Abstract Populations of invasive fishes quickly reach extremely high biomass. Before control meth... more Abstract Populations of invasive fishes quickly reach extremely high biomass. Before control methods can be applied, however, an understanding of the contaminant loads of these invaders carry is needed. We investigated differences in concentrations of selected elements in two invasive carp species as a function of sampling site, fish species, length and trophic differences using stable isotopes (δ 15 N, δ 13 C).
ABSTRACT Long‐term population trends of pallid sturgeon Scaphirhynchus albus in the lower Missour... more ABSTRACT Long‐term population trends of pallid sturgeon Scaphirhynchus albus in the lower Missouri River were evaluated via a discrete and stochastic age‐structure population viability model. The intent of this model was to (i) estimate the local pallid sturgeon population size, (ii) quantify the contribution of hatchery‐reared fish to the overall population, (iii) predict the level of natural production needed to create a self‐sustaining population, and (iv) determine the parameters that produce the largest model sensitivity. The model estimated that the wild, adult population size was approximately 6000 fish that remained in the lower Missouri River in 2012 compared to approximately 42 000 hatchery‐reared pallid sturgeon. Under the assumption of no natural recruitment, the population size will continue to decline at approximately 8% annually, with an annual egg to age‐1 survival rate of 0.00011 predicted to maintain a stable population. The model was most sensitive to survival rates of fish ≥ age‐1 and less sensitive to age‐0 survival rates and fecundity. Decreasing or increasing the female spawning interval by 1 year had minimal effect on the overall population trajectory. Recovery management planning for a species such as pallid sturgeon, which is slow‐growing, late‐maturing, and has intermittent spawning would require several years to access recovery potential and management decisions. Barring any unforeseen natural catastrophe, the pallid sturgeon population in the lower Missouri River is not in immediate danger of local extirpation; however, the population appears to be far from viable and self‐sustaining.
Migratory freshwater fish have sustained substantial declines globally due to factors such as hab... more Migratory freshwater fish have sustained substantial declines globally due to factors such as habitat loss and overharvest. Attempts at large-scale conservation plans for these fishes have been made in the USA through the Mississippi River Interstate Cooperative Resource Association (MICRA) paddlefish and sturgeon committee. The most conspicuous result of this effort has been a long-term, nearly range-wide mark-recapture database containing >35,000 encounters with individually marked paddlefish and release information on >2 million batch marked hatchery-reared paddlefish. We used data from the paddlefish stock assessment database to describe 1.) survival and recapture probabilities of paddlefish, 2.) the spatial extent of wild and stocked paddlefish movements and 3.) concomitant management implications of these survival and movements estimates. Annual survival probability estimates of wild paddlefish were lowest for the Mississippi River Basin (the Mississippi River and its tr...
Large river paradigms suggest that natural flow regimes are critical for maintaining instream hab... more Large river paradigms suggest that natural flow regimes are critical for maintaining instream habitats and promoting production and growth of native aquatic organisms. Modifications to the Missouri River, Nebraska, within the past 100 years have drastically reduced shallow water habitat, homogenized the flow regime, and contributed to declines in several native species. Despite drastic flow modifications, several metrics of the Missouri River's flow regime still vary across years. We related age-0 channel catfish growth to environmental conditions in the channelized Missouri River, Nebraska, between 1996 and 2013 using an information theoretic approach. Growth rate was most influenced by growing season duration and duration of discharges below the 25th percentile of 30-year daily Missouri River discharges. Periods of low water may be important for juvenile growth because of channel modifications that limit critical shallow water habitat during higher within-bank flows. Exclusion...
ABSTRACT Lotic systems within the Great Plains are characterized by highly fluctuating conditions... more ABSTRACT Lotic systems within the Great Plains are characterized by highly fluctuating conditions through both space and time. Fishes inhabiting these systems have adopted specific life-history strategies to survive in such environments; however, anthropogenic disturbance to prairie streams has resulted in declines and extirpation of many native stream fishes. Terrestrial protected areas (i.e., parks and reserves) are designated to support native flora and fauna and, it is assumed, to provide protection to native fishes. We assessed the presence and relative abundance of stream fish populations within protected areas along the Niobrara River in western Nebraska based on data collected during 1979, 1989, 2008, and 2011. The spatial extent of protection, landscape changes resulting in degraded physiochemical parameters, and introduced species may reduce the effectiveness of these terrestrial protected areas in protecting native fishes in Great Plains stream environments.
Contemporary conservation strategies must balance conservation needs in the face of a growing hum... more Contemporary conservation strategies must balance conservation needs in the face of a growing human population in need of drinking water, hydroelectric power generation, and navigation. Conservation strategies for great river (basin area >250,000 km2) endemic fishes, for example, are limited by impoundments that block movements and alter hydrographs but must be maintained for humans to access riverine ecosystem services. Tributaries are an important part of the riverscape of a mainstem river and have been shown in numerous instances to enhance ecosystem function of altered mainstem rivers. Tributaries are a prime driver in mainstem river biodiversity, population dynamics, and community organization and have been forwarded for use as a restoration strategy due to the numerous ecological functions they provide. The ecological benefits tributaries provide to mainstem rivers coupled with their comparatively smaller scale and lesser degree of alteration, may make conserving or restori...
