Showing papers on "Fish migration published in 1995"

The structure and components of European estuarine fish assemblages

Abstract: This paper discusses the structure of fish assemblages using information from 17 European estuarine areas (in the British Isles, Portugal, Belgium, France, the Netherlands, Germany, Norway and Spain). Binary (presence/absence) and quantitative data for each assemblage have been used to assess the assemblage structure according to taxonomy (i.e. species identity). Following this, a total of 29 functional guilds were created in order to describe the use made of an estuarine area for each taxon encountered: feeding preferences, reproduction type, substratum preferences (for bottom dwelling fish) and position within the water column (vertical preference guild). The paper focuses on the designation and determination of the proportions of the guild members of the fish assemblage within each estuary. Ecological guilds within the assemblage include estuarine residents, marine juvenile migrants, catadromous and anadromous migrants, marine seasonal users, and freshwater and marine adventitious species. Feeding guilds include detritivores, planktonic feeders, infaunal croppers and sediment ingesters, piscivores, and active predators of mobile crustaceans. Reproduction guilds include planktonic and demersal spawners and those using brood-protection. The substratum preference indicates the proportions of sand, mud, rock and vegetation dwellers, and the vertical preference denotes benthic, demersal or pelagic species. The analysis has allowed both the estuaries to be grouped according to taxonomic and guild similarity and the characterisation of a typical European estuarine fish assemblage. Within the limits posed by differing sampling methods, times of sampling and survey rationale, there is a high similarity between estuaries. The data indicate common patterns of estuarine usage irrespective of the differences between the estuaries although such patterns cannot be interpreted fully given the incomplete knowledge of their physical and anthropogenic characteristics.

Ecological integrity and fisheries ecology of the Araguaia-Tocantins river basin, Brazil

Abstract: An attempt is made to evaluate the present environmental impacts of the Tucurui dam on the fisheries and ecological integrity of the Araguaia—Tocantins basin. Management and research needs to minimize the impacts from future hydroprojects and increased human activities in the basin are also addressed. The Tocantins and Araguaia fish fauna is not especially rich by Amazonian standards (about 300 species). Total yields are also rather low (about 8800 t/y) in a river stretch of about 2500 km and unique for being concentrated (90%) in the main channel. Fisheries are heavily dependent on migratory fish and may be severely damaged as a consequence of river regulation. Downstream from the Tucurui Dam important fisheries have been drastically reduced (70%), probably by recruitment failure, lower productivity and overfishing. Upstream from the dam, however, fisheries have benefited from the higher productivity of the artificial lake, although this has not compensated for the regional economic shortages. Management based on ‘basinwise’ catch statistics and fish migration research should take account of likely future disruptions of commercial fisheries by the synergistic effects of other planned impoundments, mining, deforestation and uncontrolled sport fisheries in the middle and upper basins.

Seasonal pulses in migrations of New Zealand diadromous fish and the potential impacts of river mouth closure

Abstract: Movements of 16 diadromous New Zealand freshwater fishes between rivers and the sea show distinct seasonal pulses: most migration from the sea into rivers occurs during spring and most migration from rivers into the sea occurs during summer‐mid‐winter Inspection of life stages at which migrations occur shows that pulses in movements in both upstream and downstream directions variously involve both larval/juvenile fish and adult/prespawning fish For this reason it is unlikely that there is a general explanation for what seems, superficially, to be common timing of movements by many species The ability of diadromous fish to move between catchments through the sea gives such species the capacity to recolonise rivers where there has been extirpation as a result of perturbation This probably explains why fish species on small nearshore and offshore islands around New Zealand are almost exclusively diadromous Understanding the timing of these movements is important if river managers are to minimis

Traditional fisheries and fish ecology on the mekong river at rhone waterfalls in southern laos

