Completed Fisheries Projects

For almost a century, fishery managers have installed various types of instream structures designed to enhance reproductive and rearing habitat for fishes. Although successful at increasing fish populations, some structural designs are susceptible to damage or destruction during high flows. In addition, traditional structures do little to protect stream banks from erosion, and in some cases, increase stream bank erosion. Cross vanes and j-hooks are structures designed to increase available habitat, stabilize stream channels, and withstand flood events. The U.S. Fish and Wildlife Service and cooperating private landowners are in the process of installing cross vanes and j-hooks in Big Bear Creek, Lycoming County, Pennsylvania. A tributary to Loyalsock Creek, Big Bear Creek is an aggraded stream resulting from extensive stream bank erosion and a high sediment load released after dam removal. Big Bear Creek also lacks necessary habitat for the resident brook trout and brown trout. The installation of these structures is intended to halt the stream aggradation and bank erosion processes, enhance available trout habitat, and increase the number catchable-size game fish.

Objectives

1. Determine the short-term salmonid and non-game fish population responses to the habitat enhancement structures.

2. Determine the effects of the habitat enhancement structures on trout spawning gravel quantity and quality.

3. Determine whether the number of trout redds will increase after installing habitat enhancement structures.

4. Determine the changes in pool/riffle habitat resulting from the habitat enhancement structures.

5. Assess the quantity of microhabitat available for trout compared to microhabitat actually inhabited under enhanced, degraded, and reference habitat conditions.

Landscape variables to predict brook charr and brown trout growth and biomass in Pennsylvania streams

Patrick M. Kocovsky, Graduate Research Assistant

Robert F. Carline, Advisor

Traditionally, fisheries researchers studying stream fish populations have focused their efforts on the reach scale, emphasizing temporal variation in fish populations, and ignoring spatial variability that may be caused by broad-scale features within the landscape. Development of Geographical Information Systems (GIS) has allowed fisheries researchers to address questions pertaining to fish population dynamics processes at broader ecological scales, thus broadening the scope of research questions as well as our base of knowledge on the dynamics of fish populations. During the past decade, researchers have studied the relationships between landscape and fish community structure and composition, community diversity, stream biotic integrity, water quality, habitat quality, and fish assemblage stability, providing evidence that landscapes affect fish populations, but little research has been done on the relationship between landscapes and fish population dynamics. I intend to use existing GIS coverages of landscape-scale variables, such as land cover, geology, and soil sensitivity to acidification, and fish collection databases accumulated by the Pennsylvania Fish and Boat Commission (PFBC) to model density and biomass of wild brook trout (Salvelinus fontinalis) and brown trout (Salmo trutta) populations in Pennsylvania streams. I will first analyze fluctuations in population density over time using time series analysis to establish how variable population density is over time. Following the temporal analysis I will test several hypotheses forwarded in the literature regarding the relationships among trout density and landscape-scale factors. The outcomes of those analyses will be used to help structure a more detailed multivariate analysis to classify Pennsylvania watersheds based on trout production potential.

Approach

Research will begin with an examination of databases, followed by statistical analysis and model validation. I will produce separate models for brook charr and brown trout.

Databases - I will examine existing databases for completeness and inclusion of necessary variables.

Statistical Analyses - The modeling technique will be chosen following consultation with statisticians.

Model Validation - I will validate models by either withholding randomly chosen data sets or collecting new data.

Potential Outcomes and Uses

There are several short- and long-term uses and benefits of this research effort:

Application - If models successfully predict charr and trout density, growth, and biomass in streams using landscape-scale predictors, the methodology could be applied beyond the boundaries of Pennsylvania.

Fisheries management/conservation tool: The Pennsylvania Fish and Boat Commission (PFBC) could use the predictive models in planning subsequent fisheries inventory work, such as which streams to sample and what data to collect. For example, if models predict low biomass and poor growth for a particular stream, then a manager may not want to take the extra time and effort to collect scales for growth analysis and may prefer to employ 2-pass electrofishing (instead of 3-pass) for a population and biomass estimate.

Identification of streams with exceptionally high or low density, growth, or biomass for regulatory protection - Fishing regulations could be altered to provide protection for those populations requiring it and loosening restrictions based on biomass and growth.

