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1.
The Foveaux Strait oyster (Ostrea chilensis) fishery in southern New Zealand comprises many localised populations (oyster beds) that have survived disease mortality and 150 years of fishing. The reproductive biology of O. chilensis underlies the assumption that these populations are self-recruiting. A three-year study using passive, artificial collectors deployed in a gradient design around an isolated natal population investigated the hypothesis of self-recruitment. Spat settlement patterns measured the distributions of competent larvae as indicators of dispersal. This research also investigated the relationship between settler and brooder densities. Settler densities were not predicted by direction along or across the current, distance from the focal population, or by brooder densities. Settlement was widespread, and settlement patterns imply greater dispersal and larval mixing than previously reported. The swift currents and variable pelagic larval duration may enhance mixing and connectivity between populations. Demographically open recruitment should provide some resilience to disease mortality and fishing.  相似文献   

2.
Temporal patterns of larval brooding and settlement were investigated in a flat oyster (Ostrea chilensis) population in Tasman Bay, central New Zealand. The proportion of the population brooding larvae and larval settlement rates were monitored over 26 months. A peak period of brooding activity began in late spring and continued through summer. Maximum rates of 17% and 23% of adult oysters brooding larvae occurred in November and December, and an estimated 55–78% of adult oysters incubated larvae over the entire summer breeding period. These proportions of brooders are higher than those previously reported for Tasman Bay. A very low level of brooding activity (1%) occurred during winter. Temporal trends in larval settlement closely tracked brooding patterns. Settlement was greatest between November and January, and there were very low rates in winter. The seasonal breeding pattern in the population was intermediate between northern and southern populations, confirming a latitudinal gradient of reproductive behaviour for O. chilensis in New Zealand. Results are useful in optimising the timing of substrate deployment in an enhancement programme for the oyster fishery.  相似文献   

3.
Evidence suggests that patterns of benthic community structure are functionally linked to estuarine processes and physical characteristics of the benthos. To assess these linkages for coarse-sediment shorelines, we used a spatially nested sampling design to quantify patterns of distribution and abundance of both macroinfauna and macroepibiota. We examined replicate beach segments within a site (∼1 km), sites within areas of relatively uniform salinity and temperature (∼10 km), and areas (∼100 km) in the two major basins of Puget Sound, Washington. Because slight variations in physical characteristics of a beach can lead to significant alterations in biota, we minimized confounding physical influences by working only in the predominant shoreline habitat type in Puget Sound, a mixture of sand, pebbles and cobbles. Species richness decreased steadily from north to south along gradients of declining wave energy, increasing temperature and decreasing salinity. A few taxa were confined to the South Basin, but many more were found in the North. Most of the variability in population abundance was captured at the smaller spatial scales. Physical conditions tend to become increasingly different with distance among sites. Communities became more different from north to south as species intolerant of more estuarine conditions dropped out. There was significant spatial autocorrelation among populations on neighboring beach segments for 73 of the 172 species sampled. Populations of these benthic species may be connected via dispersal on scales of at least km in Puget Sound. Our results strengthen prior conclusions about the strong linkages between the biota and physical patterns and processes in estuaries. It is important for monitoring and impact-detection studies to account for natural variation of physical gradients across the sampling scales used. Nested, replicated sampling designs can facilitate the detection of environmental change at spatial scales ranging from global (e.g., warming or El Niño), to regional (e.g., estuary-wide changes in salinity patterns), to local (e.g., from development at a site).  相似文献   

4.
The genetic diversity and differentiation of four Zostera marina populations along the southern coast of Korea were estimated using random amplified polymorphic DNA (RAPD) markers to determine the effects of natural and anthropogenic stresses and reproductive strategy on within‐population genetic diversity. The mean number of alleles and gene diversities, indicating population genetic diversity, was highest in the Z. marina population that was exposed to repeated environmental disturbances, and lowest in the most undisturbed population. The higher genetic diversity in the disturbed population was associated with a higher contribution of sexual reproduction to population persistence. This suggests that both the level of disturbances and the reproductive strategy for population persistence contributed significantly to population genetic diversity at the study sites. According to the analysis of molecular variance (AMOVA), 76% genetic variation was attributable to differences among individuals within populations. The observed genetic differentiation (FST = 0.241) among Z. marina populations at the study sites appeared to result from reduced meadow size, increased genetic drift, and a high incidence of asexual reproduction. Increased population genetic diversity can enhance resistance and resilience to environmental disturbances; thus, this investigation of seagrass population genetics provides valuable new insights for the conservation, management, and restoration of seagrass habitats.  相似文献   

