Showing papers on "Fish migration published in 2011"

The historic influence of dams on diadromous fish habitat with a focus on river herring and hydrologic longitudinal connectivity

Abstract: The erection of dams alters habitat and longitudinal stream connectivity for migratory diadromous and potamodromous fish species and interrupts much of organismal exchange between freshwater and marine ecosystems. In the US, this disruption began with colonial settlement in the seventeenth century but little quantitative assessment of historical impact on accessible habitat and population size has been conducted. We used published surveys, GIS layers and historical documents to create a database of 1356 dams, which was then analyzed to determine the historical timeline of construction, use and resultant fragmentation of watersheds in Maine, US. Historical information on the anadromous river herring was used to determine natural upstream boundaries to migration and establish total potential alewife spawning habitat in nine watersheds with historic populations. Dams in Maine were constructed beginning in 1634 and by 1850 had reduced accessible lake area to less than 5% of the virgin 892 km2 habitat and 20% of virgin stream habitat. There is a near total loss of accessible habitat by 1860 that followed a west-east pattern of European migration and settlement. Understanding historic trends allows current restoration targets to be assessed and prioritized within an ecosystem-based perspective and may inform expectations for future management of oceanic and freshwater living resources.

Ecological Effects of Live Salmon Exceed Those of Carcasses During an Annual Spawning Migration

Abstract: We tested the hypothesis that the carcasses of anadromous Pacific salmon (Oncorhynchus spp.) constitute a significant source of nutrients in the nutrient-poor freshwaters where these fish migrate, spawn, senesce, and die. In a 110 m-long stream reach in Southeast Alaska, we retained nearly 3000 salmon carcasses and compared streamwater nitrogen (N), phosphorus (P), and the biomass of benthic biofilm in this reach with an upstream reference reach. The study spanned 5 months, bracketed the entire salmon run, and encompassed significant seasonal variation in abiotic stream conditions. Concentrations of dissolved and particulate N and P followed distinctly unimodal patterns through time, which tracked the abundance of live salmon, and we observed strong predictive relationships between live-salmon abundance and streamwater-nutrient concentrations. In contrast, we did not observe clear relationships between salmon carcasses and streamwater nutrients. Biofilm biomass within our study reaches seemed to more closely track the abundance of live salmon than the abundance of carcasses. The experimental retention of carcasses had a minor or undetectable influence on nutrient concentrations and biofilm within the study reach as compared to the reference reach. We conclude that physical factors such as temperature, discharge, nutrient limitation, and irradiance vary seasonally in ways that maximize the influence of nutrients provisioned by live salmon and minimize the influence of carcass-derived nutrients on the aspects of stream ecosystems that we examined. Overall, our results promote a new perspective on the ecological role of salmon in freshwaters, and contribute to a more mechanistic understanding of how migratory fishes can influence aquatic ecosystems.

Who are the missing parents? Grandparentage analysis identifies multiple sources of gene flow into a wild population

Abstract: In order to increase the size of declining salmonid populations, supplementation programmes intentionally release fish raised in hatcheries into the wild. Because hatchery-born fish often have lower fitness than wild-born fish, estimating rates of gene flow from hatcheries into wild populations is essential for predicting the fitness cost to wild populations. Steelhead trout (Oncorhynchus mykiss) have both freshwater resident and anadromous (ocean-going) life history forms, known as rainbow trout and steelhead, respectively. Juvenile hatchery steelhead that ‘residualize’ (become residents rather than go to sea as intended) provide a previously unmeasured route for gene flow from hatchery into wild populations. We apply a combination of parentage and grandparentage methods to a three-generation pedigree of steelhead from the Hood River, Oregon, to identify the missing parents of anadromous fish. For fish with only one anadromous parent, 83% were identified as having a resident father while 17% were identified as having a resident mother. Additionally, we documented that resident hatchery males produced more offspring with wild anadromous females than with hatchery anadromous females. One explanation is the high fitness cost associated with matings between two hatchery fish. After accounting for all of the possible matings involving steelhead, we find that only 1% of steelhead genes come from residualized hatchery fish, while 20% of steelhead genes come from wild residents. A further 23% of anadromous steelhead genes come from matings between two resident parents. If these matings mirror the proportion of matings between residualized hatchery fish and anadromous partners, then closer to 40% of all steelhead genes come from wild trout each generation. These results suggest that wild resident fish contribute substantially to endangered steelhead ‘populations’ and highlight the need for conservation and management efforts to fully account for interconnected Oncorhynchus mykiss life histories.