Abstract: Khonc (pronounced "Kawn") Falls is the site of one of the most important wildcapture riverine fisheries in tropical Asia. Khone villagers have been fishing the area for generations, and have inherited or developed an out standing array of artisanal fishing devices based on intimate knowledge of migratory, feeding and other behavior of numerous fish species. Their traditional fisheries management system is also highly developed. Khone fishing people are confronted by the decline of many species, especially of strongly migratory ones which are the main basis for the fisheries. The small cyprinid fish Cirrhinus lobatus is an ecological keystone species. It is the most abundant fish species in the Khone Falls area, and is usually the first species to migrate upstream in the December-February non-reproductive migratory period. Data on migratory C. lobatus during the June-July reproductive migratory period indicate that the species is a progynous hermaphrodite. Another important cyprinid is the large species Probarbus jullieni, caught mainly in November-Janu ary when it is migrating to spawning sites or is actually engaged in spawning activity. The history of the Probarbus fisheries in southern Laos indi­ cates that a long term decline started around 1970, with the introduction of nylon gillnets, and that it increased rapidly after 1991 when markets opened up and fisheries became increasingly capitalized and modernized. Important catfishes include Pangasius macronema and P. krempfi Pangasius macronema is the object of an unusual communal fisheries practiced by the village of Ban Hang Sadam. Pangasius krempfi is a diadromous species, spending much of its life in coastal waters of the South China Sea, but returning to the Mekong River to spawn.

A spatially explicit fitness‐based model of capelin migrations the Barents Sea

Abstract: The geographical distribution and production of the Barents Sea capelin (Mallotus villosus, Osmeridae) is modelled by the use of a state-variable optimization technique (dynamic programming), where the main objective of individuals always is to maximize fitness, or total expected reproduction (RO), by selecting the most profitable habitats through time. Fitness is gained by successful reproduction (a function of size) during the spawning season on the breeding grounds off northern Norway. The environment (predators, temperature and zooplankton prey) is determined by a meteorologically forced circulation model for the year 1980, creating a spatial and seasonal fluctuation in the environment. Predation from cod is the main source of mortality, and the distribution of the cod (Gadus morhua) stock is assumed to vary with temperature. Growth is predicted from a bioenergetic model, incorporating the cost of swimming between feeding areas and spawning grounds. Field data of the capelin stock recorded during autumn cruises from 1979 is implemented at the start of the model, and then this stock is modelled through 1980 and the first months of 1981. Model predictions are compared with the observed distribution of capelin in autumn 1980. Habitat selection has consequences for the dynamics of the population and growth of individuals, demonstrating the importance of combining external (environmental) and internal (evolutionary) forcing to understand and predict the dynamics of fish populations. This study is the first application of dynamic programming to model the dynamics and ecology of horizontal fish migration, and we suggest that the method may be developed into a useful tool for the management of short-lived species.

Assessment of the stocked or wild origin of anadromous brown trout (Salmo trutta L.) in a Danish river system, using mitochondrial DNA RFLP analysis

Abstract: Declines in the number of anadromous brown trout in the Karup River in Denmark, due to environmental degradation, led to the stocking of large numbers of hatchery trout during the 1980s. This practice was gradually replaced by stocking with the offspring of electrofished local trout The genetic contribution of the hatchery fish to the current population of anadromous trout in the river was estimated by restriction fragment length polymorphism analysis of mitochondrial DNA, using seven restriction endonucleases. Fish from the hatchery strain as well as from five locations in the river system, and from a further unstocked river were screened. Eight haplotypes were observed. The distribution and frequencies of the observed haplotypes revealed little genetic differentiation among stocked populations. The hatchery strain differed significantly from the stocked populations. One haplotype which was found at a high frequency in the hatchery strain was almost absent from the stocked populations. This suggests that the genetic contribution of the hatchery trout to the current population is much less than would be expected from the number of stocked fish. The possible reasons for the failure of the hatchery trout to contribute to the gene pool, and also the implications for conservation biology, are discussed.

Brown trout Salmo trutta released to support recreational fishing in a Norwegian fjord

Abstract: One- and two-year-old hatchery reared juveniles of seven freshwater resident and anadromous populations of Scandinavian brown trout were released in the outer and inner part of the Oslofjord and in the River Akerselva, flowing through the city of Oslo. Recapture rates were highest (mean 20.3%) for river released fish and lowest for those released in the outer (16.8%) and inner (l2.1'%1) fjord. In general, recapture rate increased with fish size at release (r=0.76). When released in fresh water, most of the recaptures were from fresh water and when released in the fjord, most recaptures were from the fjord. In general, freshwater resident stockr showed a higher degree of freshwater residency than anadromous stocks. However, mean migratory distance was longer for freshwater resident than anadromous fish. Trout moved longer distances at sea when released in the outer than in the inner fjord. Specific growth rate and size at recapture varied among release sites and stocks; they were highest for fish released in the outer fjord and lowest for river-released trout. There was no consistent diKerence in sea growth between freshwater resident and anadromous stocks. Estimated total yield was highest for fish released in the outer fjord, whereas there was no significant diff'erence in yields between trout released in the river and the inner Oslofjord.

