Streams In Connecticut Research Articles

Summer Thermal Thresholds of Fish Community Transitions in Connecticut Streams

AbstractThermal tolerances have been studied for individual fish species but few have investigated how stream fish assemblages respond along a temperature gradient and which thermal ranges act as a threshold, triggering discernible community change. The purpose of this study was to define summer temperature thresholds of fish community transitions in Connecticut streams. The program Threshold Indicator Taxa Analysis suggested that the coldwater class had a June–August mean water temperature < 18.29°C, the coolwater class 18.29–21.70°C, and a warmwater class > 21.70°C. Significant indicator species of coldwater streams were Slimy Sculpin Cottus cognatus and Brook Trout Salvelinus fontinalis. Significant indicator species of warmwater streams were Cutlip Minnow Exoglossum maxillingua, Smallmouth Bass Micropterus dolomieu, Rock Bass Ambloplites rupestris, Brown Bullhead Ameiurus nebulosus, Redbreast Sunfish Lepomis auritus and Yellow Bullhead A. natalis. The narrow 3.41°C temperature range between the coldwater and warmwater thresholds was designated as a coolwater transition zone, with potential for the presence of both coldwater and warmwater species and lack of species uniquely associated with this thermal range. Our approach based on a robust set of water temperature and fish community data should be applicable to other temperate regions and will be useful for informing development of thermal criteria, application of multimetric indices, and planning for anticipated effects of climate change.Received July 2, 2013; accepted October 8, 2013Published online January 30, 2014

Classifying the Health of Connecticut Streams Using Benthic Macroinvertebrates with Implications for Water Management

Bioassessments have formed the foundation of many water quality monitoring programs throughout the United States. Like many state water quality programs, Connecticut has developed a relational database containing information about species richness, species composition, relative abundance, and feeding relationships among macroinvertebrates present in stream and river systems. Geographic Information Systems can provide estimates of landscape condition and watershed characteristics and when combined with measurements of stream biology, provide a useful visual display of information that is useful in a management context. The objective of our study was to estimate the stream health for all wadeable stream kilometers in Connecticut using a combination of macroinvertebrate metrics and landscape variables. We developed and evaluated models using an information theoretic approach to predict stream health as measured by macroinvertebrate multimetric index (MMI) and identified the best fitting model as a three variable model, including percent impervious land cover, a wetlands metric, and catchment slope that best fit the MMI scores (adj-R (2) = 0.56, SE = 11.73). We then provide examples of how modeling can augment existing programs to support water management policies under the Federal Clean Water Act such as stream assessments and anti-degradation.

Using algal metrics and biomass to evaluate multiple ways of defining concentration-based nutrient criteria in streams and their ecological relevance

We examined the utility of nutrient criteria derived solely from total phosphorus (TP) concentrations in streams (regression models and percentile distributions) and evaluated their ecological relevance to diatom and algal biomass responses. We used a variety of statistics to characterize ecological responses and to develop concentration-based nutrient criteria (derived from ecological effects) for streams in Connecticut, USA, where urbanization is the primary cause of watershed alteration. Mean background TP concentration in the absence of anthropogenic land cover was predicted to be 0.017mg/l, which was similar to the 25th percentile of all study sites. Increased TP concentrations were significantly correlated with altered diatom community structure, decreased percent low P diatoms and diatoms sensitive to impervious cover, and increased percent high P diatoms, diatoms that increase with greater impervious cover, and chlorophyll a (P<0.01). Variance partitioning models showed that shared effects of anthropogenic land cover and chemistry (i.e., chemistry affected by land cover) represented the majority of explained variation in diatom metrics and chlorophyll a. Bootstrapped regression trees, threshold indicator taxa analysis, and boosted regression trees identified TP concentrations at which strong responses of diatom metrics and communities occurred, but these values varied among analyses. When considering ecological responses, scientifically defensible and ecologically relevant TP criteria were identified at (1) 0.020mg/l for designating highest quality streams and restoration targets, above which sensitive taxa steeply declined, tolerant taxa increased, and community structure changed, (2) 0.040mg/l, at which community level change points began to occur and sensitive diatoms were greatly reduced, (3) 0.065mg/l, above which most sensitive diatoms were lost and tolerant diatoms steeply increased to their maxima, and (4) 0.082mg/l, which appeared to be a saturated threshold, beyond which substantially altered community structure was sustained. These criteria can inform anti-degradation policies for high quality streams, discharge permit decisions, and future strategies for watershed development and managment. Our results indicated that management practices and decisions at the watershed scale will likely be important for improving degraded streams and conserving high quality streams. Results also emphasized the importance of incorporating ecological responses and considering the body of evidence from multiple conceptual approaches and statistical analyses for developing nutrient criteria, because solely relying on one approach could lead to misdirected decisions and resources.

