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1.
Trevor B. Haynes Clifford K. L. Robinson Philip Dearden 《Environmental Biology of Fishes》2008,83(4):473-484
The Pacific sand lance (Ammodytes hexapterus) is an ecologically important prey species for many vertebrate marine predators in the Pacific Northwest. In this study,
we examined the use of intertidal habitat by young of the year (YOY) sand lance in Barkley Sound, British Columbia. We selected
14 of the original 29 independent environmental variables for modelling based on univariate analysis for variable selection.
These were then used to model sand lance presence-absence using a classification tree approach. Based on our models we found
that sand lance avoided mud and intertidal eelgrass. For sites that had very little mud and no intertidal eelgrass, sand lance
preferred sediment size mean ≥1,918 μm or sites with sediment size mean ≤1,918 μm but with relatively well sorted sediment
(sorting values ≤2.56 SDs, used as a heterogeneity index of the substrate grain size). Adjacent subtidal characteristics were
not found to be important at this scale of study. This suggests intertidal substrate characteristics and presence-absence
of intertidal eelgrass are the main influences on occurrence of YOY in the intertidal. Our results support the hypothesis
that sand lance are associated with particular sediment types, however intertidal sediment types used by sand lance in our
study differ from known preferences of sand lance for subtidal sediment types. This difference may be due to unique habitat
constraints for intertidal versus subtidal regions. Although it is unknown if the results of this study are widely applicable,
the results begin to identify intertidal habitat features that are important for Pacific sand lance. 相似文献
2.
Macrophyte beds have been shown to influence organic matter retention and nutrient processing in streams. Less is known about
the extent to which plant beds contribute to abundance, biomass, and diversity of macroinvertebrate assemblages in low-order
streams. We measured aquatic invertebrate abundance, biomass, and diversity associated with plant beds and sand/gravel patches
in a low-gradient second-order stream in the Central Sand Plains of Wisconsin, USA from March to October. Invertebrate abundance
and biomass were higher on average in plant beds (2,552 m−2 and 1,575 mg m−2) than in sand/gravel patches (893 m−2 and 486 mg m−2). Although sand/gravel habitat was over three times more abundant than plant beds in the study reach, plant beds and sand/gravel
patches contributed similarly to invertebrate abundance and biomass at the whole-reach scale. The abundance and biomass of
invertebrates associated with plant beds decreased from spring to autumn. Non-insect invertebrates in the plant beds increased
in relative abundance as the year progressed. Shannon–Weiner diversity and taxa richness of invertebrates were higher in the
plant beds than in the sand/gravel habitat. Our results suggest that plant beds can represent hot spots for invertebrate abundance
and production in low-gradient streams, and have implications for stream management and restoration in these types of ecosystems.
Handling editor: S. I. Dodson 相似文献
3.
The periodicity of otolith growth increments (opaque and translucent zones) from adult red snapper (Lutjanus campechanus) was examined through a mark and recapture study (2005–2010), and laboratory holding of hatchery reared red snapper over
a 2 year period (2002–2004). Wild red snapper (n = 295) were caught hook-and-line, marked with anchor tags, injected with oxytetracycline dihydrate (OTC), and released in
the Gulf of Mexico 15–40 km south of Dauphin Island, Alabama. Marked fish were recaptured up to 2.8 years after release (n = 35) and sagittal otoliths were dissected, sectioned and examined under white and blue-violet light. The number of opaque
growth zones past the OTC mark was compared to time at liberty for each fish and supported an annual periodicity of growth
increment formation. Also, most (87%) of the hatchery reared fish showed two opaque zones that supported an annual increment
formation rate. However, an unusual timing of opaque zone formation was shown for mark-recaptured fish. Based on known timing
of OTC marking, otoliths from mark-recapture fish showed opaque zone formation from late summer (August) to early winter (December).
This fall formation of opaque zones is in contrast to previous studies and its timing may relate to the end of spawning for
this species. 相似文献
4.
