Polychlorinated biphenyl concentrations of burbot Lota lota from Great Slave Lake are very low but vary by sex

Total polychlorinated biphenyl concentrations (ΣPCBs) in whole fish were determined for 18 ripe female burbot Lota lota and 14 ripe male burbot from Great Slave Lake, a lake with no known point sources of PCBs. In addition, ΣPCBs were determined both in the somatic tissue and in the gonads for a randomly selected subset of five females and five males. Mean ΣPCBs for females and males were 2.89 and 3.76 ng/g, respectively. Thus, males were 30 % greater in ΣPCB than females. Based on ΣPCB determinations for somatic tissue and gonads, ΣPCBs of females and males would be expected to decrease by 18 % and increase by 6 %, respectively, immediately after spawning due to release of gametes. Results from a previous study in eastern Lake Erie indicated that males were 28 and 71 % greater in ΣPCB than females from populations of younger (ages 6-13) and older (ages 14-17) burbot, respectively. Thus, although younger burbot from Lake Erie were about 50 times greater in ΣPCB than Great Slave Lake burbot, the relative difference in ΣPCBs between the sexes was remarkably similar across both populations. Our results supported the contention that the widening of the difference in ΣPCBs between the sexes in older burbot from Lake Erie was attributable to a “hot spot” effect operating on older burbot, as Lake Erie has received PCB point source loadings. Our results also supported the contention that male fish expend energy at a rate between 15 and 30 % greater than that of females. Eventually, these results will be useful in developing sex-specific bioenergetics models for fish.