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1.
Fish larvae assemblages in the Gulf of California 总被引:1,自引:0,他引:1
G. AcevesMedina† S. P. A. JiménezRosenberg A. HinojosaMedina R. FunesRodríguez R. J. SaldiernaMartínez P. E. Smith‡ 《Journal of fish biology》2004,65(3):832-847
The distributional diversity and assemblages of fish larvae in the Gulf of California indicated two main seasonal stages and two transitional periods: in winter, the tropical water mass is confined to the south‐east portion of the mouth of the Gulf and larval fish assemblages are dominated by subtropical and temperate‐subarctic species; in summer; tropical water invades the Gulf and assemblages are dominated by tropical species. Both seasonal stages are separated by transitional periods coinciding with strong latitudinal temperature gradients. During the autumn and spring transitional periods, the Gulf of California splits into three regions: a northern region where temperate and subarctic species spawn from autumn to spring, a southern region dominated by tropical and subtropical species year round and a central region where tropical and temperate assemblages merge. Seasonal changes in the location of the regions, as well as the borders between them, show expansion and contraction of the northern and southern faunas related to the general oceanic circulation patterns during the year. 相似文献
2.
Franco-Gordo C.; Godinez-Dominguez E.; Suarez-Morales E. 《Journal of plankton research》2002,24(8):775-784
Spatial and seasonal variation of the ichthyoplankton assemblageswas analysed using monthly samples collected during a 1 yearcycle off the central Pacific coast of Mexico. Zooplankton sampleswere collected at 12 stations during 11 months, from December1995 to December 1996. The analysis of coastal oceanographicconditions revealed two main seasonal patterns, one relatedto the California Current influence and the other a tropicalone. A temporal recomposition of the ichthyoplankton assemblageswas found to be related to each oceanographic pattern. Duringthe California Current period (JanuaryMay) the larvalfish assemblage was respresented mainly by Auxis sp., Bentosemapanamense, Cetengraulis mysticetus, Opistonema sp., Symphuruselongatus, Gobionellus sp., Dormitator latifrons and Bregmacerosbathymaster. The tropical season assemblage (July, October andNovember) was represented by Harengula thrissina, Euthynnuslineatus, Vinciguerria lucetia, Syacium ovale, and representativesof the Eleotridae and Pomacentridae. An inshoreoffshoregradient was observed during the tropical oceanographic periods,with a thermic stratification of the water column over the shelf.Conversely, during the California Current period, with coastaladvective processes, the assemblages of fish larvae were morehomogeneous. Although a mixed, richer faunistic compositionwas expected in this transitional area, the overall biogeographicaffinity of the surveyed community remained stable even in contrastingconditions. 相似文献
3.
Comparison of inshore and offshore fish larval assemblages within the wider Yangtze River estuary (China)
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It is hypothesized that fish larvae undertake vertical movements in estuarine waters. To test this hypothesis, a sampling period was selected during times when many spring‐spawning fish reach maximum abundance in coastal waters so that spring and summer variations in larval fish assemblages could be determined in the Yangtze River estuary. Six oceanographic surveys were conducted across the salinity gradient of an inshore (freshwater) and offshore area (brackish intersection) during spring (May) and summer (August) between 2010 and 2012. The fish larval community was dominated by species of Engraulidae, Gobiidae, Champsodontidae and Mugilidae. The pre‐flexion and flexion larval stages of euryhaline marine species, which are dependent on estuaries as nursery areas, were common. The brackish and marine larval assemblage was the most abundant with taxa such as Coilia mystus and Engraulis japonicus accounting for more than 57.3% of the total catch. Spatial differences in the taxonomic composition of larval fish assemblages were evident between the inshore and offshore areas. Additionally, the Yangtze River runoff regulatory functions as affected by the Three Gorges Reservoir operational mode (hydrological alternating operations) showed weak influences on fish and habitat environments. Low salinities from high freshwater inflow limited bay anchovy production in the inshore area. 相似文献
4.
