Date of Award

1989

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Forestry, Wildlife, and Fisheries

First Advisor

Robert P. Romaire

Abstract

The acute toxicity of permethrin to red swamp crawfish (Procambarus clarkii) was evaluated in laboratory studies. The mean static acute 96-h LC50 of permethrin to red swamp crawfish 8-12 mm (0.017 g), 25-35 mm (0.64 g), 45-55 mm (2.45 g), and 65-75 mm total length (TL) (8.98 g) was 0.44, 0.85, 1.30, and 0.81 $\mu$g/L, respectively. Permethrin toxicity did not differ among immature male, mature male and female P. clarkii. Crawfish surviving permethrin exposure exhibited no differences in post-exposure growth, survival, maturity attainment, or the production of viable young when compared to non-exposed controls (P $>$ 0.2). At the third-instar stage of development, no evidence of teratogenesis was observed in crawfish produced from permethrin-exposed parents. The 24-h LC50 of permethrin to red swamp crawfish (31 to 70 mm TL) in pond water ranged from 1.0 to 3.1 $\mu$g/L. Permethrin was applied to shallow earthen ponds at concentrations of 1.0 to 3.0 $\mu$g/L and population estimates conducted 12-13 days post-treatment indicated that pond crawfish populations were reduced by 54.4 to 83.1% for P. clarkii and 100.0% for P. acutus acutus. Crawfish less than 40 mm TL had higher mortality (range of 55 to 84%) than larger crawfish (range of 42 to 79%). Among crawfish greater than 40 mm TL, mature males had higher mortality (33 to 100%) than immature males (range of 43 to 86%) and females (range of 30 to 72%). No permethrin residue could be detected in crawfish abdominal muscle (detection limit 6.7 ng/g) or hepatopancreas (detection limit 400 ng/g) by gas chromatography. The use of permethrin to effect density reduction in combination with supplemental feeding was evaluated as a management technique to minimize stunting of crawfish at sub-marketable size. Crawfish populations which were fed formulated feed at a rate of 28 kg/ha three days per week had more harvestable crawfish (greater than 75 mm TL) (mean = 29%, P = 0.01), larger mature males (means = 70 mm TL, P = 0.01), greater total weight of crawfish harvested (mean = 300 kg/ha, P = 0.18), greater number of crawfish harvested (mean = 35,470 crawfish/ha, P = 0.16), and higher CPUE (mean = 0.16 kg/trap-set, P = 0.001) than crawfish populations receiving no formulated feed from April to June.

Pages

122

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