Dispersal, growth and mortality of brown trout (Salmo trutta L.) stocked in a regulated West Norwegian river

Abstract: As part of a fishery enhancement scheme, 70 000 fingerlings of anadromous brown trout (Salmo trutta L.) were stocked in the regulated River Teigdal, western Norway. To evaluate the stocking programme 10 000 of the hatchery reared fish were marked and released at 10 different localities. The results showed that the hatchery reared fish were inferior to wild brown trout. During the first weeks densities were high in the areas of stocking, varying between 27 and 680 individuals per m2. Stocked fish colonizing adjacent areas were mostly found upstream. Very few fish were found to cross the river from the point of release. One week after stocking food consumption of the hatchery reared fish was low compared with wild trout. Stocked trout had a lower growth rate (0.05 mm d−1) than native fish (0.08 mm d−1). However, fish stocked in deeper, slower flowing areas grew faster than those stocked in shallow riffle areas. The mortality of the stocked trout was 99% from July to April, being highest during the winter. Wild fish survived better, having a mortality of 79% over the same period. The value of the stocking programme is questioned. As an alterative, methods of biotope adjustment are proposed to increase the carrying capacity of wild trout in the river.

Target spawning requirements for Atlantic salmon, Salmo salar L., in Newfoundland rivers

Abstract: In recent years, there has been increasing pressure from user groups in Newfoundland and Labrador, Canada, to manage Atlantic salmon, Salmo salar L., on a river-specific basis. The requirement to maximize benefits to users while ensuring that conservation goals are met has resulted in an initiative to develop river-specific target spawning requirements. In Newfoundland, anadromous juvenile Atlantic salmon make widespread use of lacustrine habitat for rearing. Depending on the river, lacustrine habitat can account for a substantial proportion of total production. Therefore, target spawning requirements for a number of rivers in several management areas were derived in terms of the contribution of both riverine and lacustrine habitats. The approach adopted, and derivations of associated parameter values, are reviewed, and limitations and research needs are discussed.

Fish Communities as Indicators of Environmental Quality in the West River Watershed

Abstract: The West River bordering New Haven and West Haven, Connecticut, is under evaluation for potential restoration of a former salt marsh. As part of a larger survey of biota associated with this river, the fish fauna was examined in the estuary and adjacent freshwaters. The results provide baseline data for monitoring restoration efforts and indicate the environmental health of the river. The fish communities lacked intolerant species, included significant numbers of individuals of non-native fishes, and showed low abundance and diversity of the native species, all indicating that this stretch of the river represents poor fish habitat with significant ecological disturbances. Some sites contained individuals with excessive parasites, tumors, ulcers, and fin erosion, which suggests physiological stress and potential human health hazards. These problems are localized in the vicinity of combined sewage outflows and/or storm sewer runoff from streets. They are exacerbated by periodic low flow or stagnant waters caused by the tide gates. Salt marsh restoration with tide-gate modification could improve habitat for species with commercial and recreational value and improve movement of diadromous fishes.

Smolt characteristics of small first‐time migrant, and resident Arctic charr, Salvelinus alpinus (L.), from a river system in northern Norway