Eelgrass,Zostera marina,as essential fish habitat for young‐of‐the‐year winter flounder,Pseudopleuronectes americanus (Walbaum, 1792) in Maine estuaries
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M. A. Lazzari 《Zeitschrift fur angewandte Ichthyologie》2015,31(3):459-465
Distribution and density by habitat for age‐0, young‐of‐the‐year (YOY) winter flounder, Pseudopleuronectes americanus (Walbaum, 1792), were compared for two Maine estuaries to help define essential fish habitat for this life history stage. Two estuaries (Weskeag River and Penobscot Bay) along Mid‐coast Maine were sampled monthly with daytime 1.0 m2 fixed‐frame throw traps around neap low tide, May–December over two consecutive years (2003–2004). Both eelgrass and adjacent sand/mud (20–60 cm deep) were randomly sampled with equal effort (4–12 samples per month) at two sites in both the Weskeag River and Penobscot Bay. Significantly higher densities of YOY winter flounder (2–9 cm TL) occurred in eelgrass relative to sand/mud. Density increased significantly in both habitats in 2004, and was higher in Penobscot Bay relative to the Weskeag River. YOY densities compared by eelgrass coverage within throw traps were found to be significantly higher in eelgrass that exceeded 30% coverage when compared with adjacent sand/mud areas and eelgrass coverage of 10–20%. YOY occurred in all months sampled (May–December); no density differences existed by month. These results indicate that very shallow (<0.6 m) eelgrass habitat is of key importance to YOY winter flounder in Maine estuaries and should be viewed as essential fish habitat (EFH) for this species and life stage. 相似文献
5.
The swift fox Vulpes velox Say, 1823, a small canid native to shortgrass prairie ecosystems of North America, has been the subject of enhanced conservation
and research interest because of restricted distribution and low densities. Previous studies have described distributions
of the species in the southern Great Plains, but data on density are required to evaluate indices of relative abundance and
monitor population trends. We examined regressions of swift fox density (estimated by mark-recapture) on timed-track surveys,
scat surveys, and catch-per-unit effort indices. Seventy-nine swift foxes (42 male, 37 female) were captured 151 times during
10 240 trapnights between May 2003 and December 2004 in the Panhandle of Oklahoma, USA. Density estimates, based on mark-recapture
data from autumn 2004, were 0.08–0.44 foxes/km2. Survey indices explained 51 to 76% of the variation in estimates of fox density. Our study indicates that surveys of time-to-track
encounters and scat deposition rates show promise in monitoring trends in population abundance over large areas. 相似文献
6.
Aboulghasem Roohi Ahmet E. Kideys Ameneh Sajjadi Abdolla Hashemian Reza Pourgholam Hasan Fazli Ali Ganjian Khanari Elif Eker-Develi 《Biological invasions》2010,12(7):2343-2361
Monitoring for 6 years (2001–2006) showed that the population explosion of the alien ctenophore Mnemiopsis leidyi in the southern Caspian Sea coincided with a decline in the abundance and species number of mesozooplankton. While this decline
appeared to have reduced the nourishment of sprat (also known as kilka), it seemed to have affected phytoplankton favorably
mainly due to the decrease in grazing pressure. During 2001–2002, when M. leidyi abundance and biomass were at their highest levels, abundance of dinoflagellates and cyanophytes exceeded that of diatoms.
Before the invasion (1996) and in some years after the invasion (2003, 2004 and 2006) diatom abundance was higher than the
abundance of other groups. In September 2005, an unprecedented bloom of the toxic cyanophyte Nodularia sp. was observed in the southern Caspian Sea. Disappearance of edible zooplankton such as Eurytemora spp. was among the first changes observed after the expansion of M. leidyi in the area. Some changes in the macrobenthic fauna were also conspicuous after the increase of this ctenophore. While the
biomass of some deposit feeders, such as the polychaete Nereis diversicolor and oligochaete species increased, benthic crustaceans decreased sharply in abundance during 2001–2003 and completely disappeared
during 2004–2006. Iranian catches of kilka, the most abundant and widespread zooplanktivorous fish, decreased significantly
in the southern Caspian Sea after 1999. Iranian landings of kilka dropped ~70% from 69,070 ± 20,270 t during 1995–2000 to
23,430 ± 12,240 t during 2001–2006, resulting in a loss of at least 125 million US dollars to the economy. There were also
changes in the total catches of large predators such as the kutum and mullet, which mainly feed on kilka, between 1991 and
2006. 相似文献
7.
