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At least 703 records · Page 39Linked to original sources

Migration of Sakhalin taimen (Parahucho perryi): Evidence of freshwater resident life history types

Sakhalin taimen ( Parahucho perryi ) range from the Russian Far East mainland along the Sea of Japan coast, and Sakhalin, Kuril, and Hokkaido Islands and are considered to primarily be an anadromous species. We used otolith strontium-to-calcium ratios (Sr/Ca) to determine the chronology of migration between freshwater and saltwater and identify migratory contingents of taimen collected from the Koppi River, Russia. In addition, we examined taimen from the Sarufutsu River, Japan and Tumnin River, Russia that were captured in marine waters. Transects of otolith Sr/Ca for the Sarufutsu River fish were consistent with patterns observed in anadromous salmonids. Two fish from the Tumnin River appeared to be recent migrants to saltwater and one fish was characterized by an otolith Sr/Ca transect consistent with marine migration. Using these transects as benchmarks, all Koppi River taimen were classified as freshwater residents. These findings suggest more work is needed to assess life history variability among locations and the role of freshwater productivity in controlling migratory behavior in taimen.

Tumnin River, Koppi River, Sarufutsu River↗

Assessment of juvenile coho salmon movement and behavior in relation to rehabilitation efforts in the Trinity River, California, using PIT tags and radiotelemetry

Coho salmon ( Oncorhynchus kisutch ) of the Southern Oregon/Northern California Coast (SONCC) Evolutionarily Significant Unit (ESU) is federally listed as a threatened species. The Trinity River Restoration Program (TRRP) is rehabilitating the Trinity River to restore coho salmon (coho) and other salmonid populations. In order to evaluate the program’s actions, several studies of movements and behavior of coho in the Trinity River were conducted from 2006 to 2009, including snorkel surveys and mark-recapture techniques based on Passive Integrated Transponder (PIT) tags, elastomer tags, and radio transmitters. Catch, recapture, and condition of natural sub-yearlings, along with site fidelity and emigration of hatchery-reared yearlings in rehabilitated and reference habitats, were studied. Location was important because coho were absent from the lower controlled and rehabilitated sites most of the time. However, rehabilitation did not have a significant effect on natural coho salmon at the site level. Apparent survival of radio-tagged, hatchery-reared yearling coho released downstream from Lewiston Dam was much lower in the first 10 km downstream from the release site than in other areas between Lewiston Dam and the Klamath River estuary. Estimated survival of yearling hatchery coho salmon per 100 km down to Blake’s Riffle was estimated at 64 % over the distance of the 239 km study area. Migration primarily occurred at night in the upper Trinity River; however, as yearlings moved through the lower Trinity River towards the Klamath River, estuary nocturnal migration became less. Apparent survival was generally lowest in areas upstream from the North Fork of the Trinity River.

California↗

Feeding periodicity, diet composition, and food consumption of subyearling rainbow trout in winter

Although winter is a critically important period for stream salmonids, aspects of the ecology of several species are poorly understood. Consequently, we examined the diel feeding ecology of subyearling rainbow trout ( Oncorhynchus mykiss ) during winter in a central New York stream. Rainbow trout diet was significantly different during each 4-h interval and also differed from the drift and benthos. Feeding was significantly greater during darkness (i.e. 20:00 h – 04:00 h) than during daylight hours (i.e. 08:00 h – 16:00 h), peaking at 20:00 h. Daily food consumption (1.9 mg) and daily ration (3.4 %) during winter were substantially lower than previously reported for subyearling rainbow trout in the same stream during summer. These findings provide important new insights into the winter feeding ecology of juvenile rainbow trout in streams.

New York↗

Linked foraging and bioenergetics modeling may inform fish parasite infection dynamics

The parasitic copepod Salmincola californiensis infects Pacific salmon and trout ( Oncorhynchus spp.) and often reaches high prevalence and intensity in reservoirs compared to stream systems. Recent research indicates that temperature plays a fundamental role in copepod development and fish susceptibility. Here, we expand a linked foraging and bioenergetics model to simulate infection risk. Based on juvenile salmon vertical migration patterns, we add estimates of copepod generations produced and thermal strata metrics that appear associated with copepodid aggregations and increased infection. Severe damage on hosts may be caused by the infectious copepodid, a life-stage not readily visible and thus not detectable using traditional fish screenings. We discuss model limitations, opportunities for future research, and the potential for inclusion of copepod expansion equations to existing linked bioenergetics models or observed behaviors of salmonids in other lentic systems. We demonstrate that using a temperature sensitive model framework that includes copepod infection dynamics is useful in interpreting other lines of evidence, such as fish mortality estimates. Collectively, our work provides a testable framework for future comparisons of infection potential and demonstrates how bioenergetics models may be useful in understanding host–parasite interactions.