In order to test the temporal stability within and the reproducibility of larval fish assemblages between years, the larval
fish assemblage at Helgoland Roads, North Sea (NE Atlantic) was quantitatively sampled almost daily from January 2003 to December
2005. The survey resulted in a total of 462 samples containing 50,632 larval fish of at least 42 taxa. In winter the larval
fish assemblage was mainly dominated by larvae emerging from demersal eggs. This changed gradually to larvae hatching from
pelagic eggs. Larvae from pelagic eggs dominated the ichthyoplankton assemblage in summer. A remarkably stable seasonality
in terms of dominance patterns with recurring, season-specific fish assemblages was observed over the 3 years, despite substantial
variation in environmental conditions such as a temperature difference of almost 20°C between summer and winter. The lesser
sandeel (Ammodytes marinus), was the only species which showed significant fluctuations in abundance between the years. After removal of this species
from the analysis, the dominance patterns of the remaining fish species were almost identical between years. 相似文献
5.
We examined Indiana fish assemblages using taxonomy and ecological categories to assess temporal shifts in community structure
and recent environmental relationships. Historic (1945) and recent (1996–2007) presence/absence data were compiled by subbasin
and analyzed with Nonmetric Multidimensional Scaling (NMS) ordination and by species richness. Canonical Correspondence Analysis
(CCA) was used to test taxonomic identity and ecological category abundance data for explanation with recent (1996–2007) environmental
variables. We found a decrease in assemblage heterogeneity for recent assemblages and an increase in the number of tolerant
species per subbasin. Recent Indiana streams are dominated by tolerant fishes with generalist life history strategies and
low functional variation. The use of ecological categories resulted in weaker relationships with environmental variables than
analyses with taxonomic identities. Analyses using taxonomy resulted in strong assemblage explanation from stream size and
flow variation, while analyses using ecological categories resulted in strong assemblage explanation from habitat variation
in silt substrates and flow. Analyses of recent assemblage structure using ecological categories resulted in decreased assemblage
variation among subbasins than in analyses using taxonomic identities. We found that fish assemblages of Indiana streams are
structured primarily by habitat complexity and have been altered during the past 50 years through multiple disturbances including
fragmentation, siltation, and species introductions. 相似文献
6.
《Marine Micropaleontology》1999,37(2):149-171
The geographical and depth distributions of five radiolarian plankton assemblages, defined through Q-mode Factor Analysis of 24 plankton samples, demonstrate a direct correspondence to the distribution of oceanographic water masses in the southern Gulf of California. Two assemblages are associated exclusively with water masses of the mixed-layer, two represent only subsurface water masses, and one is important in both surface and subsurface environments. The Lithomelissa thoracites group and Peridium spinipes are predominant species in water that is formed at the surface of the Guaymas Basin and subsequently is subducted southward into the Carmen Basin. Plagiocantha panarium is the predominant species in upwelled surface water at the Carmen Basin, while Tetrapyle octhacanta and Botryostrobus scutum follow the incursion of the Subtropical Water Mass into the Gulf of California through the Pescadero and Farallon Basins. Druppatractus variabilis and Porodiscus sp. B occur conspicuously in the upper layer of the Pacific Intermediate Water between approximately 400 and 700 m water depth. Statistical correlation between plankton and sediment assemblages supports previous evidence that the radiolarian thanatocoenose in the Gulf of California is composed primarily of species from the surface mixed-layer. Two exceptions to this are observed in the data. First, the upwelling plankton assemblage was not well correlated to the sediment assemblage, and second, input to the sediment during glacial stages appears to be dominated by subsurface forms. 相似文献
7.
