Habitat use and movement of the mummichog (<Emphasis Type="Italic">Fundulus heteroclitus</Emphasis>) in a restored salt marsh

The mummichog,Fundulus heteroclitus, is one of the most abundant macrofaunal components of salt marsh ecosystems along the east coast of the United States. During April–November 1998, we determined the habitat use and movement patterns of young-of-the-year (YOY) and adult mummichogs in a restored marsh, formerly a salt hay farm, and an adjacent creek in order to expand our understanding of the ecology of the species and evaluate the success of the restoration. Four major fish habitat types (large first-order natural creek, second-order created creek, linear drainage ditch, and marsh surface) were identified within the study site. Patterns of relative abundance and mark and recapture using coded wire tags were used to determine the habitat use, tidal movements, home range, and site fidelity of the species within these habitat types. A total of 14,784 fish, ranging from 20–100 mm SL, were captured with wire mesh traps and tagged, and 1,521 (10.3%) fish were recaptured. A variety of gears were used to attempt to recapture fish across all habitat types, including wire mesh traps, push nets, and otter trawls. Based on abundance and recaptures of tagged fish, the YOY and adults primarily used the shallow subtidal and intertidal areas of the created creek, the intertidal drainage ditches, and the marsh surface of the restored marsh but not the larger, first-order natural creek. At low tide, large numbers were found in the subtidal areas of the created creek; these then moved onto the marsh surface on the flooding tide. Elevation, and thus hydroperiod, appeared to influence the microscale use of the marsh surface. We estimated the home range of adults and large YOY (20–100 mm SL) to be 15 ha at high tide, which was much larger than previously quantified. There was strong site fidelity to the created creek at low tide. The habitat use and movement patterns of the mummichog appeared similar to that reported for natural marshes. Coupled with the results of other studies on the feeding, growth, and production of this species in this restoreh, the species appeared to have responded well to the restoration.     

Nekton Use of Flooded Salt Marsh and an Assessment of Intertidal Creek Pools as Low-Tide Refuges

Patterns of nekton occurrence on the salt marsh surface at high tide and in an adjacent intertidal creek pool at low tide were used to investigate movements of nekton in an intertidal basin. Paired collections were made in North Inlet estuary, SC on 67 dates over 9 years. Comparisons of high- and low-tide total abundance indicated that what remained in the creek pool at low tide was representative of the nekton on the flooded marsh. Of the 64 taxa collected, the same 8 species ranked in the top 10 in both the high- and low-tide collections. Abundances of most resident species were positively correlated with the area of marsh flooded, but mummichog (Fundulus heteroclitus), the most abundant resident, was not. Abundances of young-of-the-year transient species were not related to the extent of tidal flooding. Some transient species used the flooded marsh but did not occupy the pool at low tide, and others found in the pool did not use the marsh. Differences in abundance, biomass, and length between the marsh and pool collections indicated differences in the tendency of species and life stages to retreat downstream of the pool to the subtidal channel. Proportionately more of the nekton that were present on the flooded marsh left the intertidal basin when large changes in temperature and salinity occurred between high and low tides. More transients left the basin following higher tides, but more residents did not. The results demonstrate a wide range of taxonomic and ontogenetic patterns among nekton using intertidal salt marsh basins and the underappreciated importance of intertidal creek pools as alternative low-tide refuges.     

Salt-marsh tide pools as winter refuges for the mummichog,Fundulus heteroclitus,in New Jersey

Mummichog,Fundulus heteroclitus, were collected weekly from a southern New Jersey high-salinity salt marsh from October 1988 to June 1989 and from September 1989 to June 1990 to determine the overwintering habitat. Major habitat types sampled within the salt marsh were subtidal creek, intertidal creeks, and salt-marsh pools. Few individuals were collected in the intertidal creek or the subtidal creek from the end of October through the beginning of May for both years, when creek water temperatures were low. Both young-of-the-year and adults of both sexes were abundant in the salt-marsh pools (total lengths ranged from 29 mm to 125 mm) throughout the winter. In the spring, catch per unit effort (CPUE) within the tidal creek increased with increasing water temperature, while CPUE in marsh pools decreased with increases in estuarine water temperature. These collection patterns indicate that the majority ofF. heteroclitus may move from subtidal and intertidal creeks into salt-marsh pools in the late fall and leave in the spring. This seasonal movement could explain how fish survive winter environmental conditions because daily average water temperatures of salt-marsh pools were warmer than subtidal creek temperatures for much of the winter.     

