Abundance, movement and individual identification of leafy seadragons, Phycodurus eques (Pisces: Syngnathidae)

Abstract

The aim of this study was to estimate, for the first time, abundance and degree of movement of leafy seadragons, Phycodurus eques, at one location in southern Australia. The pattern of wear and damage to the leafy appendages was found to vary among individuals but was not a reliable method of identification of individual fish over long periods. Photographic evidence of individual facial markings was more reliable and full-grown individuals could be recognised by their facial markings for at least 11 months. We made 45 sightings in 47 dives over 14 months. Sightings were made in depths of 3-11 m over brown algae, seagrass, and sand covered with drift macroalgae. Nine individual fish were sighted and all except one were sighted at least twice (mean of five sightings, s.e. 1.2, range 1-12). Capture and recapture calculations (moment estimator algorithm) estimated 9.2 (±0.3) seadragons in the study area (density 57 fish ha-1). Resightings were made months apart, suggesting that the fish are remaining within a home range (range of 35-82 m, maximum distance between sightings for fish sighted >5 times). Information about patterns of movement of seadragons is directly relevant to management plans for this species and for marine protected areas designed to aid in their protection.