Helminth communities of the roach (Rutilus rutilus) from Kocadere stream in Bursa, Turkey: Occurrence, intensity, seasonality and their infestations linked to host fish size

Abstract

Helminth communities and their prevalence, intensity and abundance were studied with respect to seasonal variation and host size in a population of roach (Rutilus rutilus) from Kocadere stream, Turkey. A total of 113 individuals of roach were examined for helminth parasites from February 2005 to January 2006. Of the 113 R. rutilus, 72 (63.7%) were found to be infected by one or more parasite species. In total, four helminth parasite species were identified: Monogeneans - Dactylogyrus crucifer; Cestoda - Bothriocephalus acheilognathi; Nematoda - Eustrongylides sp. larvae, and Contracaecum sp. larvae. D. crucifer was the most common species in this study and a total of 1946 specimens were recorded on 66 fishes. The abundance of D. crucifer varied highly significantly during the investigation period and increased from February to March-April (peak), followed by a sharp decrease thereafter. As regards the abundance of the parasite species depending on the fish length, the highest frequency of distribution of D. crucifer was found on host with 18.5 - 21.5 cm. However, no correlation existed between fish length and parasite abundance (r = -0.08; p>0.001). The overall prevalence and mean intensity were 58.4% and 29.4, respectively. The infection levels peaked (100%) in April, May and July. This species was not detected in the November and December samples. Two B. acheilognathi were found in one fish (0.8%) whereas Eustrongylides sp. larvae and Contracaecum sp. larvae were recorded in four (3.5%) and one (0.8%) fish examined, repectively.