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1.
Fishes and invertebrate macrofauna (nekton) were sampled biweekly (July through October 1985) from the surface of tidal freshwater marshes. Samples were collected with flume nets at three different stream orders (orders 2, 3 and 4+) along a marsh stream order gradient. Twenty-five species of fishes (5,610 individuals, 17.072 kg preserved wet weight) representing 13 families, and three species of invertebrates (19,570 individuals, 13.026 kg preserved wet weight) were collected. The most abundant species were grass shrimp (Palaemonetes pugio), mummichogs (Fundulus heteroclitus), banded killifish (F. diaphanus), inland silversides (Menidia beryllina), and blue crabs (Callinectes sapidus). Invertebrate catches (mostly grass shrimp and blue crabs) were not significantly different among stations. Total numbers of fishes were significantly greater at both headwater (order 2) and main creek (order 3) stations than river (order 4+) stations, but catches of headwater and main creek stations were not significantly different. The relationship between marsh stream order and fish abundance may partly be related to the distribution of submerged aquatic vegetation (SAV) within marsh tidal creeks. Submerged aquatic vegetation decreases in abundance with increasing stream order. Some species may use SAV as a refuge from predators or as a foraging area during low tide when the marsh surface is inaccessible. The presence of SAV in tidal creeks may enhance the habitat value of adjacent marshes. 相似文献
2.
We compared nekton use ofVallisneria americana Michx. (submerged aquatic vegetation, SAV) with marsh shoreline vegetation and subtidal nonvegetated bottom (SNB) using a
1-m2 drop sampler in the oligohaline area of Barataria Bay, Louisiana. Mean densities of most abundant species were significantly
different among six habitat types. Harris mud crabRhithropanopeus harrisii, Ohio shrimpMacrobrachium ohione, blue crabCallinectes sapidus, daggerblade, grass shrimpPalaemonetes pugio, white shrimpLitopenaeus setiferus (fall), rainwater, killifishLucania parva, naked gobyGobiosoma bosc, code gobyGobiosoma robustum (fall), speckled worm eelMyrophis punctatus (fall), and gulf pipefishSyngnathus scovelli (spring), were much more abundant, and species richness also was greater, inVallisneria than over SNB.Vallisneria supported densities of most species that were similar to those in marsh vegetation, although naked goby and gulf pipefish
were more abundant inVallisneria, and speckled worm eel and saltmarsh topminnowFundulus jenkinsi were more abundant in marsh. Within theVallisneria bed, densities of Harris mud crab, rainwater killifish, and speckled worm eel were higher at sites near the marsh (SAV Inside
Edge) than at sites more distant from the marsh (SAV Outside Edge), and Ohio shrimp (fall) densities were higher in the interior
of the bed than along the edges. The mean size of blue crab was larger in marsh thanVallisneria and large inVallisneria than SNB. White shrimp did not differ in size among habitat types.Vallisneria beds may provide an important nursery habitat for young blue crab and white shrimp that use oligohaline estuarine areas.
These SAV beds can provide an alternative structural habitat to emergent vegetation during periods of low water, becauseVallisneria occurs in the subtidal and generally persists throughout the year on the Gulf coast. Species whose young thrive in low-salinity
waters and also depend on structure would benefit most fromVallisneria habitat in estuaries. 相似文献
3.
Alan T. Hitch Kevin M. Purcell Shannon B. Martin Paul L. Klerks Paul L. Leberg 《Estuaries and Coasts》2011,34(3):653-662
Increases in relative sea level are fragmenting the emergent vegetation of Louisiana’s coastal marshes. Nekton abundance is
likely impacted by salinity and whether emergent vegetation is replaced by submerged aquatic vegetation (SAV) or open water.
To assess these effects, we sampled nekton densities along a salinity gradient (categorized as freshwater, intermediate, and
brackish marsh) in fragmented and non-fragmented areas. Total nekton density increased strongly with SAV in brackish marsh
but only weakly in freshwater marsh (F
2,238 = 10.03, p < 0.0001). Freshwater and intermediate marshes had higher nekton densities when fragmented than when non-fragmented; this
relationship was reversed in brackish marsh (F
2,238 = 8.89, p = 0.0002). Fragmentation, SAV, and salinity interacted to affect the densities of Gambusia affinis, Poecilia latipinna, Cyprinodon variegates, and Lucania parva. Our results suggest that the presence of both emergent vegetation and SAV was necessary for maintaining high nekton densities,
with this combination being especially important in brackish marshes. 相似文献
4.
