Abstract: One hundred and twenty mod fish, Cirrhinus mrigala (Hamilton, 1822), were examined over a period of one year, Mard, 1998 to February, 1999 at Govt. Fish Hatchery Mian Channu Punjab, Pakistan. The parasites recovered were Lernea cyprinacea, L. polymorpa, L. oryzophila, L. lophiara and Lernaea sp. The overall prevalence was highest (43.33%) for L. cyprinacea and lowest for L. lophiara (4.16%).
Introduction
There are many species of crustaceans, particularly copepods, which parasitize fish. However the species which appear more abundantly in fish farms and which inflict injury are belonging to the genera Lernaea and Argulus (Fryer, 1956; Rushton-Mellor and Baxshall, 1994). Although the parasite fauna of fresh water and marine fish is fairly well known all over the world but unfortunately no published reports on the learned parasites of cultured fish has been documented in Pakistan. The present paper reports the prevalence of copepod parasites of the mod fish, Cirrhinus mrigala, on the government fish hatchery.
Materials and Methods
Study was conducted on Government Fish Hatchery Mian Channu, District Khanewal. During the whole study period, a rearing fish pond was chosen. The fish were caught with the help of drag net. The captured fish were transferred to large plastic water container. The fish were kept alive during examination by dipping it into water at short intervals and identified with the help of keys given by Mirza and Sharif (1996). A total of 120 Cirrhinus mrigala (Hamilton, 1822) fish were collected from March 1998 to February 1999 at monthly intervals, ten fish per month. The parasites thus collected were preserved in 5 percent formalin for taxonomical studies and brought to the laboratory, Institute of Pure and Applied Biology, Bahauddin Zakariya University, Multan. The preserved specimens were washed twice in distilled water and transferred to 10 percent KOH for 24 hours. The permanent mounts were prepared by staining with Semichon's carmine (Khurshid, 1998) and identified (Cable, 1985).
Results and Discussion
The study was started from March 1998 and continued until February 1999. One hundred and twenty mori fish, Cirrhinus mrigala, were examined from Fish Hatchery Mian Channu, for copepod ectoparasites. Five species of genus Lernaea were recovered during the present study. The species identified were Lernaea cyprinacea (Linnaeus, 1761), L. polymorpha (Yu, 1938), L. oryzophila (Monod, 1932), L. lophiara (Harding, 1950) and Lernaea sp.
Different species of the genus Lernaea had also been reported from other countries of the world. Gnanamuthu (1951) reported Lernaea chackoensis from Catla catla it Madras, India. Fryer (1956) reported Lernaea bagri, L. lophiara, L. herding, L. tilapiae, L. palati and L. barnirniall from the fishes of Lake Nyasa, North Rhodesia. Noga (1986) examined the Lernaea cruciata (LeSueur) fro Micropterus salmoides (Lecepede) in the Chowan River North Carolina, U.S.A. Woo and Shariff (1990) recovered Lernaea cyprinacea from Helostoma temmincki in Serdange Malaysia. The difference in the parasite fauna of t present study with these researchers may be due different geo-climatic conditions between the differ localities and also due to different hosts examined.
The prevalence of L. cyprinacea on mon fish was maximum (43.33%) followed by L. polymorpha (34.16%), Lernae sp. (14.16%), L. oryzophila (7.5%) and L. lophiara (4.16%). The different species of Lernaea has also been recovered Pakistan from other fishes. On Labeo rohita, the prevalen of L. polymorpha was maximum (26.66%) followed by arcuata (5%) L. lophiara (5%), L. cyprinacea (25.83%) a L. oryzophila (26.66%) (Shahzad, 1999). The prevalence L. polymorpha was found to be maximum (38.33%) Ctenopharyngodon idella followed by L. cyprina (9.166%), L. ctenopharyngodonis (4.16%) and L. lophiara (3.33%). These findings are not comparable with results of the present study. The highest prevalence Lernaea species on Cirrhinus mrigala is due to the fact that it is a bottom dweller fish and the parasitic stages present in abundance at the bottom of pond due to the water temperature (Khurshid, 1998).
Monthly prevalence of different species of Lernaea parasite was recorded (Table 1). The prevalence of L. cyprinacea was high in February (100%) and lowest in March (60%). Infestation was recorded during summer months of July and August. L. polymorpha showed maximum prevalen in January (100%) and decreased to zero in June, July and September. L. oryzophila was recovered only in (50%), May (20%), October (10%) and December (10%) In remaining months, parasites were not found. In ca L. lophiara, the infestation was found only in April (30%) and January (20%). No Infestation was recorded in one months.
| Table 1: | Overall prevalence of Lernaeid Parasites of mori, Cirrhinus mrigala |
Lernaea sp. also showed seasonal fluctuations and was maximum in winter months viz December (50%) and January (40%) and lowest in July (10 %). No infestation was recorded in other months.
In the present study, mixed infestation of various copepod Lernaeid parasites was also observed. Four species viz. L. cyprinacea, L. polymorpha, L. oryzophila and L. lophiara infested only 3 fishes out of 120. Two fishes were infested with L. cyprinacea, L. polymorpha, L. oryzophila and Lernaea sp. Only one fish was infested with L. cyprinacea, L. polymorpha and L. lophiara out of 120 hosts. L. cyprinacea, L. polymorpha and Lernaea sp. were found on 7 hosts.
The parasite burden per host of copepod Lernaeid parasites of C. mrigala was studied. L. polymorpha had highest parasite burden (4.07%) followed by L. cyprinacea (4.01%). L. lophiara (3.2%1, L. oryzophila (1.66) and Lernaea sp. (1.41%).