Quantitative data on the habitat characteristics of stream crayfish have been generally lacking and competing demands on water
resources has created a need to address this knowledge gap. We investigated day-time habitat relationships of stream crayfish
(Paranephrops planifrons White) from 793 quadrats at 30 rivers and streams in the North Island, New Zealand to develop models of koura presence–absence
and abundance. The model (stepwise GAM) included width, cover, median substrate size, edge location, velocity and depth, and
correctly predicted presence–absence of crayfish (8–39 mm OCL) at 73.4% of quadrats and of young-of-the-year (YOY) ≤8 mm OCL
at 83.4% of quadrats. Streams ranged from 1.6 to 11.5 m in width and the probability of finding both crayfish size classes
reduced sharply as streams became wider than 6 m and as the substrate became large (i.e., boulder > 256 mm). Crayfish, particularly
YOY, were most likely to be found in association with cover and at the stream edge. YOY were associated with shallow depths
and fine substrates, whereas larger crayfish showed a preference for cobble substrate. Undercut banks, leaf litter, tree roots,
and woody debris were strongly related to the presence–absence of crayfish. The model for crayfish abundance (log-linear Poisson
GAM) explained 50% of the variation between quadrats with cover, velocity, edge location, depth, and the overall crayfish
abundance at each particular stream being significant variables. Highest crayfish numbers were recorded in still or slow flowing
water, with the majority occurring where velocities were below 0.4 m/s. Water depths up to 0.7 m were sampled, but highest
numbers were found in depths of 0.2–0.3 m. Our presence–absence model determined variables that were significant over all
streams, whereas our abundance model determined variables that were significant within streams. Use of the GAMs models enabled
us to untangle the multiple factors contributing to habitat selection. Cover, velocity, and locations at the stream edge were
important determinants of both presence–absence and abundance. Generally, substrate was important when comparing between streams,
but not within streams, whereas depth was a significant determinant of abundance within streams, but not presence–absence
between streams.
Handling editor: K. Martens 相似文献
8.
In this laboratory study, we quantified substrate selection by small (<50 mm) and large (100–150 mm) ammocoetes of the least
brook lamprey (Lampetra aepyptera). In aquaria, ammocoetes were given a choice to burrow into six equally-available substrate types: small gravel (2.360–4.750 mm),
coarse sand (0.500–1.400 mm), fine sand (0.125–0.500 mm), organic substrate (approximately 70% decomposing leaves/stems and
organic sediment particles, and 30% silt and fine sand), an even mixture of silt, clay, and fine sand, and silt/clay (<0.063 mm).
Fine sand was selected with a significantly higher probability than any other substrate. Fine sand habitat is limited in many
streams, in part owing to geology, but also as a result of channelization and excessive silt/clay sedimentation, which is
a conservation concern. Our results indicate that ammocoetes of least brook lampreys are habitat specialists that prefer fine
sand habitat. Hence, availability of fine sand habitat may limit distributions and population sizes. 相似文献
9.
The interannual variability in peracarid (Crustacea: Malacostraca; Amphipoda, Isopoda, Cumacea, Tanaidacea) species composition
and diversity on the South Greenland shelf was studied at four stations over a sampling period of 3 years (2001, 2002 and
2004), using a Rauschert sled at depths of about 160 m. The South Greenland peracarids were relatively stable over the 3 years
with respect to evenness and diversity. Moderate changes in temperature and salinity had negligible effects on the species
composition, while sediment structure was found to be the most important environmental variable shaping the peracarid fauna. 相似文献
10.