An Assessment of the Reintroduction of Paddlefish to the Ohio River, Pennsylvania

Patrick Barry, Graduate Research Assistant

Robert F. Carline, Advisor

Since 1991 the Pennsylvania Fish and Boat Commission has been stocking juvenile paddlefish in the Allegheny and Ohio Rivers in an effort to restore this species to its former range. Although a few paddlefish have been captured since restoration efforts began, little is known about their survival, movement, and habitat use. We are used radio-telemetry, gill netting, and electrofishing to track cohorts of stocked paddlefish to determine (1) where they go after release, (2) how far they move from their release site, and (3) what habitat types they prefer. The telemetry phase of this project began in September 2002, when 32 paddlefish were implanted with radio transmitters and stocked into the Dashields Pool of the Ohio River. In 2003 we stocked 34 implanted paddlefish in the Hamarville Pool of the Allegheny River. Paddlefish survival was 78% in 2002 and 67% in 2003 at 9 weeks after stocking. By the fourth day after stocking, most fish ceased long range movements and tended to remain in the same habitat type. Fish were usually found in river locations that were 5.2 to 6.1 m deep with surface velocities ranging from 0.12 to 0.17 m/s. Fish preferred the tailwaters below dams and secondary channels with little or no barge traffic. Paddlefish avoided main channel habitats that were subjected to frequent barge traffic.

An Assessment of Zooplankton as a Food Resource for Paddlefish in the Ohio River

Daniel F. Counahan, Graduate Research Assistant

Robert F. Carline, Advisor

In 1991 the Pennsylvania Fish and Boat Commission began the reintroduction of juvenile paddlefish into the Ohio and Allegheny rivers. Little information is available regarding the status of these fish. This study evaluated zooplankton communities in the Ohio River because zooplankton are the primary food source for paddlefish. Zooplankton are small animals, reaching lengths of 5 mm, but are more commonly 1 mm or less. Paddlefish are able to find zooplankton because they have thousands of ampullary receptors, which can detect the electrical fields emitted by zooplankton, and they consume zooplankton by filtering water with their well-developed gill rakers. The objectives of this study were to (1) determine species composition of zooplankton in the Ohio River, (2) determine zooplankton density and biomass to assess the amount of food available for paddlefish to eat, and (3) identify important areas for paddlefish based on zooplankton density. Zooplankton were collected with a 150-mm plankton net and samples were taken monthly from May to October in two pools in Pennsylvania (Dashields and Montgomery) and one pool in West Virginia (Gallipolis). The Gallipolis pool served as a reference pool, because a naturally reproducing stock of paddlefish is present there. Densities of zooplankton in the Gallipolis pool were 3 to 4 times higher than in the Pennsylvania pools. Backwater habitats supported the highest density of zooplankton, followed by tailwaters, secondary channels, and main channels. Density and biomass of zooplankton were highest in August in all pools. Variations in zooplankton density among pools and months was largely explained by mean monthly river discharge, water temperature, chlorophyll-a concentration, and conductivity. Low densities of zooplankton in the Pennsylvania portion of the Ohio River may restrict growth of paddlefish.

Physical and Chemical Influences on Fish Populations in Small Lakes of North Central Pennsylvania

Steven Means, Graduate Research Assistant

Robert F. Carline, Advisor

Development of good fisheries management plans requires a sound understanding of the physical, chemical, and biological characteristics of lakes. Factors that may influence the population characteristics (e.g., relative abundance, size structure, and condition) of fish communities were investigated in 20 small lakes (< 55 hectares) located in the north central region of Pennsylvania. Physical, (e.g., area, depth), chemical (e.g., total dissolved solids, pH), and biological (chlorophyll-a) characteristics of the lakes were selected to identify relationships with fish population characteristics. Spring nighttime electrofishing collections were used to develop indices for catch-per-unit effort (CPUE) and catch biomass. An index that measured the quality of a fishery was also developed to standardize proportional stock density (PSD), relative stock density (RSD), CPUE of quality and preferred lengths of fish, and relative weight (Wr) variables and to rank each fishery.

Models were developed for 14 different fish variables. The primary physicochemical variables that had the greatest influence on fish population characteristics were elevation, pH, and total dissolved solids. Cooler temperatures at higher elevations resulted in a shorter growing season within the region. Elevation was also related to pH levels, because regional soils are normally more acidic with rise in elevation and land-use that could potentially buffer acidity, such as agriculture, was not present at higher elevations. The total abundance and biomass of fish were inversely related to pH, suggesting limitations in production. Total dissolved solids (TDS) represented the variation in nutrient levels among lakes. The strongest relationship with TDS was with largemouth bass variables. The relationships with largemouth bass variables demonstrated a link between the abundance and biomass of top predators and lake productivity.

Several relationships among physicochemical and biological variables have been identified. These relationships could be used to reduce the number of variables tested when studying physicochemical influences on fish communities. Unlike other studies that focus on larger lakes and reservoirs, this study identifies physicochemical and biological variables that influence populations in small lakes. The models developed in this study are useful to fish managers who attempt whole lake enhancements to improve fisheries. When evaluating lake fisheries in the region, managers should consider the effects of regional climate, soils and geology, because these factors have the greatest influence on total abundance and biomass.