Dominance of Tilapia mossambica,an introduced fish species,in three Puerto Rican estuaries

We compared species presence, abundance, and size characteristics of fish in three brackish, coastal marshes at Humacao, Roosevelt Roads, and Boqueron, Puerto Rico, in February and March 1988. The three marsh ecosystems were similar with respect to the presence of large expanses of open water bordered by emergent vegetation, creeks, and mangroves, and all had some recreational use. We sampled fish using gill nets. Tilapia (Oreochromis) mossambica were the most abundant fish, accounting for 55–79% of the samples at all three marshes. Overall, tilapia were both the largest (North Lagoon) and the smallest (Frontera Creek) at Humacao. Tilapia were most common in open lagoons rather than creeks or bays (except for Mandri Creek), and their distribution seemed unrelated to salinity. Tarpon (Megalops atlantica) were more abundant at low salinities, whereas other fish were more abundant at higher salinities.     

Evaluating salt marsh restoration in Delaware Bay: Analysis of Fish response at former salt hay farms

In a continuing effort to monitor the fish response to marsh restoration (resumed tidal flow, creation of creeks), we compared qualitative and quantitative data on species richness, abundance, assemblage structure and growth between pre-restoration and post-restoration conditions at two former salt hay farms relative to a reference marsh in the mesohaline portion of Delaware Bay. The most extensive comparison, during April–November 1998, sampled fish populations in large marsh creeks with otter trawls and in small marsh creeks with weirs. Species richness and abundance increased dramatically after restoration. Subsequent comparisons indicated that fish size, assemblage structure, and growth of one of the dominant species,Micropogonias undulatus, was similar between reference and restored marshes 1 and 2 yr post-restoration. Total fish abundance and abundance of the dominant species was greater, often by an order of magnitude, in one of the older restored sites (2 yr post-restoration), while the other restored site (1 yr post-restoration) had values similar to the reference marsh. The success of the restoration at the time of this study suggests that return of the tidal flow and increased marsh area and edge in intertidal and subtidal creeks relative to the former salt hay farms contributed to the quick response of resident and transient young-of-the-year fishes.     

Impact of Armored Shorelines on Shore-Zone Fish Density in a Mid-Atlantic,USA, Estuary: Modulation by Hypoxia and Temperature

Anthropogenic modifications of estuarine environments, including shoreline hardening and corresponding alteration of water quality, are accelerating worldwide as human population increases in coastal regions. Estuarine fish species inhabiting temperate ecosystems are adapted to extreme variations in environmental conditions including water temperature, salinity, and dissolved oxygen across seasonal, daily, and hourly time scales. The present research utilized quantitative sampling to examine the spatiotemporal distribution of shore-zone estuarine fish species in association with four unique shoreline types across a range of water temperature and dissolved oxygen conditions. Fish were collected from the intertidal and shallow subtidal region of four shoreline types, Spartina alterniflora marsh, Phragmites australis marsh, riprap, and bulkhead, in the summer and fall of 2009 and 2010. Analyses were performed to (1) compare mean fish density among shoreline types across all water conditions and (2) explore relationships of the complete fish assemblage, three functional species groupings, and two fish species (Fundulus heteroclitus and Menidia menidia) to unique shoreline/water conditions. Significantly greater mean fish densities were found along S. alterniflora shorelines than armored shorelines. Several metrics including fish density, species richness, and occurrence rates suggest S. alterniflora shorelines may serve as a form of refuge habitat during periods of low dissolved oxygen and high temperatures for various species, particularly littoral-demersal species including F. heteroclitus. Potential mechanisms that could contribute to a habitat providing refuge during adverse water quality conditions include tempering of the adverse condition (decreased temperatures, increased dissolved oxygen), predation protection, and increased foraging opportunities.     

Coastal saltmarsh development at Southern Topsail Sound,North Carolina

Topsail Sound is a marsh-filled barrier lagoon in southeastern North Carolina. This study quantified changes within a 477-ha tidal marsh located landward of Lea and Coke islands in southern Topsail Sound. Aerial photographs from 1949, 1966, and 1984 were enlarged, and sample areas of salt marsh were digitized and compared. Since 1949, Old Topsail Inlet has migrated southwest 1.2 km. As the inlet migrated, new Spartina alterniflora marsh colonized 33.2 ha of intertidal sand flats within the inlet flood tidal delta, adjacent islands, and primary tidal creeks. Landward of the flood tidal delta, site specific gains and losses of marsh were recorded. It is estimated that since 1949, approximately 34.1 ha of the marsh area occupying the zone landward of the flood tidal delta has drowned. This loss of marsh, combined with the colonization of marsh mentioned above, resulted in a net decrease of 1 ha in the total area of marsh. This study provides evidence that, although lagoonal marshes may be drowning as a result of soil waterlogging, reduced sediment supply, and sea-level rise, potential marsh environments are created by oceanic inputs of sand when inlets migrate.     