Characteristics of Macroinvertebrate and Fish Communities from 30 Least Disturbed Small Streams in Connecticut

Water quality programs in Connecticut and nationally have focused on restoring impaired waters, while modest attention has been allocated to healthy watersheds in the least disturbed condition. The objective of our study was to document the geographic location of least disturbed streams in Connecticut, describe the aquatic biota from these systems, and describe important environmental variables that may help explain the distribution of these biota. We used geographic information systems to select drainage basins by their natural attributes and by eliminating anthropogenic stressor variables in order to best approximate a least disturbed watershed condition in Connecticut. We then sampled the fish and macroinvertebrate communities, water chemistry, and associated GIS-derived watershed attributes to determine the variables that best described the sampled biota. We identified 30 least disturbed streams that had drainage areas <29 km2, whose stream order ranged from 1–4, and that contained <4% total impervious cover in the upstream watershed. Least disturbed streams were generally located in three geographic areas of the state—northwest Connecticut, northeast Connecticut, and the central Connecticut valley—and were absent from the southern coast of Connecticut and southwestern Connecticut. Cluster analysis and nonmetric multidimensional scaling of macroinvertebrate taxa in the Orders Ephemeroptera, Plecoptera, and Trichoptera showed 3 macroinvertebrate stream classes, with 12 significant indicator species (P < 0.05). Drainage area, water temperature, alkalinity, hardness, chloride, ammonia, total nitrogen (TN), and total phosphorus (TP) may explain some of the differences in taxa between macroinvertebrate stream classes. Cluster analysis and nonmetric multidimensional scaling of fish species also showed three fish stream classes, with 9 significant indicator species (P < 0.05). Drainage area, stratified drift, dam density, water temperature, total suspended solids, alkalinity, hardness, ammonia, TN, and TP may explain some of the differences in species between fish stream classes. Ninety percent of the least disturbed streams sampled contained Salvelinus fontinalis (Brook Trout), which can be considered a sentinel fish species for small, least disturbed streams in Connecticut.

SPATIAL PATTERN, DENSITY AND CHARACTERISTICS OF LARGE WOOD IN CONNECTICUT STREAMS: IMPLICATIONS FOR STREAM RESTORATION PRIORITIES IN SOUTHERN NEW ENGLAND

ABSTRACTMany streams have been modified so extensively that river managers do not have clear reference conditions to frame targets for stream restoration. Large woody debris (LWD) has long been recognized as an important influence on both geomorphic and ecologic processes in stream channels; however, there have been few studies of LWD dynamics in New England. Although this region is heavily forested today, the forest is predominantly young (70–90 years old) regrowth following a historical episode of severe deforestation. This study presents the results of an extensive census of LWD and associated stream characteristics in over 16 river kilometres of northeastern Connecticut streams and represents the first reported inventory of wood loading and sorting in Southern New England. Results of this study indicate that wood loading and jam frequencies in the study region are low: 2.5–17.8 and 0.5–5.51 per 100 m, respectively. Orientation of LWD is predominantly parallel to flow, an indication that these streams are not retaining organic matter or sediment, which has important geomorphic and ecologic implications. Results imply that stream recruitment of LWD is still lagging from the massive forest conversions of the 18th and 19th centuries. Given the low wood loadings observed in the study reaches, manual wood addition and continued forest regeneration would likely improve both habitat diversity and organic matter and fine sediment retention in these systems. Copyright © 2011 John Wiley &amp; Sons, Ltd.