The influence of wind and wave exposure on larval fish assemblages within a large bay system was investigated. Larval fishes were sampled from two areas with vastly different exposure to waves and wind, namely the windward and leeward sectors of Algoa Bay. In total, 5702 larval fishes were collected using a modified larval seine. Of these, 4391 were collected in the leeward and 1311 in the windward sector of the bay, representing a total of 23 families and 57 species. Dominant fish families included Clinidae, Engraulidae, Kyphosidae, Mugilidae, Soleidae and Sparidae, similar to the situation elsewhere, highlighting continuity in the composition of larval fish assemblages and the utilization of surf zones by a specific group of larval fishes. Nineteen estuary‐associated marine species occurred within the surf zones of Algoa Bay and dominated catches (86·7%) in terms of abundance. Postflexion larvae comprised > 80% of the catch, indicating the importance of the seemingly inhospitable surf zone environment for the early life stages of many fish species. The greatest species diversity was observed within the windward sector of the bay. Distance‐based linear modelling identified wave period as the environmental variable explaining the largest proportion of the significant variation in the larval fish assemblage. The physical disturbance generated by breaking waves could create a suitable environment for fish larvae, sheltered from predators and with an abundance of food resources. 相似文献
8.
The first step in building predictive models of larval fish assemblages is to identify the main environmental parameters which
influence their spatial and temporal structure. In this study, multivariate regression trees (MRT) were used to classify hierarchically
the effects of large-scale meteorological factors and small-scale water column factors on pre-settlement larval fish assemblages
at two sites in the lagoon at New Caledonia, southwest Pacific. The environmental conditions at one site were highly variable
spatially and temporally, but varied little at the other. In spite of these differences, MRT models revealed that identical
forcing factors influenced the structure of larval fish assemblages at both sites, with a similar hierarchy, but a different
statistical efficiency. At a large spatial scale, the seasonal variabilities in sun hours and wind (speed and/or direction)
explained 14% and 64% of the structure of larval fish assemblages at the sites of high and low variability, respectively.
At a small spatial scale, the seasonal variability in mean surface water temperature, followed by the concentration in Chl a, explained 22% and 62% of the structure of assemblages at the sites of high and low variability, respectively. The Dufrêne–Legendre
index matched characteristic families of larvae to each set of environmental conditions, and illustrated the role of sheltered,
Chl a enriched, coastal waters in producing a families-rich assemblage of fish larvae, some species of which are targeted by fishing.
This study shows that it may be possible to use environmental data, and predictions computed from MRT to design spatially
explicit models of larval fish distribution in coral-reef lagoons. 相似文献
9.
Filipe Ribeiro Maria Filomena Magalhães Maria João Collares-Pereira 《Environmental Biology of Fishes》2013,96(4):467-480
Larval fish ecology remains poorly understood in freshwater ecosystems. This study analysed the larval ecology of native and non-native fishes in a mediterranean-type watershed in Southern Iberian Peninsula. Assemblage structure of fish larvae was quantified at four distinct rivers sites, every 2 weeks between March and October 2004, and analysed against 16 variables reflecting river flow, temperature and habitat context. There was considerable spatial variation in taxonomic richness and abundance of larval assemblages, with either native or non-native fishes dominating in different sites. There was also a clear temporal separation between native and non-native fishes, with native cyprinids generally peaking earlier in the year than non-native fishes. Temporal fluctuations in larval assemblages across sites were mostly associated with variations in water temperature and transparency, but flow was an important factor shaping local assemblage structure. Larvae of native fishes appeared to found most suitable conditions in naturally flowing sites early in spring, when flow is high and water temperature stills low. These results suggest that preservation of natural flow peaks and adequate thermal contexts may be crucial for conservation of native fish fauna in mediterranean-type streams. 相似文献
10.
