Direct and Indirect Effects of Fish Predation on the Replacement of a Native Crayfish by an Invading Congener

In Ohio streams, the crayfish Orconectes rusticus is replacing O. sanborni, and herein we test how predators influence this replacement. In a field survey, crayfish were scarce when fish were abundant, suggesting that predators can adversely affect these prey. In laboratory experiments, we examined underlying mechanisms for this inverse relationship; specifically, we tested how crayfish species, adult aggression, and habitat heterogeneity influenced the predator-prey interaction. In a laboratory stream, smallmouth bass (Micropterus dolomieu) ate similar numbers of equal-sized O. rusticus and O. sanborni, but when sizes mimicked those in the field (i.e., O. rusticus 4 mm > O. sanborni), fewer O. rusticus were eaten. Fish also reduced juvenileactivity and behaviors whereas adult aggression increased the frequency of these risky responses. More affected by adult crayfish, O. sanborni should suffer disproportional predation where adults and juveniles interact. Thus, fish predators should increase replacement rates and adult aggression should further accelerate this process. Manifested through crayfish size, both indirect and direct predator effects contribute to the replacement of O. sanborni by O. rusticusA National Science Foundation Dissertation Improvement Grant, a Sigma Xi Grant-in-Aid, and the Ohio Cooperative Fish and Wildlife Research Unit provided funding

Use of non-natal estuaries by migratory striped bass (Morone saxatilis) in summer

For most migratory fish, little is known about the location and size of foraging areas or how long individuals remain in foraging areas, even though these attributes may affect their growth, survival, and impact on local prey. We tested whether striped bass (Morone saxatilis Walbaum), found in Massachusetts in summer, were migratory, how long they stayed in non-natal estuaries, whether observed spatial patterns differed from random model predictions, whether fish returned to the same area across multiple years, and whether fishing effort could explain recapture patterns. Anchor tags were attached to striped bass that were caught and released in Massachusetts in 1999 and 2000, and recaptured between 1999 and 2007. In fall, tagged striped bass were caught south of where they were released in summer, confirming that fish were coastal migrants. In the first summer, 77% and 100% of the recaptured fish in the Great Marsh and along the Massachusetts coast, respectively, were caught in the same place where they were released. About two thirds of all fish recaptured near where they were released were caught 2–7 years after tagging. Our study shows that smaller (400–500 mm total length) striped bass migrate hundreds of kilometers along the Atlantic Ocean coast, cease their mobile lifestyle in summer when they use a relatively localized area for foraging (<20 km2), and return to these same foraging areas in subsequent y

Experimental Assessment of Mortality and Hyperglycemia in Tiger Muskellunge Due to Stocking Stressors

Tiger muskellunge (the F1 hybrid of female muskellunge Esox masquinongy and male northern pike E.lucius) have survived poorly when stocked in reservoirs. To understand why, we quantified, in the laboratory, both mortality and plasma glucose responses to three common stocking stressors: dipnet handling, confinement, and temperature increase. No young-of-year hybrids died within 48 h when the temperature was abruptly increased 10C, and only 5% died when the temperature was increased 12C, but 98% died within 4 h when the temperature was increased 15C. Thus, we concluded that thermal stress is an important determinant of poststocking mortality. Mortalities in response to three multiple-stressor treatments--(1) handling and temperature increase, (2) handling, confinement at a fish density of 83 g/L, and temperature increase, and (3) handling, confinement at 135 g/L, and temperature increase--did not differ from each other or from mortality associated with a temperature increase alone. Thus, handling and moderate-density confinement during transport do not necessarily increase poststocking mortality of tiger muskellunge. Abrupt temperature increases of 12 and 15C increased peak plasma glucose concentrations significantly. Handling and confinement together caused a significant hyperglycemia both with and without a temperature increase. However, the relative magnitude of the hyperglycemia caused by individual handling and confinement stressors depended on the presence of a thermal stressor. Finally, we found that plasma glucose concentrations and mortality were not correlated. Although glucose is easily measured and sensitive to small changes in stress, it is not a good indicator of reduced survival and should not be used as such in studies intended to quantify stress-induced mortality.This research was supported in part by funds from the Federal Aid in Fish Restoration Project F-57-R. The Department of Zoology, The Ohio State University, and the Ohio Cooperative Fishery Research Unit also provided financial assistance, computer money, and equipment

Problem-solving Research for Management: A Perspective

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 problemsolving 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, problemsolving 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 differences in tools and goals of their respective trades. Unfortunately, we think neither group appreciates that successful management relies on rigorous, quantitative research that must be held accountable for providing management solutions. Managers and researchers clearly share the burden for the current state of fisheries science

Management Issues and Their Relative Priority within State Fisheries Agencies

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 issueshabitat restoration, hydropower licensing, instream flow, contaminants, introduced species, and nongame species-were of "moderate priority" nationwide. Approximately 50% of the issues varied in emphases across geographic region, and five issues were differentially emphasized in agencies with freshwater and marine responsibilities. To solve persistent problems that plague fisheries management, agencies must clearly identify high-priority management concerns and communicate their specific problem-solving needs to researchers. Results of this survey should provide a first step in identifying these management priorities and research needs

