Cal. Fish & Game Code § 8069

In any judgment, interest shall be allowed at the legal rate of interest on unsatisfied judgments, as provided in Section 685.010 of the Code of Civil Procedure, upon the amount found to have been illegally collected from the date of payment of the amount to the date of allowance of credit on account of the judgment or to a date preceding the date of the refund warrant by not more than 30 days, the date to be determined by the department.