Techniques used to increase recapture rates of dwarf seahorses (Hippocampus zosterae) in Tampa Bay: Implications for population estimates and movement patterns

Mark-recapture techniques were used to estimate population size and movement patterns of the Dwarf Seahorse (Hippocampus zosterae, Syngnathidae), a species native to the Gulf of Mexico and under review by the National Marine Fisheries Service (NMFS, USA) for consideration under the Endangered Species Act (ESA). Previous collection methods have failed to yield recapture rates high enough to use for population estimation, hypothesized to be a result of longer time durations between collections and large distances surveyed in previous studies. In this report, Dwarf Seahorses in Tampa Bay, Florida (USA) were sampled with a pushnet in a small, well-marked area (up to 40m2 per site) with more thorough and frequent resampling than previous studies. This change in the resampling resolution from earlier work increased recapture rates from 0.33% and 0.47% reported previously to 33% in the present study, demonstrating the importance of scale in sampling techniques. Increased recapture rates allowed for estimation of movement patterns, with similar movement distances and time intervals between sightings observed by sex; however, females were more likely than males to move between sites. Sex did not appear to influence recapture rates, with similar recapture rates between males and females. This project indicates that monitoring programs for the Dwarf Seahorse will need to be designed carefully as traditional sampling schemes used successfully for larger species of seahorses are unreliable or not feasible to use with smaller species