Environmental Biology of Fishes↗

Using parentage-based tagging to estimate survival of Chinook salmon fry in a large storage reservoir

Research efforts focusing on salmonid populations have highlighted the need to better understand demographic parameters for the fry and parr life stages. Monitoring these small fish presents a challenge because negative effects from handling and tagging can bias subsequent parameter estimates. Removal models and associated sampling designs represent one class of mark-recapture models with potential to be applied to very small juvenile salmon, yet existing methods associated with removal studies are not well-suited for all study environments. For example, populations residing in large storage reservoirs may yield low capture probabilities when subjected to removal sampling, making unbiased estimation of survival using traditional removal models difficult. To address this limitation, we developed a sampling design and associated model using parentage-based tagging in hatchery-raised juvenile Chinook salmon ( Oncorhynchus tshawytscha ) to estimate survival over a 2-year study period in a large storage reservoir in western Oregon, USA. Individual fish were identified to family groups, serving as replicate batch marks in a robust design removal model framework. Results from a simulation suggested that parameter estimates were unbiased even at very low capture probabilities, although the use of model constraints (i.e., covariates or constant parameter values) was necessary to achieve this. Model fitting to field data supported a trend in survival over time, with survival increasing with time since release in the first study year but decreasing in the second.

Environmental Biology of Fishes↗

An introduction to the practical and ethical perspectives on the need to advance and standardize the intracoelomic surgical implantation of electronic tags in fish

The intracoelomic surgical implantation of electronic tags (including radio and acoustic telemetry transmitters, passive integrated transponders and archival biologgers) is frequently used for conducting studies on fish. Electronic tagging studies provide information on the spatial ecology, behavior and survival of fish in marine and freshwater systems. However, any surgical procedure, particularly one where a laparotomy is performed and the coelomic cavity is opened, has the potential to alter the survival, behavior or condition of the animal which can impair welfare and introduce bias. Given that management, regulatory and conservation decisions are based on the assumption that fish implanted with electronic tags have similar fates and behavior relative to untagged conspecifics, it is critical to ensure that best surgical practices are being used. Also, the current lack of standardized surgical procedures and reporting of specific methodological details precludes cross-study and cross-year analyses which would further progress the field of fisheries science. This compilation of papers seeks to identify the best practices for the entire intracoelomic tagging procedure including pre- and post-operative care, anesthesia, wound closure, and use of antibiotics. Although there is a particular focus on salmonid smolts given the large body of literature available on that group, other life-stages and species of fish are discussed where there is sufficient knowledge. Additional papers explore the role of the veterinarian in fish surgeries, the need for minimal standards in the training of fish surgeons, providing a call for more complete and transparent procedures, and identifying trends in procedures and research needs. Collectively, this body of knowledge should help to improve data quality (including comparability and repeatability), enhance management and conservation strategies, and maintain the welfare status of tagged fish.

Reviews in Fish Biology and Fisheries↗

Histological assessment of organs in sexually mature and post-spawning steelhead trout and insights into iteroparity

Steelhead trout ( Oncorhynchus mykiss ) are anadromous and iteroparous, but repeat-spawning rates are generally low. Like other anadromous salmonids, steelhead trout fast during freshwater spawning migrations, but little is known about the changes that occur in vital organs and tissues. We hypothesized that fish capable of repeat-spawning would not undergo the same irreversible degeneration and cellular necrosis documented in semelparous salmon. Using Snake River steelhead trout as a model we used histological analysis to assess the cellular architecture in the pyloric stomach, ovary, liver, and spleen in sexually mature and kelt steelhead trout. We observed 38 % of emigrating kelts with food or fecal material in the gastrointestinal tract. Evidence of feeding was more likely in good condition kelts, and feeding was associated with a significant renewal of villi in the pyloric stomach. No vitellogenic oocytes were observed in sections of kelt ovaries, but perinucleolar and early/late stage cortical alveolus oocytes were present suggesting iteroparity was possible. We documented a negative correlation between the quantity of perinucleolar oocytes in ovarian tissues and fork length of kelts suggesting that larger steelhead trout may invest more into a single spawning event. Liver and spleen tissues of both mature and kelt steelhead trout had minimal cellular necroses. Our findings indicate that the physiological processes causing rapid senescence and death in semelparous salmon are not evident in steelhead trout, and recovery begins in fresh water. Future management efforts to increase iteroparity in steelhead trout and Atlantic salmon must consider the physiological processes that influence post-spawning recovery.