A two-year trawling and gill-netting study of vegetated and unvegetated bottoms near Parson’s Island, Maryland and near the mouth of the York River, Virginia was carried out to assess the nursery function of submerged vegetation for populations of fishes and decapod crustaceans in the Chesapeake Bay. Results revealed that vegetated bottoms supported substantially larger numbers of decapods, but not fishes, than unvegetated substrates. The lower Bay grassbed was an important nursery area for juvenile blue crabs, although neither of the grassbeds functioned as a nursery for commercially or recreationally valuable fishes. Our results suggest that: (1) further decreases in lower Bay Seagrass biomass would result in reduced numbers of adult blue crabs, but should not substantially affect populations of valuable fish species; (2) additional decreases in Upper Bay submerged vegetation should not produce dramatic change in the population sizes of either adult blue crabs or fishes. 相似文献
5.
Habitat-related densities of natant macrofauna were compared between vegetated and nonvegetated areas in aSpartina alterniflora marsh on Galveston Island, Texas. The most abundant macrofauna were crustaceans,Palaemonetes pugio, Penaeus aztecus, Penaeus setiferus, andCallinectes sapidus, and small fish,Gobiosoma bosci, Lagodon rhomboides, Leiostomus xanthurus, Fundulus similis andMicropogonias undulatus. Excluding residentsP. pugio, G. bosci andF. similis, most of the macrofauna were transient juveniles of estuarine-dependent species. Among crustaceans,P. pugio, P. aztecus, andC. sapidus were significantly more dense in vegetated habitat, butP. setiferus was not consistently more abundant in either vegetated or nonvegetated habitat. Of 29 species of fishes, 14 were usually in vegetation, 11 were more often on nonvegetated bottom, and 5 were indifferent to either habitat. Much seasonal variability in abundances ofP. aztecus, P. setiferus, andC. sapidus, but notP. pugio, could be attributed to changes in temperature, salinity and water-level. Strong selection for vegetated habitat byP. aztecus was related to the historical water-level pattern coinciding with seasonal periods of marsh flooding. Apparently, high seasonal tides during the spring and fall facilitated access to vegetated habitat in the marsh and exploitation by transientP. aztecus. In contrast, strong selection for vegetation byP. pugio, abundant year-around in the marsh, was not similarly influenced by seasonal changes in water-level. Overall, habitat-related densities and physical interactions suggest that marsh physiography together with differences in tides may greatly determine the extent to which certain estuarine macrofauna utilize marsh habitats. 相似文献
6.
A primary goal of many coastal restoration programs is to increase nekton habitat in terms of both quantity and quality. Using
shallow water ponds rehabilitated with a technique called marsh terracing, we examined the quality of nekton habitat created,
using and comparing several metrics including nekton density and diversity, functional group composition, and weight-length
relationships as indirect measures of habitat quality. We examined three paired terraced and unterraced marsh ponds in southwest
Louisiana. Nekton, submerged aquatic vegetation (SAV), and soil and water quality variables were sampled bimonthly from April
2004 through April 2005 at four subtidal habitat types: terraced nearshore, terraced open water, unterraced nearshore, and
unterraced open water. Results indicate that terraced ponds had increased the habitat value of degrading unterraced ponds
over open water areas for estuarine nekton; nekton density and richness were similar between terraced and unterraced nearshore
habitat types, but greater at all nearshore as compared to open water sites. Analysis of the distribution of nekton functional
groups and weight:length ratios indicates the terraced and unterraced pond habitats were not functioning similarly: distribution
of nekton functional groups differed significantly between habitat types with greater percentages of benthic-oriented species
at unterraced open water habitats and higher percentage of open water species in terraced ponds as compared to unterraced
ponds, and two of the six numerically dominant fish species had greater weight-length relationships in unterraced ponds as
compared to terraced ponds. This lack of functional equivalency may be attributed to environmental differences between terraced
and unterraced ponds such as water depth or SAV biomass, or the relatively young age of the terraces studied, which may not
have allowed for the development of some critical habitat variables, such as soil organic matter that was found to be significantly
lower in terraced versus unterraced ponds (p < 0.05). To properly assess the ecological equivalency of restored or rehabilitated
sites for nekton requires that we move beyond measures of nekton density, biomass, and diversity and incorporate measures
of functional equivalency, including habitat measures. 相似文献
7.
