Date of Award

1988

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Forestry, Wildlife, and Fisheries

First Advisor

Robert P. Romaire

Abstract

Stomach content analysis and stable carbon isotope ratios were used to determine diet and food assimilation of red swamp crawfish (Procambarus clarkii) and white river crawfish (Procambarus acutus acutus) in three types of commercial ponds. Crawfish stomachs contained largely macrophytes, detritus and leaf litter, and to a lesser extent aquatic insects and zooplankton. Food habits of P. clarkii and P. acutus acutus were similar, but P. acutus acutus consumed more animal material than did P. clarkii. Food habits were similar among different sizes of P. clarkii and P. acutus acutus. Seasonal stable carbon isotope ratios ($\delta\sp{13}$C) of P. clarkii and P. acutus acutus were similar. Crawfish in the open pond had higher $\delta\sp{13}$C (X = $-$18.1, P $<$ 0.01) than those in the rice (X = $-$23.5) and wooded pond (X = $-$26.7), which indicated different major food sources for crawfish in each pond. Crawfish $\delta\sp{13}$C values changed from November through May (P $<$ 0.05). Temporal change in crawfish $\delta\sp{13}$C paralleled change in $\delta\sp{13}$C values of periphyton and the increased consumption of animal material by crawfish in spring. Macrophages, detritus, periphyton and leaf litter collectively contributed 90% to crawfish growth in November, 85% in January, 61% in March and 56% in May, while insects and zooplankton contributed 6% to crawfish growth in November, 12% in January, 23% in March and 28% in May. Food consumption, digestibility coefficients, growth and energy budget of juvenile P. clarkii and P. acutus acutus were determined in the laboratory. Crawfish were fed five natural diets (rice, Oryza sativa; alligatorweed, Alternanthera philoxeroides; 120-day-old rice detritus; filamentous algae, Spirogyra spp; earthworm, Lumbricus terrestris) and two formulated diets (Purina Jumbo crawfish bait and Zeigler shrimp ration). Mean daily food consumption rate ranged from 1.6% (rice detritus) to 5.8% (earthworm). Apparent dry matter digestibility (ADMD, 60-85%) and apparent energy digestibility (AED, 63-88%) coefficients for the seven diets were similar for both crawfish species. Crawfish fed formulated diets converted 24-33% of ingested energy (K$\sb1$) and 27-38% of digested energy (K$\sb2$) to growth while crawfish fed earthworm and rice exhibited little growth (K$\sb1$ = 1% and K$\sb2$ = 2%). Crawfish fed algae, alligatorweed and rice detritus catabolized tissue to meet energy needs.

Pages

131

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