Maryland Biological Stream Survey Research Articles

Stream Conductivity: Relationships to Land Use, Chloride, and Fishes in Maryland Streams

AbstractStream conductivity reflects both landscape and anthropogenic interactions, although increasing chloride inputs from road salt in eastern North America is also important. Employing a spatially extensive database derived from the Maryland Biological Stream Survey (MBSS), we examined relationships of stream conductivity to landscape attributes and determined relationships between stream MBSS fish metrics, abundance, and biomass as well as fish assemblages by means of conductivity (as a chloride surrogate) to estimate potential effects. Background stream conductivity for the MBSS strata and Maryland L3 ecoregions ranged from 51 to 150 μS/cm, with the Piedmont having the highest background conductivity (145–160 μS/cm). For MBSS sites there were strong relationships of stream conductivity and chloride with both impervious surface and road density, and 0.26% of the MBSS sites exceeded the U.S. Environmental Protection Agency's acute chloride criterion and 1.5% the chronic chloride criterion. For the Maryland Piedmont species assemblage, observed conductivity values between 230 and 540 μS/cm caused important alterations in the biotic community as measured by the series of fish metrics, and thus affected fish species assemblages associated with chloride concentrations between 33 and 108 mg/L. Maryland coastal, coldwater, and highland species assemblages displayed variable responses of conductivity to fish metrics, abundance, and biomass. If regional conductivity and chloride levels continue to increase or remain high from road deicing owing to an increase in urbanization in a watershed or climatic changes, differences in stream fish assemblages and therefore fish diversity may become more apparent. Because of the linkage between salt usage and impervious road surfaces resulting from urbanization, it is important to manage effectively the use of road salt to protect biotic resources.Received January 24, 2012; accepted June 5, 2012

Amphibian Sampling Techniques along Maryland Coastal-Plain Streams

Amphibians and other herpetofauna may be useful in assessing the biological integrity of small streams, so determining which sampling technique maximizes encounters is important. Area-constrained surveys (ACS), used by the Maryland Biological Stream Survey, were tested against cover-board surveys, drift fences with pitfall and funnel traps, quadrat leaf-litter searches, leaf-litter bags, and electrofishing. Twenty sites within the coastal plain region of Maryland, west of the Chesapeake Bay, were sampled with each technique once a month from June 2006 through August 2006. Overall, ACS and electrofishing yielded significantly more taxa and total individuals than cover-board surveys, quadrat searches, and leaf-litter bags; drift fence captures were moderate between ACS and electrofishing and the other methods. Electrofishing and ACS collected both more taxa and more individuals more reliably through time than the other techniques used; therefore, efforts to use herpetofauna to monitor the health of small streams will benefit from incorporating these methods into a sampling protocol.

Estimating reference nutrient criteria for Maryland ecoregions

Management of stream nutrients is becoming increasingly important in order to protect both water quality and aquatic resources throughout the USA. Using an extensive water quality database from the long-term Maryland Biological Stream Survey (MBSS), we describe nutrient relationships to landscape characteristics as total nitrogen (TN) and total phosphorus (TP) of small-order, non-tidal streams in USEPA L2 and L3 ecoregions in Maryland and by MBSS stream order at the L2 and L3 ecoregion levels. To protect stream ecosystem integrity, preliminary reference nutrient estimates (TN and TP) as percentiles (25th of all stream reaches and 75th of stream reference reaches) for the six Maryland L3 ecoregions are: Blue Ridge TN 0.29 and 0.64mg/L, TP 0.0065 and 0.0090mg/L; Central Appalachians TN 0.40 and 1.0mg/L, TP 0.0060 and 0.015mg/L; Middle Atlantic Coastal Plains TN 0.93 and 2.5mg/L, TP 0.094 and 0.065mg/L; Northern Piedmont TN 1.6 and 1.8mg/L, TP 0.010 and 0.015mg/L; Ridge and Valley TN 0.40 and 0.98mg/L, TP 0.0063 and 0.012mg/L; and Southeastern Plains TN 0.33 and 0.82mg/L, TP 0.016 and 0.042mg/L. High levels of both TN and TP are present in many streams found in non-tidal watersheds associated with all Maryland ecoregions, but are especially elevated in the Northern Piedmont and Middle Atlantic Coastal Plain ecoregions, with the latter second-order streams (average TN > 2.9mg/L) significantly higher than all other ecoregion-order combinations. Across all six ecoregions, mean nutrient loading for both TN and TP was generally equivalent in first-order streams to nutrient concentrations seen in both second- and third-order streams, indicating a definite need to increase efforts in preventing nutrients from entering first-order streams. Small-order stream nutrient levels are the drivers for subsequent TN and TP inputs into the upper freshwater tidal reaches of the Chesapeake Bay, resulting in a potential risk for altered estuarine ecosystems.

