Esterase polymorphism in vitreous fluid of Pacific hake, Merluccius productus

Three regions of esterase activity designated I, II, and III were found on zymograms of vitreous fluids. Region I, the most anodal, exhibited two zones, one of which (the slower) was in all samples, occasionally accompanied by a second band which moved just ahead of it. Likewise, Region III, the most cathodal, exhibited two phenotypes, a common one-band and a rare two-band phenotype. Region II was occupied by one- and two-banded combinations of five different zones (a, b, c, d and e), which indicated that each band was the product of an allelic series of genes (EsII ^a, EsII ^b, etc.).
Only 11 of 15 expected phenotypes were encountered because of the rarity of alleles EsII ^a and EsII ^c. The most common allele, EsII ^b, had a frequency of 0.83 in Puget Sound hake and 0.60 in Pacific Ocean hake; this difference was highly significant. In the Pacific Ocean population agreement was good between observed and expected numbers, assuming Hardy-Weinberg equilibrium. In the Puget Sound samples deviations from expected frequencies did not appear in females or first-year fish, but deviations were significant in males 2 years and older; these deviations occurred as a marked deficiency of bd males combined with an excess of bb and dd males, particularly the latter. Inhibition tests indicated that these isozymes are B esterases. Estimations of molecular weight for the isozymes of Region II based on chromatographic and ultracentrifugation methods were 70,000 and 73,500, respectively.     

Interannual distribution of Pacific hake Merluccius productus larvae in the southern part of the California Current

The interannual distribution of early life stages of Pacific hake Merluccius productus , within the southern part of the California Current (32–23° N) from 1951 to 2001, was examined to describe the relationship between spawning habitat and environmental conditions. Mean annual abundance was affected by different factors along the west coast of the Baja California Peninsula. In the northern areas (Ensenada and Punta Baja), reduced abundance of larvae coincided with the El Niño and a North Pacific Ocean climatic regime shift, but in the southern areas (San Ignacio to Bahía Magdalena), the drastic reductions suggested a fishery effect for large adults of the coastal migratory population, starting in 1966. Two spawning stocks, coastal and dwarf, were evident in comparisons of latitudinal differences in occurrence of early stages and differences in temperature preferences that seemed to break at Punta Eugenia.     

Predation by a carnivorous marine copepod, Euchaeta elongata Esterly, on eggs and larvae of the Pacific hake, Merluccius productus

The predatory behavior of the carnivorous marine copepod, adultfemale Euchaeta elongata Esterly, feeding on eggs and larvaeof the Pacific hake, Merluccius productus, was examined in thelaboratory and in a natural setting. E. elongata did not feedon eggs. Predation on larvae is believed to depend on larvalswimming behavior: (1) predation rates were low on early stageyolk-sac larvae which are inactive swimmers and are relativelyundetected by the predator; (2) rates were high on middle stageyolk-sac larvae which are more active swimmers yet have a poorlydeveloped escape response; and (3) rates were low on largerlarvae which are able to escape the predator effectively. Starvedhake larvae were more vulnerable to predation due to a poorescape ability although they were less active and not easilydetected. The presence of naturally occurring alternative prey,Pseudocalanus sp., depressed the rate of E. elongata predationon hake larvae. In an analysis of field data, hake larvae andE. elongata were found to occupy the same depths in Dabob Bay.A high percentage of E. elongata collected had apparently beenfeeding on hake larvae, as indicated by the presence of pigmentsin their guts. Survival of hake larvae in late spring appearsto be relatively poor compared with early spring; poorer survivalin late spring may be due partly to an increase in the abundanceof invertebrate predators, such as E. elongata. ^*Current address: Northwest and Alaska Fisheries Center, 2725Montlake Blvd, Seattle, WA 98112, USA.     