Reviews in Fish Biology and Fisheries↗

Developing acute-to-chronic toxicity ratios for lead, cadmium, and zinc using rainbow trout, a mayfly, and a midge

In order to estimate acute-to-chronic toxicity ratios (ACRs) relevant to a coldwater stream community, we exposed rainbow trout (Oncorhynchus mykiss) to cadmium (Cd), lead (Pb), and zinc (Zn) in 96-h acute and 60+ day early-life stage (ELS) exposures. We also tested the acute and sublethal responses of a mayfly (Baetis tricaudatus) and a midge (Chironomus dilutus, formerly C. tentans) with Pb. We examine the statistical interpretation of test endpoints and the acute-to-chronic ratio concept. Increasing the number of control replicates by 2 to 3x decreased the minimum detectable differences by almost half. Pb ACR estimates mostly increased with increasing acute resistance of the organisms (rainbow trout ACRs <??? mayfly < Chironomus). The choice of test endpoint and statistical analysis influenced ACR estimates by up to a factor of four. When calculated using the geometric means of the no- and lowest-observed effect concentrations, ACRs with rainbow trout and Cd were 0.6 and 0.95; Zn about 1.0; and for Pb 3.3 and 11. The comparable Pb ACRs for the mayfly and Chironomus were 5.2 and 51 respectively. Our rainbow trout ACRs with Pb were about 5-20x lower than earlier reports with salmonids. We suggest discounting previous ACR results that used larger and older fish in their acute tests. ?? 2007 GovernmentEmployee: U.S. Geological Survey.

Water, Air, & Soil Pollution↗

Survival, travel time, and use of migration routes by juvenile steelhead in a modified river estuary

Greater understanding of the survival, travel time, and spatial distribution of juvenile salmonids among migration routes between their natal streams and the ocean is critical to the recovery of these threatened species. In the Sacramento–San Joaquin River Delta (Delta), a highly modified estuary in central California, USA, there is a critical need to evaluate how water management (e.g., water pumping) and environmental factors (e.g., water flow) impact these populations. While management actions can affect some environmental variables in the Delta, only recently have studies begun to uncover associations between these variables and key demographic parameters. In this study, we examine the effects of freshwater flows, water exports, tidal environment, and a temporary barrier on juvenile steelhead ( Oncorhynchus mykiss ) survival, travel times, and migration routing using a multiyear acoustic telemetry dataset and recent advancements in Bayesian multistate mark-recapture modeling. We found that no single covariate explained variation in juvenile steelhead population dynamics across the entire Delta, but that separate regions within the Delta showed association with specific environmental factors.

California↗

A probe-based quantitative PCR assay for detecting Tetracapsuloides bryosalmonae in fish tissue and environmental DNA water samples

A probe-based quantitative real-time PCR assay was developed to detect Tetracapsuloides bryosalmonae , which causes proliferative kidney disease in salmonid fish, in kidney tissue and environmental DNA (eDNA) water samples. The limits of detection and quantification were 7 and 100 DNA copies for calibration standards and T. bryosalmonae was reliably detected down to 100 copies in tissue and eDNA samples. The assay presented here is a highly sensitive and quantitative tool for detecting T. bryosalmonae with potential applications for tissue diagnostics and environmental detection.

Conservation Genetics Resources↗

Egg-associated transmission of IPN virus of trouts

Infectious pancreatic necrosis virus (IPN) of salmonid fishes has been isolated and identified in suspect but normal-appearing stocks of adult brook trout ( Salvelinus fontinalis ), and thus a pattern for the epizootiology of the virus has been demonstrated. Virus titers as high as 10 6.5 ID 50 were found in egg fluids from 7 of 12 fish tested. In contrast, egg homogenates contained much less virus; their maximum titer was 10 1.8 ID 50 . The presence of virus within the eggs, however, was not established. Viral neutralizing ability of serum from the same fish showed an inverse relationship to the presence of virus in “ovarian fluid.” The highest serum titers occurred in those fish from which little or no virus had been isolated.