How a Statewide Stream Survey Can Aid in Understanding Freshwater Mussel (Bivalvia: Unionidae) Ecology: Examples of Utility and Limitations from Maryland

Gaps in our knowledge of freshwater mussel life history, distribution, and ecology remain even though their study has increased considerably over the past few decades. These studies have traditionally taken place within a population, river, or larger drainage unit, but rarely across a broad landscape, such as a state. Given the imperiled status of a majority of unionid species alternative opportunities to collect valuable data cannot be overlooked. We present results from a statewide biological monitoring program (Maryland Biological Stream Survey) that has incorporated a visual survey for mussels, several example analyses using mussel-bioassessment data, and discuss the utility and limitations of incorporating freshwater mussels into stream assessments. Since 2007, we encountered 11 of the 16 mussel species extant in Maryland during assessments of wadeable streams by using an informal visual survey and recording incidental observations. On several occasions, we have discovered new populations of imperiled mussels or extended a species distribution. The biological and physiochemical data collected at sites coincident with freshwater mussels have allowed us to hypothesize factors potentially limiting species distribution, such as fish-host dynamics, habitat quality, nutrient concentration, and catchment land use. We feel that the addition of a survey effort into a biological monitoring program, invaluable data can be collected that can assist resource managers, malacologists, and researchers answer a variety of questions. Further investigation into the cost-benefits of an appropriate level of sampling effort is needed as this could vary markedly among molluscan faunal regions and by objectives.

The Nymphal Odonate Fauna of Two Watersheds in the Lower Potomac River Basin, Maryland, with Emphasis on Rare Taxa

Sixty percent of Maryland's odonate species are considered to be in need of conservation. To prioritize areas for the protection of biodiversity, the Maryland Department of Natural Resources (MD DNR) has identified 10 watersheds with the highest rates of occurrence of imperiled and rare stream species, including odonates. We examined the lotic-breeding odonate fauna of two of these high priority watersheds to determine the distribution and status of several imperiled odonate species in Maryland. Odonate nymphs from two Lower Potomac River basin watersheds, Zekiah Swamp Run and Breton Bay, were collected by volunteers and MD DNR's Maryland Biological Stream Survey from 2000–2010 and were identified to species level when possible. Thirty-four species were collected during this survey, 10 of which are state-listed species. The data collected in this survey detail the distributions, habitats, and microhabitats of rare odonates in two priority watersheds in Maryland that can be used to aid in the conservation of these species and their habitats.

Patterns of shield darter, Percina peltata, distribution in the Eastern Piedmont of Maryland, USA

Detailed analyses of habitat associations with rare species are typically constrained by limited sample size and the availability of habitat data. The dense spatial coverage of stream sampling by the Maryland Biological Stream Survey provides ample data to quantitatively examine correlations between habitat and rare species distributions. The shield darter, Percina peltata, has a widespread distribution on the Atlantic Slope of the United States, but is uncommon throughout its range in Maryland. Associations of in situ physical habitat, water chemistry, and alterations in landscape with shield darter presence in the Eastern Piedmont physiographic province in Maryland were examined. Shield darter occurrence was associated with larger sized streams in concordance with the species’ known ecology. Shield darter distribution was further associated with stream segments with deep riffle habitats with diverse velocities, low concentrations of chloride and sulfate, low levels of urbanization in upstream catchments, and several pollution intolerant fish species. Although the exact mechanism of the effects is not clear, results indicate that the shield darter is sensitive to urban development and habitat and water quality alteration that typically accompanies urbanization. Shield darter conservation in Maryland necessitates the protection and restoration of minimally urbanized watersheds where they are known to occur. The results from this study indicate that habitat information on rare species may be important in elucidating important habitat associations that are not evident via examination of community level data.