5.
In geographically extensive fish populations the potential exists for reproductive traits to vary over the population’s range but, the impact that such intrapopulation variability has on overall population reproductive potential has not been formally assessed. Here intrapopulation spatial variability in size at maturity and fecundity are demonstrated for Grand Bank American plaice (Hippoglossoides platessoides) and yellowtail flounder (Limanda ferruginea). Recognition of intrapopulation variability in these reproductive traits coupled with spatial variability in abundance resulted in an increase in estimated population total egg production (TEP) by as much as 1014 eggs for American plaice and 1015 eggs for yellowtail flounder as compared to assessment of TEP for the population as a whole. Results highlight the need to explore variability in life history traits not only between but, also within populations and emphasizes the need for sufficient spatial coverage during sampling in order to assess the reproductive potential of fish populations.  相似文献   

6.
Abstract. The population densities, spatial distributions, size frequencies, growth rates, longevity and reproductive activities of sub‐populations of the sea urchin Lytechinus variegatus were investigated over a two‐year period. Sea urchins were examined in three habitats in Saint Joseph Bay, Florida, which is within the northern limits of their distribution. Densities of sea urchins, which ranged as high as 35 individuals ·?2, fluctuated seasonally at all sites and were higher in seagrass beds comprised of Thalassia testudinum than Syringodium filiforme or on a sand flat. A cold front caused large‐scale, catastrophic mortality among adult, and especially juvenile, sea urchins in nearshore habitats of the Bay in the spring of 1993, leading to a dramatic decline in sea urchin densities at the Thalassia seagrass site. The population recovered over 6 months at this site and was attributable to immigration of new adults. Juvenile recruitment displayed both interannual and site‐specific variability, with recruitment being highest in seagrass habitats in fall and spring. The most pronounced recruitment event occurred in fall 1993 at the Thalassia site. Spatial distributions of adult individuals ascertained monthly never varied from random in the seagrass beds (T. testudinum and S. filiforme) or during spring, summer or fall months on the sand flat. Nonetheless, aggregations of adult sea urchins were observed on the sand flat in the winter months and were associated with patchy distributions of plant food resources. Juvenile sea urchins (< 25 mm test diameter) exhibited aggregations at all sites and 67 % of all juveniles under 10 mm test diameter (91 of 165 individuals observed) were found under the spine canopies of adults. Measurements of the inducibility of spawning indicated peak gametic maturity in all three sub‐populations in spring and summer. Gonad indices varied between habitats and years, but distinct maxima were detected, particularly in spring 1993 and late summer 1994. The mean gonad index of individuals at the Syringodium seagrass site was 2‐ to 4‐fold higher than the other sites in spring 1993 and gonad indices were much higher at all sites in spring of 1993 than 1994. Estimates of growth based on changes in size frequency cohorts coupled with measurements of growth bands on lantern demipyramids indicated that L. variegatus in three habitats of Saint Joseph Bay have similar growth rates and attain a mean test diameter of approximately 35 mm in one year. In contrast to populations within the central biogeographical range of the species, which may attain test diameters up to 90 mm, the largest individuals recorded in Saint Joseph Bay were 60 mm in test diameter, and almost all individuals were no more than 45 mm in test diameter or two years of age. The demographics of L. variegatus in the northern limits of their distribution appear to be strongly influenced by latitudinally driven, low‐temperature events and secondarily by local abiotic factors, especially springtime low salinities, which may negatively impact larval development and recruitment.  相似文献   

