Salt Hay Farms Research Articles

Response of Nekton to Tidal Salt Marsh Restoration, a Meta-Analysis of Restoration Trajectories

Restoration of 4049 ha of tidal wetlands was required to offset nekton losses at a power facility located on Delaware Bay, USA. Vegetation coverage, the permitted criterion for success, was compared by meta-analysis to restoration trajectories for abundance and growth of dominant nekton during the same 17-year period at two reference and five restoration sites. Mean catch per unit effort (CPUE), at both upper Bay (former Phragmites australis dominated sites) and lower Bay (former salt hay farms), were generally indistinguishable from those of the reference sites, and Hedge’s d for all sites suggested that numbers of individuals at restored locations did not differ significantly from those at the reference sites. Mean length distributions of dominant nekton in the upper Bay, however, were negative for all restoration sites combined by the end of the study. Although growth of nekton at the lower Bay restoration sites was indistinguishable from reference sites, the grand mean length for nekton measured at all sites in the Bay was negative suggesting that nekton growth at the formerly Phragmites-dominated sites failed to meet the restoration goals by the end of the study period. Thus, vegetation success criteria may not necessarily reflect recovery of animal related success criteria.

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 of Fundulus heteroclitus and Menidia 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 by F. 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 same marshes examining fish, invertebrates, and vegetation in different marsh habitats.

Long-term response of fishes and other fauna to restoration of former salt hay farms: multiple measures of restoration success

This synthesis brings together published and unpublished data in an evaluation of restoration of former salt hay farms to functioning salt marshes. We compared nine years of field measurements between three restored marshes (Dennis, Commercial, and Maurice River Townships) and a reference marsh (Moores Beach) in the mesohaline portion of Delaware Bay. In the process, we compared channel morphology, geomorphology, vegetation, sediment organic matter, fish assemblages, blue crabs, horseshoe crabs, benthic infauna, and diamondback terrapins. For fishes we compared structural (distribution, abundance) and functional (feeding, growth, survival, reproduction, production) aspects to evaluate the restored marshes in an Essential Fish Habitat context. Marsh vegetation and drainage density responded gradually and positively with restored marshes approximating the state of the reference marsh within the nine-year study period. The fauna responded more quickly and dramatically with most measures equal or greater in the restored marshes within the first one or two years after restoration. Differences in response time between the vegetation and the fauna imply that the faunal response was more dependent on access to the shallow intertidal marsh surface and intertidal and subtidal creeks than on characteristics of the vegetated marsh. The fishes in created subtidal creeks in restored marshes responded immediately and maintained fish assemblages similar to the reference marsh over the study period. The intertidal creek fish assemblages tended to become more like the reference marsh in the last years of the comparison. Overall, these results document the success of the restoration and how marshes function for both resident and transient fauna, especially fishes.

Integrating local ecological knowledge and manipulative experiments to find the causes of environmental change

In spite of the increasing use of local ecological knowledge (LEK) in various environmental studies, few methodological innovations exist to facilitate new uses. This is especially true in studies of environmental change, where standard methods of comparing LEK with scientific knowledge do little to bolster causal claims. Here, I report on a novel approach that uses LEK to formulate manipulative experiments. This interdisciplinary approach exploits LEK's rich historical observations, while employing experimental approaches to disentangle competing hypotheses and to identify underlying mechanisms. This integrated approach produces historically based, mechanistically sound explanations that can be more useful than either LEK or experimental studies alone. I illustrate this approach with recent studies of common reed (Phragmites australis) invasion in salt hay farms.

Salt marsh vegetation recovery at salt hay farm wetland restoration sites on Delaware Bay

Public Service Enterprise Group's (PSEG) Estuary Enhancement Program (EEP) restored normal daily tidal inundation and drainage to three previously diked farm sites totaling 1780 ha during the period 1996–1998 along the shoreline of the Delaware Estuary in New Jersey, USA. Normal tidal exchange was either prevented or altered by the construction of dikes and water control structures that were used to promote the growth of high marsh “salt hay” species, such as salt meadow cordgrass ( Spartina patens) and salt grass ( Distichlis spicata) at elevations below mean high tide. These elevations would normally support low marsh species, such as smooth cordgrass ( Spartina alterniflora). Prior to restoration these sites were either un-vegetated due to excessive ponding associated with poor drainage or vegetated with “salt hay” species as well as common reed ( Phragmites australis). Extensive S. alterniflora marshes occur in the vicinity of each site at similar elevations and these marshes were relied on as the source of seed for the re-establishment of S. alterniflora on the restoration sites; thus, no other planting or seeding was implemented to initiate re-vegetation. Vegetation coverage at the restoration sites as well as a naturally restored reference marsh was determined during 1996–2003 utilizing geo-referenced remote sensing data and geographic information system (GIS) analyses. Coverage by S. alterniflora or other desirable low marsh vegetation exceeded that required by New Jersey authorities to meet the restoration goal at two sites 8 years ahead of the anticipated 12-year period and re-vegetation of the third site is expected to meet its goal within the established 12-year period. Annual vegetation coverage data have been integral components of an adaptive management program utilized by PSEG to manage the restoration process at each of the sites.

