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Pacific Population (pacific + population)
Selected AbstractsInterannual variability in hatching period and early growth of juvenile walleye pollock, Theragra chalcogramma, in the Pacific coastal area of HokkaidoFISHERIES OCEANOGRAPHY, Issue 3 2007AKIRA NISHIMURA ABSTRACT Juvenile walleye pollock of the Japanese Pacific population were collected from the Funka Bay [spawning ground; 16,64 mm fork length (FL)] in spring and the Doto area (nursery ground; 70,146 mm FL) in summer. Hatch dates were estimated by subtracting the number of otolith daily increments from sampling dates, and their early growth was back-calculated using otolith radius,somatic length relationships. Interannual change of the hatching period was observed during 2000,02, and the peaks ranged from mid-February in 2000 to early-April in 2002. In 2000, when a strong year class occurred, early life history of the surviving juveniles could be characterized by early hatching and slower growth in the larval stage (<22 mm length). Higher growth rate in 2001 and 2002 did not always lead to good survival and recruitment success. Even though their growth was slow in 2000, the larvae hatched early in the season had larger body size on a given date than faster-growing larvae hatched in later season in 2001 and 2002. Bigger individuals at a certain moment may have advantage for survival. The delay of hatching period may result in higher size-selective mortality, and as a necessary consequence, back-calculated growth in 2001 and 2002 could shift towards higher growth rate, although abundance of such a year class would be at the lower level. Variability in spawning period, early growth and their interaction might have a strong relation to larval survival through cumulative predation pressure or ontogenetic changes in food availability. [source] Trophodynamic modeling of walleye pollock (Theragra chalcogramma) in the Doto area, northern Japan: model description and baseline simulationsFISHERIES OCEANOGRAPHY, Issue 2004ORIO YAMAMURA Abstract An age-structured trophodynamic model was constructed to quantitatively analyze factors affecting post-settlement mortality and growth of walleye pollock (Theragra chalcogramma) in the Doto area, the main nursery ground of the Japan Pacific population. The model included (i) multiple age classes of pollock, (ii) a generic predator, (iii) fisheries, and (iv) major prey of pollock. Major processes considered were (i) recruitment, (ii) bottom-up control of somatic growth, (iii) mortality because of predation, cannibalism and fishing, (iv) size-selective prey selection, (v) temperature-dependent bioenergetics such as conversion efficiency and daily consumption rate, and (vi) production and advective supply of prey. By assuming that pollock select prey based upon both relative abundance and predator,prey size relationships, the model accurately simulated seasonal and ontogenetic variations in the diet. However considering ontogenetic segregation, the model showed that, due to cannibalism, newly recruited fish would be totally consumed within 6 months after settlement. By considering segregation (10% overlap during spring and 0.1% during other seasons), an agreement of diet between the simulation and empirical data averaged 82.7% for the different seasons and fish sizes. Euphausiids, the most important prey of pollock, suffered the highest predation impact (22.2 ± 5.3 WWg m,2 yr,1) exceeding annual production in the model domain (17.2 ± 0.1 WWg m,2 yr,1), indicating that an advective supply of prey is necessary to support the pollock population. The daily ration of pollock during spring and summer averaged at 1.2 and 0.6% BW day,1 for small (,200 mm) and large (>200 mm) pollock, respectively; this daily ration was reduced by half during autumn and winter. [source] Sympatric spawning of Anguilla marmorata and Anguilla japonica in the western North Pacific OceanJOURNAL OF FISH BIOLOGY, Issue 9 2009M. Kuroki Extensive collections were made of the larvae of the temperate Japanese eel Anguilla japonica and the tropical giant mottled eel Anguilla marmorata in an overlapping area of the North Equatorial Current region of the western North Pacific Ocean. Collections of 189 A. marmorata and > 2500 A. japonica larvae during nine surveys from 1991 to 2007 showed that these two anguillid eels have similar spawning areas just west of the southern West Mariana Ridge. In July to August 2006 and August 2007, morphologically and genetically identified A. marmorata preleptocephali were mainly collected between 14·5,15° N and 142,142·5° E, where A. japonica preleptocephali were also caught in some of the same net tows. Fewer A. marmorata preleptocephali, however, were collected (n = 31) compared to those of A. japonica (n = c. 165), and fewer small larvae of A. marmorata were collected per tow than A. japonica (n = 1,10 and 1,294, respectively), suggesting relatively smaller spawning aggregations of A. marmorata. The distribution of preleptocephali and small larvae was wider in longitude in A. marmorata (131, 143° E) than in A. japonica (137,143° E), while the latitudinal range was almost the same (12,17° N). Although spawning by these two species overlaps both spatially and temporally, the tropical eels of the North Pacific population of A. marmorata probably have a much longer spawning season with fewer spawners, at least in summer, and recruit to a much wider latitudinal range of growth habitats. [source] Host adaptation of the fruit piercing moth, Eudocima fulloniaPHYSIOLOGICAL ENTOMOLOGY, Issue 4 2005G. V. P. Reddy Abstract., The fruit piercing moth, Eudocima fullonia (Clerck) (Lepidoptera: Noctuidae), whose larval host plants are vines of the family Menispermaceae in Asia, Africa