We evaluated nekton habitat quality at 5 shallow-water sites in 2 Rhode Island systems by comparing nekton densities and biomass,
number of species, prey availability and feeding, and abundance of winter flounderPseudopleuronectes americanus. Nekton density and biomass were compared with a 1.75-m2 drop ring at 3 sites (marsh, intertidal, and subtidal) in Coggeshall Cove in Narragansett Bay and two subtidal sites (eelgrass
and macroalgae) in Ninigret Pond, a coastal lagoon. We collected benthic core samples and examined nekton stomach contents
in Coggeshall Cove. We identified 16 species of fish, 16 species of crabs, and 3 species of shrimp in our drop ring samples.
A multivariate analysis of variance indicated differences in total nekton, invertebrates, fish, and winter flounder across
the five sites. Relative abundance of benthic invertebrate taxa did not match relative abundance of prey taxa identified in
the stomachs. Nonmetric multidimensional scaling plots showed groupings in nekton and benthic invertebrate prey assemblages
among subtidal, intertidal, and marsh sites in Coggeshall Cove. Stepwise multiple regression indicated that biomass of macroalgae
was the most important variable predicting abundance of nekton in Coggeshall Cove, followed by elevation and depth. In Rhode
Island systems that do not experience chronic hypoxia, macroalgae adds structure to unvegetated areas and provides refuge
for small nekton. All sites sampled were characterized by high abundance and diversity of nekton pointing to the importance
of shallow inshore areas for production of fishes and decapods. Measurements of habitat quality should include assessment
of the functional significance of a habitat (this can be done by comparing nekton numbers and biomass), some measure of habitat
diversity, and a consideration of how habitat quality varies in time and space. 相似文献
8.
We examined the distribution of nekton across the marsh landscape using a 1-m2 drop sampler to compare nekton densities across three different salinity zones (intermediate, brackish, saline), three pond
sizes (diameter <40 m = small, ∼250–300 m = medium, >750 m = large), and two habitat types (pond, adjacent marsh) in the Barataria
Bay Estuary, Louisiana. Nekton assemblages of ponds and the adjacent marsh appeared to be structured by the responses of individual
species to the estuarine salinity gradient at the landscape scale and to pond habitat attributes locally. Our results indicate
that ponds in the brackish and saline zones are more important nursery areas for most fishery species than ponds in the intermediate
zone. Medium and large ponds supported higher densities of most species than small ponds. Most species of nekton were associated
with vegetation structure, and individuals of these species were either concentrated among plant stems at the marsh edge or
within submerged aquatic vegetation in ponds. 相似文献
9.
Subsidence and erosion of intertidal salt marsh at Galveston Island State Park, Texas, created new areas of subtidal habitat
that were colonized by seagrasses begining in 1999. We quantified and compared habitat characteristics and nekton densities
in monospecific beds of stargrassHalophila engelmanni and shoalgrassHalodule wrightii as well as adjacent nonvegetated substrates. We collected 10 replicates per habitat type during April, July, October, and
December 2001. Most habitat characteristics varied with season. Water temperature, salinity, and dissolved oxygen were similar
among habitat types. Turbidity and depth were greatest inH. engelmanni beds and least inH. wrightii beds.H. engelmanni exhibited shorter leaves and higher shoot density and biomass core−1 thanH. wrightii. Densities of almost all dominant species of nekton (fishes and decapods) were seasonally variable, all were higher in seagrass
habitats than in nonvegetated habitats, and most were higher in one seagrass species than the other. Naked gobyGobiosoma bosc, code gobyGobiosoma robustum, bigclaw snapping shrimpAlpheus heterochaelis, and blue crabCallinectes sapidus, were most abundant inH. engelmanni. Brown shrimpFarfantepenaeus aztecus, brackish grass shrimpPalaemonetes intermedius, and daggerblade grass shrimpPalaemonetes pugio were most abundant inH. wrightii. PinfishLagodon rhomboides and pink shrimFarfantepenaeus duorarum were equally abundant in either seagrass. Most dominant nekton varied in size by month, but only two (L. rhomboides andC. sapidus) exhibited habitat-related differences in size. Nekton densities in these new seagrass habitats equaled or exceeded densities
associated with historical and current intertidal smooth cordgrassSpartina alterniflora marsh. Continued seagrass expansion and persistence should ensure ecosystem productivity in spite of habitat change. 相似文献
10.
