The effects of total dissolved solids on egg fertilization and water hardening in two salmonids--Arctic Grayling (Thymallus arcticus) and Dolly Varden (Salvelinus malma).

Previous studies have indicated that salmonid fertilization success may be very sensitive to elevated concentrations of total dissolved solids (TDS) with effects at concentrations as low as 250mgl(-1) being reported. However, interpretation of these studies is complicated by poor control performance and variable concentration response relationships. To address this, a series of experiments were performed to evaluate TDS effects on Arctic Grayling (Thymallus arcticus) and Dolly Varden (Salvelinus malma) fertilization success and identify possible mechanisms for previously observed test variability and any observed effects of TDS. Results indicate that some of the experiments reported here were likely confounded by extended milt holding times prior to experiment initiation. Milt holding times >6h were shown to significantly reduce control fertilization and corresponding concentration response relationships were variable. When milt holding time was minimized during fertilization experiments, consistent control performance with >90% control fertilization was achieved and consistent concentration response relationships were observed for both species examined. Experiments performed under these conditions indicate that Arctic Grayling and Dolly Varden fertilization success is not sensitive to elevated TDS with EC20s (concentration causing 20% effect) of >2782 and >1817mgl(-1) (the highest concentrations tested), respectively. However, TDS was shown to significantly affect embryo water absorption during the water hardening phase immediately following fertilization. The lowest observable effect concentrations (LOECs) for this endpoint were 1402 and 964mgl(-1) for Arctic Grayling and Dolly Varden, respectively. The effect of reduced embryo turgidity, due to impaired water absorption, on resistance to mechanical damage under real world conditions needs further investigation in order to understand the implications of this observed effect.