Evaluation of Walleye Embryo Survival and Larval Viability after Iodine Treatment

Abstract

Securing health and avoiding viral disease transmission are of paramount importance for stocking and management of walleyes Sander vitreus. Iodine compounds are widely used as nonselective antiviral substances; however, their adverse effects on embryo survival are less known. Our experiments investigated how maternal attributes influence the relationship between toxicity of iodine (expressed as concentrations and duration of treatment) and survival of walleyes after fertilization and during early larval growth. Eleven female and four male walleyes were collected in April 2007 from the Maumee River, Perrysburg, Ohio, and the gametes were transported unfertilized (2 h) to the laboratory. After fertilization and tannic acid treatment, embryos were exposed for 15, 30, and 180 min to iodine concentrations of 0 (control), 50, 100, 200, 400, and 800 mg/L. The calculated survival of 50% of the embryos at the eyed stage corresponded to an iodine concentration of 380 mg/L for the exposure duration of 15 min (i.e., the LD50; linear relationship). An increase in exposure time (to 30 or 180 min) significantly decreased embryo survival. Progeny from individual females varied in sensitivity to iodine treatment, particularly with respect to the high concentration (800 mg/L), but high survival in controls did not correspond to better resistance to iodine treatments. No significant differences were observed in larval walleye size or swim bladder inflation rates among various iodine exposure groups within 15 d after treatment.

Iodophor Disinfection of Walleye Eggs Exposed to Viral Hemorrhagic Septicemia Virus Type IVb

“…Disinfection with iodophor at 100 mg/L for 30 min sufficiently eliminated VHSV as detected by viral isolation, and we recommend that this concentration be used instead of 50 mg/L. However, one must also take into account the fact that hatching survival is lower in Walleye eggs in a 30-min treatment (Dabrowski et al 2009). We did not investigate the effect of a 15-min treatment with iodophor, but further experiments should investigate this.…”

“…For example, the survival of Walleye embryos and the viability of Walleye larvae were not significantly compromised by a disinfection protocol of 250 mg/L iodine for 15 min. However, using 100 mg/L iodine for 30 min resulted in reduced survival compared with controls or treatment for 15 min (Dabrowski et al 2009). In another study, the use of 100 mg/L iodine for 30 min resulted in no significant difference in survival compared with control Walleye eggs when eggs were collected on-site but significantly affected egg survival when fish were transported prior to gamete collection (Bowzer et al 2011).…”

Disinfection of teleost eggs: a review

“…In other trials, the iodine disinfection was preceded by treatment with 400 mg L −1 tannic acid for 4 min (Dabrowski et al . ).…”

“…No negative effects on swim bladder inflation could be noticed, but in two of six replicates, iodine treatment caused significant changes in larval weight (Dabrowski et al . ).…”

“…Dabrowski et al . () found significantly higher growth rates in two of six replicates at 19 days after hatching (DAH), but lower growth rates were observed in one of six replicates after 27 DAH. In other studies where this criterion was investigated, no significant impact on the growth rate of the disinfected fish larvae was encountered (Hirazawa et al .…”