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Opelika, AL, United States

Maceina M.J.,MJM Consultants | Sammons S.M.,MJM Consultants
Fisheries Research | Year: 2015

Starting in the late 1940s, fish in the upper Hudson River, New York, USA, were exposed to polychlorinated biphenyls (PCBs) from discharges from two manufacturing plants. These discharges greatly decreased in 1976, and PCB concentrations in fish generally declined between 1980 and 1991, increased in 1992-1994 due to a failure in 1991 of a structure that contained PCBs, and then decreased after 1994. To assess the impact of PCBs on fish reproductive success and recruitment, we collected yellow perch (Perca flavescens), largemouth bass (Micropterus salmoides), and brown bullhead (Ameiurus nebulosus) from 2002 to 2006 at two sites just downstream of these PCB sources. A subsample of these fish were aged; ages of remaining fish were assigned using a length:age key, and linear catch curves [loge (Number-at-age)=age] were computed. Maximum ages ranged from 11 to 16 years across species, and residual values generated from these catch-curve regressions represented relative year-class abundances produced from the late 1980s to the early 2000s. Wet-weight muscle tissue PCB concentrations in adults varied from average highs of 18-30μg/g in the late 1980s-mid 1990s to lows of 3-9μg/g by 2002 at the site nearest to the PCB sources. PCB concentrations in adult fish were unrelated to the formation of weak or strong year-classes in all three fish species. Although PCB concentrations were 2 to 8 times higher at the site nearest the PCB sources compared to a downstream site, natural mortality rates (fish harvest prohibited) derived from catch-curves were similar between sites for all three species. Thus, longevity and production of older year classes were consistent between sites. For these three species, we did not detect any PCB-mediated effect on fish recruitment at the population level at adult PCB concentrations (18-30μg/g). © 2015 Elsevier B.V. Source

Maceina M.J.,MJM Consultants | Sammons S.M.,MJM Consultants
North American Journal of Fisheries Management | Year: 2016

Abstract: Natural mortality is a vital demographic variable that is necessary for describing population dynamics and conducting fishery assessments. The instantaneous natural mortality rate (M) can be estimated through a variety of empirical methods, but they typically require extensive data collection (e.g., aging, tagging, and estimates of exploitation). Alternatively, M has been estimated using theoretically and empirically derived equations, some of which require minimal data, making their use attractive for application to information-limited fisheries. Most such equations were derived from marine stock assessments and have not been validated for freshwater fishes. We used age-frequency analyses to estimate M for unexploited populations of Largemouth Bass Micropterus salmoides, Smallmouth Bass M. dolomieu, Brown Bullheads Ameiurus nebulosus, Yellow Perch Perca flavescens, and Pumpkinseeds Lepomis gibbosus in the upper Hudson River, New York. We then compared our field-based estimates to M values predicted from nine published estimators. Using catch-curve regressions and the Robson and Chapman (1961) method, we estimated M for these populations with a sample of over 12,000 fish—nearly 2,000 of which were aged with otoliths. Variables used in the nine published estimators included maximum age, length, and weight; coefficients of the von Bertalanffy (VB) equation; the sample size used for aging; and average annual water temperature. The published estimators predicted M values that were fairly similar to our empirically derived values, although some estimators performed better than others. The mean of M values from the estimators was within ±0.12 units of the average derived from our age-frequency analyses. For the five estimators that utilized the VB growth relation, the M values were sensitive to changes in VB coefficients. For Largemouth Bass and Brown Bullheads, the unmodified VB growth functions did not conform to our observed length-at-age data, so we present modified VB equations for those species; coefficients derived from the modified equations appeared to provide more accurate predictions of M. Although the published estimators of M were primarily developed for marine fishes, they provided fairly accurate initial estimates of M (when bounded by uncertainty) for the five freshwater species we examined. Received July 10, 2015; accepted November 30, 2015 Published online April 5, 2016 © American Fisheries Society 2016. Source

Maceina M.J.,MJM Consultants | Sammons S.M.,MJM Consultants
Environmental Toxicology and Chemistry | Year: 2013

Although production and use of polychlorinated biphenyls (PCBs) ceased nearly 35yr ago, questions still remain concerning the potential chronic effects these compounds may have on wild fish, including their reproductive success. In the upper Hudson River, New York, USA, fish were exposed to PCBs primarily from 2 manufacturing plants located approximately 320km upstream of New York City, New York, from the 1940s to 1977. The authors collected yellow perch (Perca flavescens), smallmouth bass (Micropterus dolomieu), and largemouth bass (M. salmoides) using electrofishing, measured PCBs in these adults, and estimated abundance and size of their offspring at age 1 yr (age-1 fish). Fish were collected annually from 2004 to 2009 from 1 control site upstream of the PCB discharge sites and from 2 sites downstream from where PCBs were released. These sites (pools) are separated by a series of dams, locks, and canals. Muscle tissue wet weight PCB and lipid-based PCB concentrations in adults in the 2 PCB exposure pools averaged approximately 1 to 3μg/g and 100 to 500μg/g, respectively. Age-1 abundances were not related to adult PCB concentrations but were inversely related to river flow. Size of age-1 fish was slightly greater at the PCB-exposure sites. Levels of PCBs in yellow perch, largemouth bass, and smallmouth bass in the upper Hudson River did not impair or reduce recruitment or reproductive success. © 2013 SETAC. Source

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