Old Greenwich, CT, United States
Old Greenwich, CT, United States

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Hessenauer J.-M.,University of Connecticut | Vokoun J.,University of Connecticut | Davis J.,Inland Fisheries Division | Jacobs R.,Inland Fisheries Division | Odonnell E.,Inland Fisheries Division
Journal of Freshwater Ecology | Year: 2014

Recreational fishing can alter the demography and life history characteristics of fish populations. Unexploited populations are useful references for fisheries managers to place into context the extent of changes in exploited populations and the outcomes of management actions. Our objective is to characterize the largemouth bass Micropterus salmoides populations in two unexploited reservoirs in Connecticut and compare them with an exploited reservoir. Unexploited Hemlock Reservoir was characterized by large proportions of large fish in good condition with relatively low population mortality rates. Unexploited Easton Reservoir's bass proportional size distributions were more similar to exploited Mansfield Hollow Reservoir bass population. However, both unexploited reservoirs had higher catch per effort of stock-size and greater fish than Mansfield Hollow Reservoir indicating greater overall density of large fish. The study of long-term unexploited populations may become more important in the future as managers consider the evolutionary consequences of recreational exploitation. © 2014 Taylor & Francis.


Hessenauer J.-M.,University of Connecticut | Vokoun J.C.,University of Connecticut | Suski C.D.,University of Illinois at Urbana - Champaign | Davis J.,Inland Fisheries Division | And 2 more authors.
PLoS ONE | Year: 2015

Non-random mortality associated with commercial and recreational fisheries have the potential to cause evolutionary changes in fish populations. Inland recreational fisheries offer unique opportunities for the study of fisheries induced evolution due to the ability to replicate study systems, limited gene flow among populations, and the existence of unexploited reference populations. Experimental research has demonstrated that angling vulnerability is heritable in Largemouth Bass Micropterus salmoides, and is correlated with elevated resting metabolic rates (RMR) and higher fitness. However, whether such differences are present in wild populations is unclear. This study sought to quantify differences in RMR among replicated exploited and unexploited populations of Largemouth Bass. We collected age-0 Largemouth Bass from two Connecticut drinking water reservoirs unexploited by anglers for almost a century, and two exploited lakes, then transported and reared them in the same pond. Field RMR of individuals from each population was quantified using intermittent-flow respirometry. Individuals from unexploited reservoirs had a significantly higher mean RMR (6%) than individuals from exploited populations. These findings are consistent with expectations derived from artificial selection by angling on Largemouth Bass, suggesting that recreational angling may act as an evolutionary force influencing the metabolic rates of fishes in the wild. Reduced RMR as a result of fisheries induced evolution may have ecosystem level effects on energy demand, and be common in exploited recreational populations globally. © 2015 Hessenauer et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.


PubMed | Inland Fisheries Division, University of Illinois at Urbana - Champaign and University of Connecticut
Type: Journal Article | Journal: PloS one | Year: 2015

Non-random mortality associated with commercial and recreational fisheries have the potential to cause evolutionary changes in fish populations. Inland recreational fisheries offer unique opportunities for the study of fisheries induced evolution due to the ability to replicate study systems, limited gene flow among populations, and the existence of unexploited reference populations. Experimental research has demonstrated that angling vulnerability is heritable in Largemouth Bass Micropterus salmoides, and is correlated with elevated resting metabolic rates (RMR) and higher fitness. However, whether such differences are present in wild populations is unclear. This study sought to quantify differences in RMR among replicated exploited and unexploited populations of Largemouth Bass. We collected age-0 Largemouth Bass from two Connecticut drinking water reservoirs unexploited by anglers for almost a century, and two exploited lakes, then transported and reared them in the same pond. Field RMR of individuals from each population was quantified using intermittent-flow respirometry. Individuals from unexploited reservoirs had a significantly higher mean RMR (6%) than individuals from exploited populations. These findings are consistent with expectations derived from artificial selection by angling on Largemouth Bass, suggesting that recreational angling may act as an evolutionary force influencing the metabolic rates of fishes in the wild. Reduced RMR as a result of fisheries induced evolution may have ecosystem level effects on energy demand, and be common in exploited recreational populations globally.