Juvenile sciaenid fishes respond favorably to Delaware Bay marsh restoration

Former salt hay farms in Delaware Bay have been the site of extensive restorations aimed at restoring tidal flow to the sites, encouraging Spartina alterniflora (smooth cordgrass) recolonization and creating high-quality juvenile fish habitat. We assessed the 234 ha Dennis Township restoration site as habitat for juvenile Cynoscion regalis (weakfish), Leiostomus xanthurus (spot) and Micropogonias undulatus (Atlantic croaker) by comparing abundance, prey types consumed, stomach fullness and condition factor at the restored site and at a nearby reference marsh, Moores Beach. The three sciaenid species were equally or more abundant at the restored marsh. Measures of feeding were generally equal or higher at the restored site and stomach fullness was equal to or significantly higher at the restored marsh compared with the reference marsh. Fish condition, as measured by predicted weight-at-length, was generally at least equal between the sites and was occasionally higher at the restored site. At both sites, a seasonal pattern typical of mid-Atlantic estuaries of recruitment, ontogenetic change in food habits and emigration of transient fishes was apparent. Three years following restoration, the Dennis Township site provided equivalent to enhanced conditions for feeding and growth for large numbers of juvenile sciaenid fish, compared to a nearby reference site.

Delaware Bay salt marsh restoration: Mitigation for a power plant cooling water system in New Jersey, USA

In 1994 Public Service Electric and Gas of New Jersey (PSE&G), now Public Service Enterprise Group (PSEG), proposed and implemented a program to offset egg, larvae and fish losses at the cooling water intake at Salem Generating Station. The program included wetland habitat restoration, fish ladder installation, new cooling water intake technology, and a biological monitoring program. The wetland habitat restoration was the core component and the most controversial aspect of the program. It addressed two types of habitats: diked salt hay farms and wetlands dominated by Phragmites australis. The wetland restoration program used ecological engineering principles to restore approximately 4550 ha. It also protected upland buffers and other lands for a total of over 8700 ha. Eight fish ladders were installed to allow anadromous river herring to return to previously blocked spawning habitat. PSEG also implemented operational changes, installed advanced cooling water intake technology to reduce losses of invertebrates and early life stages of fish, and conducted studies of behavioral deterrents. The biological monitoring program continues to assess the abundance and distribution of juvenile coastal migratory fish species while they are in the Delaware River Estuary; it also monitors use of wetlands by fish and invertebrates.

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.

Evaluating salt marsh restoration in Delaware Bay: The response of blue crabs,Callinectes sapidus, at former salt hay farms

Marshes are important habitats for various life history stages of many fish and invertebrates. Much effort has been directed at restoring marshes, yet it is not clear how fish and invertebrates have responded to marsh restoration. The blue crab,Callinectes sapidus, uses marsh habitats during much of its benthic life. We investigated the response of blue crabs to marsh restoration by comparing crab abundance (catch per unit effort), mean size and size frequency distribution, sex ratio, and molt stages of crabs in recently restored marshes that were former salt hay farms to that of adjacent reference marshes with similar physical characteristics in the mesohaline portion of Delaware Bay. Field sampling occurred monthly (April–November) in 1997 and 1998 using replicate daytime otter trawls in large marsh creeks and weirs in smaller intertidal marsh creeks. Blue crabs were either equal or more abundant, the incidence of molting was in most months similar, and population sex ratios were indistinguishable in restored and reference marshes, suggesting that the restored areas attract crabs and support their growth. Site location had a greater effect on the sex ratio of crabs such that marshes closer to the mouth of the bay contained a higher percentage of adult female crabs. In each annual growing season (April–July), the monthly increase in crab size and, in some months (June–July), the incidence of molting at the restored sites was greater than the reference sites, suggesting that the restored sites may provide areas for enhanced growth of crabs. These results suggest that blue crabs have responded positively to restoration of former salt hay farms in the mesohaline portion of Delaware Bay.

Habitat use and movement of the mummichog (Fundulus heteroclitus) 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.