《Revue de Micropaléontologie》2016,59(1):19-32
Benthic foraminiferal composition assemblages and their temporal changes, ecological indices and foraminiferal densities are used to compare three coastal environments with different physicogeographical features in the Aegean Sea (coastal environment of Avdira–Vistonikos Gulf and Kitros–Thermaikos Gulf and open lagoonal environment of Vravron–South Evoikos Gulf). Three main foraminiferal assemblages have been recognized: a) “Assemblage A”; high degree of similarity between living and dead foraminiferal species, dominated by Ammonia beccarii, Elphidium spp. and relatively abundant and diverse miliolids, b) “Assemblage B1”; intermediate degree of similarity between live and dead assemblages, characterized by highly-abundant and well-diversified foraminiferal assemblages including the algal symbiont bearing Peneroplis pertusus together with Ammonia tepida and several small epiphytic rotaliids and miliolids, and c) “Assemblage B2”; absence of living individuals, strongly dominated by the opportunistic species A. tepida. Our results suggest a good comparison between living and dead assemblages from different coastal environments in the Aegean Sea, however the prevailing environmental conditions (vegetation cover, hydrodynamics, fresh water influx) have a strong impact on the taphonomic processes. 相似文献
11.
Beldade Ricardo; Borges Rita; Goncalves Emanuel J. 《Journal of plankton research》2006,28(11):1003-1013
In this study, we compare the composition, abundance and structureof a temperate fish larval assemblage at different depth intervals(04, 48 and 812 m) in the extreme nearshoreenvironment. We used a plankton net attached to an underwaterscooter to sample in close proximity to the rocky substrate(<50 cm). A total of 868 larvae from 27 taxa in 13 familieswere caught. The majority of larvae belonged to benthic reef-associatedspecies (Blenniidae, Gobiidae, Gobiesocidae and Tripterygiidae),the four most abundant comprising 76% of the total larvae caught.A non-metric multidimensional scaling analysis (MDS) showedthat there was a single multispecific larval patch near thesubstrate in the extreme nearshore up to 12 m depth. Nonetheless,distinct larval abundances were found in this relatively smalldepth range, with the majority of species being more abundantat the deepest interval, particularly Pomatoschistus pictusand Gobius xanthocephalus. Tripterygion delaisi was an exceptionbeing more abundant at the shallowest depth as young larvae.The density of pre-flexion larvae was not significantly differentacross depth intervals, but post-flexion larval density increasedwith depth. The full size range (from hatching to settlement)of P. pictus was present at the extreme nearshore. The innovativesampling technique used here revealed high densities of larvaeclose to the bottom, and depth was found to be an importantfactor influencing the distribution of several taxa and ontogeneticstages. The nearshore component of coastal fish larval assemblagesnear rocky substrates has been poorly studied, and our resultssuggest that the high densities of larvae found to aggregatein these environments must be taken into account when studyingdistribution and functional aspects of these assemblages. 相似文献
12.
Kelia E. Axler Esther D. Goldstein Jens M. Nielsen Alison L. Deary Janet T. Duffy-Anderson 《Global Change Biology》2023,29(15):4212-4233
The Pacific Arctic marine ecosystem has undergone rapid changes in recent years due to ocean warming, sea ice loss, and increased northward transport of Pacific-origin waters into the Arctic. These climate-mediated changes have been linked to range shifts of juvenile and adult subarctic (boreal) and Arctic fish populations, though it is unclear whether distributional changes are also occurring during the early life stages. We analyzed larval fish abundance and distribution data sampled in late summer from 2010 to 2019 in two interconnected Pacific Arctic ecosystems: the northern Bering Sea and Chukchi Sea, to determine whether recent warming and loss of sea ice has restricted habitat for Arctic species and altered larval fish assemblage composition from Arctic- to boreal-associated taxa. Multivariate analyses revealed the presence of three distinct multi-species assemblages across all years: (1) a boreal assemblage dominated by yellowfin sole (Limanda aspera), capelin (Mallotus catervarius), and walleye pollock (Gadus chalcogrammus); (2) an Arctic assemblage composed of Arctic cod (Boreogadus saida) and other common Arctic species; and (3) a mixed assemblage composed of the dominant species from the other two assemblages. We found that the wind- and current-driven northward advection of warmer, subarctic waters and the unprecedented low-ice conditions observed in the northern Bering and Chukchi seas beginning in 2017 and persisting into 2018 and 2019 have precipitated community-wide shifts, with the boreal larval fish assemblage expanding northward and offshore and the Arctic assemblage retreating poleward. We conclude that Arctic warming is most significantly driving changes in abundance at the leading and trailing edges of the Chukchi Sea larval fish community as boreal species increase in abundance and Arctic species decline. Our analyses document how quickly larval fish assemblages respond to environmental change and reveal that the impacts of Arctic borealization on fish community composition spans multiple life stages over large spatial scales. 相似文献
13.