Incorporation of DNA barcoding into a large-scale biomonitoring program: opportunities and pitfalls

Taxonomic identification of benthic macroinvertebrates is critical to protocols used to assess the biological integrity of aquatic ecosystems. The time, expense, and inherent error rate of species-level morphological identifications has necessitated use of genus- or family-level identifications in most large, statewide bioassessment programs. Use of coarse-scale taxonomy can obscure signal about biological condition, particularly if the range of species tolerances is large within genera or families. We hypothesized that integration of deoxyribonucleic acid (DNA) barcodes (partial cytochrome c oxidase subunit I sequences) into bioassessment protocols would provide greater discriminatory ability than genus-level identifications and that this increased specificity could lead to more sensitive assessments of water quality and habitat. Analysis of DNA barcodes from larval specimens of Ephemeroptera, Plecoptera, and Trichoptera (EPT) taxa collected as part of Maryland’s Biological Stream Survey (MBSS) revealed ∼2 to 3× as many DNA-barcode groups or molecular operational taxonomic units (mOTUs) as morphologically identified genera. As expected, geographic distributions for several mOTUs were tighter than for the parent genus, but few mOTUs showed closer associations with water-quality variables or physical-habitat features than did the genus in which they belonged. The need for improved protocols for the consistent generation of DNA barcodes is discussed.

Nutrient concentrations in Maryland non-tidal streams

Using a spatially extensive database from the Maryland Biological Stream Survey (MBSS), we describe nutrient relationships of small-order, non-tidal streams to Maryland watershed basins, Maryland Tributary Strategy basins, and stream order. In addition, we estimate the number of stream km affected by nutrient loading, using derived nutrient criteria. Based on the MBSS spring water quality sampling, we determined several important factors relating to nutrient levels in non-tidal streams. There are strong linear relationships of nutrients to the percentage of agriculture and forested land present within MBSS sampling strata. Both mean total nitrogen (TN) and mean total phosphorus (TP) levels for watershed basins by stream order show exceedances of derived nutrient reference criteria for Maryland. Four Maryland basins have over 85% of their stream kilometers exceeding the TN criterion, with three basins over 90% of the TP criterion. To protect small stream integrity in Maryland, we recommend an upper stream TN criterion between 1.34 and 1.68 mg/L and an upper stream TP criterion between 0.025 and 0.037 mg/L, based on quantile analyses. Elevated levels of both TN and TP are present in non-tidal streams, with subsequent nutrient inputs into the upper freshwater tidal reaches of the Chesapeake Bay.

Classifying the biological condition of small streams: an example using benthic macroinvertebrates

AbstractThe ability to classify the biological condition of unsurveyed streams accurately would be an asset to the conservation and management of streams. We compared the ability of 5 modeling methods (classification and regression trees, conditional inference trees, random forests [RF], conditional random forests [cRF], and ordinal logistic regression) to predict stream biological condition (very poor, poor, fair, or good) based on benthic macroinvertebrate Index of Biotic Integrity data taken from the Maryland Biological Stream Survey. Predictor variables included land use and land cover (e.g., impervious surface, row-crop agriculture, and population density) and landscape measures (annual precipitation and watershed area). We included 1561 sites on small nontidal streams in the Maryland portion of the Chesapeake Bay watershed. We used 1248 sites (80%) as a training data set to build models and 313 sites (20%) as an independent evaluation data set. RF and cRF models most accurately predicted observed in...