Growth and production of the mummichog (Fundulus heteroclitus) in a restored salt marsh

The mummichog,Fundulus heteroclitus, is one of the most important macrofaunal components of salt marsh surfaces and an important link to subtidal areas of the adjacent estuary along the east coast of the U.S. We estimated growth, population size, and production of the mummichog in a restored marsh in order to improve our understanding of the role of this resident fish and to evaluate the success of the restoration. The restored marsh, covering 234 ha, was a former salt hay farm located in the mesohaline portion of Delaware Bay that was restored to tidal influence in August 1996. We separated the mummichog population into two components based on life history stage and summer habitat use patterns. One component, consisting of adults and large young-of-the-year (YOY), exhibited tidal movements to and from the marsh surface and the subtidal creeks. These were examined with an intensive mark and recapture program using coded wire tags. Another component, consisting of small YOY, remained on the marsh surface throughout the tidal cycle. Throw traps were used to sample these small YOY. The mean annual population density of adults and large YOY for the entire marsh was approximately 1.2 fish m−2 and mean monthly density peaked at 2.9 fish m−2. The mean annual density of small YOY on the marsh surface was 15.1 fish m−2 and mean monthly density peaked at 41.4 fish m−2. Size and season influenced the growth rate of individual fish and instantaneous growth rates ranged from 0.03 to 2.26 mo−1. Total annual mummichog production was estimated to be 8.37 g dw m−2 yr−1, with adults and large YOY contributing 28.4% (2.38 g dw m−2 yr−1) and small YOY on the marsh surface contributing 71.6% (5.99 g dw m−2 yr−1). The seasonal use and population densities were comparable to previous studies in natural marshes while growth and production of mummichog in this restored marsh appeared to be higher. Coupled with the results of other studies on the feeding, movement, and habitat use of this species in this restored marsh, the species has responded well to the restoration.

Beneficial use of dredged material to enhance the restoration trajectories of formerly diked lands

Throughout the United States, coastal wetlands are being restored from formerly diked lands drained for agriculture. One such site, the 1620 ha Commercial Township Salt Hay Farm (CTSHF) is located on the southern Delaware Bay, USA. A common problem with these sites is their low elevation associated with long-term lack of tidal inundation and sediment accretion, compaction by heavy equipment, and oxidation associated with exposure to the atmosphere. With the reintroduction of tide, these areas, which have subsided by several meters or more, may become open water and tidal flats for extended periods before they return to wetland habitat. Different levels of subsidence also result in a wide range of marsh planforms including flats with little or no vegetation and/or semblance to the geomorphology of natural systems. The potential use of dredged materials for several aspects of the marsh restoration process—enhancing the sediment budget at low elevations, accelerating the restoration trajectories toward acceptable endpoints, improving the geomorphology of the marsh planform, providing high marsh refugia for species that depend on this habitat type for survival, reestablishing upland dike elevations for off-site protection of people and property, and stabilizing shorelines to reduce erosion rates—are the subjects of this paper. The abundance of dredged materials from channel deepening projects that will occur nation-wide, the maintenance dredging of major ports, on-site construction and other projects provide a wealth of opportunities to combine dredging needs with coastal marsh rehabilitation and restoration.

Restoration principles emerging from one of the world's largest tidal marsh restoration projects

One of the world’s largest tidal wetland restoration projects was conceived to offset the loss of nekton to oncethrough cooling at a power plant on Delaware Bay, USA. An aggregated food chain model was employed to estimate the area of tidal salt marsh required to replace these losses. The 5040 ha was comprised of two degraded marsh types – Phragmites-dominated marshes and diked salt hay farms – at eleven locations in oligo-mesohaline and polyhaline reaches of the estuary. At a series of ‘summits’ convened with noted experts in the field, it was decided to apply an ecological engineering approach (i.e., ‘self design’, and minimal intrusion) in a landscape ecology framework to the restoration designs while at the same time monitoring long-term success of the project in the context of a ‘bound of expectation’. The latter encompassed a range of reference marsh planforms and acceptable end-points established interactively with two advisory committees, numerous resource agencies, the permitting agency and multiple-stakeholder groups. In addition to the technical recommendations provided by the project’s advisors, public health and safety, property protection and public access to the restored sites were a constant part of the dialogue between the utility, its consulting scientists and the resource/permitting agencies. Adaptive management was used to maintain the restoration trajectories, ensure that success criteria were met in a timely fashion, and to protect the public against potential effects of salt intrusion into wells and septic systems, and against upland flooding. Herbicide spray, followed by prescribed burns and altered microtopography were used at Phragmites-dominated sites, and excavation of higher order channels and dike breaching were the methods used to initiate the restorations at the diked salt hay farms. Monitoring consisted of evaluating the rate of re-vegetation and redevelopment of natural drainage networks, nekton response to the restorations, and focused research on nutrient flux, nekton movements, condition factors, trophic linkages, and other specific topics. Because of its size and uniqueness, the Estuary Enhancement Program as this project is known, has become an important case study for scientists engaged in restoration ecology and the application of ecological engineering principles. The history of this project, and ultimately the Restoration Principles that emerged from it, are the subjects of this paper. By documenting the pathways to success, it is hoped that other restoration ecologists and practitioners will benefit from the experiences we have gained.