Recent increase in Nybelinia surmenicola prevalence and intensity in Pacific hake (Merluccius productus) off the United States west coast

A larval marine cestode was found in 82.0% of 834 Pacific hake (Merluccius productus) stomachs collected from 341 trawl stations along the United States west coast during the summers of 2008 and 2009. Morphology and DNA sequencing was used to identify the cestode as Nybelinia surmenicola. In an examination of 131 Pacific hake stomachs collected from the same region in 1999, N. surmenicola prevalence was 35.1%. The results from a general linear model suggested that their prevalence is influenced by year and latitude, Pacific hake size, and sex. Mean intensity of N. surmenicola in 2008-2009 was 20.22 (±1.13 SE) and was positively related to Pacific hake length and the latitude of collection. Year-1 Pacific hake (<27 cm length) had significantly lower prevalence and intensity of N. surmenicola compared to older and larger fish. Pacific hake collected south of Point Conception, California (32.5 to 35°N) had lower prevalence and intensity of N. surmenicola compared to those collected in northern latitudes (35.1 to 48.4°N). Higher N. surmenicola prevalence in Pacific hake in recent years suggests food-web fluctuations in the northern California current ecosystem caused by changes in ocean transport of zooplankton or pelagic fish distributions and warrants future monitoring as a metric for ecosystem change.     

Population Genetic Structure of Pacific Herring Clupea pallasii in the Northwestern Pacific Ocean Based on Microsatellite Analysis

Journal of Ichthyology - The population genetic structure of Pacific herring Clupea pallasii in the northwestern Pacific Ocean is studied based on the polymorphism analysis of 11 microsatellite...     

Hake,Merluccius merluccius L., in the northeastern Mediterranean Sea: a case of disappearance

Hake was not an important commercial fish in the northeastern Levant until the 1990s when a sudden increase in landings was experienced. However, following a series of profitable years, landings declined sharply. The rapid development of the trawl fleet played a role in the decline; however such an episodic event cannot be explained within the fisheries context alone. In this study the results of sparse historical trawl surveys were evaluated together with oceanographic data, and the impact of hydrographical changes on the appearance/disappearance of hake in the Levant was considered. The formation and movement of different water masses in the area seem to have primary importance for the species. The winter occurrence of modified Atlantic water that temporarily intrudes in the region may favour hake. Parallel with the increase in hake, an increase in clupeid species not common in the area was also observed. The change in the hydrography of the region, which was probably linked to the cold period that prevailed at the same time, temporarily led to an additional late summer pulse in the production cycle. The consequent increase in clupeids along with the changes in the hydrology favoured the advent of clupeid‐eating hake in the NE Levant. The growth pattern result of the modal shift in monthly length‐frequency distributions also showed that the species underwent a rapid growth phase in winter, which was most likely associated with intense feeding.     

Population Structure and Stock Identification of Eulachon (Thaleichthys pacificus), an Anadromous Smelt, in the Pacific Northwest

The genetic structure of eulachon (Thaleichthys pacificus) populations was examined in an analysis of variation of 14 microsatellite loci representing approximately 1900 fish from 9 sites between the Columbia River and Cook Inlet, Alaska. Significant genetic differentiation occurred among the putative populations. The mean F_ST for all loci was 0.0046, and there was a significant correlation between population genetic differentiation (F_ST) and geographic distance. Simulated mixed-stock samples comprising populations from different regions suggested that variation at microsatellite loci provided reasonably accurate estimates of stock composition for potential fishery samples. Marine sampling indicated that immature eulachons from different rivers, during the 2 to 3 years of prespawning life in offshore marine waters, do not mix thoroughly. For eulachons captured incidentally in offshore trawl fisheries, there was a clear geographic cline in relative abundance of eulachons from different geographic areas. The sample from northern British Columbia was dominated by northern and central coastal populations of British Columbia, the sample from central British Columbia was composed of eulachons from all regions, and the sample from southern British Columbia was dominated by Columbia River and Fraser River populations. These results have implications for the management of trawl fisheries and conservation of spawning populations in some rivers where abundance is at historically low levels.     

Population Structure of Clinical and Environmental Vibrio parahaemolyticus from the Pacific Northwest Coast of the United States

Vibrio parahaemolyticus is a common marine bacterium and a leading cause of seafood-borne bacterial gastroenteritis worldwide. Although this bacterium has been the subject of much research, the population structure of cold-water populations remains largely undescribed. We present a broad phylogenetic analysis of clinical and environmental V. parahaemolyticus originating largely from the Pacific Northwest coast of the United States. Repetitive extragenic palindromic PCR (REP-PCR) separated 167 isolates into 39 groups and subsequent multilocus sequence typing (MLST) separated a subset of 77 isolates into 24 sequence types. The Pacific Northwest population exhibited a semi-clonal structure attributed to an environmental clade (ST3, N = 17 isolates) clonally related to the pandemic O3:K6 complex and a clinical clade (ST36, N = 20 isolates) genetically related to a regionally endemic O4:K12 complex. Further, the identification of at least five additional clinical sequence types (i.e., ST43, 50, 65, 135 and 417) demonstrates that V. parahaemolyticus gastroenteritis in the Pacific Northwest is polyphyletic in nature. Recombination was evident as a significant source of genetic diversity and in particular, the recA and dtdS alleles showed strong support for frequent recombination. Although pandemic-related illnesses were not documented during the study, the environmental occurrence of the pandemic clone may present a significant threat to human health and warrants continued monitoring. It is evident that V. parahaemolyticus population structure in the Pacific Northwest is semi-clonal and it would appear that multiple sequence types are contributing to the burden of disease in this region.     