Application of the probability-based Maryland Biological Stream Survey to the state’s assessment of water quality standards

The Clean Water Act presents a daunting task for states by requiring them to assess and restore all their waters. Traditional monitoring has led to two beliefs: (1) ad hoc sampling (i.e., non-random) is adequate if enough sites are sampled and (2) more intensive sampling (e.g., collecting more organisms) at each site is always better. We analyzed the 1,500 Maryland Biological Stream Survey (MBSS) random sites sampled in 2000-2004 to describe the variability of Index of Biotic Integrity (IBI) scores at the site, reach, and watershed scales. Average variability for fish and benthic IBI scores increased with increasing spatial scale, demonstrating that single site IBI scores are not representative at watershed scales and therefore at best 25% of a state's stream length can be representatively sampled with non-random designs. We evaluated the effects on total taxa captured and IBI precision of sampling for twice as many benthic macroinvertebrates at 73 MBSS sites with replicate samples. When sampling costs were fixed, the precision of the IBI decreased as the number of sites had to be reduced by 15%. Only 1% more taxa were found overall when the 73 sites where combined. We concluded that (1) comprehensive assessment of a state's waters should be done using probability-based sampling that allows the condition across all reaches to be inferred statistically and (2) additional site sampling effort should not be incorporated into state biomonitoring when it will reduce the number of sites sampled to the point where overall assessment precision is lower.

Linking the diversity and abundance of stream biota to landscapes in the mid-Atlantic USA

The amount of human altered land surface within a watershed has long been known to influence the biota of receiving streams and waterways. In contrast, vegetation in riparian zones can filter pollutants and reduce flow velocities that incise stream channels. We examined the relationship between the built environment and water quality for streams (1st through 4th order) across three physiographic provinces of the State of Maryland, USA, including 59 watersheds with some 865 stream sampling locations. We used image data products capable of discriminating fine-scale information of the land surface, including proportional impervious, tree, grass and crop cover. Stepwise multiple linear regression and decision tree statistical approaches were used to assess the relationship between the land cover predictors and benthic indices of biological integrity (BIBI) and number of sensitive invertebrate taxa (NEPT), response variables derived from the Maryland Biological Stream Survey (MBSS). Impervious and tree cover were found to be the best predictors of stream biota, although this varied with physiographic province and the response variable of interest. The best multivariate models predicted 65% of variability in BIBI and 62% of NEPT ( p < 0.001). The configuration of tree cover across the landscape and the distance of land cover to the stream channel was found to be important in many, but not all cases for improving the predictive quality of statistical models estimating stream biota metrics. This work advances the estimation of stream health characteristics in areas where MBSS measurements do not exist but can be estimated using comparable land cover information, and informs guidelines for management and restoration.

A comparison of techniques to sample salamander assemblages along highland streams of Maryland

Amphibians may be useful indicators of biological condition in small streams so determining which sampling technique maximizes encounters at the least cost and at the optimal time of year is important. Area constrained surveys (ACS), used by the Maryland Biological Stream Survey, were tested against cover board surveys, drift fences with pitfall and funnel traps, quadrat leaf litter searches, and leaf litter bags. Sixteen, 100 m-long sites were established in headwater streams in the Savage River State Forest in Garrett County, Maryland. Each technique was randomly assigned to a 25 m stream section within each overall sampling site, and sites were sampled once each month from May to October (2005) with additional sampling in March and April (2006). Area constrained surveys yielded means of 2.7 taxa and 14.9 total individuals per sampling visit, which was significantly higher than the yield of all other methods in all months except October and March, when yields were low for all techniques. Area constrained surveys were also significantly more cost-effective per taxon and per individual compared to all other methods. September produced the most taxa and individuals, October and March produced the least, and yields for April through August were similar to September. We employed removal sampling at four sites in April 2006, but abundance could not be estimated because a significant linear decrease in the accumulated catch versus catch per unit effort did not occur for three of the sites.