Indirect environmental effects of dikes on estuarine tidal channels: Thinking outside of the dike for habitat restoration and monitoring

While the most obvious effects of dike construction and marsh conversion are those affecting the converted land (direct or intended effects), less immediately apparent effects also occur seaward of dikes (indirect or unintended effects). I analyzed historical photos of the Skagit River delta marshes (Washingto, U.S.) and compared changes in estuarine marsh and tidal channel surface area from 1956–2000 in the Wiley slough area of the South fork Skagit delta, and from 1937–2000 in the North Fork delta. Dike construction in the late 1950s caused the loss of 80 ha of estuarine marsh and 6.7 ha of tidal channel landward of the Wiley Slough dikes. A greater amount of tidal channel surface area, 9.6 ha, was lost seaward of the dikes. Similar losses were observed for two smaller North Fork tidal channel systems. Tidal channels far from dikes did not show comparable changes in channel surface areas. These results are consistent with hydraulic geometry theory, which predicts that diking reduces tidal flushing in the undiked channel remnants and this results in sedimentation. Dikes may have significant seaward effects on plants and animals associated with tidal channel habitat. Another likely indirect dike effect is decreased sinuosity in a distributary channel of the South Fork Skagit River adjacent to and downstream of the Wiley Slough dikes, compared to distributary channels upstream or distant from the dikes. Loss of floodplain area to diking and marsh conversion prevents flood energy dissipation over the marsh surface. The distributary channal has responded to greater flood energy by increasing mean channel width and decreasing sinuosity. Restoration of diked areas should consider historic habitat loss swaward of dikes, as well as possible benefits to these areas from dike breaching or removal. Habitat restoration by breaching or removal of dikes should be monitored in areas directly affected by dikes, areas indirectly affected, and distinct reference areas.     

Fish assemblage composition in constructed and natural tidal marshes of San Diego Bay: Relative influence of channel morphology and restoration history

This study evaluated the use by fish of restored tidal wetlands and identified links between fish species composition and habitat characteristics. We compared the attributes of natural and constructed channel habitats in Sweetwater Marsh National Wildlife Refuge, San Diego Bay, California, by using fish monitoring data to explore the relationships between channel environmental characteristics and fish species composition. Fishes were sampled annually for 8 yr (1989–1996) at eight sampling sites, four in constructed marshes and four in natural marshes, using beach seines and blocking nets. We also measured channel habitat characteristics, including channel hydrology (stream order), width and maximum depth, bank slope, water quality (DO, temperature, salinity), and sediment composition. Fish colonization was rapid in constructed channels, and there was no obvious relationship between channel age and species richness or density. Total richness and total density did not differ significantly between constructed and natural channels, although California killifish (Fundulus parvipinnis) were found in significantly higher densities in constructed channels. Multivariate analyses showed fish assemblage composition was related to channel habitat characteristics, suggesting a channel’s physical properties were more important in determining fish use than its restoration status. This relationship highlights the importance of designing restoration projects with natural hydrologic features and choosing proper assessment criteria in order to avoid misleading interpretations of constructed channel success. We recommend that future projects be designed to mimic natural marsh hydrogeomorphology and diversity more closely, the assessment process utilize better estimates of fish habitat function (e.g., individual and community-based species trends, residence time, feeding, growth) and reference site choice, and experimental research be further incorporated into the restoration process.     