Interplay between temperature, fish partial migration and trophic dynamics

Abstract: Whereas many studies have addressed the mechanisms driving partial migration, few have focused on the consequences of partial migration on trophic dynamics, and integrated studies combining the two approaches are virtually nonexistent. Here we show that temperature affects seasonal partial migration of cyprinid fish from lakes to predation refuges in streams during winter and that this migration in combination with temperature affects the characteristics and phenology of lower trophic levels in the lake ecosystem. Specifically, our six-year study showed that the proportion of fish migrating was positively related to lake temperature during the pre-migration growth period, i.e. during summer. Migration from the lake occurred later when autumn water temperatures were high, and timing of return migration to the lake occurred earlier at higher spring water temperatures. Moreover, the winter mean size of zooplankton in the lake increased with the proportion of fish being away from the lake, likely as a consequence of decreased predation pressure. Peak biomass of phytoplankton in spring occurred earlier at higher spring water temperatures and with less fish being away from the lake. Accordingly, peak zooplankton biomass occurred earlier at higher spring water temperature, but relatively later if less fish were away from the lake. Hence, the time between phyto- and zooplankton peaks depended only on the amount of fish being away from the lake, and not on temperature. The intensity of fish migration thereby had a major effect on plankton spring dynamics. These results significantly contribute to our understanding of the interplay between partial migration and trophic dynamics, and suggest that ongoing climate change may significantly affect such dynamics.

The Spawning Migration of Delta Smelt in the Upper San Francisco Estuary

Abstract: While there is substantial information about the upstream migration of commercially and recreation- ally important fishes, relatively little is known about the upstream migration of small-bodied species, particularly through estuaries. In the San Francisco Estuary, there is a major need to understand the behavior of delta smelt Hypomesus transpacificus, a small pelagic fish listed under the state and federal endangered species acts. The spawning migration period may be critical as upstream movements can result in entrainment in water diversions. In gen- eral, delta smelt live in the low-salinity zone of the estuary and migrate upstream for spawning. During the fall pre-migration period, delta smelt remain primarily within the low-salinity zone in the west- ern Sacramento-San Joaquin Delta and Suisun Bay. There were no significant upstream shifts of fish into fresher water during late fall, suggesting that delta smelt do not show pre-migration staging behavior. Following winter "first flush" flow events that appear to trigger migration, upstream movement rates are relatively rapid, averaging 3.6 km d -1 , a finding consistent with results from particle-tracking simula- tions, laboratory studies, and other fishes. Like some other native fishes, delta smelt apparently "hold" in upstream areas following migration; most do not spawn immediately. Overall, delta smelt fit the pat- tern of a diadromous species that is a seasonal repro- ductive migrant. Emerging data suggest that there is variability in the migration behavior of delta smelt, a pattern contrary to the reigning viewpoint that all smelt migrate in winter.

Temperature-associated population diversity in salmon confers benefits to mobile consumers

Abstract: Habitat heterogeneity can generate intraspecific diversity through local adaptation of populations. While it is becoming increasingly clear that population diversity can increase stability in species abundance, less is known about how population diversity can benefit consumers that can integrate across population diversity in their prey. Here we demonstrate cascading effects of thermal heterogeneity on trout-salmon interactions in streams where rainbow trout rely heavily on the seasonal availability of anadromous salmon eggs. Water temperature in an Alaskan stream varied spatially from 5 degrees C to 17.5 degrees C, and spawning sockeye salmon showed population differentiation associated with this thermal heterogeneity. Individuals that spawned early in cool regions of the 5 km long stream were genetically differentiated from those spawning in warmer regions later in the season. Sockeye salmon spawning generates a pulsed resource subsidy that supports the majority of seasonal growth in stream-dwelling rainbow trout. The spatial and temporal structuring of sockeye salmon spawn timing in our focal stream extended the duration of the pulsed subsidy compared to a thermally homogeneous stream with a single population of salmon. Further, rainbow trout adopted movement strategies that exploited the multiple pulses of egg subsidies in the thermally heterogeneous stream. Fish that moved to track the resource pulse grew at rates about 2.5 times higher than those that remained stationary or trout in the reference stream with a single seasonal pulse of eggs. Our results demonstrate that habitat heterogeneity can have important effects on the population diversity of dominant species, and in turn, influence their value to species that prey upon them. Therefore, habitat homogenization may have farther-reaching ecological effects than previously considered.