Genetic Population Structure of Chum Salmon in the Pacific Rim Inferred from Mitochondrial DNA Sequence Variation

We examined the genetic population structure of chum salmon, Oncorhynchus keta, in the Pacific Rim using mitochondrial (mt) DNA analysis. Nucleotide sequence analysis of about 500 bp in the variable portion of the 5′ end of the mtDNA control region revealed 20 variable nucleotide sites, which defined 30 haplotypes of three genealogical clades (A, B, and C), in more than 2,100 individuals of 48 populations from Japan (16), Korea (1), Russia (10), and North America (21 from Alaska, British Columbia, and Washington). The observed haplotypes were mostly associated with geographic regions, in that clade A and C haplotypes characterized Asian populations and clade B haplotypes distinguished North American populations. The haplotype diversity was highest in the Japanese populations, suggesting a greater genetic variation in the populations of Japan than those of Russia and North America. The analysis of molecular variance and contingency χ² tests demonstrated strong structuring among the three geographic groups of populations and weak to moderate structuring within Japanese and North American populations. These results suggest that the observed geographic pattern might be influenced primarily by historic expansions or colonizations and secondarily by low or restricted gene flow between local groups within regions. In addition to the analysis of population structure, mtDNA data may be useful for constructing a baseline for stock identification of mixed populations of high seas chum salmon.     

Population Growth of Pratylenchus penetrans on Winter Cover Crops Grown in the Pacific Northwest

Population growth of Pratylenchus penetrans on 13 fall and winter cover crops was studied in the greenhouse and field. All crops except oat cv. Saia supported population growth of P. penetrans in greenhouse experiments, although the response of P. penetrans to oat cv. Saia varied considerably between experiments. The mean ratio of the final population density/initial population density (Pf/Pi) after 16 weeks for P. penetrans added to a greenhouse soil mix was 0.09, whereas Pf/Pi values after 10 weeks for two experiments with naturally infested soil were 0.95 and 2.3. Although P. penetrans increased on sudangrass cv. Trudan 8 and sudangrass × sorghum hybrid cv. SS 222, subsequent incorporation of sudangrass vegetation into soil reduced P. penetrans populations to preplant levels. Field experiments were inconclusive but suggested that oat cv. Saia or rye cv. Wheeler may be better choices for winter cover than weed-contaminated fallow or other crops on P. penetrans-infested sites in the Pacific Northwest.     

Population genetics of Howellia aquatilis (Campanulaceae) in disjunct locations throughout the Pacific Northwest

Howellia aquatilis A.Gray (water howellia) is a federally-listed threatened aquatic plant species with limited distribution in four states: California, Idaho, Montana, and Washington. Previous studies have shown a lack of genetic variation within the species; these studies, however, have excluded samples from one or more states. There have been no published studies on the population biology or genetics of the six known California populations or their evolutionary relationship to the other Pacific Northwest populations. We used Amplified Fragment Length Polymorphisms to identify genetic variation within and among the California populations, and to compare the California populations to the Idaho, Montana, and Washington populations. Analysis of molecular variance of 92 individuals from the six California populations show that 83.8% of genetic variation is found within populations and 16.2% among populations (P < 0.001). All sampled populations from all states provide 83.7% variation within and 16.3% variation among populations (P < 0.001). A UPGMA analysis confirms there is no clear clustering of Howellia aquatilis populations within California, that the Montana populations cluster within the California populations, and, although with limited population sample sizes, the Idaho and Washington populations are distantly related to all other populations. Waterfowl migration patterns support a hypothesis for avian dispersal as a primary factor in gene flow in Howellia aquatilis.     

