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Stewart, D.R. and J.M. Long. 2016. Using an experimental manipulation to determine the effectiveness of a stock enhancement program. Journal of Freshwater Ecology 31:37-52. http://dx.doi.org/10.1080/02705060.2015.1021715
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Abstract
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March 2015
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We used an experimental manipulation to determine the impact of stocking 178-mm channel catfish Ictalurus punctatus in six large impoundments. The study design consisted of equal numbers (two) of control, ceased-stock, and stocked treatments that were sampled one year before and two years after stocking. Relative abundance, growth, size structure and average weight significantly changed over time based on samples collected with hoop nets. Catch rates decreased at both ceased-stock lakes and increased for one stocked lake, while growth rates changed for at-least one ceased-stock and stocked lake. The average weight of channel catfish in the ceased-stock treatment increased by 18 g and 365 g, whereas weight decreased by 274 g and 953 g in the both stocked lakes. The variability in observed responses between lakes in both ceased-stock and stocked treatments indicate that a one-size-fits-all stocking agenda is impractical, suggesting lake specific and density-dependent mechanisms affect channel catfish population dynamics.
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Stewart, D.R. and J.M. Long. 2016. Using hierarchical Bayesian multi-species mixture models to estimate tandem hoop-net based habitat associations and detection probabilities of fishes in reservoirs. Transactions of the American Fisheries Society 145:450-461. DOI: 10.1080/00028487.2016.1143395
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Abstract
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April 2016
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Species distribution models are useful tools to evaluate species-habitat relationships, though more often developed to evaluate factors controlling fish assemblages in lotic environment and less often in lentic systems. We evaluated species-habitat interactions for commonly captured fishes in six Oklahoma reservoirs using tandem hoop nets. We used hierarchical Bayesian multi-species N-mixture models to evaluate detection- and abundance-habitat relationships. Twelve species were captured, equating to 7,212 fish with channel catfish (46%), bluegill (25%), and white crappie (14%) comprising the majority of the catch. Detection estimates ranged from 8% to 69%, and modeling results suggested that fishes were primarily influenced by reservoir size and context, water clarity and temperature, and land-use types. Species were differentially abundant within and among habitat types, consisting of some fishes being found more abundant in turbid, less impacted (urbanization and agriculture) reservoirs with greater shoreline lengths; whereas, other species were found more often in clear, nutrient rich impoundments with generally less shoreline length and increased percentage agriculture. Our results demonstrate that habitat and reservoir characteristics may differentially benefit species and assemblage structure. This study provides a useful framework for evaluating capture efficiency for not only hoop nets but other gears used to sample fishes in reservoirs.
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Stewart, D.R. and J.M. Long. 2015. Growth and contribution of stocked channel catfish, Ictalurus punctatus (Rafinesque 1818); the importance of measuring post-stocking performance. Journal of Applied Ichthyology 31:695-703. doi:10.1111/jai.12797.
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Abstract
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May 2015
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Natural recruitment of channel catfish Ictalurus punctatus is limited in impoundments and stock enhancement is commonly used by state agencies to maintain fisheries. Advanced size fingerlings (> 175 mm total length (TL)) can be costly to rear, but survival is greater and their effectiveness has not been extensively studied for larger impoundments (> 200 ha). We evaluated stocking success of advanced size channel catfish marked with oxytetracycline (OTC) in two Oklahoma impoundments (Lakes Lone Chimney and Greenleaf). Channel catfish were marked in a solution of 700 mg L-1 of OTC for 6 hr, stocked at 178 mm TL, and both lakes sampled from May to August 2011 and 2012. Survival and marking success was high (100%), but the response to stocking, measured by relative abundance (CPUE, number of per 3-d tandem hoop net series), stocking contribution, and growth, was significantly different between the two impoundments. The differences are likely contributed to the different relative abundances between lakes Lone Chimney (80.5 fish series-1) and Greenleaf (9 fish series-1). Consequently, stocking contribution was lower at Lake Lone Chimney (3-35%) than at Lake Greenleaf (84-98%); however, relative abundance only increased at Lake Greenleaf. Average length and weight of stocked fish at age-2 only reached 230 mm TL and 85 g in Lake Lone Chimney, whereas fish stocked in Lake Greenleaf reached sizes of 340 mm TL and 280 g. The use of population indices like proportional size distribution (PSD) may misguide fishery managers as this value decreased at both reservoirs post-stocking, indicating that stocked fish contributed to the sample. But, because we could distinguish between wild and stocked fish using OTC, we were able to determine that stocking was not successful at Lake Lone Chimney. By batch-marking fish, a more direct assessment of stocking success was obtained and this option is viable for future studies.
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Stewart, D.R. and J.M. Long. 2011. Mass-marking Channel Catfish Fingerlings by Immersion in Oxytetracycline. Proceedings of the Oklahoma Academy of Science 91, 31-36.
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Abstract
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Download
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Publisher Website
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September 2012
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Oxytetracycline (OTC) has been extensively used for marking a variety of fish species,
but has never been successfully used to mark channel catfish Ictalurus punctatus. Channel
catfish fingerlings (~ 25 mm TL) obtained from the Oklahoma Department of Wildlife
Conservation at Byron Fish Hatchery were kept in Living Streams (791 to 1,018 L) equipped
with recirculation units. Marking trials consisted of immersing channel catfish in one
of three concentrations (250, 450, and 700 mg/L) OTC hydrochloride [HCl] for 6 hours.
Samples of channel catfish were obtained from each group at 1-week and 4-week postimmersion.
Lapilli otoliths and pectoral spines were removed to assess mark presence
with an epi-fluorescent compound microscope. After one week, no marks were detected
on pectoral spines for all treatments, mark detection on otoliths depended on concentration,
but never exceeded 43% (700 mg/L). After four weeks, all otoliths and pectoral
spines were determined marked for 700 mg/L OTC, 20% for fish immersed in 450 mg/L
OTC, and 0% were marked after four weeks at the 250 mg/L OTC. Results show, channel
catfish fingerlings can be successfully marked with immersion in OTC at 700 mg/L for at
least 6 hours. © 2011 Oklahoma Academy of Science.
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Long, J. M. and D. R. Stewart. 2010. Verification of otolith identity used by fisheries scientists for aging channel catfish. Transactions of the American Fisheries Society 139:1775-1779.
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Abstract
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November 2010
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Previously published studies of age estimation of channel catfish (Ictalurus punctatus) based on otoliths have reported using the sagittae and not the lapilli, which are the largest otoliths in this species. Based on scanning electron microscope (SEM) microphotographs of channel catfish otoliths, x-ray computed tomography (CT) scans of a channel catfish head, descriptions of techniques used to removed otoliths from channel catfish reported in the literature, and a sample of channel catfish otoliths received from fisheries biologists from around the country; it is clear that lapilli are most often used for channel catfish aging studies, not sagittae as has been previously reported. Fisheries scientists who obtain otoliths from channel catfish can use the information in this paper to correctly identify the otolith.
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