Abstract: Smolt characteristics were investigated in sympatric anadromous and resident Arctic charr. Salvelinus alpinus (L.), of a similar size (11-20 cm), A group of first-time migrant anadromous charr was caught while descending the Hals River and two groups of resident conspecifics were caught in Lake Storvatn. one before, and one after, the sea-run of anadromous fish had terminated. When sampled immediately after capture in fresh water the anadromous group had a higher proportion of fish visually classified as smolts. and these charr had higher gill Na+-K+ ATPase activity, higher densities of developed chloride cells in the gills, a lower condition factor, and lower plasma osmolality, than resident fish. When exposed to sea water (33%o S), only minor differences in mortality and plasma electrolyte levels were observed between anadromous and resident fish, average values of plasma osmolality and chloride concentrations being 377 mOsm and 169 mM and 387 mOsm and 174 mM, respectively. The results suggest that the first-time migrant Arctic charr had undergone some of the physiological changes that are considered typical for a parr-smolt transformation before they left fresh water. Such changes did not appear to have occurred in sympatric, resident, fish of a similar size. The parr-smolt transformation in the first-time migrants may, however, have been incomplete, because the fish did not appear to have the ability to rapidly re-establish osmo- and ionoregutatory homeostasis after direct transfer to sea water.

Chapter 14 Biochemistry of fish migration

Abstract: Publisher Summary Migration phenomena of fish are fundamental for survival of migrating species, and each migratory behavior has important meanings for their specific life history. The occurrence of migratory behavior in fish goes fin in fin with changes in their specific physiological conditions. Various physiological and metabolic changes play leading roles in making fish successful migratory species. To date, several comprehensive reviews have been published on fish migrations from various aspects, including ecology, bioenergetics, physiology, endocrinology, and evolution. However, recent developments of new techniques, especially biochemical ones, have rapidly accumulated data on endocrinological changes in hormone profiles and metabolic changes in several organs of migratory fish, which were impossible earlier. This chapter focuses on the fish migration from biochemical as well as physiological points of views with special reference to developmental and reproductive migrations in fish, particularly in salmonids. Many salmonid species exhibit the most representative migration between the parental river and the sea, and the homing migration of salmon to the maternal stream is disputably one of the most interesting and challenging phenomenon in fish biology. Other migratory species that show different migratory behaviors from salmonids, such as the catadromous eels and long distance sea migratory species (tuna, anchovy, sardine, etc.) would help to understand the mechanisms of fish migration, but to date too few reports have covered biochemical aspects of migrations to allow generalizations.

Index rivers: a key to managing anadromous fish

Abstract: A network of index rivers provides information for the management of anadromous fish stocks in the Gulf of St Lawrence. Index rivers are sites where regular observations are made of fish abundance and characteristics. This information is used particularly for Atlantic salmon to estimate stock abundance, to evaluate spawning requirements and to forecast returns. The need for timely and unbiased indicators of stock abundance is increasing. A network of index rivers would fulfil this need.

Summary Report for Bureau of Fisheries Stream Habitat Surveys : Willamette River Basin, 1934-1942, Final Report.

Abstract: This document contains summary reports of stream habitat-surveys, conducted in the Willamette River basin, by the Bureau of Fisheries (BOF, now National Marine Fisheries Service) from 1934-1942 These surveys were part of a larger project to survey streams in the Columbia River basin that provided, or had provided, spawning and rearing habitat for salmon and steelhead (Rich, 1948) The purpose of the survey was, as described by Rich, 'to determine the present condition of the various tributaries with respect to their availability and usefulness for the migration, breeding, and rearing of migratory fishes' Current estimates of the loss of anadromous fish habitat in the Columbia River Basin are based on a series of reports published from 1949-1952 by the US Fish and Wildlife Service The reports were brief, qualitative accounts of over 5000 miles of stream surveys conducted by the BOF from 1934-1946 (Bryant, 1949; Bryant and Parkhurst, 1950; Parkhurst, 1950a-c; Parkhurst et al, 1950) Despite their brevity, these BOF reports have formed the basis for estimating fish habitat losses and conditions in the Columbia River Basin (Fulton, 1968, 1970; Thompson, 1976; NPPC, 1986) Recently, the field notebooks from the BOF surveys were discovered The data is now archived andmore » stored in the Forest Science DataBank at Oregon State University (Stafford et al, 1984; 1988) These records are the earliest and most comprehensive documentation available of the condition and extent of anadromous fish habitat before hydropower development in the Columbia River Basin They provide the baseline data for quantifying changes and setting a benchmark for future restoration of anadromous fish habitat throughout the Basin The summaries contained in this book are exact replicates of the originals Due to discrepancies between the field data and the summaries, the database should be used to assess pool and substrate conditions This data is available from the Bonneville Power Administration The Bureau of Fisheries survey is unique because it is the only long-term data set that quantifies fish habitat in a manner that is replicable over time; no other similar work is known to exist Other surveys, such as Thompson and Haas (1960), inventoried extensive areas in a manner that was mostly qualitative, subjectively estimating physical characteristics like bank cover and stream shading Spawning, rearing, and resting habitat were not systematically quantified to allow comparisons over time Knowledge of past and present quantity and quality of anadromous fish habitat in the Columbia River Basin is essential to any effort to enhance fish populations Habitat condition is a key element in monitoring and evaluating progress towards the doubling goal Integration of this information into the Columbia River Fish and Wildlife Plan can provide the basis to greatly enhance understanding of past, present, and future habitat conditions in the basin to provide for improved management decisions« less