Habitat use patterns of the mummichog,Fundulus heteroclitus, in New England. I. Intramarsh variation

Although studies of intertidal habitats have contributed greatly to the field of ecology, the processes governing the use of these areas by highly mobile animals such as fish remain poorly understood. In particular, although large-scale patterns of estuarine fish abundances are well known, fine-scale patterns of habitat use have been largely overlooked. Here, I examine among and within habitat use patterns of the mummichog,Fundulus heteroclitus, in a New England salt marsh. Using minnow traps I sampled changes in mummichog habitat use among closely spaced sites within creeks, mudflat, and channel over 2 yr. The general pattern of mummichog captures was consistent among years, showing peaks in summer months and lows in winter. Use of specific habitat types was also seasonally dependent. For most of the year (fall, winter, spring) mudflat capture rates were lower than creek capture rates in the summer; however, densities in the mudflat equal or exceed those in creeks. In most months channel habitats did not differ significantly in use from either creek or mudflat habitat. Consistent patterns also occur within induividual marsh habitats.F. heteroclitus concentrate in the uppermost portion of creeks. Additionally, mudflat capture rates (August 1990) declined with increasing water depth. Diurnal habitat use is heavier than nocturnal use for all habitats. These findings demonstrate that mummichogs are restricted to areas representing a very small proportion of total available habitat and that their patterns of habitat use are strongly seasonal. Only careful experimental work can determine the relative advantages of these habitats for estuarine fish. Further comparative work is required to reveal how biological and physical parameters affecting habitat use may vary geographically.     

The value of salt marsh edge vs interior as a habitat for fish and decapod crustaceans in a Louisiana tidal marsh

Flume nets of various lengths and a 3-m seine were used to sample the fishes and macrocrustaceans using a flooded Louisiana salt marsh and the adjacent tidal creek. The experiment allowed for species-specific comparisons of the flooded marsh at the creek edge versus the interior. Of the 37,667 organisms collected in flume nets from January through November 1989, 89% were decapods (nine species) and 11% were fish (29 species). An additional 18,539 organisms (75% decapods and 25% fish) were collected from concurrent seine samples taken from July through November. Comparison of catches among different flume lengths and low tide versus high tide seine collections revealed distinct patterns of marsh habitat utilization. Densities of most organisms were highest within 3 m of the water’s edge, but significant numbers of marsh-resident fish species used the interior marshes. The edge marshes appeared to be used by both transient and resident species; however, the interior marshes were used primarily by marsh-resident species (Cyprinodontiformes andPalaemonetes sp.) that are excellent food sources for adult transient-species. Four zonations of marsh use are described for transients, residents, and rare species.     

Rates, patterns, and impacts ofPhragmites australis expansion and effects of experimentalPhragmites control on vegetation, macroinvertebrates, and fish within tidelands of the lower Connecticut River

Phragmites expansion rates (linear at 1–3% yr⁻¹) and impacts of this expansion on high marsh macroinvertebrates, aboveground production, and litter decomposition fromPhragmites and other marsh graminoids were studied along a polyhaline to oligohaline gradient. These parameters, and fish use of creeks and high marsh, were also studied inPhragmites control sites (herbicide, mowing, and combined herbicide/mow treatments).Phragmites clones established without obvious site preferences on oligohaline marshes, expanding radially. At higher salinities,Phragmites preferentially colonized creekbank levees and disturbed upland borders, then expanded into the central marsh. Hydroperiods, but not salinities or water table, distinguishedPhragmites-dominated transects. Pooled samples ofPhragmites leaves, stems, and flowers decompose more slowly than other marsh angiosperms;Phragmites leaves alone decompose as or more rapidly than those of cattail. AbovegroundPhragmites production was 1,300 to 2,400 g m⁻² (about 23% of this as leaves), versus 600–800 g m⁻² for polyhaline to mesohaline meadow and 1,300 g m⁻² for oligohaline cattail-sedge marsh. Macroinvertebrates appear largely unaffected byPhragmites expansion or control efforts; distribution and densities are unrelated to elevation or hydroperiod, but densities are positively related to litter cover. Dominant fish captured leaving flooded marsh wereFundulus heteroclitus andAnguilla rostrata; both preyed heavily on marsh macroinvertebrates.A. rostrata andMorone americana tended to be more common inPhragmites, but otherwise there were no major differences in use patterns betweenPhragmites and brackish meadow vegetation. SAV and macroalgal cover were markedly lower within aPhragmites-dominated creek versus one withSpartina-dominated banks. The same fish species assemblage was trapped in both plus a third within the herbicide/mow treatment. Fish biomass was greatest from theSpartina creek and lowest from thePhragmites creek, reflecting abundances ofF. heteroclitus. Mowing depressedPhragmites aboveground production and increased stem density, but was ineffective for control.Phragmites, Spartina patens, andJuncus gerardii frequencies after herbicide-only treatment were 0.53-0.21; total live cover was <8% with a heavy litter and dense standing dead stems. After two growing seasonsAgrostis stolonifera/S. patens/J. gerardii brackish meadow characterized most of the herbicide/mow treatment area;Phragmites frequency here was 0.53, contributing 3% cover. Both values more than doubled after four years; a single treatment is ineffective for long-termPhragmites control.     