The cumulative impacts of climate change on Fraser River sockeye salmon (Oncorhynchus nerka) and implications for management

Abstract: Anadromous Pacific salmon (Oncorhynchus spp.) are vulnerable to climate change in both freshwater and marine habitats. I use a qualitative model to assess the cumulative effects of climate change a...

The Influences of Body Size, Habitat Quality, and Competition on the Movement and Survival of Juvenile Coho Salmon during the Early Stages of Stream Recolonization

Abstract: Understanding the factors influencing the success of juvenile Pacific salmon Oncorhynchus spp. in newly colonized habitats is essential to their recovery in large areas across the West Coast of the United States and Canada. We studied biotic and abiotic factors associated with survival during the early stages of colonization and population establishment of juvenile coho salmon O. kisutch in Rock Creek, a tributary of the upper Cedar River in the Lake Washington basin of Puget Sound, Washington. The stream was occupied by resident fishes (e.g., rainbow trout O. mykiss, cutthroat trout O. clarkii, speckled dace Rhinichthys osculus, and several sculpins Cottus spp.), but adult coho salmon and other anadromous fishes had been excluded by a dam from 1901 until fish ladder installation in 2003. We defined logistic regression models and used an information-theoretic approach to predict apparent survival with various combinations of individual fish condition, location competition, and local habitat quali...

Impact of global warming on European tidal estuaries: some evidence of northward migration of estuarine fish species

Abstract: The aim of this study was to determine whether the latitudinal distribution of fish species that use estuaries to complete their entire life cycle has shifted northward as an expected consequence of global warming. The mean latitude of past fish species distributions found in 1970s’ literature was compared with the mean latitude of distributions today based on fish density indices collected in 55 tidal estuaries along the Atlantic European seaboard, from Portugal to Scotland. Among the 15 most common species, 11 displayed a positive difference between current and past mean latitudes suggesting a northward shift of the populations. Using the occurrence of subtropical species in temperate areas as an indicator of water warming, the northernmost range limit of 10 subtropical species was subsequently focused on. Six of them were recorded up to their past northern latitudinal limit. These results reinforced the idea that a number of fish species associated to estuaries have migrated northwards over the last 30 years, possibly due to water warming. These ecological changes can get important managerial implications, i.e. in the assessment of the ecological status in European directives.

Temporally stable population-specific differences in run timing of one-sea-winter Atlantic salmon returning to a large river system.

Abstract: The understanding of migration patterns can significantly contribute to conservation and management. The spawning migrations of Atlantic salmon (Salmo salar) cover thousands of kilometers from the feeding areas at sea to their natal rivers to reproduce. Migrating salmon are exposed to intensive harvest, but little is known of the population-specific differences in migration behavior. In this study, timing of return migration was investigated among one-sea-winter Atlantic salmon within a river system. By utilizing knowledge of the genetic population structure, population of origin was reliably identified for c. 1500 fish caught in mixed stock fisheries after adopting an approach to minimize the complications arising from potential nonsampled populations. Results demonstrated significant and temporally stable differences among populations as well as between sexes. Generally, female salmon from tributary populations entered fresh water first. Run timing was not however related to in-river migration distance. Rather, one-sea-winter salmon from larger populations and with a higher proportion of multi-sea-winter females arrived later in the season. These findings are a significant step toward a more thorough understanding of the salmon migration behavior and behavioral ecology, providing concrete tools for the management and conservation of the remaining indigenous Atlantic salmon stocks.

Persistent ecological effects of a salmon‐derived nutrient pulse on stream invertebrate communities