How Big of an Effect Do Small Dams Have? Using Geomorphological Footprints to Quantify Spatial Impact of Low-Head Dams and Identify Patterns of Across-Dam Variation

Citation: Fencl, J. S., Mather, M. E., Costigan, K. H., & Daniels, M. D. (2015). How Big of an Effect Do Small Dams Have? Using Geomorphological Footprints to Quantify Spatial Impact of Low-Head Dams and Identify Patterns of Across-Dam Variation. Plos One, 10(11), 22. doi:10.1371/journal.pone.0141210Longitudinal connectivity is a fundamental characteristic of rivers that can be disrupted by natural and anthropogenic processes. Dams are significant disruptions to streams. Over 2,000,000 low-head dams (<7.6 m high) fragment United States rivers. Despite potential adverse impacts of these ubiquitous disturbances, the spatial impacts of low-head dams on geomorphology and ecology are largely untested. Progress for research and conservation is impaired by not knowing the magnitude of low-head dam impacts. Based on the geomorphic literature, we refined a methodology that allowed us to quantify the spatial extent of low-head dam impacts (herein dam footprint), assessed variation in dam footprints across low-head dams within a river network, and identified select aspects of the context of this variation. Wetted width, depth, and substrate size distributions upstream and downstream of six low-head dams within the Upper Neosho River, Kansas, United States of America were measured. Total dam footprints averaged 7.9 km (3.0-15.3 km) or 287 wetted widths (136437 wetted widths). Estimates included both upstream (mean: 6.7 km or 243 wetted widths) and downstream footprints (mean: 1.2 km or 44 wetted widths). Altogether the six low-head dams impacted 47.3 km (about 17%) of the mainstem in the river network. Despite differences in age, size, location, and primary function, the sizes of geomorphic footprints of individual low-head dams in the Upper Neosho river network were relatively similar. The number of upstream dams and distance to upstream dams, but not dam height, affected the spatial extent of dam footprints. In summary, ubiquitous low-head dams individually and cumulatively altered lotic ecosystems. Both characteristics of individual dams and the context of neighboring dams affected low-head dam impacts within the river network. For these reasons, low-head dams require a different, more integrative, approach for research and management than the individualistic approach that has been applied to larger dams

Seasonal use of a New England estuary by foraging contingents of migratory striped bass

Author Posting. © American Fisheries Society, 2009. This article is posted here by permission of American Fisheries Society for personal use, not for redistribution. The definitive version was published in Transactions of the American Fisheries Society 139 (2010): 257-269, doi:10.1577/T08-222.1.Using acoustic telemetry on migratory striped bass Morone saxatilis in Plum Island Estuary (PIE), Massachusetts, we found that striped bass (335–634 mm total length) tagged in the spring and summer of 2005 (n = 14) and 2006 (n = 46) stayed in the estuary for an average of 66.0 d in 2005 and 72.2 d in 2006. Striped bass spent the most time in two specific reaches: middle Plum Island Sound and lower Rowley River. In both years, three different use-groups of striped bass were observed in PIE. Short-term visitors (n = 24) stayed in the estuary only briefly (range = 5–20 d). Two groups of seasonal residents stayed for more than 30 d, either in the Rowley River (n = 14) or in Plum Island Sound (n = 22). Within PIE, the two seasonal-resident use-groups may be foraging contingents that learn how to feed efficiently in specific parts of the estuary. These distinct within-estuary use patterns could have different implications for striped bass condition and prey impact

Discontinuities Concentrate Mobile Predators: Quantifying Organism-Environment Interactions at a Seascape Scale

Understanding environmental drivers of spatial patterns is an enduring ecological problem that is critical for effective biological conservation. Discontinuities (ecologically meaningful habitat breaks), both naturally occurring (e.g., river confluence, forest edge, drop-off) and anthropogenic (e.g., dams, roads), can influence the distribution of highly mobile organisms that have land- or seascape scale ranges. A geomorphic discontinuity framework, expanded to include ecological patterns, provides a way to incorporate important but irregularly distributed physical features into organism–environment relationships. Here, we test if migratory striped bass (Morone saxatilis) are consistently concentrated by spatial discontinuities and why. We quantified the distribution of 50 acoustically tagged striped bass at 40 sites within Plum Island Estuary, Massachusetts during four-monthly surveys relative to four physical discontinuities (sandbar, confluence, channel network, drop-off), one continuous physical feature (depth variation), and a geographic location variable (region). Despite moving throughout the estuary, striped bass were consistently clustered in the middle geographic region at sites with high sandbar area, close to channel networks, adjacent to complex confluences, with intermediate levels of bottom unevenness, and medium sized drop-offs. In addition, the highest striped bass concentrations occurred at sites with the greatest additive physical heterogeneity (i.e., where multiple discontinuities co-occurred). The need to incorporate irregularly distributed features in organism–environment relationships will increase as high-quality telemetry and GIS data accumulate for mobile organisms. The spatially explicit approach we used to address this challenge can aid both researchers who seek to understand the impact of predators on ecosystems and resource managers who require new approaches for biological conservation