An examination of spatial and temporal genetic variation in walleye pollock (Theragra chalcogramma) using allozyme, mitochondrial DNA, and microsatellite data

We used allozyme, microsatellite, and mitochondrial DNA (mtDNA) data to test for spatial and interannual genetic diversity in wall-eye pollock (Theragra chalcogramma) from six spawning aggregations representing three geographic regions: Gulf of Alaska, eastern Bering Sea, and eastern Kamchatka. Interpopulation genetic diversity was evident primarily from the mtDNA and two allozyme loci (SOD-2*, MPI*). Permutation tests ˆindicated that FST values for most allozyme and microsatellite loci were not significantly greater than zero. The microsatellite results suggested that high locus polymorphism may not be a reliable indicator of power for detecting population differentiation in walleye pollock. The fact that mtDNA revealed population structure and most nuclear loci did not suggests that the effective size of most walleye pollock populations is large (genetic drift is weak) and migration is a relatively strong homogenizing force. The allozymes and mtDNA provided mostly concordant estimates of patterns of spatial genetic variation. These data showed significant genetic variation between North American and Asian populations. In addition, two spawning aggregations in the Gulf of Alaska, in Prince William Sound, and off Middleton Island, appeared genetically distinct from walleye pollock spawning in the Shelikof Strait and may merit management as a distinct stock. Finally, we found evidence of interannual genetic variation in two of three North American spawning aggregations, similar in magnitude to the spatial variation among North American walleye pol-lock. We suggest that interannual genetic variation in walleye pollock may be indicative of one or more of the following factors: highly variable reproductive success, adult philopatry, source-sink metapopulation structure, and intraannual variation (days) in spawning timing among genetically distinct but spatially identical spawning aggregates.

Characterization of genetic biodiversity of Nile perch, Lates niloticus, Tilapiines, Haplochromine flock and Ningu (Labeo victorianus) in the Victoria Lake Basin: an overview

Genetic biodiversity is the vaflatlOn among individuals within and between units of interbreeding individuals (populations) of a species. It includes inheritable and transmittable differences that occur between individuals andlor popuhitions of a given species through reproductive interaction. There exists enormous variability among individuals andlor populations of a species for most living organisms, and most of this variation is inheritable. differences among individuals arise through mutation and via recombination of genes during meiosis. These ifferences are then transmitted to successive generations through sexual reproduction and maintained in the populations through processes such as natural selection and genetic drift. Unfortunately much of this variation is normally threatened and often in danger of extinction because most focus in conservation of natural resources is put at saving species or habitats than varieties or strains of a species

Genetic viability of Nabugabo lakes (LVR satellite lakes) fish species

Natural populations of fish species in Lake Victoria Region (LVR) have under gone dramatic changes including severe reduction in sizes, division of original stocks into disjunct subunits, and segregation into several isolated population units either within a single water body or even worse into separate waters. In addition, these changes have been either preceded or precipitated by introductions of non-indigenous species that out competed the native forms and in case of closely related species genetically swamped them through hybridisation. The latter is especially the case in Nabugabo lakes. Such events lead to fragmentation of populations, which results in reduction in genetic diversity due to genetic drift, inbreeding and reduced or lack of gene flow among independent units. Such phenomena make the continued existence of fisheries stocks in the wild precarious, more so in the face of the competition from exotic species. Species introductions coupled with growing exploitation pressure of the fisheries of these lakes have put the native stocks at risk. Nabugabo lakes harbor cichlid species that are unique to these lakes more so species of the cichlid complex. In this paper the ecological status and genetic viability of key Nabugabo lakes fish species is examined and management options are discussed.

Population structure, long-term connectivity, and effective size of mutton snapper (Lutjanus analis) in the Caribbean Sea and Florida Keys

Genetic structure and average long-term connectivity and effective size of mutton snapper (Lutjanus analis) sampled from offshore localities in the U.S. Caribbean and the Florida Keys were assessed by using nuclear-encoded microsatellites and a fragment of mitochondrial DNA. No significant differences in allele, genotype (microsatellites), or haplotype (mtDNA) distributions were detected; tests of selective neutrality (mtDNA) were nonsignificant after Bonferroni correction. Heuristic estimates of average long-term rate of migration (proportion of migrant individuals/generation) between geographically adjacent localities varied from 0.0033 to 0.0054, indicating that local subpopulations could respond independently of environmental perturbations. Estimates of average longterm effective population sizes varied from 341 to 1066 and differed significantly among several of the localities. These results indicate that over time larval drift and interregional adult movement may not be sufficient to maintain population sustainability across the region and that there may be different demographic stocks at some of the localities studied. The estimate of long-term effective population size at the locality offshore of St. Croix was below the minimum threshold size considered necessary to maintain the equilibrium between the loss of adaptive genetic variance from genetic drift and its replacement by mutation. Genetic variability in mutton snapper likely is maintained at the intraregional level by aggregate spawning and random mating of local populations. This feature is perhaps ironic in that aggregate spawning also renders mutton snapper especially vulnerable to overexploitation.