Abstract: Pulsed resource subsidies can have ecological effects that persist over time. These subsidies can be particularly important in aquatic ecosystems, which are often resource-limited. Anadromous salmon (Oncorhynchus spp.) deliver annual nutrient pulses to many freshwater ecosystems around the North Pacific. The persistent ecological consequences of this nutrient subsidy are poorly understood across the range of Pacific salmon and likely depend on stream habitat, background nutrient dynamics, and the abundance of spawning salmon. Using a model selection approach, we examined relationships among spawning salmon density, stream habitats, and the abundance and diversity of stream invertebrates ten months after salmon spawning, across 21 streams in central British Columbia, Canada. Total invertebrate abundance increased with salmon density and with higher stream temperatures. Invertebrate diversity was more closely related to stream habitat characteristics than to salmon density. These results suggest that salmon nutrients have a greater impact on stream invertebrate population sizes than on the variety of taxa that inhabit these streams. The three most common invertebrate families—grazing mayflies (Heptageniidae), predatory stoneflies (Chloroperlidae), and chironomid midges (Chironomidae)—all increased in abundance with salmon density. Stream habitat variables (temperature, pH, and substrate size) also explained significant variation in the abundances of the three groups. These results suggest that salmon nutrients retained in the watershed from previous years help support greater abundances of some invertebrate taxa. Thus the pulsed nutrient subsidy provided by spawning salmon may have ecological effects that persist many months, or even years, after it is delivered.

Effects of Growth and Reproductive History on the Egg Size–Fecundity Trade-off in Steelhead

Abstract: The allocation of energy by females into different components of reproduction is critical and includes trade-offs between egg size and number. In anadromous salmonids, it is unclear whether the allocation patterns are determined by the growing conditions experienced when the fish are in freshwater or at sea or by the female's reproductive history. We collected data on length, egg size, and fecundity from female steelhead Oncorhynchus mykiss that had spent 1 year in freshwater and then 2 (designated 1.2) or 3 years at sea (1.3) before spawning for the first time. We also collected the same data from females spawning for the second time but of the same age as those spawning after 3 years for the first time (1.1S1). The older females were longer than the younger ones, but there was considerable overlap in length. The repeat-spawning fish were shorter than fish of the same age that were spawning for the first time, which reflected the reduction in growth associated with the previous spawning migratio...

Effects of coupled natural anthropogenic factors on the community structure of diadromous fish and shrimp species in tropical island streams

Abstract: Summary 1. Overlapping river and road networks provide a framework for studying the complex interactions between natural and human systems, with river-road intersections as focal areas of study. Roads can alter the morphology of stream channels, pose barriers to freshwater fauna, provide easy access to streams for humans and non-native species and accelerate the expansion of urban development. 2. We determined what variables control the structure of diadromous fish and shrimp communities and assessed whether particular road crossings altered community structure in north-eastern Puerto Rico. We identified 24 sites that represented a range of river and road sizes across two catchments that drain El Yunque National Forest in Puerto Rico. 3. The location of natural barriers and the size of stream pools were the most important variables for predicting six of fifteen fish and shrimp distributions. Predatory fishes were predicted to be limited to areas in the river network below large, steep waterfalls, whereas adult shrimp Atya lanipes (Atyidae) were predicted to be present above these waterfalls. The fish Awaous banana was predicted to be present in pools >11.6 m wide, whereas the shrimp Xiphocaris elongata was predicted to be present in pools <10.4 m wide. The distributions of nine species were predicted poorly, but three of these species were common and three were rare. 4. Although urban and agricultural land covers were among the top three predictors of five species distributions, they were probably good predictors because they were correlated with the natural gradient. Further study is necessary to disentangle natural and anthropogenic gradients. 5. Road crossings, 10 of which were culverts, were not dispersal barriers for fishes or shrimps. On average, species were present both upstream and downstream from road crossings at 68% of sites where they occurred. Absences upstream or downstream from road crossings occurred at 16% of sites each and likely resulted from a failure to detect species. 6. Several existing features of these catchments and taxa may aid in fish and shrimp conservation. The headwaters are protected by management practices of El Yunque National Forest, connectivity within the river network has been maintained, and the diadromous life history of these organisms makes them resilient to pulsed disturbances.

Comparison of mercury concentrations in landlocked, resident, and sea-run fish (Salvelinus spp.) from Nunavut, Canada.

