In the early 1970s, dams were constructed in the upper reaches of Pamehac Brook, Newfoundland, Canada, and the headwaters of the system were diverted into the main stem of the Exploits River to facilitate waterborne transport of logs to a pulp and paper mill. This de-watered 12 km of high quality brook trout (Salvelinus fontinalis) and Atlantic salmon (Salmo salar) rearing and spawning habitat. In 1989, a project was conceived to address the man-made obstructions to fish migration and restore (re-water) the lower reaches of Pamehac Brook. This project was pursued as a partnership between the Environment Resources Management Association (a local conservation group), Abitibi-Price Inc. (a pulp and paper company), the Environmental Partners Fund (of Environment Canada), and the Canadian Department of Fisheries and Oceans.
2. The restoration of Pamehac Brook in August 1990 included replacement of the control dams with bridges and culverts and removal of the diversion dyke to re-water the stream. Habitat surveys conducted before and after the project indicated a gain in fluvial habitat of 450 units (1 unit=100 m2), a 62% increase, through re-watering of the stream channel. Improved access was provided to 175 habitat units in the headwaters which had previously been obstructed.
3. Population estimates of juvenile fish from electrofishing surveys were used to document the rate of recolonization of the re-watered habitat and to estimate the increase in fish production potential. Results suggested limited response by fish populations in the initial 2 years after restoration. Electrofishing results in 1996 indicated a dramatic increase in biomass of larger juvenile salmon and trout (>0+), attributable to the increased habitat area and altered microhabitat conditions, in part, related to creation of standing water areas from beaver dams. Population estimates in 1996, in consideration of available fluvial habitat, indicated a production potential of juvenile fish of 330 kg, an 18-fold increase from pre-project estimates. © 1998 John Wiley & Sons, Ltd.
TL;DR: Taimen conservation in the Baikal region is impossible without adoption and implementation of a dedicated rehabilitation program that includes the protection of remaining populations and habitat, and possibly introduction of hatchery-reared fish in selected areas where habitat remains, but parental stocks are low.
TL;DR: Although there was a large increase in the percentage of salmonids with pinniped-caused abrasions between 1991 and 1996, fewer than 3% of the fish were judged to have abrasions sufficiently severe to adversely affect their survival to spawning, suggesting that pinnipes may be an increasingly serious problem for Columbia basin salmonids.
Abstract: At Bonneville Dam (Columbia River, 235 km from the mouth), the percentage of anadromous adult Pacific salmon Oncorhynchus spp. with abrasions (scars or wounds) caused by pinnipeds has increased from 2.8% in 1991 to 25.9% in 1996 for sockeye salmon O. nerka and from 10.5% in 1991 to as much as 31.8% in 1994 for spring–summer chinook salmon O. tshawytscha. Although there was a large increase in the percentage of salmonids with pinniped-caused abrasions between 1991 and 1996, fewer than 3% of the fish were judged to have abrasions sufficiently severe to adversely affect their survival to spawning. Larger, earlier-migrating chinook salmon were more likely to have abrasions than smaller, later-migrating fish. Similar trends were not found for sockeye salmon. Although these results suggest that pinniped predation may be an increasingly serious problem for Columbia basin salmonids, a lack of data that relates abrasions to pinniped-caused mortality makes it impossible to accurately estimate the magnitude...
TL;DR: Embryos of sockeye salmon Oncorhynchus nerka were transplanted from Shuswap Lake, British Columbia, to tributaries of Lake Ohau in the South Island of New Zealand in 1901, giving rise to a self-sustaining freshwater resident population that spawns primarily in Larch Stream north ofLake Ohau.
Abstract: Embryos of sockeye salmon Oncorhynchus nerka were transplanted from Shuswap Lake, British Columbia (BC), to tributaries of Lake Ohau in the South Island of New Zealand (NZ) in 1901. This single shipment gave rise to a self-sustaining freshwater resident population that spawns primarily in Larch Stream north of Lake Ohau. We compared the genotypic (using protein electrophoresis) and phenotypic traits of the NZ O. nerka with anadromous (sockeye salmon) and nonanadromous (kokanee) populations of the species in the Shuswap Lake system. Genetic analysis confirmed that the transplanted fish had been sockeye salmon, not kokanee, and allele frequencies in the current NZ population were not significantly different from those in anadromous sockeye salmon from Scotch Creek, BC. The NZ O. nerka developed two life history patterns: some spent their entire rearing period in Lake Ohau, whereas others migrated downstream from Lake Ohau after 1 year to mature in Lake Benmore. These latter “migrants” grew faster a...