Summary Report for Bureau of Fisheries Stream Habitat Surveys : Clearwater, Salmon, Weiser, and Payette River Basins, 1934-1942, Final Report.

Abstract: This document contains summary reports of stream habitat surveys, conducted in Idaho, by the Bureau of Fisheries (BOF, now National Marine Fisheries Service) from 1938-1942.. These surveys were part of a larger project to survey streams in the Columbia River basin that provided, or had provided, spawning and rearing habitat for salmon and steelhead (Rich, 1948). The purpose of the survey was, as described by Rich, 'to determine the present condition of the various tributaries with respect to their availability and usefulness for the migration, breeding, and rearing of migratory fishes'. The Idaho portion of the survey consisted of extensive surveys of the Clearwater, Salmon, Weiser, and Payette River Subbasins. Current estimates of the loss of anadromous fish habitat in the Columbia River Basin are based on a series of reports published from 1949-1952 by the U.S. Fish and Wildlife Service. The reports were brief, qualitative accounts of over 5000 miles of stream surveys conducted by the BOF from 1934-1946 (Bryant, 1949; Bryant and Parkhurst, 1950; Parkhurst, 1950a-c; Parkhurst et al., 1950). Despite their brevity, these BOF reports have formed the basis for estimating fish habitat losses and conditions in the Columbia River Basin (Fulton, 1968, 1970; Thompson, 1976; NPPC,more » 1986). Recently, the field notebooks from the BOF surveys were discovered. The data is now archived and stored in the Forest Science DataBank at Oregon State University (Stafford et al., 1984; 1988). These records are the earliest and most comprehensive documentation available of the condition and extent of anadromous fish habitat before hydropower development in the Columbia River Basin. They provide the baseline data for quantifying changes and setting a benchmark for future restoration of anadromous fish habitat throughout the Basin. The summaries contained in this book are exact replicates of the originals. Due to discrepancies between the field data and the summaries, the database should be used to assess pool and substrate conditions. This data is available from the Bonneville Power Administration. The Bureau of Fisheries survey is unique because it is the only long-term data set that quantifies fish habitat in a manner that is replicable over time; no other similar work is known to exist. Other surveys, such as Thompson and Haas (1960), inventoried extensive areas in a manner that was mostly qualitative, subjectively estimating physical characteristics like bank cover and stream shading. Spawning, rearing, and resting habitat were not systematically quantified to allow comparisons over time. Knowledge of the past and present quantity and quality of anadromous fish habitat in the Columbia River Basin is essential to any effort to enhance fish populations. Habitat condition is a key element in monitoring and evaluating progress towards the doubling goal. Integration of this information into the Columbia River Fish and Wildlife Plan can provide the baseline information to greatly enhance understanding of past, present, and future habitat conditions in the basin to provide for improved management decisions.« less

Funktionalität von Potamalfischaufstiegshilfen im Marchfeldkanalsystem

Abstract: This article describes studies undertaken to test the performance of diversion channels in lowland river sections, using abiotic and biotic characteristics. Critical passages in an installation facilitating the upstream migration of fish are usually the transitions between basins. Increased flow velocities (v) > 1 m/s have been seen to occur only at individual points, with a sufficient proportion of cross-sectional area remaining where v < 1 m/s, as can be demonstrated by the graph showing equivelocity contours. In 1993, 7500 fish of 28 species passed the two fish migration facilities studied. After adaption of the facilities, the rate increased to 60000 fish of 36 species in 1994. The suitability of the diversion channel for many small fish species and/or fry has been established

Annual Coded Wire Tag Program; Missing Production Groups, 1994 Annual Report.