Relationships among nutrients, chloride and biological indices in urban Maryland streams

Using a spatially extensive urban database constructed from the Maryland Biological Stream Survey (MBSS), we describe the relationships of nutrients in small-order streams to eight defined categories of percent catchment urbanization, correlations between chloride and conductivity in urban streams, and relationships between nutrients and chloride with two Maryland-specific indices of biotic integrity for benthic macroinvertebrates and fish assemblages. Stream nutrients become elevated with increasing percent catchment urbanization, followed by increases in all four measured nitrogen species and total phosphorus at catchment urbanization levels greater than 10%. There was a strong collinear relationship (r2 = 0.90) between chloride and conductivity (trimeans) across all eight urbanization classes, where Cl (mg/L) = −0.397 + 0.188*conductivity (μS/cm). Critical values for all water quality parameters with the two Maryland biological indices were derived using quantile regression, with significant regressions developed for 11 of 16 water quality parameters and the two biotic indices. For nitrate (NO3-N), the critical thresholds between fair and poor stream quality for the two Maryland biological indices were 0.83 mg/L (benthic macroinvertebrate assemblages) and 0.86 mg/L (fish assemblages). Increasing stream nutrient and chloride levels, associated with widespread catchment urbanization intensity, now affect many small streams in Maryland, with implications for decreasing water quality in major tributaries and the Chesapeake Bay.

Spatial statistical models that use flow and stream distance

We develop spatial statistical models for stream networks that can estimate relationships between a response variable and other covariates, make predictions at unsampled locations, and predict an average or total for a stream or a stream segment. There have been very few attempts to develop valid spatial covariance models that incorporate flow, stream distance, or both. The application of typical spatial autocovariance functions based on Euclidean distance, such as the spherical covariance model, are not valid when using stream distance. In this paper we develop a large class of valid models that incorporate flow and stream distance by using spatial moving averages. These methods integrate a moving average function, or kernel, against a white noise process. By running the moving average function upstream from a location, we develop models that use flow, and by construction they are valid models based on stream distance. We show that with proper weighting, many of the usual spatial models based on Euclidean distance have a counterpart for stream networks. Using sulfate concentrations from an example data set, the Maryland Biological Stream Survey (MBSS), we show that models using flow may be more appropriate than models that only use stream distance. For the MBSS data set, we use restricted maximum likelihood to fit a valid covariance matrix that uses flow and stream distance, and then we use this covariance matrix to estimate fixed effects and make kriging and block kriging predictions.

Improving biological indicators to better assess the condition of streams

Biological indicators of stream condition are in use by water resource managers worldwide. The State of Maryland and many other organizations that use Indices of Biotic Integrity (IBIs) must determine when and how to refine their IBIs so that better stream condition information is provided. With completion of the second statewide round in 2004, the Maryland Biological Stream Survey (MBSS) had collected data from 2500 stream sites, more than doubling the number of sites that were available for the original IBI development. This larger dataset provided an opportunity for the MBSS to address the following shortcomings in the original IBIs: (1) substantial disturbance apparent in some reference sites, (2) fish IBIs could not be applied to very small streams, (3) natural variability within IBIs (based on regions) resulted in some stream types (e.g., coldwater and blackwater streams) receiving lower IBI scores and (4) one IBI was not able to discriminate degradation as desired (i.e., Coastal Plain fish IBI). Therefore, development of new fish and benthic macroinvertebrate IBIs was undertaken to achieve the goals of: (1) increased confidence that the reference conditions are minimally disturbed, (2) including more natural variation (such as stream size) across the geographic regions and stream types of Maryland and (3) increased sensitivity of IBIs by using more classes (strata) and different metric combinations. New fish IBIs were developed for four geographical and stream type strata: Coastal Plain, Eastern Piedmont, warmwater Highlands and coldwater Highlands streams; new benthic macroinvertebrate IBIs were developed for three geographical strata: Coastal Plain, Eastern Piedmont and Highlands streams. The addition of one new fish IBI and one new benthic macroinvertebrate IBI partitioned natural variability into more homogeneous strata. At the same time, smaller streams (i.e., those draining catchments <300 ac), which constituted a greater proportion of streams (25%) sampled in Round Two (2000–2004) than Round One (1995–1997), because of the finer map scale, were included in the reference conditions used to develop the new IBIs. The resulting new IBIs have high classification efficiencies of 83–96% and are well balanced between Type I and Type II errors. By scoring coldwater streams, smaller streams and to some extent blackwater streams higher, the new IBIs improve on the original IBIs. Overall, the new IBIs provide better assessments of stream condition to support sound management decisions, without requiring substantial changes by cooperating stream assessment programs.