Genetic relationships among federally-endangered Alasmidonta heterodon within the Delaware River basin

Kristine M. Playfoot, Graduate Research Assistant

Erin M. Snyder, Advisor

The dwarf wedge mussel, Alasmidonta heterodon, is a small wedge-shaped freshwater mussel found in streams and rivers of the Atlantic coastal region from North Carolina to eastern New Brunswick. It seems to prefer slow to moderate flow conditions but shows no obvious preference for substrate type. The mussel is a long-term brooder that spawns in late summer or early fall and releases glochidia the following spring. Suspected hosts are the tessellated darter, Johnny darter, mottled sculpin, Atlantic salmon, and slimy sculpin.

The dwarf wedge mussel is currently the only federally endangered Atlantic slope species. Although historically known from approximately 70 locations within 15 major drainages, only about two dozen populations remain, many of which are sparse and non-sustaining. One of the few remaining reproductive populations is found within the Neversink River, a mid-size tributary of the Delaware River near Port Jervis, New York. Recent surveys have revealed the existence of two additional Alasmidonta heterodon populations within the Delaware River basin, one within the mainstem of the upper river and a second within a small coldwater tributary of the middle river. Both new populations fall within management units of the National Park Service, thus information on their population size, reproductive status, hosts, habitat range, and threats is required for proper management. Of particular interest are the genetic relationships among the three populations, inasmuch as they not only are geographically isolated within the basin, but they inhabit different sized streams with different physical properties. The potential for isolation and adaptation among these populations thus exists.

Objective

The objective of this project is to determine the extent to which the three known populations of Alasmidonta heterodon within the Delaware River basin are genetically diverse. This information is essential to understanding if these populations should be managed separately or as a single unit.

Approach

Tissue samples of the inner mantle lining will be collected from Alasmidonta heterodon from each of the mainstem Delaware River (PA/NY), the Neversink River (NY), and Flat Brook (NJ) for genetic analysis.

A partial DNA library will be constructed from digested genomic DNA, and primers for each marker will be developed from sequences flanking the microsatellites.

Polymerase chain reaction will be used to amplify the genomic DNA, and conditions will be optimized for each primer set.

The mixture will be subjected to capillary electrophoresis on a genetic analyzer, and software will be used to score, bin, and output allelic (and genotypic) data.

Statistical analyses will be performed to determine genotypic linkage disequilibrium and population differentiation, and to calculate F_ST statistics.

Riparian Zone Restoration and Stream Quality

Mary C. Walsh, Graduate Research Assistant

Dr. Robert F. Carline, Advisor

Sediment originating from intensively grazed pastures was linked to depressed reproduction of brown trout in Spring Creek, a limestone stream in the West Branch of the Susquehanna River basin. Public agencies and private organizations initiated a project in 1990 that was designed to restore degraded riparian areas and reduce sediment loading. Improvements included stabilizing eroding stream banks, installing rock-lined animal accesses and stream crossings, and constructing fences along the streams. Restoration efforts were concentrated in two tributaries to Spring Creek. There were 4.1 km of stream flowing through unfenced riparian pastures in the Slab Cabin Run basin, and 67% of this stream length was improved and well maintained through 2003. There were 2.5 km of stream flowing through unfenced pastures in the Cedar Run basin, and 98% of this stream length was improved and well maintained through 2003. Upper Spring Creek, which had no unfenced riparian pastures was used as a reference. The objective of this study was to quantify the effects of streambank fencing and stabilization in Slab Cabin Run and Cedar Run. We measured channel morphology, substrate composition, stream temperatures, discharge, water quality, macroinvertebrate, and fish communities prior to restoration in 1991-1992. Restoration activities occurred during 1992-1998, and post-restoration assessments were completed in 2001-2003. Stream bank fencing resulted in revegetation of eroded banks with primarily grasses and a few shrubs. No trees were planted, and none invaded the buffer zone. Stream channel morphology did not change after restoration. Total suspended solids (TSS) during baseflow in Cedar Run declined by 36 to 45% and in Slab Cabin Run TSS declined by 77 to 82% after restoration, though below average discharge contributed 3 somewhat to these reductions. During storm flow there were significant reductions in TSS in one of two years in Cedar Run and in both years in Slab Cabin Run. There were no significant changes in concentrations of nitrogen or phosphorus after restoration. The amount of fine sediments in the substrate of Cedar Run declined after restoration, but similar changes were not evident in Slab Cabin Run. There was no indication that stream temperatures changed as a result of stream bank restoration. Composition of the macroinvertebrate communities did not change, but there were significant increases in densities of macroinvertebrates after restoration. Composition of the fish communities and densities of wild brown trout were similar before and after restoration. In summary, stream bank fencing and bank stabilization led to revegetation of eroding stream banks, reductions in total suspended solids, and increases in densities of macroinvertebrates.

