Donna L. Parrish

FAVORABLE FORAGING LOCATIONS FOR YOUNG ATLANTIC SALMON: APPLICATION TO HABITAT AND POPULATION RESTORATION

Declines in the populations of salmonid fishes have generated major interest in conservation and restoration of wild populations and river habitats. We used a foraging-based model, combined with field observations and surveys, to predict individual habitat use, and to assess the effects of stream habitat conditions and management practices on the potential for reestablishing Atlantic salmon, Salmo salar. Using a model based on a simple trade-off between increasing prey encounter rate and decreasing salmon capture success with increasing stream current velocity, we predicted favorable foraging locations for salmon in their first (age-0) spring and summer. We tested, in six streams, whether (1) salmon preferred locations (=microhabitats) that were predicted to yield high consumption rates, (2) salmon growth and survival was greater in streams with a greater proportion of preferred, profitable, microhabitats, and (3) stream habitat remediation (introduction of large in-stream structures such as large woody d...

Spatially Explicit Bioenergetic Analysis of Habitat Quality for Age-0 Atlantic Salmon

Abstract Spatial and temporal variation in growth conditions for young juveniles may determine the ultimate success of salmonid populations. To assess this aspect of habitat quality, we developed a spatially explicit bioenergetics model to predict age-0 Atlantic salmon Salmo salar growth rate potential (GRP) in rearing streams of the Connecticut River, from the time of stocking in the spring, to the end of the summer. During the first month after stocking, there appears to be a paucity of suitable habitat. Most available habitat is predicted to result in low foraging success of small fish and to be energetically stressful because of the combination of high spring discharge and low water temperature. Although less than 14% of available habitat was predicted to support positive growth in the spring, 47% of the fish we observed occupied microhabitats predicted to yield positive growth, indicating the importance of habitat selection. In contrast, from mid-June to August, 67% of available habitat was predicted...

Migration Timing of Atlantic Salmon Smolts Relative to Environmental and Physiological Factors

Abstract We determined the migration timing of fry-stocked smolts of Atlantic salmon Salmo salar relative to environmental and physiological factors, by using net weirs and counting fences in three tributaries of the West River, Vermont. Smolt migration began in late April and early May when water temperature was 5°C, peak movements occurred in early and mid-May at temperatures exceeding 8°C, and migration was complete by early June. Within this seasonal window, significant differences in migration timing and gill Na+,K+-ATPase activity occurred among tributaries. In both years of the study, smolts tended to migrate earlier and exhibit greater gill Na+,K+-ATPase activity in the warmest tributary than in the coolest tributary. Smolt migration timing differed most among tributaries in mid-May when (1) water temperatures were more than 8°C, (2) smolts peaked in gill Na+,K+-ATPase activity, and (3) discharge peaked, stimulating smolt migration. Smolts captured after the migratory period had lower gill Na+,K+-...

Migration delays caused by anthropogenic barriers: modeling dams, temperature, and success of migrating salmon smolts

Disruption to migration is a growing problem for conservation and restoration of animal populations. Anthropogenic barriers along migration paths can delay or prolong migrations, which may result in a mismatch with migration-timing adaptations. To understand the interaction of dams (as barriers along a migration path), seasonally changing environmental conditions, timing of Atlantic salmon (Salmo salar) downstream migration, and ultimate migration success, we used 10 years of river temperature and discharge data as a template upon which we simulated downstream movement of salmon. Atlantic salmon is a cool-water species whose downstream migrating smolts must complete migration before river temperatures become too warm. We found that dams had a local effect on survival as well as a survival effect that was spatially and temporally removed from the encounter with the dam. While smolts are delayed by dams, temperatures downstream can reach lethal or near-lethal temperatures; as a result, the match between com...

Spatial and Temporal Patterns of Food Use by White Perch and Yellow Perch in Lake Erie

ABSTRACT We determined spatial and temporal feeding patterns of white perch (Morone americana) and yellow perch (Perca flavescens) in Lake Erie by analysis of stomach contents. Diets were compared across years (1983–1985), seasons, basins of the lake (western and central), and depth in the western basin. Diets of these two fish species were generally similar, although white perch tended to use more zooplankton, while yellow perch consumed more Chironomidae, Sphaeriidae, and fishes. In other instances, competition apparently led to resource partitioning that resulted from differences in ontogenetic feeding requirements and mouth position between white perch and yellow perch.