A Drift Card Study in Monterey Bay, California, September 1971 to April 1973: Annual Report, Part 4, 1973

Drift cards were released in Monterey Bay, California, to detect seasonal variations in the California Current system, and seasonal and diurnal wind variations in the immediate vicinity of the bay. About 23% of the cards were recovered, although the recovery rate varied from about 5% in the winter to about 60% in the late summer. Drift card speeds ranged from 1 to 8 km/day, in the winter and summer months respectively. Good agreement was observed between geostrophic current, wind, drogue, and drift card data, although drift cards were observed to be primarily wind driven. A weekend bias in drift card recoveries was observed for the entire period of study; however, it was less pronounced for those cards released during the summer months. Two bogus releases were used to estimate the discovery lag time, reported position accuracy, and longshore drift currents. Diurnal winds were observed during a 24-hour study, and indicated daily variations in the wind field may be as important as seasonal changes in moving surface water. The drift card speed was observed to be about 3% of the wind velocity, and 1 m/sec was estimated as the minimum effective wind. The wind factor, ranging from 2.2% to 4.0%, was used to estimate the actual paths of drift cards and to examine the role of diurnal winds in affecting surface water movement. (PDF contains 79 pages)

Genetic and morphological identification of pelagic juvenile rockfish collected from the Gulf of Alaska

Pelagic juvenile rockfish (Sebastes spp.) collected in surveys designed to assess juvenile salmonids and other species in the Gulf of Alaska in 1998 and 2000–2003 provide an opportunity to document the occurrence of the pelagic juveniles of several species of rockfish. Often, species identification of rockfish is difficult or impossible at this stage of development (~20 to 60 mm), and few species indigenous to Alaska waters have been described. Use of mitochondrial DNA markers for rockfish species allowed unequivocal identification of ten species (S. aleutianus, S. alutus, S. borealis, S. entomelas, S. flavidus, S. melanops, S. pinniger, S. proriger, S. reedi, and S. ruberrimus) in subsamples from the collections. Other specimens were genetically assignable to groups of two or three species. Sebastes borealis, S. crameri, and S. reedi were identified using morphological data. Combining genetic and morphological data allowed successful resolution of the other species as S. emphaeus, probably S. ciliatus (although S. polyspinis cannot be totally ruled out), and S. polyspinis. Many specimens were initially morphologically indistinguishable from S. alutus, and several morphological groups included fish genetically identified as S. alutus. This paper details the characteristics of these pelagic juveniles to facilitate morphological identification of these species in future collections. (PDF file contains 32 pages.)

Genetic improvement and effective dissemination: keys to prosperous and sustainable aquaculture industries

There is an increasing demand for fish in the world due to a growing population, better economic situation in some sectors, and greater awareness of health issues in relation to food. Since capture fisheries have stagnated, fish farming has become a very fast growing food production system. In this presentation, the author gives an overview of the technologies that are available for genetic improvement of fish, and briefly discuss their merit in the context of a sustainable development. He also discusses the essential prerequisites for effective dissemination of improved stock to farmers. It is concluded that genetic improvement programs based on selective breeding can substantially contribute to sustainable fish production systems. Furthermore, if such genetic improvement programs are followed up with effective dissemination strategies, they can result in a positive impact on farmers' incomes.

Potential applications of reproductive and molecular genetic technologies in the selective breeding of aquaculture species

The use of reproductive and genetic technologies can increase the efficiency of selective breeding programs for aquaculture species. Four technologies are considered, namely: marker-assisted selection, DNA fingerprinting, in-vitro fertilization, and cryopreservation. Marker-assisted selection can result in greater genetic gain, particularly for traits difficult or expensive to measure, than conventional selection methods, but its application is currently limited by lack of high density linkage maps and by the high cost of genotyping. DNA fingerprinting is most useful for genetic tagging and parentage verification. Both in-vitro fertilization and cryopreservation techniques can increase the accuracy of selection while controlling accumulation of inbreeding in long-term selection programs. Currently, the cost associated with the utilization of reproductive and genetic techniques is possibly the most important factor limiting their use in genetic improvement programs for aquatic species.