Abstract: In 1989, the U.S. Fish and Wildlife Service (Service) received funding from the Bonneville Power Administration (BPA) to initiate a program of coded-wire tagging production groups of anadromous fish that did not have representative groups marked for evaluation. The purpose of the program is to mark a representative group of fish from each production release. The three objectives of the program are: (1) To estimate the survival of each release group, (2) To estimate the contribution of each release group to ocean and in river fisheries, and (3) To estimate the straying rate of hatchery fish. This information will be used to evaluate hatchery practices and individual broodstocks. It will also enable salmon harvest managers to manage harvest of excess hatchery fish while protecting the threatened or endangered stocks. In order to meet these objectives, a minimum of one marked group of fish for each production release is necessary for evaluation. The level of marking varies according to the hatchery's location, species of fish, and age at release. All fish released from the various facilities along with mark/unmarked release ratios are reported to the Pacific States Marine Fisheries Commission (PSMFC). All fish recovered in the various fisheries or at themore » hatchery are sampled to recover coded-wire tags. This information is then reported to the PSMFC along with sampling rates. Contribution to various fisheries and survival of the release groups can then be estimated from this information.« less

Summary Report for Bureau of Fisheries Stream Habitat Surveys : Umatilla, Tucannon, Asotin, and Grande Ronde River Basins, 1934-1942, Final Report.

Abstract: This document contains summary reports of stream habitat surveys, conducted in the Umatilla and Grande Ronde River basins, by the Bureau of Fisheries (BOF, now National Marine Fisheries Service) from 1938-1942. These surveys were part of a larger project to survey streams in the Columbia River basin that provided, or had provided, spawning and rearing habitat for salmon and steelhead (Rich, 1948). The purpose of the survey was, as described by Rich, 'to determine the present condition of the various tributaries with respect to their availability and usefulness for the migration, breeding, and rearing of migratory fishes'. Current estimates of the loss of anadromous fish habitat in the Columbia River Basin are based on a series of reports published from 1949-1952 by the U.S. Fish and Wildlife Service. The reports were brief, qualitative accounts of over 5000 miles of stream surveys conducted by the BOF from 1934-1946 (Bryant, 1949; Bryant and Parkhurst, 1950; Parkhurst, 1950a-c; Parkhurst et al 1950). Despite their brevity, these BOF reports have formed the basis for estimating fish habitat losses and conditions in the Columbia River Basin (Fulton, 1968, 1970; Thompson, 1976; NPPC, 1986). Recently, the field notebooks from the BOF surveys were discovered. The datamore » is now archived and stored in the Forest Science DataBank at Oregon State University (Stafford et al., 1984; 1988). These records are the earliest and most comprehensive documentation available of the condition and extent of anadromous fish habitat before hydropower development in the Columbia River Basin. They provide the baseline data for quantifying changes and setting a benchmark for future restoration of anadromous fish habitat throughout the Basin. The summaries contained in this book are exact replicates of the originals. Due to discrepancies between the field data and the summaries, the database should be used to assess pool and substrate conditions. This data is available from the Bonneville Power Administration. The Bureau of Fisheries survey is unique because it is the only long-term data set that quantifies fish habitat in a manner that is replicable over time; no other similar work is known to exist. Other surveys, such as Thompson and Haas (1960) inventoried extensive areas in a manner that was mostly qualitative, subjectively estimating physical characteristics like bank cover and stream shading. Spawning, rearing, and resting habitat were not systematically quantified to allow comparisons over time. Knowledge of the past and present quantity and quality of anadromous fish habitat in the Columbia River Basin is essential to any effort to enhance fish populations. Habitat condition is a key element in monitoring and evaluating progress towards the doubling goal. Integration of this information into the Columbia River Fish and Wildlife Plan can provide the baseline information to greatly enhance understanding of past, present, and future habitat conditions in the basin to provide for improved management decisions.« less

