Craig P. Paukert

Defining conservation priorities for freshwater fishes according to taxonomic, functional, and phylogenetic diversity

To date, the predominant use of systematic conservation planning has been to evaluate and conserve areas of high terrestrial biodiversity. Although studies in freshwater ecosystems have received recent attention, research has rarely considered the potential trade-offs between protecting different dimensions of biodiversity and the ecological processes that maintain diversity. We provide the first systematic prioritization for freshwaters (focusing on the highly threatened and globally distinct fish fauna of the Lower Colorado River Basin, USA) simultaneously considering scenarios of: taxonomic, functional, and phylogenetic diversity; contemporary threats to biodiversity (including interactions with nonnative species); and future climate change and human population growth. There was 75% congruence between areas of highest conservation priority for different aspects of biodiversity, suggesting that conservation efforts can concurrently achieve strong complementarity among all types of diversity. However, si...

Climate Change Effects on North American Inland Fish Populations and Assemblages

Climate is a critical driver of many fish populations, assemblages, and aquatic communities. However, direct observational studies of climate change impacts on North American inland fishes are rare. In this synthesis, we (1) summarize climate trends that may influence North American inland fish populations and assemblages, (2) compile 31 peer-reviewed studies of documented climate change effects on North American inland fish populations and assemblages, and (3) highlight four case studies representing a variety of observed responses ranging from warmwater systems in the southwestern and southeastern United States to coldwater systems along the Pacific Coast and Canadian Shield. We conclude by identifying key data gaps and research needs to inform adaptive, ecosystem-based approaches to managing North American inland fishes and fisheries in a changing climate.

An Overview of Northern Pike Regulations in North America

Abstract Northern pike (Esox lucius) is a popular sport fish in the United States and Canada that is currently managed for multiple angler uses. However, there has been increased concern over lower quality (i.e., smaller fish) northern pike populations. In 1997, the Esocid Technical Committee (ETC) of the North Central Division of the American Fisheries Society surveyed natural resource agencies about their northern pike management. In addition, a round-table discussion on the quality of northern pike management was conducted in 1999. This paper is a summary of the ETC findings. In some cases, northern pike regulations have existed since the late 1800s, but most states and provinces did not use regulations until the 1950s or 1960s. Some agencies currently manage northern pike for angling quality (i.e., more large fish), others have few or no northern pike regulations, and some agencies manage for quality in some water bodies and do not manage northern pike at all in other water bodies. In general, states ...

The added complications of climate change: understanding and managing biodiversity and ecosystems

Ecosystems around the world are already threatened by land-use and land-cover change, extraction of natural resources, biological disturbances, and pollution. These environmental stressors have been the primary source of ecosystem degradation to date, and climate change is now exacerbating some of their effects. Ecosystems already under stress are likely to have more rapid and acute reactions to climate change; it is therefore useful to understand how multiple stresses will interact, especially as the magnitude of climate change increases. Understanding these interactions could be critically important in the design of climate adaptation strategies, especially because actions taken by other sectors (eg energy, agriculture, transportation) to address climate change may create new ecosystem stresses.

Road crossing designs and their impact on fish assemblages of Great Plains streams

Abstract A mark–recapture field study was conducted to determine fish passage at 5 concrete box culverts and 5 low-water crossings (concrete slabs vented by culverts) as well as 10 control sites (below a natural riffle) in Flint Hills streams of northeastern Kansas. Additionally, we tested the upstream passage of four fish species native to Great Plains streams (Topeka shiner Notropis topeka, green sunfish Lepomis cyanellus, red shiner Cyprinella lutrensis, and southern redbelly dace Phoxinus erythrogaster) through three simulated crossing designs (box culverts, round corrugated culverts, and natural rock riffles) at water velocities of 0.1 to 1.1 m/s in an experimental stream. The field study indicated that cyprinids were twice as likely to move upstream of box culverts than low-water crossings and 1.4 times as likely to move upstream of control reaches than any crossing type. The best models indicated that the proportion of cyprinids that moved upstream increased with decreased culvert slope and length,...

