Study on biology of freshwater leech. nephelopsis obscura. effect on rainbow trout (oncorhynchus mykiss and its control with some chemicals

III SUMMARY PhD Thesis STUDY ON BIOLOGY OF FRESHWATER LEECH, NEPHELOPS IS OBSCURA, EFFECT ON RAINBOW TROUT ( ONCORHYNCHUS MYKISSS AND ITS CONTROL WITH SOME CHEMICALS Nairn SA?LAM Fırat University Graduate School of Natural and Applied Sciences Department of Aquaculture 1997, Page: 118 In this study, biological characters including feeding, growth, breeding and egg laying, morphological features, movement, behaviour and abundance of freshwater leech, N. obscura were investigated. Life- cycle of N. obscura was determined by parasitic interactions with trout {Oncorhynchus myJr/ss). In order to control N. obscura the most appropriate chemical substance was determined by using 100 ppm, 200 ppm, 300 ppm, 500 ppm, 1000 ppm, 1500 ppm, 2000 ppm, 2500 ppm, 5000 ppm, 10000 ppm, 20000 ppm and 40000 ppm concentration of Formalin, Lysol and Neguvon solution in laboratory. The highest abundance (8.86+1.25 individual/m2 and 8.86+1.21 individual/m2) of N. obscura was found in June and July; the lowest abundance (2.37+0.04 individual/ m2) of N. obscura was found in December. It was determined that N. obscura can feed on fish, Tubifex andIV Gammarus in water. In laboratory condition, it becomes mature in 13 month and it produces egg. It was also observed that one N. obscura gives average 1.89+0.24 (1-4, n=19) cocoon and cocoon has average 3.48+0.28 (1-8, n=50. Interestingly, 9333-96.67 % of M obscura died after egg lay. From hatching to developed stage, 33.44±0.86 % (+Sx) of the young of leech died. When M obscura attacked to rainbow trout, it attacked to eyes and fins, eats them and wounded area of body surface may bleed. In order to prevent invasion and also parasite transmission of N. obscura; it exposed to 200 ppm Formalin for 1 10-170 minute, 300 ppm for 60-1 10 min., 500 ppm for 40-45 min, 1000 ppm for 15 min and 1500 ppm for 10 min. and the most effective concentration was observed. Lysol was letal to fish but not to leeches. Neguvon has stopped N. obscura s movemend and its attaching ability. When N. obscura was transfferred to clean water after exposing to Neguvon solution, it became alive again. Formalin was found to be effective to larvae in cocoon Lysol was relatively effective but Neguvon was not effective. KEY WORDS: Freshwater leech, Nephelopsis obscura, Morphology, Biology, Parasitic effect, Trout, Formalin, Lysol, Neguvon