The utilization of an intertidal salt marsh creek by larval and juvenile fishes: Abundance,diversity and temporal variation

The utilization of an intertidal salt marsh creek in South Carolina during January 1977 was determined by sampling every third ebb tide for 13 days. All fishes leaving the creek during that period were captured in a channel net. This procedure produced a time-series of samples which permitted analysis of the fish community occupying the intertidal creek at all times of day and night. A total of 14,730 larval, juvenile, and adult fishes comprising at least 22 species in 16 families were collected. The most common larval and juvenile fishes wereLeiostomus xanthurus, Mugil spp.,Myrophis punctatus leptocephali,Lagodon rhomboides, Paralichthys spp., andMicropogon undulatus. Catch sizes for all species varied widely between samples. No diurnal-nocturnal pattern in catches was evident forL. xanthurus, Mugil spp.,L. rhomboides andM. undulatus. M. punctatus was taken in large numbers only when the flood tide occurred during the day, while moreParalichthys spp. larvae were taken in late afternoon-evening flood tide samples. The most common invertebrate,Palaemonetes pugio, was taken in large quantities only in late afternoon-night flood tide samples. Three diversity indices were computed for each sample. Values for all indices varied widely between successive samples. The results emphasize a high degree of utilization of the intertidal creek habitat by larval and juvenile fishes. The diurnal-nocturnal activity patterns of some species, and the wide variation in catch size of the other species can permit use of the intertidal salt marsh habitat with reduced competition for available space and energy.     

Tidal utilization of nekton in Delaware Bay restored and reference intertidal salt marsh creeks

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.     

Marsh-creek connectivity: Fish use of a tidal salt marsh in Southern California

Salt marsh habitats influenced by southern California's mixed, semi-diurnal tides are, on average, accessible to fishes less than 16% of the time. However, five species (four natives, one oxotic) and a variety of juvenile and adult size classes were collected on the marsh surface during a year-long sampling from June 1997 through June 1998 at Sweetwater Marsh National Wildlife Refuge on San Diego Bay.Fundulus parvipinis andGillichthys mirabilis were the most abundant fish species using the marsh. Analyses of their guts revealed that the marsh surface provides a rich foraging area for fishes on high spring tides.F. parvipinnis with marsh access consumed six times as much food as fishes restricted to creek habitats (on a g-food g-fish^?1 basis) and also fed on additional prey types. Because the salt marsh is an important foraging area for fishes, we recommend that restoration projects (especially those intended to mitigate lost fish habitat) include vegetated areas with interconnecting tidal creeks.     

Species diversity and emergence patterns of nematocerous flies (Insecta: Diptera) from three coastal salt marshes in prince Edward Island, Canada

Emerging insects were monitored every 10 days between early May and late August 1993, from tidal pools in three coastal salt marshes on Prince Edward Island, Canada. The salt marsh pools ranged from about 1 m² to > 1,000 m² in surface area, and had salinities ranging from 11–27‰ Water temperatures through the study period ranged from 4–46°C. Most of the emerging insects were flies (Diptera; 85%), and two-thirds of these were in the sub-Order Nematocera, mainly Chironomidae, Ceratopogonidae, and Culicidae. Forty-three species of Nematocera were identified, although most of these were rare occurrences, and twelve of the species are undescribed. No consistent relationships were found between abundance or diversity and pool size or marsh for Nematocera species overall, although some species showed a statistical preference for a particular marsh or pool size. Emergence patterns were consistent between marshes for species found in different marshes, but overall patterns were highly variable, depending upon species.     

A comparison of dimension-adjusted catch data methods for assessment of fish and crab abundance in intertidal salt marshes

Sample collection methods and data standardization techniques accounting for marsh physiography were tested for mobile aquatic fauna in two intertidal pocket salt marshes in Sarah’s Creek, a tributary to the York River in Virginia. Fish and blue crab populations were described and compared as numbers per cubic meter of total marsh volume and numbers per square meter of total marsh area. These methods increase the accuracy of the analyses of sampled populations by relying on fewer assumptions than traditionals random sampling methods. Depending upon the season and the species compared, statistical differences were observed between dimension-adjusted data within the same sampled populations. Our data suggest that accurate population profiles can be determined if collection methods and data adjustments are based on the ecology, behavior, and life-history stage of the target species.     