Abstract: Mercury concentrations ([Hg]) in Arctic food fish often exceed guidelines for human subsistence consumption. Previous research on two food fish species, Arctic char (Salvelinus alpinus) and lake trout (Salvelinus namaycush), indicates that anadromous fish have lower [Hg] than nonanadromous fish, but there have been no intraregional comparisons. Also, no comparisons of [Hg] among anadromous (sea-run), resident (marine access but do not migrate), and landlocked (no marine access) life history types of Arctic char and lake trout have been published. Using intraregional data from 10 lakes in the West Kitikmeot area of Nunavut, Canada, we found that [Hg] varied significantly among species and life history types. Differences among species–life history types were best explained by age-at-size and C:N ratios (indicator of lipid); [Hg] was significantly and negatively related to both. At a standardized fork length of 500 mm, lake trout had significantly higher [Hg] (mean 0.17 µg/g wet wt) than Arctic char (0.09 µg/g). Anadromous and resident Arctic char had significantly lower [Hg] (each 0.04 µg/g) than landlocked Arctic char (0.19 µg/g). Anadromous lake trout had significantly lower [Hg] (0.12 µg/g) than resident lake trout (0.18 µg/g), but no significant difference in [Hg] was seen between landlocked lake trout (0.21 µg/g) and other life history types. Our results are relevant to human health assessments and consumption guidance and will inform models of Hg accumulation in Arctic fish. Environ. Toxicol. Chem. 2011; 30:1459–1467. © 2011 SETAC

Migration delays and mortality of adult Atlantic salmon (Salmo salar) en route to spawning grounds on the River Allier, France

Abstract: During summer periods when water temperatures are high, Atlantic salmon Salmo salar are forced to halt their migration. This phenomenon was observed in our study in the River Allier in France. Between 200 and 1200 S. salar have come to spawn in the River Allier every year for the last 2 decades, but the population has suffered a severe decline. In 2009, 30 individuals were radio tracked; of these, 11 died during the summer period, while the other 19 resumed their migration in the fall. This mortality level was higher amongst the S. salar that arrived towards the end of the migration period, i.e. those individuals that tended to spend the summer in the lower, warmer stretch of the river. In view of the continuing rise in freshwater temperatures, measures are urgently needed to reduce the impact of increased temperatures on fish in the River Allier. This could be achieved by (1) promoting summer delays further upstream by making it easier for fish to pass through dams and (2) by protecting the spawning adults, particularly in the locations of summer halt. This study is consistent with a growing body of literature that suggests that climate change could have devastating effects on the upstream migration phase of anadromous salmonids.

Parental migration, climate and thermal exposure of larvae: spawning in southern regions gives Northeast Arctic cod a warm start

Abstract: Temporal variability in environmental conditions met by early life stages is consid- ered a key driver of fluctuations in recruitment and abundance of fish stocks. Variability in spawn- ing grounds selected by the parental population can change the environmental conditions encountered by the offspring, with consequences for recruitment. We compared how changes in spawning ground distribution and interannual climatic variation influenced the temperature exposure of eggs and larvae of Northeast Arctic cod Gadus morhua along the Norwegian coast. By using a general circulation model and 20 yr of forcing data, we tracked eggs and larvae from various spawning grounds and mapped temperature exposure, potential growth rate and theoret- ical survival probabilities in space and time. We found that the temperature history integrated over the early larval stages decreased by almost 4°C from southern to northern spawning grounds. Thus, variations in spawning ground usage have the potential to outweigh the interannual envi- ronmental variability, and consequently, shifts in spawning grounds may be more important than climatic variability in determining recruitment success. The long-term northbound shift and trun- cation of spawning grounds of the Northeast Arctic cod is thought to be caused by a size-selective trawl fishery in the Barents Sea, which promotes smaller and early maturing individuals to spawn farther north. This selection could increase offspring vulnerability to climatic changes, thereby strengthening the link between climate and recruitment.

Environmental controls of phenology of high-latitude Chinook salmon populations of the Yukon River, North America, with application to fishery management

Abstract: Mundy, P. R., and Evenson, D. F. 2011. Environmental controls of phenology of high-latitude Chinook salmon populations of the Yukon River, North America, with application to fishery management. – ICES Journal of Marine Science, 68: 1155–1164.Phenologies of a number of anadromous fish species have been demonstrated to vary in concert with environmental factors that change with global warming, such as water and air temperatures. Anadromous fishery managers will need advice from models of phenology, or migratory timing, as functions of environmental factors in those harvest areas where annual migratory timing can vary sharply. Such models are also necessary to advise fishery managers on how and when global warming projections of the IPCC model ensemble should be factored into regulatory decisions. Specifically, we demonstrate that the annual timing of marine exit of Yukon River Chinook salmon (Oncorhynchus tshawytscha) at 63°N 165°W for 1961–2009 varied in close concert with modelled sea surface temperature, air temperature, and sea ice cover. The best linear model for 1961–2009 combines sea surface and air temperatures to explain 59% of the annual variability in migratory timing (ice cover is available only for 1970–2009). Changes in phenology of high-latitude Chinook salmon are expected in response to global warming. As average temperatures increase, the frequency of earlier migrations is expected to increase, making management of the fishery more challenging.