Effects of Predation and Environment on Quality of Yellow Perch and Bluegill Populations in Nebraska Sandhill Lakes

We investigated factors that may influence the quality (e.g., high abundance, size structure, condition, and growth) of yellow perch Perca flavescens and bluegill Lepomis macrochirus populations in Nebraska sandhill lakes. Physical (e.g., lake depth, vegetation coverage), chemical (e.g., alkalinity, conductivity), and biological (e.g., chlorophyll a, invertebrate abundance) char- acteristics of 30 natural lakes were determined in 1998 and 1999. Growth, condition, and size structure were not density-dependent for bluegills or yellow perch in these shallow ( ,4 m maximum depth) lakes. However, bluegill abundance, size structure, and condition were positively related to yellow perch abundance, size structure, and condition. Bluegill quality tended to increase with increased emergent vegetation, whereas yellow perch quality was not correlated with any physi- cochemical variable measured. Submergent vegetation coverage ranged from 5% to 97% of lake surface area and was not related to panfish quality. The mean relative weight (Wr) of larger (15- 20 cm) bluegills was positively associated with high Daphnia and Cyclops abundance, whereas the mean Wr of 20-25-cm yellow perch was not related to invertebrate abundance. Higher relative abundance and lower proportional stock density of largemouth bass Micropterus salmoideswere positively related to panfish quality, even in lakes up to 341 ha. Quality panfish populations in the Nebraska sandhills are influenced by predators, prey, and the environment. However, based on the high correlation coefficients, largemouth bass may be most influential in structuring the quality of bluegill and yellow perch populations in these shallow natural lakes.

Development of a Bioenergetics Model for Humpback Chub and Evaluation of Water Temperature Changes in the Grand Canyon, Colorado River

Abstract The construction of Glen Canyon Dam above the Grand Canyon (Arizona) has reduced the water temperature in the Colorado River and altered the growth rate and feeding patterns of the federally endangered humpback chub Gila cypha. A bioenergetics model for humpback chub was developed and used to examine how warmer water temperatures in the lower Colorado River (achieved through a temperature control device [TCD] at Glen Canyon Dam) might influence their growth rate and food requirements. Parameter values for humpback chub were developed by Monte Carlo filtering and fitting to laboratory growth. Parameter bounds were established from the literature for Gila species, random parameter sets were selected within these bounds, and the growth of modeled humpback chub was compared with criteria from a laboratory growth experiment at 24°C. This method of parameter estimation could be applied to other imperiled fishes where physiological studies are impractical. Final parameter values were corroborated by com...

Effect and Acceptance of Bluegill Length Limits in Nebraska Natural Lakes

Abstract Bluegill Lepomis macrochirus populations in 18 Nebraska Sandhill lakes were evaluated to determine if a 200-mm minimum length limit would increase population size structure. Bluegills were trap-netted in May and June 1998 and 1999, and a creel survey was conducted during winter 1998–2001 on one or two lakes where bluegills had been tagged to determine angler exploitation. Thirty-three percent of anglers on one creeled lake were trophy anglers (i.e., fishing for large (≥250 mm) bluegills), whereas 67% were there to harvest fish to eat. Exploitation was always less than 10% and the total annual mortality averaged 40% across all 18 lakes. The time to reach 200 mm ranged from 4.3 to 8.3 years. The relative stock density of preferred-length fish increased an average of 2.2 units in all 18 lakes with a 10% exploitation rate. However, yield declined 39% and the number harvested declined 62%. Bluegills would need to reach 200 mm in 4.2 years to ensure no reduction in yield at 10% exploitation. Both yield...

Effects of Implanted Transmitter Size and Surgery on Survival, Growth, and Wound Healing of Bluegill

Abstract Surgically implanted transmitters generally should be less than 2% of body weight. However, laterally compressed fish such as bluegill Lepomis macrochirus may be more affected by transmitter size because of their small body cavity. Previous research on the effects of transmitters on laterally compressed centrarchids has given little attention to transmitter size or shape. We evaluated the effects of two transmitter sizes (approximately 1% and 2% of fish body weight) on survival, tag loss, growth, and healing of bluegill over a 10-week period. Both transmitters were similar in width and height but differed in length. Ten fish each were implanted with one of the two transmitter sizes, 11 fish were subjected to surgery only, and 10 fish were used as controls. No fish died immediately as a result of the surgery. However, two fish implanted with a large transmitter expelled their transmitters between weeks six and eight, including one fish that subsequently died in week seven. At 2 weeks after surgery...

Physiological Basis of Climate Change Impacts on North American Inland Fishes

Global climate change is altering freshwater ecosystems and affecting fish populations and communities. Underpinning changes in fish distribution and assemblage-level responses to climate change are individual-level physiological constraints. In this review, we synthesize the mechanistic effects of climate change on neuroendocrine, cardiorespiratory, immune, osmoregulatory, and reproductive systems of freshwater and diadromous fishes. Observed climate change effects on physiological systems are varied and numerous, including exceedance of critical thermal tolerances, decreased cardiorespiratory performance, compromised immune function, and altered patterns of individual reproductive investment. However, effects vary widely among and within species because of species, population, and even sex-specific differences in sensitivity and resilience and because of habitat-specific variation in the magnitude of climate-related environmental change. Research on the interactive effects of climate change with other e...