Scientists attach tags to animals in order to recognise individuals in a population.
This is mainly because it is a notoriously difficult animal to tag or mark. Individual starfish need to be able to be identified over long periods of time to allow adequate data on these variables to be collected. These include dyes, brands, harnesses, plastic T-bar tags, spine clipping, cable ties, monofilament nylon looped around arms and the insertion of stainless steel wire through the disc. All these techniques have been unsuccessful in identifying individual starfish over long periods. Natural features such as colouration, number of arms, and position of other external characters have proven unwieldy and impractical for identifying large numbers of starfish.