Large-scale marsh restoration efforts were conducted to restore normal salt marsh structure and function to degraded marshes
(i.e., former salt hay farms) in the mesohaline lower Delaware Bay. While nekton response has been previously evaluated for
the marsh surface and subtidal creeks in these marshes, little effort has been focused on intertidal creeks. Nekton response
in intertidal creeks was evaluated by sampling with seines to determine if restored (i.e., former salt hay farms restored
in 1996) and reference (i.e., natural or relatively undisturbed) salt marshes were utilized by intertidal nekton in a similar
manner. The overall nekton assemblage during June–October 2004–2005 was generally comprised of the same species in both the
restored and reference marshes. Intertidal creek catches in both marsh types consisted primarily ofFundulus heteroclitus andMenidia menidia, with varying numbers of less abundant transient species present. Transient nekton were more abundant at restored marshes
than reference marshes, but in insufficient numbers to cause differences in nekton assemblages. In both marsh types, low tide
stages were characterized by resident nekton, dominated byF. heteroclitus, while high tide stages were characterized by a variable mix of transient and resident nekton. Assemblage level analyses
indicated that intertidal creeks in restored and reference marshes were generally utilized in a similar manner by a similar
nekton assemblage, so restoration efforts were deemed successful. This is in agreement with multiple comparative studies from
the ame marshes examining fish, invertebrates, and vegetation in different marsh habitats. 相似文献
11.
The tidally inundated marsh surface is an importnat site for energy exchanges for many resident and transient species. In
many areas along the East Coast of the U.S. the dominant vegetation,Spartina alterniflora, has been replaced by the common reed (Phragmites australis). This shift has caused concern about the impact ofPhragmites on marsh fauna but research in this area has been limited. During 1997 and 1998, we examined the effect ofPhragmites on fish and decapod crustacean use of the marsh surface in the brackish water reaches of the Mullica River, in southern New
Jersey, U.S. Fish and decapod crustaceans were sampled with an array of shallow pit traps (rectangular glass dishes, 27.5×17.5×3.7
cm) and with flumes (1.3 m wide×10 m long of 3.2-mm mesh). Fish (2–60 mm TL) dominated pit trap collections withFundulus heteroclitus andFundulus luciae significantly more abundant atSpartina sites.Fundulus heteroclitus was also the dominant fish (15–275 mm TL) collected in flumes but collections with this gear, including a number of species
not collected in pit traps, showed no distinct preferences for different marsh vegetation types. Decapod crustaceans (1–48
mm CW) collected in pit traps were generally less abundant than fishes withCallinectes sapidus andPalaemonetes spp. most abundant inSpartina, whileRhithropanopeus harrisii was most abundant inPhragmites. The same decapod crustacean species (2–186 mm CW) dominanted the flume collections and, similar to the pattern of fish collected
by the flumes, there were no distinct habitat preferences for different marsh vegetation types. As a result of these observations,
with different sampling techniques, it appears there is an overall negative effect ofPhragmites on larval and small juvenile fish but less or no effect on larger fish and decapods crustaceans. 相似文献
12.