7.
Studies focusing on the effect of invasive species on the genetic diversity of native marine invertebrates remain scant. Here we report diversity among French populations of the intertidal gastropod Ocenebra erinacea (Linnaeus, 1758) sampled in the presence and absence of the invasive Ocenebra inornata (Recluz, 1851). Between 1999 and 2004, a total of 352 individuals of O. erinacea was collected from 15 sites (five of which had the invasive present) and was genotyped at the mitochondrial locus Cytochrome Oxidase 1 (cox1). No statistical difference was observed between polymorphism levels recorded within native populations exposed to the invasive, compared with populations sampled in the absence of O. inornata. No sign of native population decline was detected in response to the invader. While significant shifts in native O. erinacea population sizes have previously been reported in the literature, genetic effects may take longer to accumulate, or may be undetectable without a larger panel of genetic markers. By contrast, large genetic distances and significant population differentiation were recorded between Atlantic and Mediterranean O. erinacea samples, suggesting that these populations have distinct evolutionary histories. Comparison of genetic divergence within the closely related genus Nucella suggests that the Atlantic populations of O. erinacea and those from Thau Lagoon in the Mediterranean may belong to different species or subspecies.  相似文献   

8.
The reproductive biology and population dynamics of the cirolanid isopod Excirolana armata (Dana, 1853) were analysed through monthly samples from December 2003 to November 2005 on Una beach, São Paulo state (24° S), in Southeastern Brazil. Sampling was performed along three transects established from the base of foredunes to the waterline. On Una beach, E. armata showed continuous reproduction with higher abundances of ovigerous females in winter and spring (July–November) with a higher peak of juveniles in spring (November 2004). The fecundity ranged from 2 to 18 eggs/embryos per female, depending on the female length. The incubation period was estimated as 2 months. The life span of males and females was nearly 1 year. The short life span and the high energetic expenditure inherent to reproduction with maternal care, probably kept females from producing more than one brood in their lifetime. When comparing the population of E. armata on Una beach (24° S) with populations in Southern Brazil (32° S), Uruguay (34° S) and Argentina (36° S), it was verified that several biological population traits (length of the smallest juvenile, length of the largest individual, length of the smallest and largest ovigerous females, range of fecundity and life span) tended to increase at higher latitudes, whereas other traits (instantaneous rate of mortality and the curvature parameter of von Bertalanffy growth function) tended to decrease. However, comparing E. armata on Una beach (24° S) with a population situated at a close latitude (25° S), unexpected differences in relation to population structure and to growth demonstrated and reinforced the importance of density‐dependent factors over life history traits of E. armata on dissipative beaches.  相似文献   

9.
Polycyclic aromatic hydrocarbon (PAH) distributions and sources are characterized in 96 sediment samples from 24 210Pb-dated cores collected at locations in the greater Puget Sound. The highest PAH concentrations are found within a few kilometers of several sources including industrial facilities in northern Puget Sound, urban areas in central Puget Sound, and river systems draining coal-bearing strata. Regional patterns of combustion-derived PAH in surficial sediments indicate little atmospheric or waterborne exchange of PAH between different regions of the Sound. Significant subsurface maxima in combustion-derived PAH concentrations (210Pb dated at the 1950s) occur only in sediment cores collected near urban centers. Perylene apparently derives from erosion of a terrestrial source with little or no evidence of in situ production at depth in sediment cores. Coal fragments are carriers of a characteristic suite of alkylated phenanthrene, chrysene, and picene derivatives concentrated near river mouths in central and southern Puget Sound.  相似文献   

10.
Detailed comparisons of the larvae of four species of New Zealand oyster (Saccostrea glomer‐ata, Crassostrea gigas, Ostrea lutaria, and a new species of Ostrea) and one Chilean oyster (Ostrea chilensis) showed that larvae of species other than O. lutaria and O. chilensis share certain features. One conspicuous feature is a distinct tract, termed here the posterior dorsal sulcus, which runs from the posterior margin of prodissoconch I to the valve margin of prodissoconch II; other characteristic features are an umbonate, inequivalve shell and a provinculum bearing distinct teeth. The larvae of O. lutaria and O. chilensis, in contrast, lack the posterior dorsal sulcus, are nonumbonate, and have nearly equal valves with an edentulous provinculum. These distinctive features, together with other adult features, suggest that the two species are more appropriately included in a separate genus. The name Tiostrea is proposed for the new genus. Certain supraspecific groupings within the Ostreinae need to be re‐examined in the light of breeding experiments.  相似文献   