Predicting Water Quality Impaired Stream Segments using Landscape-Scale Data and a Regional Geostatistical Model: A Case Study in Maryland

In the United States, probability-based water quality surveys are typically used to meet the requirements of Section 305(b) of the Clean Water Act. The survey design allows an inference to be generated concerning regional stream condition, but it cannot be used to identify water quality impaired stream segments. Therefore, a rapid and cost-efficient method is needed to locate potentially impaired stream segments throughout large areas. We fit a set of geostatistical models to 312 samples of dissolved organic carbon (DOC) collected in 1996 for the Maryland Biological Stream Survey using coarse-scale watershed characteristics. The models were developed using two distance measures, straight-line distance (SLD) and weighted asymmetric hydrologic distance (WAHD). We used the Corrected Spatial Akaike Information Criterion and the mean square prediction error to compare models. The SLD models predicted more variability in DOC than models based on WAHD for every autocovariance model except the spherical model. The SLD model based on the Mariah autocovariance model showed the best fit (r(2) = 0.72). DOC demonstrated a positive relationship with the watershed attributes percent water, percent wetlands, and mean minimum temperature, but was negatively correlated to percent felsic rock type. We used universal kriging to generate predictions and prediction variances for 3083 stream segments throughout Maryland. The model predicted that 90.2% of stream kilometers had DOC values less than 5 mg/l, 6.7% were between 5 and 8 mg/l, and 3.1% of streams produced values greater than 8 mg/l. The geostatistical model generated more accurate DOC predictions than previous models, but did not fit the data equally well throughout the state. Consequently, it may be necessary to develop more than one geostatistical model to predict stream DOC throughout Maryland. Our methodology is an improvement over previous methods because additional field sampling is not necessary, inferences about regional stream condition can be made, and it can be used to locate potentially impaired stream segments. Further, the model results can be displayed visually, which allows results to be presented to a wide variety of audiences easily.

Use of Maryland Biological Stream Survey Data to Determine Effects of Agricultural Riparian Buffers on Measures of Biological Stream Health

This study was undertaken to determine the importance of riparian buffers to stream ecology in agricultural areas. The original Maryland Biological Stream Survey (MBSS) data set was partitioned to represent agricultural sites in Maryland's Coastal Plain and Piedmont regions. ANOVA, multiple linear regression (MLR), and CART regression tree models were developed using riparian and site catchment landscape characteristics. MBSS data were both stratified by physiographic region and analyzed as a combined data set. All models indicated that land management at the site was not the controlling factor for fish IBIs (FIBI) at that site and, hence, using FIBI to evaluate site-scale factors would not be a prudent procedure. Measures of instream habitat and location in the stream network were the dominant explanatory factors for FIBI models. Both CART and MLR models indicated that forest buffers were influential on benthic IBIs (BIBI). Explanatory variables reflected instream conditions, adjacent landscape influence, and chemistry in the Coastal Plains sites, all of which are relatively site specific. However, for Piedmont sites, hydrologic factors were important, in addition to adjacent landscape influence, and chemistry. Both Coastal Plain and Piedmont CART models identified several hydrologic factors, emphasizing the dominant control of hydrology on the physical habitat index (PHI). Riparian buffers were a secondary influence on PHI in the Coastal Plain, but not in the Piedmont. Between 40% and 70% of the variation in FIBI, BIBI, and PHI was explained by the "easily obtainable" variables available from the MBSS data set. While these are empirical results specific to Maryland, the general findings are of use to other locations where the establishment of forest buffers is considered as an aquatic ecosystem restoration measure.