Three factors affecting the structure of nekton communities 9fishes and decapod crustaceans) in eelgrass beds were identified and evaluated: contiguous shoreline type, distance from shore, and macrophyte biomass. Throw traps (1 m2) were used to sample eelgrass nekton at seven locations in Great South Bay (New York, U.S.) along Fire Island National Seashore from May through October 1995. Abundances ofGobiosoma ginsburgi, Apeltes quadracus, andOpsanus tau were significantly higher in eelgrass beds adjacent to salt marshes.Menidia menidia, Syngnathus fuscus, Pseudopleuronectes americanus, andPalaemonetes pugio were significantly more abundant in eelgrass adjacent to beaches. Regression analyses indicated thatSyngnathus fuscus, Pseudopleuronectes americanus, andAnguilla rostrata abundances were positively related to eelgrass biomass, andApeltes quadracus andGobiosoma ginsburgi abundances were highest at moderate levels of macroalgae biomass. The distance of an eelgrass bed from shore was also important. Species generally associated with salt marshes (Fundulus heteroclitus, Cyprinodon variegatus, Lucania parva, andPalaemonetes pugio) were more abundant in eelgrass near the marsh shore. Abundances ofApeltes quadracus, Syngnathus fuscus, Menidia menidia, Hippolyte pleuracanthus, andCrangon septemspinosa increased with distance from the shoreline. Shoreline type, distance from shore, and macrophyte biomass appear to affect the abundance and distribution of some nekton species. The effect of shoreline type may be related to the distribution of macrophyte biomass; the biomasses of eelgrass and macroalgae were significantly higher along beach and marsh shorelines, respectively. Explaining within-habitat variability and identifying microhabitat preferences for nekton will aid in the proper design of future studies and habitat restoration efforts. 相似文献
13.
It is often presumed that salt marshes provide a predation refuge for small fishes, but predation risks have rarely been compared in intertidal and subtidal habitats, making the importance of salt marshes as a predation refuge speculative. We measured relative survival of tethered mummichog (Fundulus heteroclitus) in four habitats in a salt marsh?Ctidal creek system: unvegetated and vegetated intertidal areas and the subtidal creek at high and low tide. At high tide, mummichog in the intertidal zone had significantly higher survival than in the subtidal creek in June through August. Survival rates in unvegetated and vegetated intertidal habitats were not significantly different, suggesting that higher intertidal survival was due to less abundant predators compared with the creek, rather than predators being less effective in vegetation. The lower predation risk experienced by mummichog in the intertidal marsh suggests that access to intertidal habitats will be important for production of small estuarine fishes. 相似文献
14.
Habitat use,temporal abundance variability,and diet of blue crabs from a New Jersey estuarine system
In a long-term, spatially comprehensive beam trawl survey of the Navesink River-Sandy Hook Bay estuary, the blue crabCallinectes sapidus was one of the most abundant species. Seasonal changes in abundance were evident, with low abundances in summer followed
by peak abundances in the fall, after juveniles recruited to the estuary. We saw no long-term trends in abundance during the
5 yr study. Location in the navesink River or Sandy Hook Bay explained most of the variance in abundance within any one survey.
In diet analyses, we found evidence of cannibalism in all seasons, but in the size range of crabs caught in this study (10–180
mm), we did not find a relationship between cannibalism and juvenile crab abundance. Within surveys, crabs divided into 20
mm size categories showed no sizerelated differences in location within the estuary or among 7 habitat types examined (algae
bed, amphipod bed, beach, channel, marsh edge, mid-depth, and sandbar). Channels and sandbars tended to exhibit lower crab
abundance than other habitats. Shallow habitats with and without cover were equally preferred by juvenile blue crabs, implying
that the presence of structure was not critical. Spatial models of crab abundance (<- 80 mm carapace width) to environmental
data were fit from several seasons of intensive sampling in the Navesink River-Sandy Hook Bay estuary between summer 1996
and spring 1998. These models indicated that fine-grained sediments, tmmperature, depth, and salinity were good indicators
of crab abundance in spring, summer, and fall. Using these spatial models and environmental data collected in subsequent seasons
(summer 1998−fall 1999), we were able to predict blue crab abundance in the river as evidenced by significant correlations
between predicted and observed abundances. For the size range of crabs examined here, physical conditions may be as important
as structural habitat types or cannibalism in determining habitat use in northerly estuaries. 相似文献
15.