Application of an in Situ Growth Model: Inferred Instance of Interspecific Trophic Competition between Anadromous Fishes of Prudhoe Bay, Alaska

Abstract: A previously described in situ growth model was used to predict the summer growth of age-1 and age-2 broad whitefish Coregonus nasus in the Sagavanirktok River delta near Prudhoe Bay, Alaska, during 1990–1992. Comparisons of observed versus predicted weekly growth increments over the entire 9-year study (1982 and 1985–1992) yielded r = 0.789 (N = 77; P < 0.01) for age- I fish and r = 0.522 (N = 70; P < 0.01) for age-2 fish. Based on daily comparisons of observed versus predicted mean fork length, the model was able to predict growth in 1991 and 1992 with mean squared errors (MSE) of 3.0 and 1.8 mm for age- I fish and 6.5 and 21.2 mm for age-2 fish. Results were similar to those previously described for 1982 and 1985–1989. The model failed noticeably in 1990 for age-1 fish (MSE = 48.6), and model fit for age-2 fish (MSE = 29.9) was the poorest of the 9 years examined. Poor model fit for both year-classes in 1990 was attributed to a divergence of observed from predicted growth; observed growth bega...

Snake River Sockeye Salmon Captive Broodstock; Research Element, 1993 Annual Report.

Abstract: In 1991, the National Marine Fisheries Service listed Snake River sockeye salmon Oncorhynchus nerka as endangered under the Endangered Species Act of 1973. Initial steps to recover the species include the establishment of captive broodstocks at the Eagle Fish Hatchery in Eagle, Idaho. Research and recovery activities for sockeye conducted by the Idaho Department of Fish and Game during the period of April 1993 to April 1994 are covered by this report. Eight anadromous adults (two female and six male) returned to the Redfish Lake Creek trap this year and were spawned at the Sawtooth Hatchery near Stanley, Idaho. Fecundity was 3160 for each female. The mean fertilization rate was 52% for female {open_quotes}A{close_quotes} and 65% for female {open_quotes}B.{close_quotes} Captive broodstock also spawned as well as residual sockeye captured in a Merwin trap in Redfish Lake. Spawning data from 72 fish spawned during this period is included in this report. Captive broodstock also matured later than normal (winter and spring 1994). Fish were spawned and samples were taken to investigate reasons for poor fertilization rates. Twenty-four out migrants of 1991 were selected for return to Redfish Lake for volitional spawning. Releases were made in August of 1993. All fish were implanted with sonic tags and tracking of this group began soon after the release to identify spawning-related activities. A research project is being conducted on captive broodstock diets. The project will investigate the effect of diet modification on spawn timing, gamete quality, and fertilization rates. A second project used ultrasound to examine fish for sexual maturity. The goal was to obtain a group a fish to be released f or volitional spawning. A total of 44 fish were found to be mature. The performance of all captive groups held at Eagle are included in this report.

Pink Salmon Migration in Relation to Sea Surface Temperature and Day-Length in the Open Sea.

Abstract: Our aim was to describe the migratory process of pink salmon Oncorhynchus gorbuscha and to examine the relationship between the migration and physical environments (sea surface temperature and day-length). From tag data for 4, 876 individuals for the past thirty years, we examined distribution change, migratory speed and day-length during open sea migration. The open sea distribution was consistent with 4-11°C sea surface waters as found by past studies. Mean migratory speed was 31.5±27.8km/day. Migratory speed was significantly correlated with day-length, and pink salmon tended to migrate fast around the summer solstice. This result suggests that the photoperiod is an important factor related to the spawning migration of pink salmon.

Smolting of Hatchery-Reared Steelhead Transferred as Eyed Eggs from the Northern to the Southern Hemisphere

Abstract: The effects of a Northern-to-Southern Hemisphere shift on the growth and smolting of steelhead (Oncorhynchus mykiss) were monitored by reference to physiological criteria. Eyed eggs were imported from the Alsea River Trout Hatchery, Oregon, USA (latitude 44°N), to the Lake Rupanco Experimental Hatchery in Chile (latitude 41°S). This transfer of eggs resulted in a notable variation in the age and size at which fish smolted. A minimum smolting size of about 10 cm was observed in the first southern spring of life, when fish were 7–8 months old. Fish that did not reach this size smolted in the second spring of life at age 20 months. Based on our current understanding of the effects of environmental variations on smolt physiology, we offer guidelines for increasing the efficiency of smolt production for this anadromous salmonid in the Southern Hemisphere.