Click here for the final report

Restoration of Spawning Habitat for Trout

Erin M. Snyder, Co-Principal Investigator

Robert F. Carline, Co-Principal Investigator

Big Spring Creek, south-central Pennsylvania, once supported a “world class sustaining brook trout population” according to state natural resource professionals. Over the past 50 years, wild brook trout have nearly disappeared from this limestone stream, and several species of hatchery trout and naturalized brown trout now share habitat where brook trout are still present. State resource agencies and private conservation groups are strongly in favor of restoring native brook trout to this stream. A number of changes have occurred in Big Spring Creek, which singly or in combination may have contributed to the loss of wild brook trout. A state fish hatchery was constructed next to Big Spring, which is the sole source of water to the stream’s headwaters. In the past, a commercial fish hatchery also operated in the vicinity. The channel morphology has been altered by old mill dams, which have been largely removed, though remnants of these structure continue to influence flow patterns. There is ample evidence of stream bank erosion and an absence of hiding cover for adult trout. The stream substrate is embedded, and it is apparent that trout would have a difficult time displacing these sediments during spawning. Some of this embeddedness may be due to calcium carbonate precipitation. The Pennsylvania Fish and Boat Commission is prepared to commit substantial funds to restore the physical habitat of Big Spring, but to do so, they need to know what factors are responsible for the loss of spawning habitat.

Click here for the final report

Possible Effects of Perchlorate on Endocrine and Reproductive Systems of Goldfish

Neil Crouch, Graduate Research Assistant

Erin M. Snyder, Advisor

Perchlorate anion (ClO4-) is a contaminant of ground water and surface water in locations throughout the United States. Perchlorate is a powerful oxidant used in solid rocket fuels, missiles, munitions, matches, fireworks, and air bag inflators. Sources of environmental contamination generally occur near military test sites and chemical manufacturing plants. Perchlorate is capable of blocking thyroid function in animals by competitive inhibition of iodide accumulation by thyroid follicular cells; iodide is required for synthesis of thyroid hormones. Recent studies indicate that waterborne perchlorate can produce effects on the thyroid in aquatic vertebrates, including fish. Because thyroid hormones influence the reproductive system in fish, the potential may exist for perchlorate to impact fish reproductive function. Methods: To test for sublethal effects of perchlorate on fish reproductive and thyroid system function, adult male and female common goldfish (Carassius auratus) were exposed to environmentally relevant concentrations of perchlorate in a laboratory flow-through exposure system. Fish were subjected to 7 different treatments consisting of combinations of perchlorate concentration measured in exposure water and exposure duration. Treatments were control - 30 d, 14 ppb - 30 d, 130 ppb - 30 d, 1200 ppb - 30 d, 31,000 ppb - 30 d, control - 60 d, and 31,000 ppb - 60 d. Six exposure tanks (10 fish per tank) were assigned to each treatment, with 3 replicate tanks containing males and 3 containing females. Photoperiod and temperature were conducive to spring gonadal recrudescence in goldfish. Endpoints used to assess reproductive system function included gonadosomatic index (GSI); gonad histology; plasma sex steroid hormone concentrations including 17b-estradiol (E2), testosterone (T), and 11-ketotestosterone (11-KT); and plasma estrogen to androgen ratios (E2:T, E2:11-KT). Endpoints used to assess thyroid activity included histology of thyroid follicles in the head kidney and in the subpharyngeal region. Thyroid follicle activity was assessed histologically by measuring epithelial cell height (ECH) with a digital imaging system. In addition, a new subjective nonparametric rank-order assessment method was designed to assign a thyroid activity score for head kidney (HK) and pharyngeal thyroid (PT) follicles in each fish. Results: Exposure to 31,000 ppb ClO4- for 30 or 60 d caused a significant increase in PT activity, as assessed by activity score and ECH, in females. For PT in males, there were no significant differences in ECH among treatment groups, but exposure to 31,000 ppb ClO4- for 60 d caused a significant increase in PT activity score. HK thyroid activity score increased in females exposed to 1200 ppb ClO4- for 30 d or to 31,000 ppb for 30 d or 60 d. HK thyroid activity score increased in males only after exposure to 31,000 ppb ClO4- for 60 d. Female goldfish appear to be more sensitive than males with regard to response of thyroid follicle activity to perchlorate exposure. There were no significant differences in GSI among treatment groups for either sex, and GSI were within normal ranges for goldfish undergoing spring gonadal recrudescence. Although there were statistically significant differences in plasma sex steroid concentrations among fish of the same sex in different treatment groups, the differences did not appear to be directly dose-related, and the mean or median plasma sex hormone concentrations remained within normal ranges for goldfish. Conclusions: Adult goldfish demonstrated increases in thyroid follicle activity when exposed to environmentally relevant concentrations of waterborne perchlorate; the minimum concentration of perchlorate that produced a change in thyroid follicle histology was 1200 ppb (30 d exposure, female HK thyroid follicle activity score). Results currently available indicate that exposure to waterborne perchlorate at environmentally relevant concentrations under the described conditions produced no serious effects on the reproductive system function in goldfish. However, histological assessment of ovarian follicle atresia has not been completed.