The coastal ocean off south-western Australia is characterisedby the southward-flowing Leeuwin Current, which suppresses theupwelling typically associated with other eastern boundary currentsin the southern hemisphere. This results in a unique environmentfor the transport and survival of planktonic fish larvae. Thehorizontal and vertical structure of larval fish assemblagesoff south-western Australia was investigated during winter (August2003) and summer (January 2004), and related to these unusualregional oceanographic and biological processes. Larval fishwere sampled along a four station transect running from theinner continental shelf to offshore waters, using depth-integratedbongo net tows and depth-stratified EZ net tows. The distributionof taxa across the shelf and offshore was strongly influencedby the current regime at the time of sampling. Larval fish assemblagestructure reflected the distinctive oceanographic conditionsfound during each season, and vertical depth distributions oflarvae affected their horizontal location. Continental shelfsamples were dominated by larvae of pelagic fishes, such asclupeiform species (e.g. Sardinops sagax), whereas offshoreassemblages were characterised by larvae of oceanic families,such as Myctophidae and Phosichthyidae. The winter cruise (August2003) was completed during a time of strong, southerly LeeuwinCurrent flow, whereas the northward-flowing Capes Current, incombination with surface offshore Ekman transport, predominatedduring summer. The vertical depth preferences of larvae wereparticularly influential in affecting their horizontal position;especially so for surface-dwelling larval fishes found duringsummer. This study represents the first documentation of thevertical structure of ichthyoplankton assemblages in the oligotrophicwaters off south-western Australia. 相似文献
14.
Carrada Gian Carlo; Fresi Eugenio; Marino Donato; Modigh Monica; D'Alcala Maurizio Ribera 《Journal of plankton research》1981,3(2):291-314
Quantitative and qualitative distribution of surface phytoplankton,as related to hydrographic conditions, was studied in the Gulfof Naples in February 1979. Previous work has shown that the Gulf of Naples is a diversifiedecosystem, due to geographic and hydrographic features as wellas man made eutrophication, that can be subdivided into twomajor parts: a coastal subsystem and an open water one. Hydrographic analysis of the winter situation at the surfacefully confirms this picture, as it identifies two distinct watermasses corresponding respectively to surfaced Tyrrhenian IntermediateWater and to Coastal Surface Water. The structural analysisof phytoplankton reveals three assemblages of species characterizingdifferent water types: 1 - the Ischia and Procida channels affectedby the advection of Volturno river and Cuma outfall plumes;2 - the coastal area of the Gulf proper, namely the bays ofPozzuoli, Naples and Castellammare; 3 - the open waterhemislocated beyond the 100 m isobath. The channel area assemblage is dominated by diatoms, particularlyby fast growing species, such as Asterionella japonica, severalspecies of Chaetoceros and Rhizosolenia hebetata f. semispina.The coastal assemblage is identified, among others, by the diatomsCerataulina bergonii, Hemiaulus sinensis; the dinoflagellatesGlenodinium lenticula, Exuviaella compressa and Porella perforata.The open water assemblage is characterized by the diatoms Coscinodiscuscurvatulus and Hemidiscus cuneiformis, the dinoflagellate Amphidiniumacutissimum and the coccolithophore Coccolithus haeckelii. 相似文献
15.