Sibship reconstruction for inferring mating systems, dispersal and effective population size in headwater brook trout (Salvelinus fontinalis) populations

Brook trout Salvelinus fontinalis populations have declined in much of the native range in eastern North America and populations are typically relegated to small headwater streams in Connecticut, USA. We used sibship reconstruction to infer mating systems, dispersal and effective population size of resident (non-anadromous) brook trout in two headwater stream channel networks in Connecticut. Brook trout were captured via backpack electrofishing using spatially continuous sampling in the two headwaters (channel network lengths of 4.4 and 7.7 km). Eight microsatellite loci were genotyped in a total of 740 individuals (80–140 mm) subsampled in a stratified random design from all 50 m-reaches in which trout were captured. Sibship reconstruction indicated that males and females were both mostly polygamous although single pair matings were also inferred. Breeder sex ratio was inferred to be nearly 1:1. Few large-sized fullsib families (>3 individuals) were inferred and the majority of individuals were inferred to have no fullsibs among those fish genotyped (family size = 1). The median stream channel distance between pairs of individuals belonging to the same large-sized fullsib families (>3 individuals) was 100 m (range: 0–1,850 m) and 250 m (range: 0–2,350 m) in the two study sites, indicating limited dispersal at least for the size class of individuals analyzed. Using a sibship assignment method, the effective population size for the two streams was estimated at 91 (95%CI: 67–123) and 210 (95%CI: 172–259), corresponding to the ratio of effective-to-census population size of 0.06 and 0.12, respectively. Both-sex polygamy, low variation in reproductive success, and a balanced sex ratio may help maintain genetic diversity of brook trout populations with small breeder sizes persisting in headwater channel networks.

Evaluating effects of water withdrawals and impoundments on fish assemblages in southern New England streams, USA

Abstract Balancing aquatic conservation and water supply is becoming a major global issue for urban landscapes. The purpose of this study was to evaluate the ecological effects of stream‐flow alterations via water withdrawals and impoundments on fish assemblage structure. Electric fishing data were collected at 33 wadeable streams in Connecticut, located in the Southern New England region of USA. Fish sampling was conducted directly downstream of water withdrawals for municipal and agricultural water supply, and study sites differed in potential water withdrawal rates and the presence of impoundments. Regression analysis showed that water withdrawal rate was more important than other natural and anthropogenic factors (e.g. landcover and stream size) in explaining several fish assemblage metrics. Stream sites with high withdrawal rates were generally characterised by lower proportions of fluvial dependent fishes (fish which need flowing water to complete a portion of their life history) and benthic invertivores (fish which feed on bottom‐dwelling stream insects in riffle habitat), and had a greater percent composition of macrohabitat generalists, particularly members of the family Centrarchidae. Some assemblage metrics responded linearly with increasing magnitude of water withdrawals, but others were non‐linear. Results are consistent with ecological theory that alteration of the natural flow regime will impact stream biota.

Stormwater and Aquatic Life: Making the Connection Between Impervious Cover and Aquatic Life Impairments for TMDL Development in Connecticut Streams

Stormwater can be a significant source of stressors to aquatic stream biota in many urban areas. The 2006 List of Connecticut Waterbodies Not Meeting Water Quality Standards has a total of 105 stream segments that do not meet aquatic life goals established in Connecticut’s Water Quality Standards. At least 58% of these waterbodies have stressors related to urbanization as the suspected cause of the impairment (e.g. stormwater, habitat modifications, erosion, sedimentation etc.). Modeling stormwater impacts can be challenging due to their episodic nature. In many instances, surrogate measures of stormwater impacts may provide useful benchmarks when data are unavailable to support more complex stormwater models. The State of Connecticut, Department of Environmental Protection (DEP), has developed an Impervious Cover (IC) model applicable in situations where the most probable cause of the aquatic life support impairment is stormwater. An IC target of 12% was established for developing Total Maximum Daily Loads (TMDLs) based on correlating the percent IC upstream of macroinvertebrate monitoring locations with a final assessment of passing or failing Connecticut's aquatic life standards. Connecticut DEP has used the IC Model to develop a TMDL for a small stream in Eastern Connecticut and has engaged stakeholders to focus stormwater management efforts to restore aquatic life in the brook.