Abstract Populations of invasive fishes quickly reach extremely high biomass. Before control meth... more Abstract Populations of invasive fishes quickly reach extremely high biomass. Before control methods can be applied, however, an understanding of the contaminant loads of these invaders carry is needed. We investigated differences in concentrations of selected elements in two invasive carp species as a function of sampling site, fish species, length and trophic differences using stable isotopes (δ 15 N, δ 13 C).
ABSTRACT Long‐term population trends of pallid sturgeon Scaphirhynchus albus in the lower Missour... more ABSTRACT Long‐term population trends of pallid sturgeon Scaphirhynchus albus in the lower Missouri River were evaluated via a discrete and stochastic age‐structure population viability model. The intent of this model was to (i) estimate the local pallid sturgeon population size, (ii) quantify the contribution of hatchery‐reared fish to the overall population, (iii) predict the level of natural production needed to create a self‐sustaining population, and (iv) determine the parameters that produce the largest model sensitivity. The model estimated that the wild, adult population size was approximately 6000 fish that remained in the lower Missouri River in 2012 compared to approximately 42 000 hatchery‐reared pallid sturgeon. Under the assumption of no natural recruitment, the population size will continue to decline at approximately 8% annually, with an annual egg to age‐1 survival rate of 0.00011 predicted to maintain a stable population. The model was most sensitive to survival rates of fish ≥ age‐1 and less sensitive to age‐0 survival rates and fecundity. Decreasing or increasing the female spawning interval by 1 year had minimal effect on the overall population trajectory. Recovery management planning for a species such as pallid sturgeon, which is slow‐growing, late‐maturing, and has intermittent spawning would require several years to access recovery potential and management decisions. Barring any unforeseen natural catastrophe, the pallid sturgeon population in the lower Missouri River is not in immediate danger of local extirpation; however, the population appears to be far from viable and self‐sustaining.
Migratory freshwater fish have sustained substantial declines globally due to factors such as hab... more Migratory freshwater fish have sustained substantial declines globally due to factors such as habitat loss and overharvest. Attempts at large-scale conservation plans for these fishes have been made in the USA through the Mississippi River Interstate Cooperative Resource Association (MICRA) paddlefish and sturgeon committee. The most conspicuous result of this effort has been a long-term, nearly range-wide mark-recapture database containing >35,000 encounters with individually marked paddlefish and release information on >2 million batch marked hatchery-reared paddlefish. We used data from the paddlefish stock assessment database to describe 1.) survival and recapture probabilities of paddlefish, 2.) the spatial extent of wild and stocked paddlefish movements and 3.) concomitant management implications of these survival and movements estimates. Annual survival probability estimates of wild paddlefish were lowest for the Mississippi River Basin (the Mississippi River and its tr...
Large river paradigms suggest that natural flow regimes are critical for maintaining instream hab... more Large river paradigms suggest that natural flow regimes are critical for maintaining instream habitats and promoting production and growth of native aquatic organisms. Modifications to the Missouri River, Nebraska, within the past 100 years have drastically reduced shallow water habitat, homogenized the flow regime, and contributed to declines in several native species. Despite drastic flow modifications, several metrics of the Missouri River's flow regime still vary across years. We related age-0 channel catfish growth to environmental conditions in the channelized Missouri River, Nebraska, between 1996 and 2013 using an information theoretic approach. Growth rate was most influenced by growing season duration and duration of discharges below the 25th percentile of 30-year daily Missouri River discharges. Periods of low water may be important for juvenile growth because of channel modifications that limit critical shallow water habitat during higher within-bank flows. Exclusion...
ABSTRACT Lotic systems within the Great Plains are characterized by highly fluctuating conditions... more ABSTRACT Lotic systems within the Great Plains are characterized by highly fluctuating conditions through both space and time. Fishes inhabiting these systems have adopted specific life-history strategies to survive in such environments; however, anthropogenic disturbance to prairie streams has resulted in declines and extirpation of many native stream fishes. Terrestrial protected areas (i.e., parks and reserves) are designated to support native flora and fauna and, it is assumed, to provide protection to native fishes. We assessed the presence and relative abundance of stream fish populations within protected areas along the Niobrara River in western Nebraska based on data collected during 1979, 1989, 2008, and 2011. The spatial extent of protection, landscape changes resulting in degraded physiochemical parameters, and introduced species may reduce the effectiveness of these terrestrial protected areas in protecting native fishes in Great Plains stream environments.
Contemporary conservation strategies must balance conservation needs in the face of a growing hum... more Contemporary conservation strategies must balance conservation needs in the face of a growing human population in need of drinking water, hydroelectric power generation, and navigation. Conservation strategies for great river (basin area >250,000 km2) endemic fishes, for example, are limited by impoundments that block movements and alter hydrographs but must be maintained for humans to access riverine ecosystem services. Tributaries are an important part of the riverscape of a mainstem river and have been shown in numerous instances to enhance ecosystem function of altered mainstem rivers. Tributaries are a prime driver in mainstem river biodiversity, population dynamics, and community organization and have been forwarded for use as a restoration strategy due to the numerous ecological functions they provide. The ecological benefits tributaries provide to mainstem rivers coupled with their comparatively smaller scale and lesser degree of alteration, may make conserving or restori...
Uploads
Papers by Mark Pegg