Ruzzante D.E.,Dalhousie University | McCracken G.R.,Dalhousie University | Parmelee S.,Dalhousie University | Hill K.,Dalhousie University | And 3 more authors.
Proceedings of the Royal Society B: Biological Sciences | Year: 2016

The relationship between the effective number of breeders (Nb) and the generational effective size (Ne) has rarely been examined empirically in species with overlapping generations and iteroparity. Based on a suite of 11 microsatellite markers, we examine the relationship between Nb, Ne and census population size (Nc) in 14 brook trout (Salvelinus fontinalis) populations inhabiting 12 small streams in Nova Scotia and sampled at least twice between 2009 and 2015. Unbiased estimates of Nb obtained with individuals of a single cohort, adjusted on the basis of age at first maturation (a) and adult lifespan (AL), were from 1.66 to 0.24 times the average estimates of Ne obtained with random samples of individuals of mixed ages (i.e. Nb(adj2)=mean (Ne(mixed ages))). In turn, these differences led to adjusted Ne estimates that were from nearly five to 0.7 times the estimates derived from mixed-aged individuals. These differences translate into the same range of variation in the ratio of effective to census population size (Ne(adj2)= Nc) within populations. Adopting Ne(adj2) as the more precise and unbiased estimates, we found that these brook trout populations differ markedly in their effective to census population sizes (range approX.0.3 to approX.0.01). Using AGENE, we then showed that the variance in reproductive success or reproductive skew varied among populations by a factor of 40, from Vk/k ≈ 5 to 200. These results suggest wide differences in population dynamics, probably resulting from differences in productivity affecting the intensity of competition for access to mates or redds, and thus reproductive skew. Understanding the relationship between Ne, Nb and Nc, and how these relate to population dynamics and fluctuations in population size, are important for the design of robust conservation strategies in small populations with overlapping generations and iteroparity. © 2016 The Author(s) Published by the Royal Society. All rights reserved.


Palkovacs E.P.,University of California at Santa Cruz | Hasselman D.J.,University of California at Santa Cruz | Argo E.E.,University of California at Santa Cruz | Gephard S.R.,Inland Fisheries Division | And 4 more authors.
Evolutionary Applications | Year: 2014

A major challenge in conservation biology is the need to broadly prioritize conservation efforts when demographic data are limited. One method to address this challenge is to use population genetic data to define groups of populations linked by migration and then use demographic information from monitored populations to draw inferences about the status of unmonitored populations within those groups. We applied this method to anadromous alewife (Alosa pseudoharengus) and blueback herring (Alosa aestivalis), species for which long-term demographic data are limited. Recent decades have seen dramatic declines in these species, which are an important ecological component of coastal ecosystems and once represented an important fishery resource. Results show that most populations comprise genetically distinguishable units, which are nested geographically within genetically distinct clusters or stocks. We identified three distinct stocks in alewife and four stocks in blueback herring. Analysis of available time series data for spawning adult abundance and body size indicate declines across the US ranges of both species, with the most severe declines having occurred for populations belonging to the Southern New England and the Mid-Atlantic Stocks. While all alewife and blueback herring populations deserve conservation attention, those belonging to these genetic stocks warrant the highest conservation prioritization. © 2013 The Authors. Evolutionary Applications published by John Wiley & Sons Ltd.