Variation in Reproductive Characters of Hatchery-released Sockeye Salmon, Oncorhynchus nerka, Returning to the Lake Shikotsu and the Bibi River of Central Hokkaido, Japan

Abstract: Adult anadromous sockeye salmon (Oncorhynchus nerka) returning to the Bibi River, which were originally derived from Lake Shikotsu resident sockeye salmon, and adult resident sockeye salmon in Lake Shikotsu were examined for variation in body size, fecundity, and egg size. Both groups of adults originated from hatchery-released juveniles. Larger adult females had higher fecundity. Fecundity and fork length was observed to fit allometric formula within each population. There was no relationship between fork length and egg size in Lake Shikotsu resident sockeye salmon or in age-I.1 anadromous sockeye salmon from Bibi River although the anadromous sockeye salmon were approximately 65% larger in fork length than the resident sockeye salmon. Age-1.2 anadromous sockeye salmon, however, had eggs about 12% larger than did resident sockeye and age-1.1 anadromous sockeye salmon. In hatchery-released sockeye salmon having a constant gametic effort without breeding comptition and parental care, egg size may be stable within a cohort or a population regardless of body-size variation, although fecundity is expressed by the function of body size affected by environmental factors. Therefore, analyses of fecundity and egg size in hatchery-released sockeye salmon population may be useful to assessument of stock status and biological monitoring, respectively, for anadromous stocks in the North Pacific Ocean.

Habitat Quality and Anadromous Fish Production on the Warm Springs Reservation. Final Report.

Abstract: The number of anadromous fish returning to the Columbia River and its tributaries has declined sharply in recent years. Changes in their freshwater, estuarine, and ocean environments and harvest have all contributed to declining runs of anadromous fish. Restoration of aquatic resources is of paramount importance to the Confederated Tribes of the Warm Springs (CTWS) Reservation of Oregon. Watersheds on the Warm Springs Reservation provide spawning and rearing habitat for several indigenous species of resident and anadromous fish. These streams are the only ones in the Deschutes River basin that still sustain runs of wild spring chinook salmon, Oncorhynchus, tshawytscha. Historically, reservation streams supplied over 169 km of anadromous fish habitat. Because of changes in flows, there are now only 128 km of habitat that can be used on the reservation. In 1981, the CTWS began a long-range, 3-phase study of existing and potential fish resources on the reservation. The project, consistent with the Northwest Power Planning Council`s Fish and Wildlife Program, was designed to increase the natural production of anadromous salmonids on the reservation.

Electrofishing survey of the Great Miami River, September 1994 Annual Report

Abstract: Fish sampling by electroshocking in the Great Miami River upstream and downstream the Fernald site (September 25 and 26, 1994) was designed to determine changes in the health of the fish community compared to the previous ten years and to collect samples for uranium analyses in fish fillets. Samples of 853 fish, from 27 species, eight families and three sites at river mile (RM) 38, RM 24, and RM 19 provided seventy-eight samples for uranium analyses by an independent laboratory. The biomass of fish caught per hour was greatest at RM 24 > RM 19 > RM 3 8. The diversity index and the heaviest fish community was RM 24 > RM 38 > RM 19. The pooled site at RM 38 near Hamilton was diagnostically separated from the other sites by the young-of-the-year (YOY) golden redhorse, smallmouth bass and golden shiner. The darns at Hamilton acted as an effective barrier against fish migration upriver. Larger freshwater drum, gizzard shad, channel catfish and flathead catfish, which might be expected in rapid current reaches of mid-sized rivers characterize RM 24. The pool at RM 19 was distinguished from the others by YOY gizzard shad, bluegill, and longear sunfish. Thus the fish community in 1994 was separated ecologically by the physical features of the habitat more than by water quality differences between sites. These data suggest that the Fernald effluents in September were having no detectable effects on the distribution of fishes, independent of changes in habitat quality separated on physical attributes of the river channel at each site.