Adaptive trade-offs in juvenile salmonid metabolism associated with habitat partitioning between coho salmon and steelhead trout in coastal streams

Abstract: 1. Adaptive trade-offs are fundamental to the evolution of diversity and the coexistence of similar taxa and occur when complimentary combinations of traits maximize efficiency of resource exploitation or survival at different points on environmental gradients. 2. Standard metabolic rate (SMR) is a key physiological trait that reflects adaptations to baseline metabolic performance, whereas active metabolism reflects adaptations to variable metabolic output associated with performance related to foraging, predator avoidance, aggressive interactions or migratory movements. Benefits of high SMR and active metabolism may change along a resource (productivity) gradient, indicating that a trade-off exists among active metabolism, resting metabolism and energy intake. 3. We measured and compared SMR, maximal metabolic rate (MMR), aerobic scope (AS), swim performance (UCrit) and growth of juvenile hatchery and wild steelhead and coho salmon held on high- and low-food rations in order to better understand the potential significance of variation in SMR to growth, differentiation between species, and patterns of habitat use along a productivity gradient. 4. We found that differences in SMR, MMR, AS, swim performance and growth rate between steelhead trout and coho salmon were reduced in hatchery-reared fish compared with wild fish. Wild steelhead had a higher MMR, AS, swim performance and growth rate than wild coho, but adaptations between species do not appear to involve differences in SMR or to trade-off increased growth rate against lower swim performance, as commonly observed for high-growth strains. Instead, we hypothesize that wild steelhead may be trading off higher growth rate for lower food consumption efficiency, similar to strategies adopted by anadromous vs. resident brook trout and Atlantic salmon vs. brook trout. This highlights potential differences in food consumption and digestion strategies as cryptic adaptations ecologically differentiating salmonid species. 5. We hypothesize that divergent digestive strategies, which are common and well documented among terrestrial vertebrates, may be an important but overlooked aspect of adaptive strategies of juvenile salmonids, and fish in general.

Partial Migration in a Robust Brown Trout Population of a Patagonian River

Abstract: Life history plasticity, particularly partial migration (i.e., coexistence of resident and anadromous forms), probably plays a major role in the ability of brown trout Salmo trutta to dominate food webs after introduction into Patagonian rivers. We documented brown trout establishment, distribution, and life history variation in relation to habitat features in the Rio Grande, Tierra del Fuego, Argentina. Results support the hypothesis that Rio Grande brown trout developed an anadromous life history form (“sea trout”) two decades after introduction in relation to localized food limitation as the population expanded throughout the basin. Tributary streams with only resident fish were narrower and had significantly higher levels of specific conductance and soluble reactive phosphorus than streams that were inhabited by both resident and anadromous brown trout. Invertebrate biomass was two to three times higher and juvenile brown trout density was significantly higher in resident-only sites than in s...

APPLYING INSTREAM FLOW INCREMENTAL METHOD FOR THE SPAWNING HABITAT PROTECTION OF CHINESE STURGEON (Acipenser sinensis)

Abstract: The Chinese sturgeon, Acipenser sinensis, is an anadromous species that spawns in the Yangtze River and Pearl River of China. Its population has declined dramatically since the construction of the Gezhouba Dam (GD) in 1981 and then with the impoundment of the Three Gorges Dam (TGD) upstream of the GD in 2003. This paper presents a quantitative method based on the instream flow incremental method to explore the relationship between the fish spawning habitat and the operations of the GD and TGD, aiming to find a solution for conservation of the species. A two-dimensional hydrodynamic model was built with the River2D to simulate the hydraulic behaviour of the stream below the GD. Habitat suitability index was determined by the biological data of the fish collected in the field. The two parts were then integrated through a geographical information system developed via ArcGIS to outline the fish habitat area variation with flows. The decision support system is applied to set up a habitat time series for validating the assumption that more habitats have the potential to support more fish. The fish habitat results for alternative instream flow schemes are then compared with one another for defining the optimal flow requirements and evaluating effects of reservoir operation alternatives in order to improve the operation management for the GD and TGD projects. The results show that the optimal flow for spawning of the fish is about 7000-13000m(3)/s and the optimal inlets combination is where the inflow comes from two power plants. Copyright (C) 2009 John Wiley & Sons, Ltd.