PubMed | University of Southern Maine, New York University, Yale University, Duke University and 2 more.
Type: Journal Article | Journal: Evolutionary applications | Year: 2014

A major challenge in conservation biology is the need to broadly prioritize conservation efforts when demographic data are limited. One method to address this challenge is to use population genetic data to define groups of populations linked by migration and then use demographic information from monitored populations to draw inferences about the status of unmonitored populations within those groups. We applied this method to anadromous alewife (Alosa pseudoharengus) and blueback herring (Alosa aestivalis), species for which long-term demographic data are limited. Recent decades have seen dramatic declines in these species, which are an important ecological component of coastal ecosystems and once represented an important fishery resource. Results show that most populations comprise genetically distinguishable units, which are nested geographically within genetically distinct clusters or stocks. We identified three distinct stocks in alewife and four stocks in blueback herring. Analysis of available time series data for spawning adult abundance and body size indicate declines across the US ranges of both species, with the most severe declines having occurred for populations belonging to the Southern New England and the Mid-Atlantic Stocks. While all alewife and blueback herring populations deserve conservation attention, those belonging to these genetic stocks warrant the highest conservation prioritization.


PubMed | Inland Fisheries Division and Dalhousie University
Type: Journal Article | Journal: Proceedings. Biological sciences | Year: 2016

The relationship between the effective number of breeders (Nb) and the generational effective size (Ne) has rarely been examined empirically in species with overlapping generations and iteroparity. Based on a suite of 11 microsatellite markers, we examine the relationship between Nb, Ne and census population size (Nc) in 14 brook trout (Salvelinus fontinalis) populations inhabiting 12 small streams in Nova Scotia and sampled at least twice between 2009 and 2015. Unbiased estimates of Nb obtained with individuals of a single cohort, adjusted on the basis of age at first maturation () and adult lifespan (AL), were from 1.66 to 0.24 times the average estimates of Ne obtained with random samples of individuals of mixed ages (i.e. [Formula: see text]). In turn, these differences led to adjusted Ne estimates that were from nearly five to 0.7 times the estimates derived from mixed-aged individuals. These differences translate into the same range of variation in the ratio of effective to census population size [Formula: see text] within populations. Adopting [Formula: see text] as the more precise and unbiased estimates, we found that these brook trout populations differ markedly in their effective to census population sizes (range approx. 0.3 to approx. 0.01). Using AgeNe, we then showed that the variance in reproductive success or reproductive skew varied among populations by a factor of 40, from Vk/k 5 to 200. These results suggest wide differences in population dynamics, probably resulting from differences in productivity affecting the intensity of competition for access to mates or redds, and thus reproductive skew. Understanding the relationship between Ne, Nb and Nc, and how these relate to population dynamics and fluctuations in population size, are important for the design of robust conservation strategies in small populations with overlapping generations and iteroparity.