Effects of bridge and road construction on Spring Creek: Route 26 transportation improvement project

Curtis J. Gill and Kirk A. Patten, Graduate Research Assistants
Adam M. Smith, Research Technician
Robert F. Carline, Advisor

Spring Creek, Centre County, Pennsylvania, is classified by the Department of Environmental Protection as a High Quality Coldwater stream. The stream supports a healthy population of wild brown trout, and it provides a substantial amount of recreational fishing, which makes a significant contribution to the economy. Recent studies indicate that sediment loading from agricultural activities and urban stormwater reduce reproductive success of brown trout in a 5-mile reach of stream. Since 1990, a significant portion of agricultural land in the upper Spring Creek watershed has been fenced and stream banks have been stabilized to alleviate this problem. These activities resulted in a more than 50% reduction in total suspended solids from one tributary.

Construction of the Park Avenue interchange and the bridge across Spring Creek at Rock Road was at the upper end of the stream reach targeted for sediment reduction. Local conservation groups and state agencies expressed concern over the potential increase in sediment loads as a result of these construction activities. The intent of this study was to monitor stream sediment loads, stream substrate composition, macroinvertebrate communities, and trout spawning sites during and immediately after construction to determine effects, if any, of construction activities on Spring Creek.

Objectives

1. Determine the sediment load attributable to construction activities near the Park Avenue interchange and the bridge crossing Spring Creek along Rock Road,

2. Assess composition of stream substrates upstream and downstream of the construction sites,

3. Assess macrobenthic communities upstream and downstream of construction sites, and

4. Assess the distribution and density of trout spawning sites upstream and downstream of construction sites.

Executive Summary

The goal of this project was to monitor stream sediment loads, stream substrate composition, macroinvertebrate communities, and trout spawning sites during and immediately after construction to determine effects, if any, of road construction activities adjacent to Spring Creek. This project began in September 1999, about the same time that construction activities were started near the Park Avenue interchange and the Rock Road bridge crossing. Sampling continued through May 2003.

Water monitoring equipment was installed on Spring Creek upstream and downstream of construction areas near the Park Avenue interchange and the Rock Road bridge crossing. Water samples were collected at hourly intervals during 118 storm events. Total suspended solids at the upstream and downstream stations near the Park Avenue interchange were similar indicating no measurable sediment loading from this construction site until July 2001 when concrete drainage channels were constructed at the site. After concrete drainage channels were added to the site, total suspended solids increased at the downstream monitoring station. At the Rock Road bridge crossing, total suspended solids at the downstream station were frequently higher than at the upstream station. Total sediment load was about 14% higher at the downstream station compared to the upstream station, which indicates sediment contribution from this site. Stream substrate composition and other variables measured at both construction sites (benthic macroinvertebrate communities, and numbers of trout spawning sites) were similar at the upstream and downstream sampling stations.

Click here for the final report (pdf document)

Pennsylvania Fish Distribution Patterns: Anthopogenic Influences and the Status of Rare Fishes

David G. Argent, Graduate Research Assistant

Robert F. Carline, Advisor

Management of aquatic systems requires the ability to identify areas where species currently occur, but conservation of aquatic systems requires the additional identification of where species could potentially occur or where species historically occurred. As a first step in documenting long-term changes in Pennsylvania fish assemblages, I have assembled a statewide historical data base using geographic information systems software. This database contains information on fish distribution over the past 100 years for rivers and streams. Utilizing this information, I have developed several research questions and generated several significant results that are being used to guide the future management of Pennsylvania’s fishes.

Research Questions:

1) Have Pennsylvania’s fish communities changed over the last 100 years?

2) Are there specific geographic areas where communities are experiencing increases or decreases in their diversity?