Mitsuhiko Sano 《Ichthyological Research》1998,45(1):13-18
The temperate annual goby,Sagamia geneionema, showed pronounced spatial variation in recruitment among 8 isolated sand patches within a 1-ha area at Aburatsubo, Miura
Peninsula, central Japan. Investigations were conducted to determine if such among-patch variation stemmed from differences
in patch attributes, including patch size, sediment grain size, food availability, and densities of predators and heterospecific
residents. No relationship between recruit density and each of the 5 attributes measured was found, although among-patch variability
in patch attributes was apparent. This result suggests that recruitment was not influenced by patch characteristics. The mechanisms
that produce among-patch variation in recruitment may be explained in part, by the aggregating behavior of presettlement individuals
in the water column above the sand patches. 相似文献
11.
12.
Stephanie S. Bauerfeind Anett Theisen Klaus Fischer 《Journal of Insect Conservation》2009,13(3):271-277
While there is agreement that both habitat quality and habitat network characteristics (such as patch size and isolation)
contribute to the occupancy of patches by any given species, the relative importance of these factors is under debate. This
issue is of fundamental ecological importance, and moreover of special concern for conservation biologists aiming at preserving
endangered species. Against this background we investigated patch occupancy in the violet copper Lycaena helle, one of the rarest butterfly species in Central Europe, in the Westerwald area (Rhineland-Palatinate, Western Germany). Occupied
(n = 102) differed from vacant (n = 128) patches in altitude, size, connectivity, availability of wind shelter, in the abundance of the larval host-plant,
in the abundance of a grass species indicating favorable habitat conditions and in the abundance of nitrophilous plants. Overall,
patch occupancy was primarily determined by patch size, connectivity and the abundance of the larval host plant, while all
other parameters of habitat quality were of subordinate importance. Therefore, our findings suggest that even for extremely
sedentary species such as L. helle habitat networks are decisive and—next to the preservation of habitat quality—need to be an integral part of any conservation
management for this species. 相似文献
13.
Changes in dietary composition and its effects on the fatty acid (FA) composition of young-of-the-year (YOY) pumpkinseed (Lepomis gibbosus) from an artificial reservoir (Mirgenbach—northeastern France) were related to body size as shown by stomach content and
FA analyses. Comparisons were made between three size classes of fishes: 25–35 mm total length (TL), 35–45 mm TL and 45–55 mm
TL. Diets of the youngest L. gibbosus (TL ≤ 35 mm) consisted mainly of zooplanktonic microcrustaceans and Chironomidae. Ontogenetic development influenced the
FA composition of L. gibbosus. Older YOY L. gibbosus showed an increase in proportions of monounsaturated FA proportions and a decrease in polyunsaturated FA and mainly essential
FA (particularly docosahexaenoic acid). The low ω3/ω6 ratio and low PUFA content (mainly on DHA) suggested that L. gibbosus would not transfer the benefits of consuming ω3 PUFA up the food web. 相似文献
14.
Jennifer C. Selgrath Kevin A. Hovel 《Journal of experimental marine biology and ecology》2007,353(2):253-264
Habitat edges frequently possess distinct ecological conditions that affect interactions such as competition and predation. Within a species' preferred habitat, the structural complexity and resource availability of adjacent habitats may influence the effect of edges on ecological processes. In nearshore waters of New England, American lobsters (Homarus americanus) inhabit fragmented cobble reefs that often are bordered by unvegetated sediment and occasionally by seagrass. We determined whether proximity to cobble patch edges, microhabitat characteristics within cobble habitat, and the type of habitat adjacent to cobble patches (seagrass or unvegetated sediment) influence the density and survival of juvenile and adult American lobsters in Narragansett Bay, Rhode Island, USA. We surveyed naturally occurring cobble patches and artificial cobble reefs to determine how the odds of finding lobsters varied with distance from the edge and habitat type. Additionally, we tethered lobsters at different distances from the edge inside and outside of cobble patches to determine how lobster relative survival varied with edge proximity and habitat type. In cobble habitat, the odds of finding large lobsters (adolescents and adults > 40 mm carapace length (CL)) were highest near patch edges regardless of adjacent habitat type, whereas smaller lobsters (e.g. emergent juveniles 15-25 mm CL) were more abundant in patch interiors when seagrass bordered cobble patches. The odds of finding lobsters also increased with the relative amount of cobble cover within patches. In predation experiments, lobster relative survival after 6 h was lowest outside of cobble and increased toward cobble patch interiors, but after 24 h this trend disappeared or reversed. Seagrass appeared to offer greater refuge for lobsters than did unvegetated sediment. Our results suggest that proximity to patch edges influences lobster distribution and survival, and that edge effects on lobsters vary with life history phase and with the type of habitat adjacent to cobble patches. 相似文献
15.