News Article | October 7, 2016
Site: phys.org

Zebra mussels' invasion of North American water bodies has resulted in the loss of billions of dollars in ecological services, human recreation, and in mitigation and control of mussel fouling in potable water, power station and industrial raw water facilities. "A female zebra mussel can produce up to a million externally fertilized eggs within a single spawning season that develop into planktonic larvae," said Robert McMahon, professor emeritus of biology and principal investigator on the new grant from the Texas Parks and Wildlife Department. "The larvae are dispersed on water currents to settle throughout an invaded water body. Once settled, zebra mussels reach maturity within one year of life. Thus, they can rapidly develop very high densities after invasion disrupting aquatic ecosystems. In addition, they settle in and foul industrial raw water facilities," he added. Zebra mussels (Dreissena polymorpha) are small bivalve mollusks. Most are about the size of a human fingernail, but they can grow to a length of nearly 2 inches. They were introduced to North America from Europe via transatlantic shipping, first appearing in the Great Lakes in 1988. From there they made their way to the Mississippi, Hudson, St. Lawrence, Ohio, Missouri, Huron, Colorado, Canadian and Arkansas Rivers, invading the major drainages of the Mississippi and other rivers in all but the far northwestern United States. Major mussel infestations now occur in Texas water bodies on the drainages of the Red, Trinity and Brazos Rivers. Zebra mussels attach themselves to rocks and other hard surfaces, or to the shells of other mussels, by byssal threads, which are silky fibers made from proteins. This allows them to form encrustations which can be several shells thick and can lead to densities of 100,000 individuals per meter squared, which are not uncommon in infested waters, McMahon said. McMahon is joined on the project by Brian Van Zee, director of Fisheries Management Office, Region 1, Inland Fisheries Division, TP&WD; and by Monica McGarrity, Austin Aquatic Invasive Species team leader, Inland Fisheries Division, Habitat Conservation Branch, TP&WD. The research is a continuation of an ongoing project initiated by McMahon at Lake Texoma in 2011 and continued at Lake Ray Roberts in 2012, Lake Belton in 2014 and recently invaded Lake Lewisville and Eagle Mountain Lake earlier this year. The researchers will use monthly samples from infested Texas lakes to estimate mussel spring and fall cohort growth rates and life spans, juvenile settlement rates, periods when mussel planktonic larvae are capable of settlement, impact of water temperature on annual variation in mussel nutritional condition, and chlorophyll a and total phosphate concentrations in the water column as a measure of overall lake productivity. "Our study has a special emphasis on understanding the causes of the zebra mussel population collapses that have occurred in Texas lakes and other warm, southwestern water bodies," McMahon said. In three Texas lakes - Texoma, Ray Roberts and Belton - a rapid increase in the number of zebra mussels has been followed by a sharp decline. The mussels can starve themselves out by removing plankton, phosphates and nitrates from the water, and flooding may also lead to a decrease in their numbers. Some Texas lakes with low calcium concentrations, particularly in East Texas, are resistant to zebra mussel invasion because mussels require relatively high calcium concentrations in order to thrive. McMahon said constant monitoring of infested lakes is needed, and added it may be years before the full impact of the mussels on lakes' water quality and biodiversity is known. "We've seen that in some reservoirs, they'll eat themselves out of house and home and the population will crash, but then it reaches a stage where they'll come back and the population will stabilize at some level," Van Zee said. "Once they become established in a reservoir, there's not really a way to eradicate them." Van Zee met McMahon in 2009 when zebra mussels were first found in Texas and says McMahon's expertise has been highly beneficial as state authorities try to find the best way to handle the mussels' invasion of Texas. "Dr. McMahon has been a great asset to the Texas Parks & Wildlife Department with his knowledge and experience," Van Zee said. "He's a phenomenal resource for us in dealing with this problem." The Texas Parks and Wildlife Department has been making a concerted effort over the last several years to educate recreational boaters about zebra mussels and how not to be vector for their introduction to other uninfested Texas water bodies, McMahon said. The campaign involves educating boaters to "Clean, Drain and Dry" their watercraft to make sure that they are not moving zebra mussels and their larvae or other invasive aquatic organisms between water bodies. "It is now the law in Texas that boaters must drain all water from their boats on leaving any water body so they do not carry zebra mussel larvae to any other water body," McMahon said. "As boaters and marina operators become better informed about the dangers associated with unintentional overland transport of zebra mussels and other aquatic invasive plants and animals, it is expected that the number of newly infested Texas lakes will decline through time, and eventually new introductions will cease." Clay Clark, department chair and professor of biology, said that McMahon's ongoing work in studying zebra mussels serves an important role in keeping the public informed about a serious threat to water quality and aquatic life in Texas lakes, and also demonstrates the University's commitment to Global Environmental Impact, one of the main tenets of the University's Strategic Plan 2020: Bold Solutions | Global Impact. "Dr. McMahon has been studying the biology and control of invasive aquatic invertebrates such as zebra mussels for many years and his wealth of knowledge will serve the Texas Parks & Wildlife Department very well in this project," Clark said. "There's no one better suited to do this research." McMahon received his Ph.D. in Zoology from Syracuse University in 1972 and began his career at UTA the same year. He has served as associate dean for the College of Science as well as dean of the University's Honors College. He was named professor emeritus in biology in 2010. He received the UTA Award for Distinguished Record of Research in 1990 and in 2015 was presented a Lifetime Achievement Award from the National Invasive Species Council.

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