Virology↗

Acoustics as a tool for the assessment of Great Lakes forage fishes

Sharp reductions in forage fish populations in Lake Michigan have raised concerns about the continued ability of the forage stocks to support large populations of lake trout and other salmonid predators. There was a need for a more comprehensive and accurate estimate of forage fish abundance and distribution to evaluate these concerns. In response, cooperative diel surveys of the Lake Michigan forage species were conducted in late summer 1987 and spring 1989 with acoustics, midwater and bottom trawls.

Fisheries Research↗

An egg injection method for assessing early life stage mortality of polychlorinated dibenzo- p -dioxins, dibenzofurans, and biphenyls in rainbow trout, (Oncorhynchus mykiss)

To characterize the risk that polychlorinated dibenzo-p-dioxins (PCDDs), dibenzofurans (PCDFs), and biphenyls (PCBs) pose to salmonid early life stage survival, we developed a method to expose rainbow trout (Oncorhynchus mykiss) eggs to graded doses of PCDD, PCDF, and PCB congeners, using 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) as a prototype. Rainbow trout eggs were injected 24&ndash;50 h post-fertilization with 0.2 &mu;l of 50 mM phosphatidylcholine (PC) liposomes (control) or 0.2 &mu;l of 5&ndash;7 graded doses of TCDD incorporated into 50 mM PC liposomes. Injection volume never exceeded 0.6% egg volume. Immediately following injection, the injection site was sealed with Super glue&reg;, resulting in 92&ndash;97% of TCDD dose retained by the egg. Following both egg injection and waterborne egg exposure. TCDD toxicity in rainbow trout was manifested by half-hatching mortality but predominantly by sac fry mortality associated with hemorrhages, pericardial edema, and yolk sac edema. TCDD LD 50 s, following injection and waterborne exposure of rainbow trout eggs, were 421 (331&ndash;489) and 439 (346&ndash;519) pg TCDD/g egg (LD 50 , 95% fiducial limits), respectively. As in rainbow trout, TCDD toxicity in lake trout (Salvelinus namaycush) following the same two routes of exposure was manifested by half-hatching mortality but predominantly by sac fry mortality preceded by hemorrhages and yolk sac edema. LD 50 s, based on the dose of TCDD in lake trout eggs, were 47 (21&ndash;65) and 65 (60&ndash;71) pg/g following injection and waterborne exposure, respectively. The egg injection method is ideal for assessing the relationship between early life stage mortality in rainbow trout and graded egg doses of individual PCDD, PCDF, or PCB congeners.

Aquatic Toxicology↗

Digestibility and energy values of intact, disrupted and extracts from brewer's dried yeast fed to rainbow trout (Oncorhynchus mykiss)

Although fish meal has historically been used as the primary source of protein in fish feeds, brewer's dried yeast (BDY) is presently being investigated as a primary replacement for fish meal. As little is known about the ability of fish to utilize BDY, studies were conducted to study bioavailability of intact BDY as well as several fractions derived from the disrupted yeast to rainbow trout. Dried BDY was fed to rainbow trout and digestibility and energy values were determined. When the yeast cells were fully disrupted, the absorption of nitrogen increased by more than 20% and the metabolizable energy of the yeast by more than 10%. Energy and nitrogen digestibility were further increased after the removal of all wall material and separation of nitrogen into amino acid and nucleic acid fractions. Disruption of the cell wall significantly increased the nutritional value of BDY for salmonid fishes. The findings suggest that further research be conducted on the use and economy of BDY as a primary nitrogen source in fish feeds.

Animal Feed Science and Technology↗

Smolt physiology and endocrinology

Hormones play a critical role in maintaining body fluid balance in euryhaline fishes during changes in environmental salinity. The neuroendocrine axis senses osmotic and ionic changes, then signals and coordinates tissue-specific responses to regulate water and ion fluxes. Rapid-acting hormones, e.g. angiotensins, cope with immediate challenges by controlling drinking rate and the activity of ion transporters in the gill, gut, and kidney. Slow-acting hormones, e.g. prolactin and growth hormone/insulin-like growth factor-1, reorganize the body for long-term acclimation by altering the abundance of ion transporters and through cell proliferation and differentiation of ionocytes and other osmoregulatory cells. Euryhaline species exist in all groups of fish, including cyclostomes, and cartilaginous and teleost fishes. The diverse strategies for responding to changes in salinity have led to differential regulation and tissue-specific effects of hormones. Combining traditional physiological approaches with genomic, transcriptomic, and proteomic analyses will elucidate the patterns and diversity of the endocrine control of euryhalinity.

