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United States Department of Agriculture

Agricultural Research Service

Title: Stable Carbon Isotope Ratios and Standard Production Data As Indices of Golden Shiner Performance in Pond Feedng Trials.

Authors
item Lochmann, Rebecca - UAPB
item Gatlin, Delbert - TAMU
item RAWLES, STEVEN

Submitted to: Journal of Applied Aquaculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 1, 2000
Publication Date: January 20, 2001
Citation: LOCHMANN, R., GATLIN, D.M., RAWLES, S.D. STABLE CARBON ISOTOPE RATIOS AND STANDARD PRODUCTION DATA AS INDICES OF GOLDEN SHINER PERFORMANCE IN POND FEEDNG TRIALS.. JOURNAL OF APPLIED AQUACULTURE. 2001. v.11.(3) p.21-34.

Interpretive Summary: Economic analysis indicates that Baitfish production in the United States must intensify for this industry to grow. High-density fish farming, however, reduces the amount of natural food available and increases the need for prepared feeds. The use of natural vs. prepared food by golden shiners stocked at high and low densities was examined by measuring changes in the stable carbon isotope ratio (C13/C12) of fish in feeding trials. The trials were conducted simultaneously at the University of Arkansas-Pine Bluff (UAPB) and Texas A&M University (TAMU). Ten 0.1-acre ponds per site were regularly fertilized with rice bran of known C13/C12 ratio and stocked at a rate of 300,00/ac (UAPB) or 150,000/ac (TAMU). Fish in five ponds/site were fed a complete diet of known C13/C12 ratio, while fish in the remaining ponds were not fed. The ratio of C13/C12 in natural foods (plankton) also was measured. The change in the stable carbon isotope ratio of unfed fish was compared to that of fed fish at each site after 8 weeks of growth. Pond water quality was similar at both sites. Natural food was less available at TAMU than at UAPB. Weight gain of fish at low stocking density (TAMU) was higher than that of fish at high density (UAPB). The carbon isotope ratio of fish at UAPB changed little, precluding discrimination of food source. The carbon isotope ratio of fed fish at low density approached that of the prepared diet, while the carbon isotope ratio of the unfed fish resembled that of the plankton and rice bran fertilizer. At high density, growth increased as more diet was fed up to a maximum, then decreased with more diet input. Golden shiners at low densities may use more prepared feed when natural food is low; at high densities decreased growth may be exacerbated by high feeding rates.

Technical Abstract: The assimilation of different food sources by golden shiners in ponds was examined in concurrent 8-wk feeding trials at the University of Arkansas - Pine Bluff (UAPB) and Texas A&M University (TAMU). Ten 0.04-ha ponds per site were periodically fertilized with rice bran (defatted) of known stable carbon isotope ratio (C13/C12) and stocked at a rate of 750,000/ha UAPB) or 375,000/ha (TAMU). Fish in five ponds per site were fed a complete diet of known carbon isotope ratio, while fish in the remaining ponds were not fed. The C13/C12 ratio of plankton was periodically determined and the assimilation of natural foods by unfed fish was compared to that of fish fed prepared diet. Growth and water quality data were compared to changes in the stable carbon isotope ratio (delta-C13) as an index of food sources. Weight gain and fish isotope ratio were regressed separately against feed amount, Secchi depth (a measure of plankton productivity), dissolved oxygen (DO), fed vs. unfed treatments, and study site to determine their relationships. Natural productivity was lower at TAMU than at UAPB, while pond temperature and minimum DO levels were similar at both sites. Weight gain of fish at TAMU (low density) was higher than that of fish at UAPB (high density), regardless of treatment. Delta-C13 of fish at UAPB changed little during the trial, precluding discrimination of food source. Delta-C13 of fed fish at TAMU approached that of the prepared diet, while delta-C13 of the unfed fish resembled that of the plankton and rice bran. Weight gain increased with diet input up to a maximum, then decreased with more diet input. Golden shiners at low densities may use more prepared feed when natural food is low; at high densities decreased growth may be exacerbated by high feeding rates.

Last Modified: 9/10/2014
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