Stream salamanders as indicators of stream quality in Maryland, USA

Biological indicators are critical to the protection of small, headwater streams and the ecological values they provide. Maryland and other state monitoring programs have determined that fish indicators are ineffective in small streams, where stream salamanders may replace fish as top predators. Because of their life history, physiology, abundance, and ubiquity, stream salamanders are likely representative of biological integrity in these streams. The goal of this study was to determine whether stream salamanders are effective indicators of ecological conditions across biogeographic regions and gradients of human disturbance. During the summers of 2001 and 2002, we intensively surveyed for stream salamanders at 76 stream sites located west of the Maryland Coastal Plain, sites also monitored by the Maryland Biological Stream Survey (MBSS) and City of Gaithersburg. We found 1,584 stream salamanders, including all eight species known in Maryland, using two 15 × 2 m transects and two 4 m2 quadrats that spanned both stream bank and channel. We performed removal sampling on transects to estimate salamander species detection probabilities, which ranged from 0.67-0.85. Stepwise regressions identified 15 of 52 non-salamander variables, representing water quality, physical habitat, land use, and biological conditions, which best predicted salamander metrics. Indicator development involved (1) identifying reference (non-degraded) and degraded sites (using percent forest, shading, riparian buffer width, aesthetic rating, and benthic macroinvertebrate and fish indices of biotic integrity); (2) testing 12 candidate salamander metrics (representing species richness and composition, abundance, species tolerance, and reproductive function) for their ability to distinguish reference from degraded sites; and (3) combining metrics into an index that effectively discriminated sites according to known stream conditions. Final indices for Highlands, Piedmont, and Non-Coastal Plain regions comprised four metrics: number of species, number of salamanders, number of intolerant salamanders, and number of adult salamanders, producing classification efficiencies between 87% and 90%. Partial validation of these indices was obtained when a test of the number of salamanders metric produced an 82% correct classification of 618 MBSS sites surveyed in 1995-97. This study supports the use of stream salamander monitoring and a composite stream salamander index of biotic integrity (SS-IBI) to determine stream quality in Maryland.

Threatened Fishes of the World: Etheostoma sellare (Radcliffe &amp; Welsh) 1913 (Percidae)

Common name: Maryland darter. Conservation status: Federally endangered (U.S. Fish & Wildlife Service 1967), critical habitat designated 29 August 1984 (U.S. Fish & Wildlife Service 1984). Also considered endangered by the State of Maryland. Identification: Diagnosed from all other darters by an asymmetrical caudal fin base and broad head, and from members of the subgenus Etheostoma by a short flattened genital papilla in females and narrowly connected branchiostegal membranes (Page 1983). No other darter on the middle Atlantic Slope has four dark, forwardly directed, oblique saddles across the back and incomplete dark bars of pigment on the lower half of the body below the lateral line (Knapp 1976). Maximum length 70 mm SL. Distribution: Known only from three sites in the vicinity of the Fall Line, at head of Chesapeake Bay. Described from a single specimen taken in Swan Creek in 1911. In 1965 E. sellare was also found in Swan Creek and its largest tributary, Gasheys Run. All recent records (post 1965) are from the lower-most riffle on Deer Creek, immediately above its confluence with the Susquehanna River in Harford County, Maryland. Prior to impoundment by Conowingo Reservoir in 1928, the mainstem Susquehanna River in this area was characterized by rocky shoals and ledges, with many shallow raceways and runs, which likely would have provided optimal habitat for E. sellare. Abundance: During 1965, 110 specimens were taken from the Deer Creek population. This species has not been found in such numbers since, and no specimens have been observed since 1989, despite extensive recent survey efforts (Raesly, pers. comm. and Maryland Biological Stream Survey). Habitat and ecology: The riffle on Deer Creek that supported the largest known population ranges from 12 to 25 m wide, with rubble near the head of the riffle and increasing amounts of silt and gravel toward the sides and foot. Rooted aquatic plants, mostly Podostemum ceratophyllum, are seasonally abundant. Swan Creek and Gasheys Run are much smaller streams with a limited amount of suitable habitat. Swan Creek is now severely degraded with extensive silt deposits. Diet of 35 individuals taken on 10 November 1965 included large numbers of snails (Knapp 1976). The only other darter taxa known to consume snails in quantity are the members of the Percina subgenus Imostoma. The broad head and wide gape of E. sellare may facilitate ingestion of snails. Reproduction: Spawning is believed to occur in late April or early May (Knapp 1976). Females develop a swollen white pad on the urogenital papilla, while the male papilla is short and shows little seasonal variation. Nuptial tubercles are not developed. Threats: Urban/suburban development related to proximity to the Baltimore–Philadelphia metropolitan complex, with associated changes in sediment and nutrient loading, flow and thermal regimes. Observed declines during the 1980s were correlated with increased sediment deposition (Raesly, pers. comm.). Impoundment of Conowingo Reservoir (and subsequent manipulation of flows downstream) reduced potential habitat in the mainstem Susquehanna. Introduced populations of E. blennioides and E. zonale have recently expanded in the lower Susquehanna drainage, and may compete with E. sellare for resources. Conservation action: Maryland DNR and the U.S. Fish & Wildlife Service have implemented a recovery plan (U.S. Fish & Wildlife Service 1985) with goals of managing streamside buffer zones to reduce sedimentation and agricultural pollution, maintenance and improvement of water quality. Intensive surveys of the basin have not documented specimens since 1988. The last remaining habitat that has not been thoroughly surveyed is the mainstem Susquehanna River below Conowingo Reservoir. The extreme flow fluctuations produced by Conowingo Reservoir make this habitat difficult to sample effectively. Survey work in the mainstem should be a top priority. Recent efforts to delist the darter are ill-founded without additional survey work.