Genetic Diversity of Clinical and Environmental Vibrio parahaemolyticus Strains from the Pacific Northwest

Since 1997, cases of Vibrio parahaemolyticus-related gastroenteritis from the consumption of raw oysters harvested in Washington State have been higher than historical levels. These cases have shown little or no correlation with concentrations of potentially pathogenic V. parahaemolyticus (positive for the thermostable direct hemolysin gene, tdh) in oysters, although significant concentrations of tdh⁺ V. parahaemolyticus strains were isolated from shellfish-growing areas in the Pacific Northwest (PNW). We compared clinical and environmental strains isolated from the PNW to those from other geographic regions within the United States and Asia for the presence of virulence-associated genes, including the thermostable direct hemolysin (tdh), the thermostable-related hemolysin (trh), urease (ureR), the pandemic group specific markers orf8 and toxRS, and genes encoding both type 3 secretion systems (T3SS1 and T3SS2). The majority of clinical strains from the PNW were positive for tdh, trh, and ureR genes, while a significant proportion of environmental isolates were tdh⁺ but trh negative. Hierarchical clustering grouped the majority of these clinical isolates into a cluster distinct from that including the pandemic strain RIMD2210633, clinical isolates from other geographical regions, and tdh⁺, trh-negative environmental isolates from the PNW. We detected T3SS2-related genes (T3SS2β) in environmental strains that were tdh and trh negative. The presence of significant concentrations of tdh⁺, trh-negative environmental strains in the PNW that have not been responsible for illness and T3SS2β in tdh- and trh-negative strains emphasizes the diversity in this species and the need to identify additional virulence markers for this bacterium to improve risk assessment tools for the detection of this pathogen.     

The Population Genetic Organization of Pacific Cod Gadus macrocephalus in the North Pacific Based on Microsatellite Analysis

Journal of Ichthyology - Six groups have been identified in the species' population structure based on the analysis of microsatellite markers' polymorphism in Pacific cod Gadus...     

我国盾叶薯蓣居群遗传结构分析

利用随机扩增多态DNA(RAPD)标记,分析研究了中国11个盾叶薯蓣居群82个个体的遗传多样性与遗传结构,15个寡聚核苷酸引物扩增共得到108条带,其中96条为多态带,占88．89％。Shannon多样性指数(I)为0．3093,居群水平的变异从0．1564到0．3098,物种水平的Nei基因多样度(h)为0．2499,居群水平的变化范围为0．1607到0．2137。遗传变异分析表明,物种水平的基因分化系数Gst为0．3415,居群间的基因流Nm为0．9641,居群间遗传交换小。分子方差分析(AMOVA)表明,居群内变异为68．96％,地区间变异为19．45％,居群问变异为11．58％。聚类结果以长江为界,将盾叶薯蓣分为南北两个大类群。研究结果对盾叶薯蓣种质的迁地保护有重要意义。     

Population Genetic Structure of Wild Boars in Poland

The analysis involved wild boars from the Lublin region, Warmia and Mazury, and Wielkopolska. The study material comprised muscle tissue samples collected from 100 wild boars. We analysed loci S0008, SW1129, SW986, SW1465, SW1492, SW1514, SW2532, SW461, SW841, SW2021, and SW2496 [1, 2]. The largest number of specific alleles, i.e. in six loci, was observed in wild boars from Warmia and Mazury; in turn, there were only two alleles in the group of wild boars from Lublin, and no alleles in individuals from Wielkopolska. The average value of the observed heterozygosity was H_o = 0.51, and the average value of expected heterozygosity was H_e = 0.63. PIC was another analysed indicator, with its lowest value determined for wild boars from the Wielkopolska region (0.53), and the highest value (0.62) was found for the animals from Warmia and Mazury. In the study population of wild boars, we also determined the F_ST index, which was 0.073, and N_m had a value greater than 3 (3.15); therefore, it can be concluded that the number of migrants per generation was 3. Both coefficients confirm the possibility of gene transfer and reproduction within and between the analysed populations of the wild boars. In our study, we observed a greater genetic distance between the wild boar populations from Wielkopolska and the Lublin and Warmia and Mazury regions in spite of the smaller geographical distance of these lands. This may be caused the less extensive network of ecological corridors as well as the occurrence of anthropogenic barriers e.g. large urban centres, an extensive network of roads, and the high volume of traffic in the direction of the capital.