Movement of three non‐salmonid fish species through a low‐gradient vertical‐slot fishway

Abstract: Well-designed fishways have assisted in restoring migrations and rehabilitating riverine fish species in all continents The performance of fishways varies greatly with their type, design and operating regime, and with the species involved Vertical-slot fishways are widely used to overcome low-level barriers, especially for non-salmonids Important issues remain in the design of fishways to meet performance and cost criteria, including the relationship between fishway bed gradient and the fish that ascend, and whether resting pools are needed Models of species' movement patterns can inform fishway designers about likely fish response to various design options, and can lead to improved efficiency and effectiveness Models of general movement patterns of three potamodromous non-salmonid fishes in the Murray River, Australia, were developed from empirical data in a low-gradient vertical-slot fishway The models integrate data on times of entry and exit, ascent rates, and whether fish continued to ascend during the night These fish species did not favour resting pools Ascent rates of fish ≥120 mm were more closely related to fish behaviour than to length; for a given fishway height, reducing bed slope by increasing the number of pools may slow the ascent of such fish, whereas enlarging pool volumes increases costs Copyright © 2010 John Wiley & Sons, Ltd

FISH MIGRATIONS | The Biology of Fish Migration

Abstract: Migration is the synchronous, directed movement of a large segment of a population between discrete habitats. Approximately 2.5% of all known fish species undergo migration at least once during their life cycle, although the physical scale of migration may vary over four orders of magnitude, from hundreds of meters to thousands of kilometers. There are many challenges associated with migration, and numerous factors can influence the migratory success of individuals. This article discusses several of these challenges, with an emphasis on understanding the behavioral and physiological processes that facilitate long-distance migration in fishes.

Surface trawl survey for U.S. origin Atlantic salmon Salmo salar

Abstract: A surface trawl survey (2001–2005) in Penobscot Bay, Maine, USA, and the nearshore Gulf of Maine waters was conducted to investigate early marine dynamics of a hatchery-dependent Atlantic salmon Salmo salar population from a severely modified river system Data generated were used to evaluate the effect of stocking location and time on migration success and to describe the migratory pathways and environments that post-smolts traverse Significant differences in early migration success were detected among different stocking groups, but subsequent marine survival was independent of stocking group While the post-smolt population was primarily composed of hatchery origin smolt-stocked fish, other life-stage stocking strategies (ie parr stocking) represented a higher proportion of the population than previously assumed Catch distribution suggests evidence of an initial marine migratory pathway out of the dynamic Penobscot Bay environment The hypothesized benefits of a predator refuge based on the co-occurring species complex is considered minimal for emigrating post-smolts given a mismatch in the size overlap among species and low abundance of other co-occurring diadromous populations These data can be used to modify current management actions to optimize S salar recovery and inform future research agendas

Characteristics of spawning ground fidelity by a diadromous fish: a multi-year perspective

Abstract: Spawning site fidelity has long been documented for anadromous salmonids, and more recently in estuarine and marine fish. The level of fidelity has implications for population dynamics, conservation, and management. This study extended a previous examination of spawning ground fidelity for common snook, Centropomus undecimalis. We used seines to sample 28 km of Gulf of Mexico beaches, spawning grounds for snook, during spawning season (May through September) from 2007 through 2010. Of 3,304 snook tagged, 171 unique fish were recaptured a total of 186 times and, of those, 166 fish (97.08%) (181 recaptures = 97.31%) were recaptured on the same island where they were tagged. One hundred seven of the recaptures occurred in the same year they were tagged, and 79 occurred one or more years after they were tagged, indicating fidelity was expressed within and across years. Distance between tag and recapture locations within and among years demonstrated fidelity at a spatial scale much smaller than barrier island (mean distance between tag and recapture =1.59 ± 0.12 km; island lengths 6.8, 8.9 and 12.4 km). Furthermore, mapping of capture locations revealed clumped distribution of snook on spawning grounds, further suggesting snook propensity for specific locations. Fish size had no effect on fidelity. We conclude that common snook show a high level of spawning site fidelity in southwest Florida, which may result in spawning group segregation, may influence the response of snook to disturbances, and may have implications for adult-to-nursery ontogenetic connections.

