Ichthyocol, also known as fish glue, is a natural adhesive derived from fish skin. It has been used for centuries in various applications ranging from bookbinding to woodworking. However, if you need to find alternatives to ichthyocol, several options are available. One alternative is rabbit skin glue, which functions similarly to fish glue and is often used by artists and craftsmen. Other alternatives include hide glue, bone glue, and gelatin glue. All of these alternative glues are derived from animal products and have similar properties. So, if you're looking for a glue that can replace ichthyocol, there are several options to choose from depending on your specific needs.