11.
Paphies donacina (Spengler, 1793) populations were surveyed at 11 low tide sites on surf beaches along Pegasus Bay, Canterbury, New Zealand, during summer 1998. Random sampling was not feasible. At the non‐random sites chosen the average number of tuatua per 5 m of shoreline ranged between 0.1 and 62. Total wet weight biomass m‐2 was highest at the southern sites in the Bay. There were site‐related differences in length frequency distributions of tuatua populations. Northern populations included a wide length range and southern populations were dominated by larger bivalves. Average shell length increased significantly with distance south, being close to 40 mm at Waikuku and 80 mm at Taylors Mistake. The shell length: width and weight relationships were similar for tuatua collected over the whole geographic range. Average dry weight condition index varied significantly between sites (ANOVA F= 23.3, d.f. = 10, 329) depending on the length distribution of the contributing population. Where populations included a wide length range the condition index was positively correlated with shell length but in populations dominated by larger bivalves there was either no relationship or a negative relationship with shell length. Juvenile tuatua were found at average densities between 81 and 1200 m‐2 at all sites except Taylors Mistake. The mean length of recruits ranged from 2.2 to 3.1 mm and shell length was independent of both juvenile and adult density. These results are discussed in relation to the environmental and other factors thought to influence population structure and recruitment of tuatua in Pegasus Bay.  相似文献   

12.
Distributions of five of the more toxic heavy metals have been assessed for Puget Sound sediments. Twenty-one Kasten cores were collected for the study. Analysis by Zeeman-corrected graphite-furnace atomic absorption spectroscopy has made possible the accurate and precise determination of silver and cadmium in Puget Sound sediment cores for the first time. Data show that Puget Sound is moderately impacted by anthropogenic Ag, Hg, Pb and Cu. No enrichment of Cd was found. The study also indicates that Puget Sound is quite well mixed with respect to the residence time of particle-bound metals. Toxic metal accumulation sites in the central Sound are determined almost exclusively by grain size, rather than proximity to sources. Estimates are made of trace metal fluxes to the sediments as a function of sediment type and areal distribution.  相似文献   

13.
The sea surface is an important habitat for the developmental stages (eggs and larvae) of many fish and invertebrates; it is also a concentration point for anthropogenic contaminants entering the sea. Studies were conducted to determine the extent to which the sea surface of Puget Sound was toxic to the early life history stages of fish. Three urban bays with suspected contamination, a rural reference bay, and a Central Sound site were compared. Surface-dwelling eggs and organisms (zooneuston) were collected with a surface-skimming neuston net and their densities enumerated. Sand sole (Psettichthys melanostictus) embryos were exposed in the field and laboratory to the sea-surface microlayer. To develop a useful year-round approach to monitoring sea-surface toxicity, larval development of anchovies, kelp bass, and sea urchins was also evaluated as an indication of sea-surface microlayer toxicity.During the spawning season (February and March), urban boys in Puget Sound had lower concentrations of sand sole eggs and neustonic organisms on the sea surface than did the rural bayor Central Sound reference sites. Compared to the reference sites, laboratory exposure to surface microlayer samples collected from urban bay sites generally resulted in more chromsomal aberrations in developing sole embryos, reduced hatching success of sole larvae, and reduced growth in trout cell cultures. In situ hatching success of sole eggs was reduced by half or more in urban bays compared to reference sites.Toxicity was associated with visible surface slicks and, in urban bays, increased with increasing surface pressure (dynes cm−1). Results to be reported separately (Part II) indicate that toxicity is strongly correlated with the presence of high concentrations of polycyclic aromatic hydrocarbons and metals in the sea-surface microlayer. The toxicity of SMIC samples was similar when evaluated by sole, anchovy, kelp bass, or sea urchin tests. A sea-surface monitoring program could use sea urchin embryos to evaluate site-specific sea-surface toxicity throughout the year.  相似文献   

