Spatial pattern and patchiness during ontogeny: post-settled Gadus morhua from coastal Newfoundland     

Methven  David A.; Schneider  D. C.; Rose  George A. 《ICES Journal of Marine Science》2003,60(1):38-51

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Characteristics of Habitats Used by
Enteroctopus dofleini in Prince William Sound and Cook Inlet,Alaska     

David Scheel 《Marine Ecology》2002,23(3):185-206

Abstract. Habitat characteristics associated with the giant Pacific octopus, Enteroctopus dofleini (Wülker 1910), were studied in Prince William Sound and Port Graham, Alaska, from beach walk, SCUBA and submersible surveys at depths of 0 to 197 m. Octopus counts on beach walk transects were positively correlated with soft substrates (sand, gravel or broken rubble), the presence of boulders, and dense kelp cover immediately offshore of the transect; and negatively correlated with depth on SCUBA transects. No significant habitat correlations were found with counts on submersible transects. On beach walks, octopus counts were reduced on hard substrates to 38 % of the counts on soft substrates. Counts increased five‐fold in the presence of boulders over counts in their absence, and increased fifteen‐fold adjacent to dense (> 75 %) kelp cover over counts adjacent to sparse (< 25 %) kelp cover. On SCUBA transects, the average density at less than 5 m depth was over five times that below 5 m. No trends in octopus size or sex ratio were detected with depth. Den use was inversely correlated with depth although there was no indication that den availability declined with depth. Octopuses were found at densities from 0 to 2.5 per 1000 m². These densities were only 1 to 50 % of densities of the same species recorded in British Columbia in the late 1970s and early 1980s. Few data are available to test recruitment, mortality, and habitat selection hypotheses that would account for differences between habitats. However, the presence of the highest octopus densities in intertidal and very shallow subtidal areas indicates the likely importance of near‐shore, shallow‐water habitats, and highlights the vulnerability of octopus populations to changes in these habitats.  相似文献   

Experimental analysis of recruitment patterns of coral reef fishes in seagrass beds: Effects of substrate type, shape, and rigidity     

Yohei Nakamura  Hiroyuki Kawasaki  Mitsuhiko Sano 《Estuarine, Coastal and Shelf Science》2007,71(3-4):559-568

Habitat choice of reef fish larvae at settlement is one of the mechanisms proposed to explain spatial patterns in the distribution of fishes and the corresponding spatial structure of communities. Field experiments using Pomacentridae were conducted at Iriomote Island, southern Japan, in order to determine if rare recruitment of coral reef fishes in seagrass beds is due to larval settlement preference. When three types of natural patch treatments (branching coral patch, seagrass patch, and control without patches) were established in cleared seagrass squares in the center of a seagrass bed, four pomacentrid species, Amblyglyphidodon curacao, Dischistodus prosopotaenia, Cheiloprion labiatus, and Dascyllus aruanus, recruited exclusively onto the coral patches, indicating that larvae distributed in the seagrass bed may have preferred a coral rather than seagrass substrate as a settlement habitat. The effects of differences in physical shape (grid structure for branching coral vs. vertical structure for seagrass leaves) and rigidity (rigid substrate for coral vs. flexible substrate for seagrass) between coral and seagrass substrates on such recruitment patterns were investigated using artificial coral and seagrass units. When artificial habitat units with predator exclusion cages were established in the cleared seagrass squares as above, high densities of A. curacao and D. prosopotaenia recruits were observed on the rigid rather than flexible habitat units (both unit types having similar shape), whereas differences in recruit numbers of the two species were unclear in differently shaped units. These results demonstrated that even though pomacentrid larvae are distributed in the seagrass bed, they do not settle on the seagrass substrate owing to their habitat choice being partially based on a preference for substrate rigidity. Moreover, non-recruitment of C. labiatus and D. aruanus on artificial habitat units suggested that the presence of living coral substrates rather than physical shape/rigidity of substrates are an important cue for habitat choice of these fishes.  相似文献   

细基江蓠繁枝变种在浙江越冬的研究   总被引：1，自引：0，他引：1  

裴鲁青  骆其君 《海洋湖沼通报》1992,(4):63-69

应用从湛江引入,并在浙江自然越冬后生长正常的,以及从海口新引入的细基江蓠繁枝变种,作为实验材料进行越冬保种研究。本文首次报道了不同的种藻密度、培养液比重、水层、光强、底质及人为低温处理,对存活和生长的影响。结果表明:新引入的种藻具生长快、对环境的剧烈变化敏感;已越冬的种藻更能适应低温低比重的条件。以0.3m左右的水层,比重1.010,避免直射强光的低光照,能够安全保种越冬。低温干冻比水冻更易致死。可以经受7天的0℃低温。砂质的底质有利于越冬保种。在浙江普通的育苗室内就可以进行越冬,越冬后,死亡率低于0.07％/d。  相似文献   