Manual for starch gel electrophoresis: A method for the detection of genetic variation

The procedure to conduct horizontal starch gel electrophoresis on enzymes is described in detail. Areas covered are (I) collection and storage of specimens, (2) preparation of tissues, (3) preparation of a starch gel, (4) application of enzyme extracts to a gel, (5) setting up a gel for electrophoresis, (6) slicing a gel, and (7) staining a gel. Recipes are also included for 47 enzyme stains and 3 selected gel buffers. (PDF file contains 26 pages.)

Genetic improvement and utilisation of indigenous tilapia in southern Africa: final technical report, December 1st 1998 to June 31st, 2002

Mozambique tilapia (Oreochromis mossambicus) is an indigenous tilapia species in southern Africa, until now the majority of genetic research has been carried out on Asian species of tilapia but this project aims to look at this African species. Those most suited to further development in aquaculture in southern Africa have now been identified. The genetic characterisation of strains has been completed. This information has aided the choice of strains for use in small scale aquaculture and for genetically male tilapia (GMT) production. They will form the basis of future strategies for further genetic improvement, and management of genetic diversity of Mozambique tilapia. The information will also contribute towards responsible management and development of genetic resources, particularly with regard to indigenous species of tilapia. Good progress has been made with the adaptation and implementation of producing the supermale fish required to produce all male offspring, resulting in faster growing populations of tilapia. The presence of the project and its associated activity has been a catalyst for a surge in interest in tilapia culture throughout southern Africa. [PDF contains 183 pages]

Surface drift charts for the Eastern Tropical Pacific Ocean

ENGLISH: For the region of the Eastern Tropical Pacific Ocean between 0° and 300 N, and between 1200 W and the coastline of the Americas, charts of surface drift have been prepared for each month of the year. These should be of interest to both mariners and oceanographers. SPANISH: Cartas de la deriva de superficie para la región del Océano Pacífico Oriental Tropical, comprendida entre 0° y 30° N., Y 120° O. y la línea de la costa de las Américas fueron preparadas por cada mes del año. Estas pueden interesar tanto a los marinos como a los oceanógrafos. (PDF contains 23 pages.)

On drift and diel vertical migration of bottom invertebrates of the Amur. [Translation from: Zoologicheskie Zhurnal 42 1601-1612, 1963.]

Planktobenthos was sampled in 1957-58 in the river Amur. A determination of the kind of organisms drifting in the mass of water of the Amur was carried out. Of special interest for the authors was the activity of drifting of benthic larvae.

Comparative drift studies on streams in lower Austria (Flysch, gneiss and chalk formations) [Translation from: Schweizerische Zeitschrift fur Hydrobiologie 30 138-185, 1968.]

Seasonal changes and flooding have an extraordinarily great influence on the drift of organisms. The free water space plays the main part in the provision of food for some fish (Salmo trutta - trout): drift and content of the stomach are balanced here (Simuliidae): whereas others (Thymallus vulgaris) only selectively chose certain animals living at the bottom (molluscs). The total drift, drift of organisms and drift of organic material and minerals, plays a main role in the rate of production in streams. Besides the biology of the organisms living on the river bed, also the geological and hydrographical situation of the area plays a very important role for the composition of the drift. During the years 1964-1966 three streams in the characteristical geological formations flysch, gneiss and chalk of lower Austria were studied in regard to their drift. The Tulln (above St. Christopen), the Krems (above Senftenberg) and the Schwarza (above Hirschwang) seemed to be ideal for this comparative study because they are easy to reach. After summarising the hydrography and chemistry of examined rivers, the author examines the relationship between water level and total drift and the stratification of the total drift before analysing the drift of living organisms. Also considered are seasonal changes of drift of organisms and drift of exuviae.

Genetic engineering of microorganisms: free release into the environment

Genetic engineering now makes possible the insertion of DNA from many organisms into other prokaryotic, eukaryotic and viral hosts. This technology has been used to construct a variety of such genetically engineered microorganisms (GEMs). The possibility of accidental or deliberate release of GEMs into the natural environment has recently raised much public concern. The prospect of deliberate release of these microorganisms has prompted an increased need to understand the processes of survival, expression, transfer and rearrangement of recombinant DNA molecules in microbial communities. The methodology which is being developed to investigate these processes will greatly enhance our ability to study microbial population ecology.