A. Luísa Machado Yves Ferrand François Gossmann António M. Silveira David Gonçalves 《European Journal of Wildlife Research》2008,54(2):205-214
The Eurasian Woodcock Scolopax rusticola is a resident species in Azores, Madeira and Canaries (Macaronesian archipelagos) in contrast to its mainly migrant continental
populations. The biology and ecology of these insular populations are still poorly known; however, woodcocks are hunted in
Azores and Madeira. This work aims to continuing bridging the gap between scientific knowledge and game management of woodcocks
in Azores. Working at Pico Island, the main objectives were: (a) to characterize the roding activity of these insular populations,
(b) to select the best period of the breeding season to perform a roding survey and (c) to evaluate how sensitive is this
method to variations in abundance because of hunting. From January to July 2002, the number of contacts with roding birds
(males) was recorded, at dusk, at three observation points. Roding started in the beginning of February and lasted until late
June/early July. The weekly variation in the number of contacts was similar in all points, strongly suggesting that the roding
survey should be performed between the beginning of March and middle April. Two of the three observation points, located in
an area where woodcock hunting is allowed in alternate years, were surveyed between March 1 and April 15, 2001–2005. The two
points presented a similar annual variation pattern in the number of contacts, also suggesting stability in abundance. Sex
ratio among birds bagged during three consecutive hunting seasons (October–November, 2002–2004) or among birds collected periodically
during two winters (2000–2002) was equal to one, suggesting that annual fluctuations by the roding survey can be extended
to the female fraction. 相似文献
16.
Ingestion rates and selectivity of the Arctic pelagic amphipod Themisto libellula were studied experimentally in Kongsfjorden (Svalbard, 78°N) during the summer period. Feeding incubations were conducted
on naturally occurring copepod communities at different concentrations ranging from 25 to 250 preys L−1. The ingestion rates increased with food availability from 1.3 to 17.7 preys ind−1 day−1, which corresponded to 0.3–11% of body carbon day−1. Despite the high prey concentration used in the experiments the satiation level was not reached. We suggested that T. libellula is able to take the maximum benefit from dense patches of preys, which represent a good adaptation to the high variability
in food supply characteristic of polar environment. Copepodids stage III of Calanus spp. appeared to be the preferred preys of T. libellula. Smaller copepods such as Oithona similis and Pseudocalanus spp., were also selected but only when their relative abundance exceeded 25% of the total prey available. The potential predation
impact of T. libellula is discussed in relation to the mesozooplankton small-scale patchiness and predator abundance. 相似文献
17.
Fragmentation of natural vegetation creates one of the largest threats to plant–pollinator interactions. Although fragmentation impacts on plant populations have been explored in many, mainly herbaceous, species, the response of wild mass‐flowering species is poorly known. Here, we studied 28 heathland patches dominated by the mass‐flowering shrub Rhododendron ferrugineum, each presenting different R. ferrugineum floral display sizes (total inflorescence number per patch) and patch isolation (median distance to the three nearest patches). We assessed the impacts of these two factors on (i) heathland patch visitor assemblage (considering R. ferrugineum versus surrounding community) and (ii) R. ferrugineum flower visitation rate and pollen transfer limitation (comparing seed set from emasculated to pollen‐supplemented flowers). We found that diversity and abundance of bees visiting R. ferrugineum in heathland patches significantly decreased with decreasing R. ferrugineum floral display, while overall visitor density per patch and flower visitation rate increased. Moreover, a decrease in massive floral display and increase in patch isolation resulted in reduced visitor density in the surrounding community. Even in patches with few individuals, we found disproportionate visitor abundance in R. ferrugineum compared to the surrounding community. Finally, pollen transfer limitation in R. ferrugineum was neither affected by visitation rate nor by patch attributes. By disproportionally attracting pollinators from co‐flowering species, and probably promoting geitonogamous pollen transfer, the mass‐flowering trait appears adequate to compensate, in terms of conspecific pollen transfer, for the decrease in visitor diversity and abundance and in mate availability, which usually result from population fragmentation. 相似文献
18.