and Australia, is thought to have adapted to Erythrina spp. in the Pacific and Papua New Guinea and has been designated as a separate biotype from the Australasian and African biotype. To test the hypothesis that the Pacific population of E. fullonia is a biotype, feeding trials with the host plants Tinospora homosepala Diels (Menispermaceae) and Erythrina variegata Linn. (Fabaceae) were conducted in Guam. The results indicate that the Guam population of E. fullonia is a biotype that has expanded its host range from its normal Menispermaceae plants to Erythrina species, possibly due to genetic changes and/or the presence of closely related alkaloids in both the species and paucity of menisperms. [source] Pacific Islands Families Study: behavioral problems among two-year-old Pacific children living in New ZealandTHE JOURNAL OF CHILD PSYCHOLOGY AND PSYCHIATRY AND ALLIED DISCIPLINES, Issue 5 2007Janis Paterson Background:, The aim of this study was to determine (1) the prevalence of behavioral problems among two-year-old Pacific children living in New Zealand, (2) ethnic differences in behavioral problems, and (3) relationships between maternal and socio-demographic variables and problem child behavior. Methods:, Data were gathered from the Pacific Islands Families (PIF) Study. Mothers of a cohort of 1398 Pacific infants born in Auckland, New Zealand during 2000 were interviewed when the children were two years of age. Maternal reports (1028) of child behavior were obtained using the Child Behavior Checklist (CBCL). Results:, In the PIF cohort, 15.6% of children were in the clinical range with one or more deviant scores from the seven syndrome scales, and 14% were in the borderline range. The prevalence rate of internalizing problems was 17.1% in the clinical range and 8.9% in the borderline range. The prevalence rate of externalizing problems was 6.6% in the clinical range and 13.7% in the borderline range. The prevalence rate of total problems was 14.2% in the clinical range and 9.6% in the borderline range. Discipline and maternal education were significantly associated with elevated externalizing scores. Household size, maternal education, cultural orientation, and number of years living in New Zealand were significantly associated with internalizing scores. Child ethnicity was significantly associated with internalizing, externalizing and total problem behavior scores. In the clinical range, child ethnicity and gender were significantly associated with the prevalence of problem behavior. Conclusions:, Cross-ethnicity differences in CBCL scores were found, which illustrates the diversity in the Pacific population in New Zealand. Such findings highlight the way in which preschool behavior problems may vary within specific cultural settings and underscore the need for in-depth research to explore these unique contexts. [source] Voice variance may signify ongoing divergence among black-legged kittiwake populationsBIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 2 2009HERVE MULARD Acoustic features are important for individual and species recognition. However, while dialectal variations in song characteristics have been described in many songbirds, geographical divergence in vocal features across populations has seldom been studied in birds that are not thought to have song-learning abilities. Here, we document marked differences in the vocal structure of calls of two populations of black-legged kittiwakes (Rissa tridactyla), a seabird whose call is considered as not being learned from other individuals. We found that calls vary both within and between populations. Within-population variation may convey individual identity, whereas the marked differences in frequency and temporal parameters observed between the two populations may reveal ongoing divergence among kittiwake populations. Moreover, we were unable to detect any sex signature in adult calls in a Pacific population (Middleton, Alaska), while these were detected in an Atlantic population (Hornøya, Norway), potentially affecting sexual behaviours. Despite the fact that these calls seemed to change over the reproductive season and across years, the individual signature remained fairly stable. Such vocal differences suggest that Pacific and Atlantic populations may be undergoing behavioural divergences that may reveal early stages of speciation, as is suggested by molecular data. © 2009 The Linnean Society of London, Biological Journal of the Linnean Society, 2009, 97, 289,297. [source] VICARIANCE AND DISPERSAL ACROSS BAJA CALIFORNIA IN DISJUNCT MARINE FISH POPULATIONSEVOLUTION, Issue 7 2003Giacomo Bernardi Abstract., Population disjunctions, as a first step toward complete allopatry, present an interesting situation to study incipient speciation. The geological formation of the Baja California Peninsula currently divides 19 species of fish into disjunct populations that are found on its Pacific Coast and in the northern part of the Gulf of California (also called the Sea of Cortez), but are absent from the Cape (Cabo San Lucas) region. We studied the genetic makeup of disjunct populations for 12 of these 19 fish species. Phylogeographic patterns for the 12 species can be separated into two major classes: a first group (eight species) showed reciprocal monophyly and high genetic divergence between disjunct populations. A second group (four species) displayed what appeared to be panmictic populations. Population structure between Pacific Coast populations, across the Punta Eugenia biogeographic boundary, was also evaluated. While dispersal potential (inferred by pelagic larval duration) was a poor predictor of population structure between Gulf of California and Pacific populations, we found that population genetic subdivision along