Habitat Structure,Disturbance, and Equilibrium in Crustacean Communities*     

Geoffrey R. F. Hicks 《Marine Ecology》1982,3(1):41-51

Abstract. Using data from studies on alga-dwelling harpacticoid copepods from New Zealand and Britain and shallow water decapods from a variety of habitats in the Pacific and Caribbean, an analysis is made of the contribution of physical and biotic habitat structures to the generation and maintenance of crustacean species richness. The relation between the number of species and the complexity of the habitat is, in equilibrium communities, positive and essentially linear. Accordingly, Gray's (1979) and Stenseth's (1979) theoretical predictions are endorsed whereby species-abundance curves are, at equilibrium, expected to follow a log-normal distribution, whereas departures from the log-normal are anticipated in disturbed environments. Such departures reflect either increased dominance or inequalities in the species-abundance hierarchy. Because of their adaptable life-history traits, certain opportunist species are identified as those contributing most to departure points. The impact on community equilibrium of natural disturbance processes such as turbidity, exposure, and substratum transience is assessed.  相似文献   

The Fish Assemblage of a Newfoundland Estuary: Diel, Monthly and Annual Variation     

D. A. Methven  R. L. Haedrich  G. A. Rose 《Estuarine, Coastal and Shelf Science》2001,52(6):669

Twice monthly sampling over two 16 month periods at a shallow site on Newfoundland's east coast showed the fish assemblage to be dominated by four taxa (Gasterosteus aculeatus, G. wheatlandi, Osmerus mordax, Gadus spp.) that accounted for 96% of the individuals collected. Of the 16 479 fish measured, 65% were adults based on the estimated size of first spawning. The fish assemblage was dominated (86%) by species with demersal eggs, several of which spawn at the same shallow sites used by juveniles as nursery sites. Coastal spawning and demersal eggs maintain offspring in coastal nursery areas where survival is thought to be increased. Number of species and number of fish were both correlated with water temperature being highest from mid-summer to early autumn and lowest in winter. Temperature, time of spawning, and movements of juveniles and adults facilitated grouping species into five assemblages based on seasonal abundance: seasonal periodic species (summer and winter), regular species, regular species collected in all seasons except winter, and occasional (rare) species. At the diel scale, two consistent species groupings were observed: species that showed no significant difference between day and night and species caught primarily at night. Number of night species exceeded day species by a factor of two. No seine-caught species in shallow water exhibited significantly higher catches during the day. Observations by SCUBA divers indicated some species were more abundant during day time at slightly deeper depths. This observation in conjunction with day and night seining in shallower water, suggests these species aggregate in deeper water during day and move to shallow waters at night.  相似文献   

Effect of placer mining on suspended sediment in reaches of sensitive fish habitat     

S. B. Pentz  R. A. Kostaschuk 《Environmental Geology》1999,37(1-2):78-89

 The McQuesten River system in central Yukon Territory, Canada, contains placer mines and reaches of sensitive fish habitat. Suspended sediment is supplied to the system by erosion of previously mined disturbed areas, bank erosion, resuspension of placer sediment deposited on bars, and active placer-mine discharges. Direct discharge from active placer mines did not have a large impact on suspended sediment in reaches of sensitive fish habitat in 1994–1995, although only two mines were active and concentrations did periodically exceed water quality objectives. Erosion of previously mined disturbed areas had a pronounced effect on suspended sediment during spring snowmelt and summer rainstorms in 1994–1995. Deposits in previously mined areas should be stabilized to reduce erosion and its downstream impact on fish habitat. Received: 10 November 1997 · Accepted: 30 March 1998  相似文献   

The interplay of sediment characteristics,depth, water temperature,and ocean currents shaping the biogeography of lancelets (Subphylum Cephalochordata) in the NW Pacific waters          下载免费PDF全文

Hsiu‐Chin Lin  Jen‐Ping Chen  Benny K K Chan  Kwang‐Tsao Shao 《Marine Ecology》2015,36(3):780-793