Book chapter↗

Hepeviruses of fish

Originally reported from California, the cutthroat trout virus (CTV) has now been isolated from eight species of salmonids in North America. Early work focused on the replication and physical characteristics of the small, round virus, but not until 20 years later was it determined to be most closely related to viruses causing hepatitis E in humans or infecting avian and mammalian hosts. The genome of CTV consists of 7269 nucleotides of positive-sense, single-stranded RNA with a genome organization similar to other members of the family Hepeviridae , although the amino acid sequence identity appears low enough to support creation of a novel genus. While CTV has not been associated with acute disease in fish, the virus was able to form persistently infected cell cultures that may aid research in treatment of hepatitis E-like viruses affecting humans or other animals. Interestingly, trout exposed to CTV were protected for about a month against subsequent exposure to Infectious hematopoietic necrosis virus . Replicating agents suspected to be CTV can be confirmed by polymerase chain reaction (PCR) and sequencing.

Book chapter↗

Hepeviruses of aquatic organisms

Originally reported in California, the cutthroat trout virus (CTV) has now been isolated from nine species of salmonids in North America. Early work focused on the replication and physical characteristics of the virus, but 20 years later was determined to be most closely related to the hepatitis E virus. The small genome is positive-sense, single-stranded RNA similar to other members of the family Hepeviridae , which now contains its own genus Piscihepevirus with two distinct genotypes, CTV-1 and CTV-2. While CTV has not been associated with acute disease in fish, the virus could form persistently infected cell cultures that may aid research in treating hepatitis E-like viruses affecting humans or other animals. Interestingly, trout exposed to CTV were protected for about a month against subsequent exposure to the infectious hematopoietic necrosis virus. Replicating agents suspected to be CTV can be confirmed by polymerase chain reaction (PCR), quantitative PCR, and sequencing. Other unclassified hepeviruses detected in fish using viral metagenomics include Wenling fish hepevirus, Wenling moray eel hepevirus, Murray–Darling carp hepevirus, and eastern mosquitofish hepevirus. The family Hepeviridae has been placed in the order Hepevirales together with the family Matonaviridae (rubella virus), with member viruses having amino acid homology in the helicase and replicase regions of the nonstructural proteins. In addition, using next-generation sequencing, a hepe-like sequence was characterized in diseased giant freshwater prawn Macrobrachium rosenbergii and named Crustacea hepe-like virus 1. Thus the family Hepeviridae continues to expand among aquatic animal hosts.

Book chapter↗

Na+/K+/2Cl- cotransporter and CFTR gill expression after seawater transfer in smolts (0+) of different Atlantic salmon (Salmo salar) families

Smoltification involves morphological and physiological changes in the gills that prepare anadromous salmonids to osmoregulate efficiently in seawater. In a previous study, we found that different families of Atlantic salmon (Salmo salar) smolts vary in their ability to osmoregulate when abruptly transferred to cold seawater and that these differences are correlated with gill Na+/K+ ATPase activity. Here we extend these findings to test whether other key transport proteins, namely Na+/K+/2Cl- contransporter (NKCC) and the Cl- channel or cystic fibrosis transmembrane conductance regulator (CFTR), play a significant role in osmoregulatory differences between families. To facilitate molecular analysis of NKCC, we first isolated a gill cDNA containing the complete coding region (1147 aa) of an isoform previously reported as a partial sequence. Phylogenetic analysis showed that this isoform is most closely related to isoforms of the NKCC1a subfamily found in European eel and Mozambique tilapia. In a second step, we quantified NKCC protein abundance as well as mRNA expression levels for NKCC1a and two CFTR isoforms (CFTRI and CFTRII) in 0+ smolts from three families prior to and following seawater transfer. The family with the lowest salinity tolerance also showed significant increases in gill NKCC1a mRNA after seawater transfer. Taken together with our previous study, these data indicate that family differences in expression of transport proteins are in part related to salinity tolerance, although the best indicator of osmoregulatory performance between families may be gill Na+/K+ ATPase activity and CFTR I mRNA levels, rather than Na+/K+ ATPase and NKCC1a mRNA levels or NKCC protein abundance. ?? 2007 Elsevier B.V. All rights reserved.

Aquaculture↗