the Pacific Coast at Punta Eugenia was always positively correlated with differentiation between Pacific and Gulf of California populations. Vicariant events, ongoing gene flow, and ecological characteristics played essential roles in shaping the population structures observed in this study. [source] Remarkably low mtDNA control-region diversity and shallow population structure in Pacific cod Gadus macrocephalusJOURNAL OF FISH BIOLOGY, Issue 5 2010M. Liu To investigate the genetic diversity and describe the population structure in Gadus macrocephalus, a 452 base pair (bp) fragment of the mitochondrial DNA control region was analysed in 259 individuals. The results showed remarkably low nucleotide diversity and a lack of genealogical structure. Small but significant genetic differentiations, however, were detected among north-western Pacific populations, but no large-scale regional differences were detected. These results indicate that populations of G. macrocephalus in the north-western Pacific are genetically subdivided and represent evolutionary lineages that should be managed individually. [source] Global population structure of the tope (Galeorhinus galeus) inferred by mitochondrial control region sequence dataMOLECULAR ECOLOGY, Issue 3 2009C. L. CHABOT Abstract In order to properly manage and conserve exploited shark species, detailed analyses of their population structure is needed. Global populations of Galeorhinus galeus are in decline due to the exploitation of the fishery over the past 80 years. Currently, the genetic structure of eastern Pacific populations of G. galeus is not known and recent observations in the northeastern Pacific suggest an increase in numbers. To evaluate gene flow among populations of G. galeus, 116 samples were collected and analysed from six geographically dispersed locations: Australia, North America, South Africa, South America (Argentina and Peru), and the UK. Analysis of 968 to 1006 bp of the 1068-bp mitochondrial control region revealed 38 unique haplotypes that were largely restricted to their collecting locality. Significant genetic structure was detected among populations (,ST = 0.84; P < 0.000001) and migration estimates were low (Nm = 0.05,0.97). Due to an apparent lack of migration, populations of G. galeus appear to be isolated from each other with little to no gene flow occurring among them. As a consequence of this isolation, increasing numbers of G. galeus in the northeastern Pacific can be best explained by local recruitment and not by input from geographically distant populations. [source] Genetic diversity enhanced by ancient introgression and secondary contact in East Pacific black mangrovesMOLECULAR ECOLOGY, Issue 11 2008ALEJANDRO NETTEL Abstract Regional distribution of genetic diversity in widespread species may be influenced by hybridization with locally restricted, closely related species. Previous studies have shown that Central American East Pacific populations of the wide-ranged Avicennia germinans, the black mangrove, harbour higher genetic diversity than the rest of its range. Genetic diversity in this region might be enhanced by introgression with the locally restricted Avicennia bicolor. We tested the hypotheses of ancient hybridization using phylogenetic analysis of the internal transcribed spacer region (ITS) of the nuclear ribosomal DNA and intergenic chloroplast DNA; we also tested for current hybridization by population level analysis of nuclear microsatellites. Our results unveiled ancient ITS introgression between a northern Pacific Central American A. germinans lineage and A. bicolor. However, microsatellite data revealed contemporary isolation between the two species. Polymorphic ITS sequences from Costa Rica and Panama are consistent with a zone of admixture between the introgressant ITS A. germinans lineage and a southern Central American lineage of A. germinans. Interspecific introgression influenced lineage diversity and divergence at the nuclear ribosomal DNA; intraspecific population differentiation and secondary contact are more likely to have enhanced regional genetic diversity in Pacific Central American populations of the widespread A. germinans. [source] Patterns of genetic variation do not correlate with geographical distance in the reef-building coral Pocillopora meandrina in the South PacificMOLECULAR ECOLOGY, Issue 7 2005H. MAGALON Abstract Dispersal may be a critical factor in the ability of reef-building corals to recover after major disturbances. We studied patterns of geographical structure using four microsatellite markers in seven South Pacific populations of Pocillopora meandrina, a major coral species from Polynesia. Variation within populations showed evidence of heterozygote deficiency. Genetic differentiation between populations was detected at a large scale (2000 km) between the Tonga and the Society Islands. Within the Society Islands, four of the five studied populations from Bora Bora, Moorea and Tahiti were not significantly different from each other. Unexpectedly, one of the three populations surveyed in Moorea was genetically different from the other two populations of this island (that were 5 and 10 km apart), and from the populations of the other two surveyed islands in this archipelago. We cannot rule out the possibility that this pattern is an equilibrium state, whereby short-range dispersal is locally more differentiating than long-range dispersal, as has been suggested by similar patterns reported in other studies. An alternative explanation that is globally consistent with all observations is that this is the signature of a large-scale destruction event, as for instance a bleaching event, followed by the recent restoration of populations by new colonists. [source] | |||||||||||||