Fish pass assessment in the rivers of Catalonia (NE Iberian Peninsula). A case study of weirs associated with hydropower plants and gauging stations

Abstract: Fish pass assessment in the rivers of Catalonia (NE Iberian Peninsula). A case study of weirs associated with hydropower plants and gauging stations This study evaluated the effectiveness of fish passes in Catalan rivers (NE Iberian Peninsula). The aim was to test current functionality to enhance these structures for the purpose of optimising their management. We analysed river connectivity and fish pass facilities to generate information to improve the design, construction, management and assessment of solutions related to fish passage in Catalan rivers according to international best practices. In 2006, a preliminary evaluation of the locations and effectiveness of fish pass facilities in Catalonia was conducted through direct inspection of 78 fishways. Most of them were retro-fitted solutions using broad-spectrum technical structures, mainly pool fishway or pool pass facilities. An analysis of the effectiveness of 7 of the new fish passes (4, 2 and 1 passes in the Ter, Ebro and Tordera rivers, respectively) was performed between 2006 and 2009. The fish passes were located in weirs associated with hydropower plants and gauging stations. Our preliminary assessment of fish connectivity was based on a field visit and collection of information to populate a database of existing obstacles and associated fishways and calculation of the new version of the ICF index (river connectivity index) for all of them. Several methodologies were used to check the effectiveness of a selection of fish pass solutions, most of which were based on passage rates directly or indirectly estimated for each species. Direct estimation techniques involved the installation of fish traps upstream of the facility at the exit of the fish pass and visual counts. Indirect estimation techniques compared the fish population structure on each side of the obstacle in river sections with equivalent hydrology and habitat characteristics using electric fishing or trapping systems, group mark-recapture methods and individual mark-recapture methods (PIT tags). The results showed that (1) existing solutions to improve fish migration in Catalonia are insufficient (only present at approximately 8% of obstacles), and where they do exist, thefish passes are usually inadequate or poorly maintained. (2) Fish passes are generally inadequate or insufficient for the total native fish fauna from each water body. Additionally, with few exceptions, fish passage rates are too low, and in most cases, only fish with a high capacity to overcome obstacles or the largest individuals succeed in migrating. (3) Fish pass effectiveness agrees with the results of the new version of the ICF index.

Bibliometric analysis of diadromous fish research from 1970s to 2010: a case study of seven species

Abstract: The aim of this study was to explore the research trends and the evolution of publications covered on diadromous fish from 1970s to 2010. We conducted a bibliometric analysis on seven patrimonial species: Atlantic salmon (Salmo salar), Brown and Sea trout (Salmon trutta), Allis shad (Alosa alosa), Twaite shad (Alosa fallax), Eel (Anguilla Anguilla), Sea lamprey (Petromyzon marinus) and River lamprey (Lampetra fluviatilis). We used bibliometric techniques on the total number of research (articles, books, and conferences) in all country in function of main fields such as growth/age, reproduction, migration, habitat, aquaculture, diseases, diet, abundance, fisheries, climate change, toxicology, dams/fishways, genetics, taxonomy, modelling, resource management, and stocking. The results revealed a clear difference in the evolution of scientific studies by species and by countries. The analysis comparisons showed the intensity of certain topics by species with the emergence of new ones, the economic impact on sciences and the increased support of conservation plan management for certain species, such as salmon and lamprey in France. This study also emerged that French research is not always consistent with the international trend which suggests the dominance of management systems on scientific studies.

Seasonal Patterns of Movement and Residency by Striped Bass within a Subestuary of the Chesapeake Bay

Abstract: Although often generalized as anadromous, striped bass Morone saxatilis show varying degrees of residency in natal estuaries and exhibit diverse seasonal migration patterns in estuarine and coastal waters. Most coastal striped bass originate from the Chesapeake Bay, but the bay and its subestuaries also harbor substantial numbers of striped bass throughout the year. The degree to which resident striped bass inhabit individual subestuaries was evaluated by use of acoustic telemetry. We investigated seasonal patterns of movement within and outside of the Patuxent River, a centrally located, intermediate-size subestuary of the Chesapeake Bay. A fixed acoustic receiver array was deployed in the Patuxent River, and 42 acoustic-tagged striped bass were monitored for a 2-year period (2008–2009). Seasonal patterns of movement within the subestuary were similar between years and were generally consistent with overall anadromous behavior: striped bass moved downestuary during winter to points outside the P...