14.
The effect of climate change on natural oyster recruitment has the potential to disrupt many of the ecosystem services oysters provide. Due to the temperature‐sensitivity of reproduction, oyster recruitment may shift as water temperatures rise. A biological imprint of climate change was revealed in a multi‐decadal time series of recruitment of non‐native Pacific oysters (Crassostrea gigas) in the main stem of Hood Canal, Washington, USA, extracted from historic fishery documents. Water in July and August warmed significantly from 1945 to 1995 (0.028 ± 0.004°C per year [±SE]) and accounted for an increase in Pacific oyster recruitment (7% per year, 0.028 ± 0.006 spat per year on log scale [±SE]); recruitment also strongly tracked inter‐annual variability in summer water temperature. Methods used to collect historical data were repeated in 2013–2015 when recruitment of both Pacific oysters and native Olympia oysters (Ostrea lurida) were recorded in main stem and lower Hood Canal. Both historic and modern data show large variation within and between years for temperature as well as recruitment. The modern data add information regarding spatial variation, in that recruitment patterns in the two regions of Hood Canal were decoupled. As temperatures continue to increase, non‐native Pacific oysters are likely to be favored over Olympia oysters, which recruit earlier at lower temperatures and presently contribute less than half of total oyster recruits. Future recruitment, however, may be limited by environmental factors other than temperature, a point indicated particularly in Hood Canal where many subtidal species already respond strongly to gradients in dissolved oxygen.  相似文献   

15.
In Arcachon Bay, a macrotidal coastal lagoon in southwest France, growth rates of cockles Cerastoderma edule (L.) differ greatly between locations. Sampling of populations at different tidal levels showed that the mean shell length was significantly and positively correlated with immersion time, whereas no correlation was found with population density and microphytobenthos biomass. Transplants of cockles between two intertidal sites were used to examine the relative importance of habitat and site of origin for growth rate and condition index. Artifacts due to manipulation were assessed, i.e. the impact of enclosures on growth, conditon index and mortality. During a 5-mo reciprocal transplant experiment, growth rates of the transplanted cockles and the cockles already present were similar, whereas the sites of origin did not affect growth rate. Condition index, however, displayed significant differences in relation to both transplant and origin sites. During a further 6-mo experiment in which cockles were transplanted from one site to four new sites, growth was mainly influenced by tidal level. These results indicate that net growth started when cockles were immersed 30% of the time. It is concluded that, on the scale of Arcachon Bay (156 km2), differences in growth and condition between cockle populations are largely phenotypic. Tidal level (i.e. food supply and emersion stress) accounts for most of these differences, but the existence of genetically or physiologically different populations cannot be excluded.  相似文献   

16.
The occurrence of the invasive nonindigenous copepod Oithona davisae Ferrari and Orsi, 1984, is reported for the first time in the Aegean Sea. The data we collected in August 2017 from 14 stations along the Turkish coast of the Aegean Sea reveal the spatial distribution of O. davisae between the openning of the Dardanelles Strait in the north and the Izmir Bay in the south. The O. davisae individuals, in seven mesozooplankton samples collected from a single station, were consistently found in the inner part of the Izmir Bay from April 2015‐October 2016. The abundance of female O. davisae ranged from 4 ind./m3 in April 2015 to 31,524 ind./m3 in July 2016 and contributed to the total oithonid female population by 10.8% in April 2015 and 92.8% in September 2016. Our results show that this species is well established in the inner part of Izmir Bay and that it has become a permanent component of the copepod community in the area.  相似文献   

