Browsing by Author "Jeffrey A. Buckel, Committee Member"

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    A Bioenergetics Assessment of Temperature and Food Consumption Effects on Growth of Reservoir Striped Bass.
    (2006-08-07) Davias, Lori Anna; Kevin Gross, Committee Member; Jeffrey A. Buckel, Committee Member; James A. Rice, Committee Chair
    I examined the influence of temperature and food availability on growth of striped bass Morone saxatilis in seven North Carolina reservoirs. Reduced condition and summer mortality events of stocked striped bass in some southern reservoirs have been attributed to the habitat 'squeeze' of high summer temperatures and low dissolved oxygen (DO). However, in a recent study of Lakes Badin and Norman, NC, Thompson et al. (2005) intensively studied striped bass thermal selection, diet, mortality, and energetics, and concluded that food consumption was more important than temperature in explaining the large differences in growth between the systems. Following on this study, I analyzed striped bass growth, diet, predator and prey energy densities, and temperature experience in each of an additional five reservoirs in 2003-2005. Striped bass growth and thermal experience varied widely across all seven reservoirs. Fish growth to age-7 varied from less than 2kg to nearly 6 kg, and fish spent between 0 and 87 days in very warm (≥27°C) water during summer stratification. Striped bass from lakes that experienced the most severe summer temperature also exhibited relatively fast growth. Simulations of a Wisconsin bioenergetics model parameterized for striped bass estimated that striped bass annual consumption varied between 3,144g for age-2 fish in Lake Gaston and 24,616g for age-5 fish in Jordan Lake. I also used the bioenergetics model to test for the relative effects of water temperature and food consumption on growth by conducting a series of "habitat exchange simulations." In this approach I simulated how much the growth of a particular size fish in one reservoir might change if it had experienced the temperature or food consumption of a similarsized fish in another reservoir. The difference in growth predicted when exchanging consumption was greater than that resulting from exchanging temperature for every pair of lakes compared except for those including Lake Rhodhiss. This lake had an extended period over the summer where striped bass could remain in preferred 20°C habitat, and simulations where these temperatures were combined with high food consumption resulted in the greatest annual growth for striped bass. However, my results stress that regardless of temperature, low food consumption will only yield moderate to slow growth of striped bass. On the other hand, striped bass subjected to very warm temperatures can maintain good growth but only if adequate forage exists. Knowledge of availability and abundance of clupeid prey, in addition to information on thermal conditions, is thus especially important for management of striped bass in southern reservoirs.
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    Evaluation of nursery habitat: an ecophysiological approach
    (2008-11-11) Del Toro-Silva, Felix Manuel; David B. Eggleston, Committee Member; Jeffrey A. Buckel, Committee Member; Derek D. Aday, Committee Member; John M. Miller, Committee Chair
    DEL TORO SILVA, FELIX M.: Evaluation of nursery habitat: an ecophysiological approach. Abiotic conditions can determine biomass production within habitats and this can influence the relative contribution of nursery habitats to adult populations, yet few studies have addressed how the interactions of abiotic parameters can influence production. Through a combination of laboratory experiments, simulation modeling, and field experiments the effects of abiotic dynamics on fish growth were examined. The objective of the study were to: (1) assess the effects of oxygen and temperature dynamics on growth; (2) test three indices of metabolic capacity (MMS, RMR, LOC) as indicators of fish performance relative to these dynamics; (3) develop a simulation model to predict growth based on abiotic conditions; (4) validate the model in four nursery areas within the Pamlico River Estuary; (5) compare habitat classification based on model results with juvenile abundance classification. Results showed significant individual and interaction effects of oxygen and temperature on growth. No significant abiotic effects on RMR were detected, but significant effects were detected for the other two indices (MMS and LOC). MMS indices showed a pattern similar to the observed growth rates in response to temperature and oxygen treatments. The model was successfully parameterized with laboratory data and validated through simulations of field trials. The model successfully reproduced growth rates in the field using environmental data (oxygen, temperature and salinity) as input variables and more importantly, it reproduced in a fine temporal scale dynamics of growth rate within the simulations. Comparisons of habitat classification between juvenile abundance and model simulations were not possible because environmental conditions during field experiments were so sever that most of the experiments resulted in negative growth rates. Overall, the study demonstrated the importance of abiotic dynamics on individual performance and resulting biomass production within a habitat and that the ecophysiological framework is an adequate model to develop and test hypothesis of mechanism affecting production within nursery habitats.