3) Are there specific areas where unique fishes occur?

4) Can methodologies be developed to aid the conservation of Pennsylvania’s fishes?

5) Is there a relationship between fish community assemblages and land use influences?

6) Can landscape variables be used to predict fish habitat?

Overview of Results:

1) Eleven fishes have been extirpated from Pennsylvania rivers and streams, and seven fishes that were previously considered extirpated are present in contemporary collections.

2) Forty-five fishes have been introduced into Pennsylvania outside its borders, or from within its major drainage basins.

3) Eighty-percent of 104 delineated watersheds experienced reductions in fish species richness over the last 100 years, of at least one species.

4) Species richness appears highest throughout the Ohio and Allegheny river drainages.

5) A high degree of collinearity exists among several land use types, indicating multiple anthropogenic terrestrial land use practices.

6) Watersheds that showed species declines, had significantly higher proportions of agricultural land and developed land, while those watersheds with relatively stable fish communities had higher amounts of forested land.

7) Using the overall distribution and abundance of a given species over a 32-year period as the criteria to evaluate fish species' rarity status – I classified 54 of Pennsylvania’s fishes as either endangered, threatened, or candidate. This represents nearly 35% of Pennsylvania’s native fish fauna, a 5% increase over those classified as of January 1, 1999.

8) The Ohio River drainage, which contains over 69% of Pennsylvania’s rare fishes, constitutes 30% of Pennsylvania’s total land area, but less than 10% of the land in the Ohio River Drainage is publicly owned, and little of that supports rare fishes. These results suggest that future conservation efforts (e.g., land acquisition or new management strategies) may need to be implemented to preserve Pennsylvania’s rare fishes.

9) Using several broad landscape variables: presence in a major drainage basin, presence in a physiographic region, median watershed slope, level of watershed disturbance, and watershed-stream size, a habitat model was developed.

10) Using these variables species presence in a watershed was predicted with a 73% accuracy. Significantly more habitat area, measured in square kilometers, exists for fishes than has been sampled over the last 50 years.

11) Watersheds in the Allegheny River drainage, in the Pittsburgh Low Plateau Section, of medium size (3-4 order), with moderate slope (2-4%), and moderate watershed disturbance (25-75%) are predicted to have the highest diversity of fishes.

Dynamics and feeding ecology of the unexploited walleye population of Pymatuning Sanctuary, Pennsylvania, 1997-98

Patrick M. Kocovsky, M.S. in Wildlife and Fisheries Science

Robert F. Carline, Advisor

Studies of the dynamics of unexploited fish populations are rare in the fisheries literature. Walleyes are one of the most sought-after fish species by recreational anglers throughout North America and are an important commercial fish species in Canada. Pymatuning Sanctuary in Crawford County, Pennsylvania, was formed in the mid-1930's following construction of a flood control dam on the upper Shenango River. Native and stocked populations of walleyes and numerous other fish species contributed to establishment of the fish populations that exist there today. Fishing has been prohibited on the Sanctuary since its creation. Fishery managers in Pennsylvania rely on stocking of walleye fry to enhance and maintain walleye fisheries throughout the Commonwealth, and most of the stocked fry come from eggs taken from walleyes in Pymatuning Sanctuary. Because of its value to Pennsylvania's walleye management program, and because it has never been exploited, the Pymatuning Sanctuary walleye population is a unique and important resource.

A pilot study conducted in 1993 on the dynamics of the Sanctuary walleye population raised concerns about high adult walleye density, potentially high adult mortality, and reliance of adult walleyes on gizzard shad as a primary food source despite apparently decreasing gizzard shad abundance. We sought to more thoroughly investigate the dynamics and feeding ecology of the unexploited walleye population of Pymatuning Sanctuary. We studied population dynamics during the spring spawning run and feeding ecology Ma- through October 1997-1998.

Primary Objectives

1) to describe the dynamics of the walleye population in terms of adult population size and density, growth, mortality, and recruitment to adult stock

2) to describe walleye feeding ecology in terms of seasonal consumption and diet composition for young-of-the-year, juvenile, and adult walleyes

3) to examine the relationship between walleye feeding, condition, growth, and the thermal regimen of Pymatuning Sanctuary (objective added following 1997 field season)

Secondary Objective

4) to develop a new surface area estimate and map of the Sanctuary (objective added following the 1997 field season)

Principle Research Findings:

· The open water surface area of the Sanctuary has decreased from 1,012 ha in the mid 1930's to approximately 530 ha in 1998, a 48% reduction since the reservoir was created. A large wetland occupied the site now flooded by the Sanctuary, which has decreased in surface area as the wetland has expanded. We speculate further reduction in Sanctuary surface area is likely as the wetland continues to expand to its pre-impoundment boundary.