Combining biological indicators of watershed condition from multiple sampling programs—a case study from Maryland, USA

Abstract Freshwater biological monitoring and assessment programs using biological indicators of ecological integrity (biocriteria) are integral to successful water resources planning and decision making. In the United States, the Clean Water Act requires every state to evaluate whether or not the designated aquatic life use (defined in its water quality standards) is being attained for each river and stream, and to submit a biennial list of impaired waters for US Environmental Protection Agency (EPA) approval. Economic constraints (personnel, equipment, transportation, laboratory, and data management costs) on water quality monitoring present a considerable challenge to states in reaching this goal. Many US states are using biocriteria-based statewide monitoring of the condition of surface waters to meet this challenge. The sampling effort of state monitoring programs, however, is often not sufficient to provide reliable estimates of stream condition for individual watersheds. Fortunately, other organizations such as county and municipal governments, regional water management authorities, and volunteer watershed groups are also gathering valuable stream monitoring data. When more than one monitoring program is conducted in a local watershed, it is desirable to integrate the estimates to (1) provide consistent estimates of stream condition, (2) increase the effective sample size and hence precision of the estimates, and (3) improve the spatial coverage of the stream network. In this paper, we show how a composite estimator can be used to combine the results of more than one probability-based survey to estimate mean condition in watersheds. As an example, we estimate the mean Fish Index of Biotic Integrity (IBI) for the Seneca Creek watershed in the State of Maryland, combining estimates from the Maryland Biological Stream Survey (MBSS) and the Montgomery County Stream Monitoring Program. Separate estimates are provided for the network of streams that are in the sample frame of both surveys and for the expanded stream network covered only by the Montgomery County survey. The composite estimate of mean Fish IBI for the streams common to both programs has a lower standard error than the MBSS estimate and yields a consistent estimate of stream condition that can be used to evaluate Seneca Creek watershed for inclusion in the State’s priority list of impaired waters. For the expanded stream network, the composite estimation also increased the precision of the mean Fish IBI relative to the Montgomery County estimate. The combination of surveys across space result in increased precision because of increased sample sizes and the application of weights that minimize the variance, and hence can provide more definitive classification of water bodies and reduce the need for follow-up monitoring. Integration of survey estimates can improve communication with the public and ultimately lead to more reliable water resource management decisions. State, provincial, and regional authorities in the US and other countries can use the composite indicator estimation technique presented here to derive more information from their limited monitoring resources and make better water resource protection decisions.