C. Dang X. de Montaudouin J. Bald F. Jude N. Raymond L. Lanceleur I. Paul-Pont N. Caill-Milly 《Hydrobiologia》2009,630(1):139-148
Knowledge of temporal variation in nearshore Laurentian Great Lakes fish assemblages is important for understanding species–habitat
associations, how abiotic and biotic influences vary temporally, and when sampling should occur. Using spring and fall seining
data from Lake Erie beaches, we compared day and night fish assemblages and tested for differences among sampling periods.
Beaches were utilized by a diverse collection of Lake Erie basin fishes (one-third of known species). During all sampling
periods, catches were dominated by cyprinid species (53–91%), and by invertivores and planktivorous fishes. Diel differences
were detected in abundance, species richness and assemblage structure. Multivariate analyses (canonical analysis of principal
coordinates) indicated that season had a larger influence on fish assemblage structure than diel period. Given observed temporal
variation in assemblage structure, studies of Laurentian Great Lakes beach fishes should be restricted to a single time period
(e.g. day-time spring sampling), or adopt sampling designs that permit diel period and season to be included as factors in
analyses. Second, the large seasonal variation in assemblage composition combined with higher night species richness indicates
that night sampling during both spring and fall would be the most efficient and comprehensive approach for beach fish inventory.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.
Handling editor: J. Trexler 相似文献
16.
River environments are characterized by extreme spatial and temporal variation in the physical environment. The relationship
of fish assemblages to environmental variation is poorly understood in many systems. In Chile zonation patterns of fish assemblages
have been documented in several Andean river drainages. Coastal river drainages are comparatively small, but inordinately
important because of their highly endemic flora and fauna and their proximity to major human populations. For conservation
purposes it is important to understand what environmental factors affect assemblage structure of fishes especially in the
comparatively high diversity coastal drainages. We studied patterns of fish distribution and abundance in three rivers of
the coastal, Andalien drainage near Concepción, Chile. We used multi-dimensional scaling analyses to compare patterns among
zones (rithron, transition and potamon) and high and low flow seasons. Species assemblages differed by zone, but not with
season. Assemblages consisted of nested subsets of species characterized by their range of distribution among zones. One species
group was composed of widespread species that occurred in all three zones, another species group consisted of species found
only in transitional and potamal zones, and a final group was comprised of species found only in the potamal zone. The potamal
zone contained the most diverse and abundant fish assemblage. Fish assemblages were related to both water quality and habitat
structure variables. This study suggests that the key to conserving the diversity of native fish communities in coastal Chilean
rivers is in the conservation of potamal regions. Unfortunately, most protected areas in Chile are in the depauperate headwaters
of drainages. Protection of only headwaters is clearly inadequate and will not contribute to the conservation of this unique
freshwater fish fauna. 相似文献
17.
Shore fish community structure off the Jordanian Red Sea coast was determined on fringing coral reefs and in a seagrass-dominated
bay at 6 m and 12 m depths. A total of 198 fish species belonging to 121 genera and 43 families was recorded. Labridae and
Pomacentridae dominated the ichthyofauna in terms of species richness and Pomacentridae were most abundant. Neither diversity
nor species richness was correlated to depth. The abundance of fishes was higher at the deep reef slope, due to schooling
planktivorous fishes. At 12 m depth abundance of fishes at the seagrass-dominated site was higher than on the coral reefs.
Multivariate analysis demonstrated a strong influence on the fish assemblages by depth and benthic habitat. Fish species richness
was positively correlated with hard substrate cover and habitat diversity. Abundance of corallivores was positively linked
with live hard coral cover. The assemblages of fishes were different on the shallow reef slope, deep reef slope and seagrass
meadows. An analysis of the fish fauna showed that the Gulf of Aqaba harbours a higher species richness than previously reported.