· The summer thermal regimen in the Sanctuary was unfavorable for walleyes in 1998, and was likely an important factor in adult walleye condition, feeding, and growth. Summer temperatures were above the thermal optimum (22°C) for walleyes from mid-June through early September both years, which likely resulted in significant thermal stress. The sanctuary is shallow and homothermous, forcing walleyes to remain in unfavorably warm water all summer.

· Population dynamics:

- The adult walleye population in PS is very large and its density is up to 7 times that of other populations reported in the primary literature regardless of level of exploitation.

- Most adult walleyes are large; 50% are over 500 mm and 5% are over 600 mm TL.

- Adult mortality was 32-41%, which is within the range of values reported for other walleye populations, but higher than expected for an unexploited population. Managers frequently assume natural mortality is approximately 10%.

- Adult walleye grow slowly in Pymatuning Sanctuary, attaining on average 67% of their maximum length by maturity (age-2 or age-3 for males, age-3 to age-4 for females).

- Adults were relatively long-lived. Maximum estimated age (from otoliths) was 17 yrs.

- Autumn catch-per-unit-effort (CPUE) of young-of-the-year (YOY) walleyes in 1997 was quite high (>2 fish^·h^-1), but CPUE the following spring was 64% lower, suggesting high winter mortality. Loss of YOY during winter greatly reduces potential recruitment.

- Our results are consistent with predictions for unexploited fish populations - longer lives, longer adult lengths, high proportions of large fish and larger populations are all predictable in the absence of exploitation. Slow growth and higher than anticipated mortality may be attributable to high density, but the effects of the unfavorable thermal regimen are probably very important (see feeding results below).

· Feeding ecology:

- Adult walleyes fed most actively in autumn and least actively in summer both years. A large proportion of adult walleyes had empty stomachs during summer, and those that were feeding had low volume of food during the period when temperatures were above the optimum. Adult relative weights remained low throughout summer 1998 and were highly negatively correlated with temperature. This period of simultaneous low feeding activity, low food consumption, and high metabolism due to high temperatures may be a significant source of mortality for adult walleyes in the Sanctuary.

- Gizzard shad were an important food item for adults only in autumn. Centrarchids, yellow perch, and invertebrates were the only food items consumed during spring and summer. Scales and changes in relative weight during summer-autumn suggest adults increased in weight only in autumn when gizzard shad were the bulk of the diet.

- Age-0 walleyes consumed bluegills more than any other species. Age-0 walleye diet was restricted almost exclusively to bluegills in autumn 1998 because of exceptionally rapid growth of other forage species. Rapid growth of forage species may have been related to summer thermal regimen.

Future Sanctuary Research

Habitat use

Results of our population dynamics and feeding ecology studies suggest further research on walleye habitat usage during the warm summer months. Adult walleye CPUE during summer was the lowest of the year, suggesting walleye inactivity or that walleyes are using areas of the Sanctuary not sampled during our feeding ecology study (we sampled all of the accessible shorelines - about 65%). We will propose a telemetry study of adult walleyes to determine which areas of the Sanctuary are used by adults during the summer and to determine if walleyes are finding previously unknown thermal refugia.

Egg quality

Hatchery personnel have observed apparently decreasing hatching success of eggs collected from Pymatuning Sanctuary walleyes over the last few years. There is concern that high adult density, large female size, old female age, and poor diet may be contributing to poor egg quality. We will propose a study to determine the relationship between female size, egg hatching success, survival of fry to exogenous feeding, and several egg quality parameters for eggs collected from Pymatuning Sanctuary walleyes.

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Morphological divergence of an introduced population of banded darters

Patrick M. Kocovsky, Graduate Research Assistant

Jay R Stauffer, Jr., Professor of Ichthyology

Banded darters (Etheostoma zonale) are native to the Allegheny River drainage in Pennsylvania. In the late 1960's banded darters were introduced via a baitbucket introduction into the Pine Creek basin in North-central Pennsylvania. Following hurricane Agnes in 1974, banded darters spread throughout the Susquehanna River drainage, where they are now the most abundant darter species in many streams, having displaced some native darters such as the tessellated darter (E. olmstedi). I used sheared principle components analysis to compare 24 morphometric and 5 meristic characters of banded darters collected from an introduced population in Pine Creek in 1971 and 1999 to that of banded darters collected from a native population in 1966 and 1998 to determine what morphological divergence, if any, had occurred in the introduced population and between the introduced population and a nearby native population since the introduction event.