Lancelets (or amphioxus) are often found within the soft bottom of shallow tropical and temperate seas. The present study is the first to provide a fine‐scale biogeography of five species of lancelets (Asymmetron lucayanum, Branchiostoma belcheri, Branchiostoma japonicum, Epigonichthys cultellus, and Epigonichthys maldivensis) in the NW Pacific and examine the effects of multiple environmental parameters. From multivariate analyses, the distribution and abundance patterns of lancelets were explained by a combination of factors comprising depth, temperature of the collecting month, mean temperature of the coldest month in the year, medium particle size and silt/clay ratio of the sediments. In addition, ocean currents also affect their distribution range. The major occurrence of A. lucayanum and E. maldivensis was associated with the warm Kuroshio current, but E. maldivensis exhibited higher tolerance to low salinity and low temperature, and preferred substrata of slightly larger grain size, a lower ratio of suspended sediments, and deeper water. The closely related B. belcheri and B. japonicum exhibited fine‐scale habitat differentiation, and B. japonicum was abundant along the southern coast of China, where the salinity is lower in winter because of the China Coastal Current and the substratum is composed of very coarse sand with suspended sediments. Branchiostoma belcheri occurred in low abundance and was only recorded in Northern Taiwan and the Taiwan Banks. Epigonichthys cultellus was found only at the Taiwan Banks, which had deep water, coarse sand, and a negligible amount of suspended sediments.  相似文献   

Detecting subpixel deciduous components to complement traditional land cover classifications in Southwest Finland     

《International Journal of Applied Earth Observation and Geoinformation》2015

To ensure successful conservation of ecological and cultural landscape values, detailed and up-to-date spatial information of existing habitat patterns is essential. However, traditional satellite-based and raster classifications rely on pixels that are assigned to a single category and often generalized. For many fragmented key habitats, such a strategy is too coarse and complementary data is needed. In this paper, we aim at detecting pixel-wise fractional coverage of broadleaved woodland and grassland components in a hemiboreal landscape. This approach targets ecologically relevant deciduous fractions and complements traditional crisp land cover classifications. We modeled fractional components using a k-NN approach, which was based on multispectral satellite data, assisted by a digital elevation model and a contemporary map database. The modeled components were then analyzed based on landscape structure indicators, and evaluated in conjunction with CORINE classification. The results indicate that both broadleaved forest and grassland components are widely distributed in the study area, principally organized as transition zones and small patches. Landscape structure indicators show a substantial variation based on the fractional threshold, pinpointing their dependency on the classification scheme and grain. The modeled components, on the other hand, suggest high internal variation for most CORINE classes, indicating their heterogeneous appearance and showing that the presence of deciduous components in the landscape are not properly captured in a coarse land cover classification. To gain a realistic perception of the landscape, and use this information for the needs of spatial planning, both fractional results and existing land cover classifications are needed. This is because they mutually contribute to an improved understanding of habitat patterns and structures, and should be used to complement each other.  相似文献   

The influence of relative sediment supply on riverine habitat heterogeneity   总被引：1，自引：0，他引：1  

Sarah M. Yarnell  Jeffrey F. Mount  Eric W. Larsen 《Geomorphology》2006,80(3-4):310-324

The diversity of aquatic habitats in streams is linked to physical processes that act at various spatial and temporal scales. Two components of many that contribute to creating habitat heterogeneity in streams are the interaction between sediment supply and transport capacity and the presence of local in-stream structures, such as large woody debris and boulders. Data from previously published flume and field studies and a new field study on tributaries to the South Yuba River in Nevada County, California, USA, were used to evaluate the relationship between habitat heterogeneity, local in-stream structural features and relative sediment supply. Habitat heterogeneity was quantified using spatial heterogeneity measures from the field of landscape ecology. Relative sediment supply, as expressed by the sediment supply/transport capacity ratio, which controls channel morphology and substrate textures, two key physical habitat characteristics, was quantified using a dimensionless bedload transport ratio, q. Calculated q values were plotted against an ecologically meaningful heterogeneity index, Shannon's Diversity Index, measured for each study reach, as well as the percent area of in-stream structural elements. The results indicate two potential mechanisms for how relative sediment supply may drive geomorphic diversity in natural river systems at the reach scale. When less mobile structural elements form a small proportion of the reach landscape, the supply/capacity ratio dictates the range of sediment textures and geomorphic features observed within the reach. In these settings, channels with a moderate relative sediment supply exhibit the highest textural and geomorphic diversity. In contrast, when less mobile structural elements are abundant, forced local scour and deposition creates high habitat heterogeneity, even in the presence of high relative sediment supply.  相似文献