Effects of egg and sperm maturation and spawning on the distribution and elimination of a polychlorinated biphenyl in rainbow trout (Salmo gairdneri).

Distribution and elimination of $\text{2,5,2′,5′-}\text{tetrachloro}{}^{14}\text{C}\text{]}\text{biphenyl}$ (4-CB) were studied for 1 year after exposing female and male rainbow trout to the compound in water and then transferring the fish to a hatchery raceway. The fish were exposed in December, weights of the maturing eggs and sperm began to increase in June, and the fish began to spawn in October. From January through August elimination of 4-CB was slow with a $\text{t}\text{1}\text{2}$ for whole body elimination of 1.76 years in females and 1.43 years in males. However, during the spawning season whole body elimination was more rapid in both sexes; $\text{t}\text{1}\text{2}\text{= 0.52}\text{year}$ in females and 0.54 year in males. The increased elimination rate appeared primarily to be due to the voiding of 4-CB containing eggs and sperm as opposed to enhanced elimination of 4-CB from extragonadal tissues. Prior to the enhanced elimination there was a redistribution of 4-CB residues within the fish's body. This was characterized by a depletion of 4-CB from eyes and periorbital fat, followed later in time, by a reduction in 4-CB content of visceral fat. Temporally related to this was an accumulation of 4-CB residues in maturing eggs and sperm. Thus, redistribution of 4-CB occurred during spermatogenesis and vitellogenesis and preceded the enhanced elimination of 4-CB from the whole fish when the gametes were spent from the body. The overall significance of this study is that it underlines the enhancing effect of egg and sperm maturation and spawning on whole body elimination of polychlorinated biphenyls in fish.