Principle Research Findings

· Banded darters in Pine Creek differed significantly in some morphological and meristic characters from banded darters taken from a geographically proximal native population. Morphometric and meristic characters related to base length of the anal fin and positioning of the anal-fin in relation to other morphological landmarks accounted for the most variation in fish shape. ]

· A "founder effect" is the most plausible explanation for the observed differences in morphology. A founder effect occurs when a small number of individuals of a parent population are introduced into or invade a new environment to form a population that is genetically isolated from the parent population. Accidents of gene assortment that result in the founder population having different gene frequencies than the parent population at some or many gene loci will have a great effect on character divergence. Restriction or elimination of gene flow between the founder population and the parent population causes a change in the selective value of many gene loci within the founder population, which eventually results in establishment of a new genetic equilibrium within the founder population.

Future Darter Research

In June 2000 we began a collaborative effort with Rich Raesly, Frostburg State University, to perform an analysis of allozyme diversity in the introduced banded darter population. We will identify gene loci previously found to have multiple alleles in native populations, and then examine those loci for multiple alleles in the exotic population. A similar comparison performed in the late 1980’s revealed several mono-allelic loci in the exotic population that were poly-allelic in native populations. This research will augment our morphological analysis and shed additional light on the evolutionary processes occurring in the banded darter population in Pine Creek.

Accumulation of PCBs in Hatchery Trout

Robert F. Carline, Principal Investigator

Patrick M. Barry, Research Technician

H. George Ketola, USGS, Great Lakes Science Center, Tunison Lab of Aquatic Science

EXECUTIVE SUMMARY

Routine testing in 1998 revealed polychlorinated biphenyls (PCBs) in edible tissues of trout from Pennsylvania Fish and Boat Commission (PFBC) hatcheries. PCB levels in some tissue samples exceeded thresholds for the issuance of consumption advisories. Preliminary testing also revealed low levels of PCBs in commercial trout diets. Although all PFBC hatcheries use the same commercial feeds, PCB levels in trout vary among hatcheries, which suggests that hatchery water supplies and trout feeds are both contributing to PCBs in trout flesh. This study focused on the role of fish feeds in the accumulation of PCBs in hatchery-reared trout. The objectives were to identify potential sources of PCBs in hatchery trout, to determine the relation between PCB concentrations in diets and body burdens of PCBs in hatchery trout, to determine if PCB concentrations in hatchery trout vary seasonally, and to determine the assimilation rate and net accumulation of PCBs in hatchery trout. A 6-month feeding trial using four experimental diets was employed to determine the relation between PCB concentrations in feed and fish fillets. A 12-month feeding trial using one diet was conducted to examine seasonal variation in PCB concentrations in trout fillets. And, a 3-week experiment was run to measure net absorption of PCBs by trout.

The study was conducted at the Benner Spring Fish Research Facility. We fed groups of rainbow trout four specially formulated diets with PCB concentrations ranging from 69 to 280 ng/g. Trout were sampled monthly to assess growth and PCB concentrations in fillets and in the remainder of the carcass. Semi-permeable membrane devices (SPMD) were employed in the hatchery supply water to detect the presence of PCBs. At the end of the feeding trial, chromic oxide was added to each of the diets, which were fed for 2 weeks. Analyses of feces for chromic oxide and PCBs were used to compute net absorption of PCBs. One group of trout was fed one of the diets for 12 months and these fish were sampled monthly to assess growth and PCB levels in fillets.

Trout grew from 22 g to 190 g after 6 months and there was no relation between growth and PCB concentrations in feed. After trout fed for one month, PCB concentrations in fillets reached levels proportional to PCB concentrations in their feed and remained at that level for the remainder of the trial. We found a positive relationship between concentrations of PCBs in feed and in trout fillets, which ranged from 54 to 94 ng/g. Net absorption of PCBs averaged 87% and was not affected by PCB concentration. The SPMDs revealed low levels of PCBs in hatchery supply water. We computed a mass balance budget for PCBs by accounting for the amount consumed, assimilated, and stored in tissues. This analysis suggested that the entire body burden of PCBs could be accounted for by PCBs in the feed and that uptake of PCBs from supply water was not an important source of contamination. There was no evident seasonal variation in PCB concentrations of trout fed for 12 months. After 6 months, PCB concentrations in fillets gradually increased, which was due in part to increases in the lipid content of trout flesh.

We conclude that the FDA standard of <200 ng/g (0.2 ppm) PCBs in finished fish feeds is adequate to ensure that trout raised to catchable size will have fillet concentrations <100 ng/g PCBs, the level at which Pennsylvania advises the public to limit fish consumption to one meal per week or less.