Namyi Chae 《Journal of Plant Biology》2011,54(2):101-111
The consequence of changing pattern of precipitation on soil CO2 emission is poorly understood in montane forest ecosystems under monsoon climate in Asia. In this paper, the results of 3-year
field measurements are reported on the annual soil respiration (R
s) from a temperate deciduous broad-leaved forest (Quercus serrata and Carpinus laxiflora) in Korea, and its interannual variations are examined associated with changing precipitation. Based on biweekly chamber
measurements from 2001 to 2004, the annual soil CO2 emission averaged to be 7.8 t C ha−1 with an annual variability of ∼20%. The soil temperature explained 22–97% of seasonal variations of R
s each year whereas the water-filled porosity (WFP) and precipitation pattern had a major effect on the observed interannual variation. The optimum values of WFP during the main growing season depended not only on the amount but also on the intensity and frequency of precipitation.
These results indicate that the changes in catchment hydrology can significantly alter the carbon sink/source strength of
forest ecosystems in monsoon Asia. 相似文献
19.
Adnan R. Al-Azri Sergey A. Piontkovski Khalid A. Al-Hashmi Joaquim I. Goes Helga R. do Gomes 《Aquatic Ecology》2010,44(2):449-461
We present data from a long time-series study to describe the factors that control phytoplankton population densities and
biomass in the coastal waters of Oman. Surface temperature, salinity, nutrients, dissolved oxygen, chlorophyll a (Chl a), and phytoplankton and zooplankton abundance of sea water were measured as far as possible from February 2004 through February
2006, at two stations along the southern coast of the Gulf of Oman. The highest concentrations of Chl a (3 mg m−3) were recorded during the southwest monsoon (SWM) when upwelling is active along the coast of Oman. However, results from
our study reveal that the timing and the amplitude of the seasonal peak of Chl a exhibited interannual variability, which might be attributed to interannual differences in the seasonal cycles of nutrients
caused either by coastal upwelling or by cyclonic eddy activity. Monthly variability of SST and concentrations of dissolved
nitrate, nitrite, phosphate, and silicate together explained about 90% of the seasonal changes of Chl a in the coastal ecosystem of the Gulf of Oman. Phytoplankton communities of the coastal waters of Oman were dominated by diatoms
for most part of the year, but for a short period in summer, dinoflagellates were dominant. 相似文献
20.
Stephen F. Matter 《Oecologia》1997,110(4):533-538
The relationship between population density and the size of host plant patches was investigated for the red milkweed beetle
Tetraopestetraophthalmus inhabiting unmanipulated patches of Asclepias syriaca. The resource concentration hypothesis proposes that density-area patterns, specifically that of increasing herbivore density
with patch size, are primarily a function of movement between host plant patches. This research investigated the degree to
which movement accounted for density-area patterns. Poisson regression analysis of beetle abundance versus milkweed patch
size revealed that beetle density tended to increase with patch size. The pattern of density and patch size resulted from
local reproduction and residence time. The density of emerging beetles tended to increase with patch size while emigration
rates were unrelated to patch size. Immigration rates were constant with patch size for male beetles, and decreased with patch
size for female beetles. Net flux of beetles (immigration – emigration) did not vary with patch size for male beetles and
decreased with patch size for female beetles. Comparisons are made between this system and previously studied systems where
movement plays a significant role in forming density area patterns. Additionally, several hypotheses are presented which may
account for greater in situ recruitment and residence time in large patches.
Received: 23 February 1996 / Accepted: 8 January 1997 相似文献