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River Fishes (river + fish)
Selected AbstractsConservation and management implications of fine-scale genetic structure of Gulf sturgeon in the Pascagoula River, MississippiJOURNAL OF APPLIED ICHTHYOLOGY, Issue 4 2004M. A. Dugo Summary The anadromous Gulf sturgeon occurs along the north central coast of the Gulf of Mexico and is federally listed as threatened. We analyzed fine-scale patterns of Gulf sturgeon population structure, focusing on the Pascagoula River drainage of Mississippi, in reference to movement patterns as determined via telemetry and capture data. We genotyped 361 Gulf sturgeon using eight microsatellite loci including samples from the Pascagoula, Pearl, Escambia, Yellow, Choctawhatchee, and Apalachicola river drainages. Pairwise FST estimates indicated that genetic structure occurs at least at the drainage level. The Pascagoula and Pearl rivers form a western group, demonstrating 100% bootstrap support for a division with drainages to the east. Assignment tests detected non-natal genotypes occurring in all drainages. According to assignment tests, the Pascagoula supports an admixture of individuals, containing minimal influence from drainages to the east (2%) and substantial interaction with the Pearl River (14.1%). The occurrence of Pascagoula River fish in the Pearl was non-reciprocal, observed at 1.1%. After accounting for non-natal genetic diversity within the Pascagoula, there remained a disparity between a pooled Pascagoula group and the only documented spawning site within the drainage located in the Bouie River. We interpret this as an indication of a second genetic stock within the Pascagoula River drainage. Radio telemetry data suggest that spawning likely occurs in the Chickasawhay River, in areas isolated from the Bouie River spawning site by about 350 river kilometers. We emphasize the utility of integrating field and molecular approaches when delineating fine-scale patterns of population structure in anadromous fishes. [source] Sources of Phenotypic and Genetic Variation for Seawater Growth in Five North American Atlantic Salmon, Salmo salar, StocksJOURNAL OF THE WORLD AQUACULTURE SOCIETY, Issue 3 2010William R. Wolters In 2003, pedigreed families were obtained from two St. John's River sources, Penobscot River, Gaspè, and landlocked salmon stocks. Eyed eggs were disinfected upon arrival, and incubated in separate hatching jars. Fry were transferred prior to first feeding into individual 0.1-m3 tanks receiving 8 L/min of oxygen-saturated freshwater from a recirculating biological filtration system. At approximately 30 d after the initiation of feeding, fish densities were equalized to 250 fish/tank, fed 5% of the tank's total biomass in 3,4 daily feedings. When the fish were approximately 40 g, approximately 30 fish from each family were pit tagged and stocked communally into three replicated 10-m3 smolt tanks. Approximately 1 mo prior to stocking into sea cages for performance evaluations, evaluations of serum chloride levels and gill Na+, K+ -ATPase activity were measured on subsamples from all stocks in freshwater and following seawater challenge. Smolts were stocked into sea cages in June 2005, harvested in February 2007, and evaluated for carcass weight, sex, and stage of sexual maturity. Data were analyzed by the mixed model ANOVA to determine the random effects of sire and dam (sire), and the fixed effects of sex, salmon stock, ploidy level, and replicate smolt tank on carcass weight with smolt weight as a covariate. Sire and dam variance components were significantly different from zero, and the fixed effects of salmon stock, sex × stock interaction, and smolt weight at stocking were significant (P < 0.05). There were no significant differences among sexes, replicate smolt tank, or ploidy level for carcass weight. Overall, St. John's River fish had the fastest growth with a carcass weight >4.1 kg compared with the slowest growth in landlocked fish at 1.7 kg. Grilsing was also highest in St. John's River fish (ca. 4,6%) and lowest in Penobscot River fish (0%). The sire heritability for carcass weight calculated from the sire variance component using the mixed model ANOVA or MTDFREML was 0.26 ± 0.14. Data were used to calculate breeding values on captive sibling adult brood fish, and a line selected for carcass weight was spawned in the fall of 2007, and eggs from these fish were released to industry. [source] Long distance migration and marine habitation in the tropical Asian catfish, Pangasius krempfiJOURNAL OF