Densities of juvenile and postlarval Farfantepenaeus aztecus, F. duorarum, and Litopenaeus setiferus were compared in vegetated fringing marsh and adjacent nonvegetated areas over a range of environmental conditions in Mobile Bay, Alabama. Densities of all three species were significantly greater in vegetated than nonvegetated areas, with 82% of all penaeids found in vegetated areas. Among vegetated sites, significantly lower densities were found in oligohaline areas, whereas mesohaline areas had the highest densities. Significant positive correlations were found between density and salinity for F. aztecus and F. duorarum but not for L. setiferus. Emergent vegetation is important habitat for F. aztecus and F. duorarum as reported from other locations, and our data support a similar conclusion for L. setiferus. Shoreline emergent marsh vegetation is particularly important in Mobile Bay as it represents the only extensive vegetated habitat readily available to F. aztecus, F. duorarum, and L. setiferus. 相似文献
16.
Much effort has been directed recently at restoring marshes, by the removal of the invasive common reed,Phragmites australis, yet it is not clear how fish and invertebrates have responded either to the invasion ofPhragmites or to marsh restoration. The blue crab,Callinectes sapidus, uses marsh habitats during much of its benthic life. We investigated the response of blue crabs toPhragmites invasion and restoration efforts by comparing crab abundance (catch per unit effort), mean size and size frequency distribution,
sex ratio, and molting of crabs in three physically similar areas differing in marsh vegetation;Spartina-dominated,Phragmites-dominated, and a treated area (Phragmites removed and now dominated bySpartina) in one marsh in the upper portion of Delaware Bay. Field sampling occurred monthly (April to November) from 1999 to 2001
using replicate daytime otter trawls in large marsh creeks. Crabs were categorized by carapace width into recruits (<30 mm),
juveniles (30–115 mm), and adults (>115 mm). Juveniles dominated the system, representing 69.4% of all crabs. Similar monthly
increases in mean size and molting patterns during the growing season (May–August) occurred inSpartina (natural and treated sites) andPhragmites sites suggesting that, subtidal habitats, used for molting, in these areas do not differ. More juveniles in the feeding molt
stage (i.e., intermolt) than in other molt stages and more recruits predominantly in the feeding molt stage than adults were
inSpartina, suggesting differences in the marsh surfaces used as feeding habitats withSpartina being preferred. Sex ratios of each life history stage were skewed towards males, but this was related to the low salinity
of Alloway Creek, rather than marsh surface vegetation. Our results suggest that marsh surface vegetation influences the way
blue crabs use marsh surface habitats, thus restoration efforts focusing on changing vegetation type may have a positive influence
on blue crabs. 相似文献
17.
R. T. Kneib 《Estuaries and Coasts》1997,20(1):214-230
Variability in early life stages of species that are permanent residents of the estuarine nekton is poorly understood, especially in systems with extensive areas of emergent vegetation (e.g., salt marshes and mangroves). Sampling small mobile nekton in these shallow intertidal habitats presents a difficult methodological challenge. Simulated aquatic microhabitats (SAMs) were used to collect the early life stages of resident nekton that remained on the emergent marsh surface after it was exposed by the tide and could not be adequately sampled by traditional methods. Where the intertidal is a prominent areal component of the estuary, a large portion of young nekton could be overlooked using other common survey methods (e.g., plankton tows or block nets). Populations of young fishes and natant crustaceans were monitored for a year at 3-d to 6-d intervals from both low and high intertidal elevations within each of two marsh sites on Sapelo Island, Georgia, USA. Three species accounted for >99% of the 41,023 individuals collected. These were the killifishesFundulus heteroclitus (57.0%) andF. luciae (4.0%), and the daggerblade grass shrimp,Palaemonetes pugio (38.4%). YoungF. heteroclitus were used in field enclosure experiments to relate abundance data to actual areal densities. Average annual estimated density of young nekton on the surface of the intertidal marsh at low tide was 7.2 individuals m?2. Early life stages of estuarine resident species, particularly those with demersal young, are not affected by the same physical processes influencing larval supply and recruitment variability in marine-spawned species. In salt marshes, biotic factors (e.g., adult reproductive activity, predation, and food limitation) may be more important as proximate causes of variation during the early life histories of resident nekton. 相似文献
18.