Flow,stress and sediment resuspension in a shallow tidal channel

In October of 2004, a 3-d observational program to measure flow and sediment resuspension within a coastal intertidal salt marsh was conducted in the North Inlet/Winyah Bay National Estuarine Research Reserve located near Georgetown, South Carolina. Current and acoustic backscatter profiles were obtained from a moored acoustic Doppler current profiler (ADCP) deployed in a shallow tidal channel during the spring phase of the tidal cycle under high discharge conditions. The channel serves as a conduit between Winyah Bay, a large brackish estuary, and North Inlet, a saline intertidal coastal salt marsh with little freshwater input. Salinity measurements indicate that the water column is vertically well mixed during flood, but becomes vertically stratified during early ebb. The stratification results from brackish (15 psu) Winyah Bay water entering North Inlet via the tidal channel, suggesting an exchange mechanism that permits North Inlet to receive a fraction of the poor water quality and high discharge flow from upland rivers. Although maximum flood currents exceed maximum ebb currents by 0.2 m s⁻¹, suspended sediment concentrations are highest during the latter ebb phase and persist for a longer fraction of the ebb cycle. Even though the channel is flood-dominated, the higher concentrations occurring over a longer fraction of the ebb phase indicate net particulate transport from Winyah Bay to North Inlet during spring tide accompanied by high discharge. Our evidence suggests that the higher concentrations during ebb result from increased bed friction caused by flow asymmetries and variations in water depth in which the highest stresses occur near the end of ebb near low water despite stronger maximum currents during flood.     

Responses of fish and macrobenthic assemblages to hydrologic disturbances in Tijuana Estuary and Los Peñasquitos Lagoon,California

Changes in the assemblages of fishes and benthic macro-invertebrates were evaluated in relation to wastewater inflows at Tijuana Estuary and impounded streamflows and mouth closure at Los Peñasquitos Lagoon. Freshwater from sewage spills or winter rains lowered water salinities and had major impacts on the channel organisms of both southern California coastal wetlands. Benthic infaunal assemblages responded more rapidly to reduced salinity than did fishes, with continued salinity reduction leading to the extirpation of most species. Both the fish and benthic invertebrate assemblages became dominated by species with early ages of maturity and protracted spawning seasons. Between-system comparisons showed that good tidal flushing reduced negative impacts on both the fish and benthic assemblages.     

AreSpartina marshes a replaceable resource? A functional approach to evaluation of marsh creation efforts

Marsh creation has come into increasing use as a measure to mitigate loss of valuable wetlands. However, few programs have addressed the functional ecological equivalence of man-made marshes and their natural counterparts. This study addresses structural and functional interactions in a man-made and two natural marshes. This was done by integrating substrate characteristics and marsh utilization by organisms of two trophic levels. Sediment properties, infaunal community composition, andFundulus heteroclitus marsh utilization were compared for a man-madeSpartina salt marsh (between ages 1 to 3 yr) in Dills Creek, North Carolina, and adjacent natural marshes to the east and west. East natural marsh and planted marsh sediment grain-size distributions were more similar to each other than to the west natural marsh due to shared drainage systems, but sediment organic content of the planted marsh was much lower than in either natural marsh. This difference was reflected in macrofaunal composition. Natural marsh sediments were inhabited primarily by subsurface, deposit-feeding oligochaetes whereas planted marsh sediments were dominated by the tube-building, surface-deposit feeding polychaetesStreblospio benedicti andManayunkia aestuarina. Infaunal differences were mirrored inFundulus diets. Natural marsh diets contained more detritus and insects, because oligochaetes, though abundant, were relatively inaccessible. Polychaetes and algae were major constituents of the planted marshFundulus diet. Though naturalmarsh fish may acquire a potentially less nutritive, detritus-based diet relative to the higher animal protein diet of the planted marsh fish,Fundulus abundances were markedly lower in the planted marsh than in the natural marshes, indicating fewer fish were being supported. LowerSpartina stem densities in the planted marsh may have provided inadequate protection from predation or insufficient spawning sites for the fundulids. After three years, the planted marsh remained functionally distinct from the adjacent natural marshes. Mitigation success at Dills Creek could have been improved by increasing tidal flushing, thereby enhancing, access to marine organisms and by mulching withSpartina wrack to increase sediment organic-matter content and porosity. Results from this study indicate that salt marshes should not be treated as a replaceable resource in the short term. The extreme spatial and temporal variability inherent to salt marshes make it virtually impossible to exactly replace a marsh by planting one on another site.