FISH BIOLOGY, Issue 3 2007Z. Hogan A synthesis of catch data from southern Laos and life-history information indicate that adult Pangasius krempfi, an important Asian catfish, migrates up the Mekong River from the South China Sea in Vietnam past Cambodia, arriving in southern Laos each year in May. Strontium concentrations in the otoliths of river-caught P. krempfi are, on average, three to four times higher than the levels of strontium in the otoliths of related freshwater species, indicating marine and estuary habitation for fish caught in southern Laos. Pangasius krempfi muscle tissue samples from the same fish also exhibit stable isotope (,15N and ,13C) values characteristic of marine environments. The results of this investigation support the conclusion that P. krempfi is anadromous, spending a part of its life at sea and in the brackish water of the Mekong Delta before returning to spawn in fresh water. The fish travels at least 720 km to the Khone Falls in southern Laos, and possibly further. Spawning probably occurs in fresh water from June to August at which time young fish move down the Mekong River to the Mekong Delta. The data answer a previously unresolved question (the long-distance migratory behaviour of P. krempfi) and have important implications for the management and conservation of Mekong River fishes. [source] Long-term effective population size of three endangered Colorado River fishesANIMAL CONSERVATION, Issue 2 2002Daniel Garrigan The extant genetic variation of a population is the legacy of both long-term and recent population dynamics. Most practical methods for estimating effective population size are only able to detect recent effects on genetic variation and do not account for long-term fluctuations in species abundance. The utility of a maximum likelihood estimator of long-term effective population size based upon the coalescent theory of gene genealogies is examined for three endangered Colorado River fishes: humpback chub (Gila cypha), bonytail chub (Gila elegans) and razorback sucker (Xyrauchen texanus). Extant mitochondrial DNA (mtDNA) variation in humpback chub suggests this species has retained its historical equilibrium genetic variation despite recent declines in abundance. The mtDNA variation in razorback suckers indicates the population was quite large and expanding prior to recent declines and that rare alleles still survive in the remnant populations. The remaining mtDNA variation in bonytail chub indicates that dramatic, recent declines may have already obliterated a substantial portion of any historical variation. The results from long-term effective population size analyses are consistent with known natural history and illustrate the utility of the analysis for endangered species management. [source] Priority habitats for the conservation of large river fish in the Ganges river basinAQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS, Issue 4 2007Uttam Kumar Sarkar Abstract 1.Three classes of habitat used by groups of fish species classified as conservation and management priorities were developed for the Gerua River (also known as the Girwa River, Karnali River) in the Ganges river basin. This river is large (mean annual discharge ca 1500 m3 s,1, up to 900 m wide), surrounded by protected lands of India and Nepal, and upstream of major diversions and river alterations. 2.Fish and habitat sampling was conducted at 45 sites from 2000 to 2003. Data were analysed for 2172 fish of 14 species. Species and life stages found occupying a statistically distinct subset of the river habitats were grouped to identify classes of river habitat for conservation. 3.Most species and life-stage groups specialized on specific habitat conditions revealed by multivariate analyses of variance and a principal component analysis. The most numerous and diverse group (six species, 15 life stages) was associated with deep depositional habitats with sandy substrate. Two species covering three life stages were primarily oriented to erosional habitat marked by fast current velocity with pebble and cobble substrate. A third group of three species of adults and juveniles were intermediate in habitat use. 4.River conservation for fish faunas should maintain both erosional and depositional channel habitats with depths, substrates, and current velocity inclusive of the ranges reported. The erosional and depositional nature of the key habitats requires that rivers be maintained with flows capable of channel-forming functions. Copyright © 2006 John Wiley & Sons, Ltd. [source] | |||||||||||||