Comparison of snorkeling and electrofishing for estimating abundance and size structure of brook trout and brown trout in two southern New England streams

Abundance and size structure of brook trout Salvelinus fontinalis and brown trout Salmo trutta determined by snorkeling were compared with estimates determined by electrofishing depletion in 30 habitat units of two Connecticut streams. Snorkel counts were significantly correlated ( P<0.001) to electrofishing depletion estimates for two length groups of each species, although the strength of correlations varied between species, streams, and length groups of trout. Some regression equations that predicted electrofishing depletion estimates from snorkel counts were significantly improved with the addition of independent variables describing large woody debris. Regression parameters indicated that snorkel counts were underestimated in habitat units that contained substantial amounts of large woody debris. Overall, length–frequency distributions obtained by snorkeling were similar to those obtained by electrofishing. In one case, the frequency of brown trout less than 15 cm determined by snorkeling was slightly overestimated relative to electrofishing, while the frequency of 15.0–22.9 cm brown trout was slightly underestimated by snorkeling relative to electrofishing. These results suggest that snorkel counts may be a reliable alternative to electrofishing depletion for estimating trout abundance and size structure in habitat units of small- to mid-size Connecticut streams. However, the consideration of woody debris variables may significantly improve the predictive ability of electrofishing depletion estimates based on snorkel counts.

Catch-and-Release Management of a Trout Stream Contaminated with PCBs

Abstract Due to health risks associated with PCB contamination, the Connecticut Department of Environmental Protection chose to apply catch-and-release regulations to the Housatonic River, which had previously supported one of the most popular put-and-take trout fisheries in Connecticut. The management change was successful in maintaining a highly rated recreational fishery. Stocked brown trout Salmo trutta survived up to five summers and grew to maximum total lengths of about 400 mm. Through 5 years, fish stocked as adults (254–305 mm) and yearlings (152–229 mm) had average annual survivals of 39 and 42%, respectively. Survival of fingerlings (< 152 mm) averaged 22%. With holdover trout present after the first year of catch-and-release management, 50-66% of the fish caught by anglers exceeded the maximum length of 305 mm of trout stocked for put-and-take purposes in other Connecticut streams. Also, an average of 38% more trout by number and 210% more trout by weight were caught and released than were sto...

Biomass and nutrient removals from commercial thinning and whole-tree clearcutting of central hardwoods

The objective of this research was to evaluate the impacts of increasing product removal on biomass and nutrient content of a central hardwood forest ecosystem. Commercial thinning, currently the most common harvesting practice in southern New England, was compared with whole-tree clearcutting or maximum aboveground utilization. Using a paired-watershed approach, we studied three adjacent, first-order streams in Connecticut. During the winter of 1981–82, one was whole-tree clearcut, one was commercially thinned, and one was designated as the untreated reference. Before treatment, living and dead biomass and soil on the whole-tree clearcut site contained 578 Mg ha−1 organic matter, 5 Mg ha−1 nitrogen, 1 Mg ha−1 phosphorus, 5 Mg ha−1 potassium, 4 Mg ha−1 calcium, and 13 Mg ha−1 magnesium. An estimated 158 Mg ha−1 (27% of total organic matter) were removed during the whole-tree harvest. Calcium appeared to be the nutrient most susceptible to depletion with 13% of total site Ca removed in whole-tree clearcut products. In contrast, only 4% (16 Mg ha−1) of the total organic matter and ⩽2% of the total nutrients were removed from the thinned site. Partial cuts appear to be a reliable management option, in general, for minimizing nutrient depletion and maximizing long-term productivity of central hardwood sites. Additional data are needed to evaluate the long-term impacts of more intensive harvests.

April streamflow

Heavy spring rains that fell across the nation frequently during April and early May pushed streamflows in many states to record or near‐record high levels, according to a regular month end check on water resources by the U. S. Geological Survey (USGS), Department of the Interior.USGS hydrologists said new record high flows for April were measured at streams in Kansas, North Carolina, South Carolina, Nebraska, and Nevada. Near‐record high flows for the month were recorded on streams in Connecticut, Pennsylvania, Iowa, and Missouri.