Photographic identification based on unique, polymorphic colour patterns: A novel method for tracking a marine crustacean Ashley J. Frisch ⁎ , Jean-Paul A. Hobbs School of Marine and Tropical Biology, James Cook University, Townsville, Qld 4811, Australia ARC Centre of Excellence for Coral Reef Studies, James Cook University, Townsville, Qld 4811, Australia Received 16 July 2007; accepted 18 July 2007 Abstract Mark–recapture techniques are an important tool for estimating population parameters of vagile organisms. However, the application of marks (tags) to crustaceans is problematic due to tag-loss during moulting of the exoskeleton. Accordingly, we investigated the use of external colour patterns to distinguish (via photographic identification) individuals of a common marine crustacean (painted crayfish, Panulirus versicolor). Colour patterns were found to be highly polymorphic and individually unique, such that all crayfish in a sample of 59 could be individually identified. When 30 of these crayfish were recaptured after 6–36 months at liberty, colour patterns were unchanged, despite moulting during the inter-census period. It was concluded that (1) photographic identification is an effective method for tracking P. versicolor through time and space, and (2) this method of identification may be useful in capture–recapture investigations of other invertebrate species that display polymorphic colour patterns. This result is significant given the logistical, ecological and ethical problems of attaching tags to crustaceans, as well as invertebrates in general. © 2007 Elsevier B.V. All rights reserved. Keywords: Crustacea; Intra-specific variation; Mark–recapture; Photographic identification; Polymorphism; Spiny lobster 1. Introduction Mark–recapture techniques have been used exten- sively in studies of animal ecology, most often for determining patterns in abundance, growth, survivor- ship and behaviour of vagile organisms (Stonehouse, 1978). However, it is not always possible to mark (tag) certain types of animals, either because they are problematic to tag, or they are protected by law from disturbance (e.g. cetaceans, Hammond et al., 1990). As an alternative, it is often possible to identify individual animals from variations in natural marks and (or) polymorphic colour patterns. If so, identification may be achieved by comparing photographs (of individual animals) that were taken at different points in time. Although photographic identification (photo-id) has been widely employed to study vertebrates (e.g. Persat, 1982; Hammond et al., 1990; Doody, 1995; Anderson and Goldman, 1996; Kelly, 2001), this technique has apparently never been used to track the movements of invertebrates, despite the presence of polymorphic colour patterns in many species (e.g. Vianna, 1986; Whiteley et al., 1997). One group of invertebrate animals that is particularly difficult to track through time and space is the Crustacea Journal of Experimental Marine Biology and Ecology 351 (2007) 294 – 299 www.elsevier.com/locate/jembe ⁎ Corresponding author. School of Marine and Tropical Biology, James Cook University, Townsville, Qld 4811, Australia. Tel.: +61 7 47816273; fax: +61 7 47251570. E-mail address: ashley.frisch@jcu.edu.au (A.J. Frisch). 0022-0981/$ - see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.jembe.2007.07.008