17.
The plant reproductive effort, the seed germination rate and the seedling survival and development of Zostera marina (eelgrass) were assessed in four populations (Fuzeta, Culatra, Barrinha and Armona) at the species’ southern distribution limit in the Eastern Atlantic, the Ria Formosa lagoon. Germinated seeds were individually placed in Petri dishes with natural sandy sediments and kept in a culture chamber at the same temperature and salinity conditions as the natural environment. In addition, seeds from three different depths of Fuzeta population were cultivated in outdoor mesocosms. The populations of Fuzeta and Barrinha showed higher seed production and the seeds produced were heavier than the other populations. The germination of the seeds both in the laboratory and in the outdoor tanks began c. 8–12 weeks after the collection of the flowering shoots at a water temperature of 22 °C. The spontaneous germination in the laboratory (2.4–5.3%) and in the mesocosm experiment (5.6–8.9%) was low and from all the germinated seeds (n = 20) only three reached the seedling stage. The spontaneously germinated seeds from Fuzeta survived for a longer period than those from Barrinha, but only the germinated seeds of Barrinha reached the seedling stage (one‐leaf seedling stage). In outdoor tanks, higher seed germination and earlier seedling emergence (2 weeks after seeding) and survival (for 208 days) occurred for the seeds obtained from the shallow meadow. The reproductive effort of Z. marina populations of Ria Formosa showed that flowering shoots and seed traits are site‐specific. The low reproductive success indicated by the low germination and seedling survival suggests a bottleneck in the species’ reproductive cycle that may account for the scarce presence of the species in Ria Formosa lagoon. The high water temperatures of Ria Formosa in winter may partly explain this bottleneck. Increased temperatures due to climate change may reduce even further the sexual reproduction of Z. marina in its southern distributional limit in the Eastern Atlantic.  相似文献   

18.
采用线粒体Cytb基因测序技术研究了我国不同海域4个长蛸(Octopus variabilis)群体的种群遗传结构。结果表明,232bp的Cytb基因片段在4个群体90个个体中共检测到38个多态位点、12个单倍型,单倍型多样性指数H达0.854±0.015,核苷酸多样性指数Pi达0.059±0.005,平均核苷酸多样性指数K达13.526,显示出较高的遗传变异。种群遗传结构分析表明,4个群体间均存在极显著的遗传分化(P<0.01),除大连与青岛两群体间外,其它两两群体间的基因流均小于1。聚类分析表明,4个群体明显分化为三大类群,一个类群由大连和青岛群体组成,一个由温州群体组成,另一个由东山群体组成;遗传距离分析表明,东山类群与其它类群之间可能为亚种水平的分化,而其它类群之间仍为种内群体间分化。长蛸这种种群遗传结构形成原因可能与其较弱的种群扩散能力有关,另外冰川期地理历史因素及我国海域的洋流作用可能也参与了长蛸种群遗传结构的形成。  相似文献   

19.
As part of a multinational workshop on marine environmental quality, sediments were collected from seven sites in Vancouver Harbour and analyzed for polynuclear aromatic hydrocarbons (PAHs) and organochlorines (OCs), and for trace metals. English sole were collected from five sites, and muscle was analyzed for trace metals and liver for OCs. As expected, sediment PAH and OC concentrations and tissue OC concentrations were higher at sites east of the First Narrows, compared to the outer harbor and reference sites. Sediment PAH concentrations east of the First Narrows were similar to concentrations at moderately contaminated sites in Puget Sound, south of Vancouver Harbour. In contrast, concentrations of OCs in sediments and tissue were low to moderate, even at relatively contaminated sites within Vancouver Harbour. Although several trace metals in sediments were higher than in contaminated sediments from Puget Sound, trace metals measured in fish muscle were lower.  相似文献   

20.
The slipper limpet Bostrycapulus odites has recently been reported as an introduced species on the Spanish Mediterranean coast. Another species in the family Calyptraeidae, Crepidula fornicata, is a problematic invasive species in the Northeast Atlantic, which makes the closely related Bostrycapulus introduction a matter of concern. Information on the biology of B. odites in its natural environment can facilitate predictions on where the species could find favourable conditions for settlement and expansion. Size and sex were recorded for individuals in four populations over 2600 km of the Southwestern Atlantic shoreline, in Argentina and Brazil, covering the whole native latitudinal range of this widely distributed species. Animals were collected by hand in the intertidal or by SCUBA in subtidal locations; specimens were examined to determine shell length, sex, and the presence and number of brooded egg capsules in females. Mean shell length for the whole population did not differ significantly among populations. However, this species experiences sequential hermaphroditism (protandrism), and the size at sexual maturity (minimum male size) increased significantly with latitude. The fecundity of females at all sites increased with size, and the number of brooded egg capsules as well as the average size of capsules was larger in bigger individual females; however, mean fecundity varied among sites independent of mean female body size. This limpet species modifies its reproductive traits with local conditions, and sexual characters develop earlier in more temperate localities.  相似文献   

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