A transponder chip was implanted subcutaneously in approximately 100 sea otters as a permanent identification device. The chips were also implanted in shark, bat rays, and rock cod involved in growth and age studies.

The passive, integrated transponder tag has an electromagnetic coil and a custom-designed microchip that sends out an analog signal at 40 kHz only when excited by a scanning wand, giving it an extended life. Each transponder chip is programmed during its manufacture with a unique 10-digit alpha - numeric code. When reading the identification code, the scanning wand energizes the passive transponder chip using electromagnetic energy. The chip is the size of a pencil lead: 12mm in length, 2 mm in diameter, and 54 mg in weight. it is encased in a biomedically-safe glass envelope. Implanting tools include a spring-loaded syringe that uses either a 12 mm or 32 mm depth limiter or a 12 cc plastic syringe modified with a displacer and a 12 gauge needle. Tagging with transponder chips causes no disfigurement, external marks, or discomfort on the tagged animal and provides permanent identification for the animal's lifetime.