Movements and food habits of striped bass ( Morone saxatilis ) in Delaware Bay (USA) salt marshes: comparison of a restored and a reference marsh

There has been much recent interest in restoration of salt-marsh habitats to their natural structure and function. However, the criteria for success of such restorations are not well-defined. As part of a larger program to evaluate the restoration of a former salt-hay farm bordering Delaware Bay, New Jersey, USA, we monitored the response of a large predator, the striped bass Morone saxatilis, to the restoration. During June to October 1998 we compared tidal and diel movements and food habits of juvenile and adult striped bass (n = 82, 212 to 670 mm fork length) between a restored marsh and an adjacent reference marsh with similar physical characteristics (depth, salinity, temperature). Striped bass movements at both sites were characterized by ultrasonic tracking with small, surgically implanted tags (21 d rated battery-life). Striped bass (n = 23, 421 to 610 mm fork length) were tagged and released near the main creek mouths at both the restored (n = 14) and reference (n = 9) marshes. At both sites, striped bass tended to move up the main creek during ebb tide. At the restored site, ebb tide upstream-movements ranged from 0.1 to 3.5 km from the main creek mouth (mean = 1.2 km). During the upstream movement, the fish typically stopped every 200 to 300 m (presumably to feed) for 1 to 2 h. At the reference site, few of the tagged fish moved farther than 100 to 200 m upstream from the main channel mouth at ebb tide, perhaps in response to somewhat lower dissolved oxygen at this site. During flood tide, tagged fish at both sites moved out into Delaware Bay, where they remained within 200 to 500 m of the creek mouth. Striped bass were sampled with gill nets to determine additional aspects of habitat use and food habits. Striped bass in both marshes were much more abundant at creek mouths (catch per unit effort, CPUE = 1.17) than in the upper reaches of the creeks (CPUE = 0.13). In the creek mouths, CPUE was greater at the restored site (CPUE = 1.8) than at the reference site (CPUE = 0.5). At both sites, most fish (approx. 80%) were collected on the late ebb or early flood tides, i.e. around low tide, when prey were presumably concentrated at the creek mouths. Stomach contents of bass from both restored and reference marshes (n = 59, 212 to 670 mm fork length) revealed that striped bass were eating mostly blue crab (Callinectes sapidus), grass shrimp (Palaemonetes vulgaris), sand shrimp (Crangon septemspinosa), mummichog (Fundulus heteroclitus), and various unidentifiable fishes (probably anchovies, Anchoa mitchilli, and Atlantic silverside Menidia menidia). In conclusion, the restored marsh supported larger numbers of striped bass than the reference marsh, but there was little difference in the pattern of creek utilization or food habits at either site. Thus, the restored marsh appears to be functioning in a similar manner to the reference marsh for these large predators.

Success criteria and adaptive management for a large-scale wetland restoration project

We are using a 20+ year photographic history of relatively undisturbed and formerly diked sites to predict the restoration trajectories and equilibrium size of a 4,050 ha salt marsh on Delaware Bay, New Jersey (USA). The project was initiated to offset the loss of finfishes from once-through cooling at a local power plant. We used a simple food chain model to estimate the required restoration size. This model assumed that annual macrophyte detritus production and benthic algal production resulted in production of finfishes, including certain species of local interest. Because the marsh surface and intertidal drainage system are used by many finfishes and are the focal points for exchange of detrital materials, the restoration planning focused on both vegetational and hydrogeomorphological parameters. Recolonization bySpartina spp. and other desirable taxa will be promoted by returning a natural hydroperiod and drainage configuration to two types of degraded salt marsh: diked salt hay (Spartina patens) farms and brackish marsh dominated byPhragmites australis. The criteria for success of the project address two questions: What is the “bound of expectation” for restoration success, and how long will it take to get there? Measurements to be made are macrophyte production, vegetation composition, benthic algal production, and drainage features including stream order, drainage density, channel length, bifurcation ratios and sinuosity. A method for combining these individual parameters into a single success index is also presented. Finally, we developed adaptive management thresholds and corrective measures to guide the restoration process.

Avian utilisation of a tidally restored salt hay farm

A salt marsh near Heislerville, NJ, USA, formerly diked and drained for the production of salt hay Spartina patens, was restored to tidal inundation following breaching of the dikes. More frequent tidal flooding resulted in an 88% reduction in S. patens but a 98% increase in tall S. alterniflora and a 97% increase in surface water. Waders, waterfowl, shorebirds and gulls increased in both number of species and number of individuals while the number of individuals and species of passerines declined significantly when compared with a nearby salt hay farm in which tides were severely restricted. Total bird biomass was far greater on the tidally restored marsh.