Growth, nutritional composition, and hematology of Arctic charr (Salvelinus alpinus) exposed to toxaphene and tapeworm (Diphyllobothrium dendriticum) larvae.

Toxaphene, an organochlorine pesticide, is the major contaminant of Arctic charr (Salvelinus alpinus) in the Canadian Arctic. The objective of this study was to investigate the combined effects of toxaphene exposure and infection by the larval stage of the cestode Diphyllobothrium dendriticum on fish growth, nutritional composition, and hematology. Hatchery-reared Arctic charr were subjected to one of four treatments: (1) oral administration of corn oil (control); (2) single oral dose of 10 microg/g wet wt toxaphene dissolved in corn oil; (3) exposure to 15 larval D. dendriticum; and (4) exposure to toxaphene and D. dendriticum in combination. The experiment was run for 104 days. Mean final toxaphene concentrations in charr muscle were 0.121, 0.336, 0.131 and 0.458 microg/g wet wt in each treatment group, respectively. Exposure to toxaphene and D. dendriticum decreased fish growth and condition as well muscle lipid and protein content. However, toxaphene did not increase the susceptibility of Arctic charr to parasite infection. Overall, 25 of 40 fish (62.5%) exposed to larval D. dendriticum became infected. Parasitized charr had decreased hematocrits and increased lymphocyte:erythrocyte ratios. Although total blood cell counts were decreased in all treatments compared with controls, differential leucocyte counts were unaffected. Our results suggest that toxaphene does not moderate Arctic charr resistance to D. dendriticum and there is no contaminant-parasite interaction at environmental levels.