The comparison with fish communities on other reefs around the Arabian Peninsula and Indian Ocean supported the recognition
of an Arabian subprovince within the Indian Ocean. The affinity of the Arabian Gulf ichthyofauna to the Red Sea is not clear.
Received in revised form: 2 November 2001
Electronic Publication 相似文献
18.
Fish assemblages on artificial and natural reefs in the Flower Garden Banks National Marine Sanctuary, USA 总被引:5,自引:0,他引:5
Visual censusing was used to characterize fish assemblages on artificial and natural reefs located within the boundaries
of the Flower Garden Banks National Marine Sanctuary (FGBNMS) in the northwestern Gulf of Mexico. Emphasis was placed on determining
spatial and temporal patterns in habitat utilization by fishes on an offshore artificial reef (Mobil Platform HI-A389A). Overall,
43 species were observed during diurnal surveys in the upper 24 m of the artificial reef. Midwater pelagic fishes (i.e., carangids
and scombrids) accounted for over 50% of all taxa enumerated on the artificial reef; however, these taxa were transient members
of the assemblage and were observed infrequently. Labrids, pomacentrids, and serranids were the dominant reef-dependent taxa.
Distinct trends in vertical, diel, and seasonal abundances were observed for juvenile and adult fishes. Of the three designated
depth zones (upper 1.5–9.0, middle 9.0–16.5; lower 16.5–24.0 m), abundance and species diversity were lowest in the upper
zone. Nocturnal counts were characterized by a marked reduction or complete absence of most species, due in part to twilight
cover-seeking and movement activities. Seasonal variation in community composition and species abundance (May versus September)
was primarily due to recruitment of juveniles (0-age fishes) to the artificial reef in late summer. Increases in total fish
abundance (all taxa combined) coincided with both increasing habitat rugosity and degree of fouling. Species richness on natural
coral reefs in the FGBNMS was higher than on the artificial reef. Unlike the artificial reef, fish assemblages on the natural
reefs were dominated by a single family (Pomacentridae) which accounted for over 50% of all individuals observed.
Accepted: 1 August 1996 相似文献
19.
20.
Despite the fact that flow and channel morphology are two critical factors that need to be taken into account when considering
the conservation or restoration of river environments, there are no reports on the response of fish assemblages to changes
involving both variables in combination. This study examined the response of fish assemblages to artificially induced changes
in flow discharge in an experimental stream that had simple (a glide reach) and complex (pool–riffle reach) morphologies.
When the flow of the glide reach was increased, the fish assemblage structure changed from one dominated by the demersal species
Misgurnus anguillicaudatus and Cobitis sp. to one dominated by the water-column species Zacco platypus and Gnathopogon elongatus. In the pool–riffle reach, the fish assemblage structure changed from one dominated by Cobitis sp. and Z. platypus to one dominated by Plecoglossus altivelis altivelis. When the flow discharge was low, the fish assemblages of both reach types resembled each other in being dominated largely
by demersal species, but when flow was increased these similarities faded and distinct assemblages emerged. In the glide reach,
increasing the flow volume caused a linear increase in both water depth and velocity and a gradual increase in the diversity
of water-column species, their relative abundance, and size. The number of Z. platypus increased fivefold whereas the number of M. anguillicaudatus decreased to less than a quarter of their original number. In the pool–riffle reach, the number of P. altivelis altivelis grew conspicuously although increased flow produced no clear increase in depth or velocity. Calculation of the availability
of physical habitat environments suitable for Z. platypus and P. altivelis altivelis in each reach type indicated that preferable habitat for both species was more available in the glide reach. The lower abundance
of P. altivelis altivelis in the glide reach was attributed to the relatively low availability of algal food resource due to the sand-predominated
substrate whereas pebbles predominated in the pool–riffle reach providing good conditions for algal growth. Our findings suggest
the need for a framework for considering environmental flow that takes into account variables such as channel morphology and
food resource conditions. 相似文献