Frank Jordan 《Estuaries and Coasts》2002,25(2):288-295
I examined the relative importance of beds of tapegrass (Vallisneria americana) and adjacent unvegetated habitats to juvenile and adult (6–35 mm standard length) rainwater killifish (Lucania parva) over a large spatial scale within the St. Johns River estuary, Florida. Abundance of rainwater killifish did not differ between oligohaline and tidal freshwater portions of the estuary and this species was relatively rare at opposite ends of the St. Johns River estuary. The presence of rainwater killifish at a given site was determined in part by large-scale variation in environmental factors such as habitat complexity and salinity. When present at a site, rainwater killifish were found almost exclusively in structurally complex beds of tapegrass. Behavioral observations in the laboratory indicated that rainwater killifish preferred vegetated over unvegetated habitats in the absence of both potential prey and predators and that use of vegetated habitats increased further upon addition of predatory largemouth bass (Micropterus salmoides). A laboratory predation experiment indicated that survival of rainwater killifish exposed to largemouth bass was significantly higher in vegetation than over open sand. Strong preferences for structurally complex vegetation likely reflect an evolved or learned behavioral response to risk of predation and help explain habitat use of rainwater killifish in the St. Johns River estuary. 相似文献
19.
In Grand Bay National Estuarine Research Reserve (Grand Bay NERR), Mississippi, we used quantitative drop sampling in three
common shallow estuarine habitats—low profile oyster reef (oyster), vegetated marsh edge (VME), and nonvegetated bottom (NVB)—to
address the dearth in research comparing nekton utilization of oyster relative to adjacent habitats. The three habitats were
sampled at two distinct marsh complexes within Grand Bay NERR. We collected a total of 633 individual fishes representing
41 taxa in 22 families. The most diverse fish family was Gobiidae (seven species) followed by Blennidae and Poeciliidae (three
species each). We collected a total of 2,734 invertebrates representing 24 taxa in 11 families. The most diverse invertebrate
family was Xanthidae (six species) followed by Palaemonidae (five species). We used ordination techniques to examine variation
in species relative abundance among habitats, seasons, and sampling areas, and to identify environmental gradients correlated
with species relative abundances. Our resulted indicated that oyster provided a similarly complex and important function as
the adjacent VME. We documented three basic trends related to the importance of oyster and VME habitats: 1) Oyster and VME
provide habitat for significantly more species relative to NVB, 2) Oyster and VME provide habitat for rare species, and 3)
Several species collected across multiple habitats occurred at higher abundances in oyster or VME habitat. We also found that
salinity, temperature, and depth were associated with seasonal and spatial shifts in nekton communities. Lastly, we found
that the relative location of the two marsh complexes we studied within the context of the whole estuary may also explain
some of the temporal and spatial differences in communities. We conclude that oyster habitat supported a temporally diverse
and spatially distinct nekton community and deserves further attention in research and estuarine conservation efforts. 相似文献
20.
The use of the Tejo estuary, Portugal, salt marsh creeks by nekton was examined based on sampling surveys with a fyke net
from September 1998 until August 2001. From the 20 taxa (14 fish species, 5 decapod crustacean species, and 1 cephalopod species)
identified in the studied creeks, 16 were regularly caught throughout the sampling period. The shrimpPalaemonetes varians was the most numerically abundant species in the creeks, while the biomass was dominated by the mulletLiza ramada. The nekton assemblage was mainly represented by marine-estuarine opportunist species, comprising 85% of the total. A high
seasonality was detected on the species abundance patterns: the most abundant species (P. varians, Crangon crangon, L. ramada, Pomatoschistus microps, Syngnathus sp., andAnguilla anguilla) occurred throughout the sampling period,Sardina pilchardus, Dicentrarchus, labrax, andAtherina boyeri were particularly abundant in spring and summer, andEngraulis encrasicholus, Liza aurata, Gambusia holbrooki, Palaemon longirostris, andPalaemon serratus were most abundant in autumn and winter.L. ramada occurred in the tidal creeks in high numbers during neap tides, while the majority of the remaining taxa were most abundant
during spring tides, suggesting a differential pattern of habitat use occording to species. 相似文献