Problem-solving Research for Management: A Perspective

Abstract We convened a symposium titled “Problem-solving Research for Management: Shared Responsibilities” at the 123rd annual meeting of the American Fisheries Society in Portland, Oregon. Our symposium sought to encourage researchers and managers to work together more effectively by reviewing successful research projects that have incorporated problem-solving approaches. In this first paper, we carefully define and distinguish between management and research by exploring the goals and tools of each discipline. In our view, problem-solving for management, as an iterative approach of which research is a major component, serves as a template for improving the relationship between managers and researchers as well as contributing to the solution of management problems. To improve the less-than-stellar record of interaction between these two groups, not only must problem-solving approaches be incorporated into the effort, but managers and researchers also must come to recognize, appreciate, and understand the...

Habitat Selection of Predator and Prey: Atlantic Salmon and Rainbow Smelt Overlap, Based on Temperature and Dissolved Oxygen

Abstract We investigated the predator-prey interactions of two pelagic species, landlocked Atlantic salmon Salmo salar and rainbow smelt Osmerus mordax, in a large-lake ecosystem. Our goal was to determine the overlap of habitats selected, based on profiles of temperature and dissolved oxygen (DO). We used hydroacoustics to ascertain the seasonal habitat selection of rainbow smelt and gill nets to sample Atlantic salmon in the Inland Sea of Lake Champlain, Vermont. We identified patterns of smelt habitat selection by overlaying the acoustically determined vertical distributions of smelt onto profiles of water temperature and DO. To verify species composition of acoustical targets, we performed midwater trawls using a stepped-oblique method and found that rainbow smelt constituted 99.5% of trawl catches. Trawl catches and acoustic fish density were correlated, indicating that acoustic targets represented trawled fish. Atlantic salmon habitat selection was estimated from temperature and DO profiles taken at...

Importance and Predictability of Cannibalism in Rainbow Smelt

Abstract Cannibalism is a key interaction between young of year (age-0) and older fish in many freshwater ecosystems. Density and spatial overlap between age-groups often drive cannibalism. Because both density and overlap can be quantified, the magnitude of cannibalism may be predictable. Our study considered cannibalism in rainbow smelt Osmerus mordax in Lake Champlain (New York–Vermont, United States, and Quebec, Canada). We used acoustic estimates of the density and distribution of age-0 and yearling-and-older (age-1+) rainbow smelt to predict cannibalism in the diets of age-1+ fish during 2001 and 2002. Experienced density, a measure combining density and spatial overlap, was the strongest predictor (R 2 = 0.89) of the proportion of cannibals in the age-1+ population. Neither spatial niche overlap (R 2 = 0.04) nor age-0 density (R 2 = 0.30) alone was a good predictor of cannibalism. Cannibalism among age-1+ rainbow smelt was highest in June, lowest in July, and high in September owing to differences ...

Using abiotic and biotic factors to predict the range expansion of white perch in Lake Champlain

Abstract White perch ( Morone americana ) invaded Lake Champlain, New York-Vermont, in the mid-1980s, yet abundance of white perch and those factors controlling their abundance are unknown. To predict the expansion of white perch, we differentiated between the most likely factors affecting white perch abundance; habitat characteristics or an invasion gradient (i.e., abundance is greater near the point of entry). Therefore, we addressed three questions: 1) where are white perch currently established; 2) what is the relation of white perch abundance to environmental variables and to an invasion gradient; and 3) based on the most likely factors affecting abundance, where will white perch become abundant in Lake Champlain? Fish communities were sampled and ten environmental variables were measured at sites along the eastern shore of Lake Champlain. Among sites and across seasons, two abiotic factors (turbidity and conductivity) had the greatest effect on white perch abundance. Biotic factors, yellow perch ( Perca flavescens ) abundance and chlorophyll a, however had lesser effects. We predict white perch will not become abundant in habitats with low water conductivity, turbidity and chlorophyll a, and a high abundance of potential competitors. Our predictions are consistent with data from other systems, which indicate environmental characteristics are likely more important than an invasion gradient in contributing to white perch colonization.

Management Issues and Their Relative Priority within State Fisheries Agencies

Abstract For researchers and managers to work together for greatest mutual benefit, researchers must understand what issues fisheries managers consider most important. To assess management priorities, we conducted a mail survey asking U.S. state fisheries agencies to identify the priority, based on personnel time, they place on 12 fisheries management issues. Based on an 88% response rate, we determined relative emphases across (1) management issues, (2) geographic regions, and (3) freshwater or marine orientations. Issues directly linked to sport and commercial fishers, i.e., stocking, harvest regulations, fishing pressure, and exploring recruitment, were of paramount importance in all agency time budgets. The issue that included conflict, policy, and human dimensions concerns also was identified as “high priority.” Six other issues—habitat restoration, hydropower licensing, instream flow, contaminants, introduced species, and nongame species—were of “moderate priority” nationwide. Approximately 50% of t...