An examination of the population dynamics of syngnathid fishes within Tampa Bay,Florida,USA

Seagrass ecosystems worldwide have been declining, leading to a decrease in associated fish populations, especiallythose with low mobility such as syngnathids (pipefish and seahorses). This two-year pilot study investigated seasonal patterns indensity, growth, site fidelity, and population dynamics of Tampa Bay (FL) syngnathid fishes at a site adjacent to two marinas underconstruction. Using a modified mark-recapture technique, fish were collected periodically from three closely located sites thatvaried in seagrass species (Thalassia spp., Syringodium spp., and mixed-grass sites) and their distance from open water, but hadconsistent physical/chemical environmental characteristics. Fish were marked, photographed for body size and gender measurements,and released the same day at the capture site. Of the 5695 individuals surveyed, 49 individuals were recaptured, indicatinga large, flexible population. Population density peaks were observed in July of both years, with low densities in late winter andlate summer. Spatially, syngnathid densities were highest closest to the mouth of the bay and lowest near the shoreline. Sevenspecies of syngnathid fishes were observed, and species-specific patterns of seagrass use emerged during the study. However,only two species, Syngnathus scovelli and Hippocampus zosterae, were observed at high frequencies. For these two species, bodysize decreased across the study period, but while S. scovelli's population density decreased, H. zosterae's increased. Across six ofthe seven species, population size declined over the course of this preliminary study; however, seasonal shifts were impossible todistinguish from potential anthropogenic effects of

Seagrass ecosystems worldwide have been declining, leading to a decrease in associated fish populations, especially those with low mobility such as syngnathids （pipefish and seahorses）. This two-year pilot study investigated seasonal patterns in density, growth, site fidelity, and population dynamics of Tampa Bay （FL） syngnathid fishes at a site adjacent to two marinas under construction. Using a modified mark-recapture technique, fish were collected periodically from three closely located sites that varied in seagrass species （Thalassia spp., Syringodium spp., and mixed-grass sites） and their distance from open water, but had consistent physical/chemical environmental characteristics. Fish were marked, photographed for body size and gender measurements, and released the same day at the capture site. Of the 5695 individuals surveyed, 49 individuals were recaptured, indicating a large, flexible population. Population density peaks were observed in July of both years, with low densities in late winter and late summer. Spatially, syngnathid densities were highest closest to the mouth of the bay and lowest near the shoreline. Seven species of syngnathid fishes were observed, and species-specific patterns of seagrass use emerged during the study. However, only two species, Syngnathus scovelli and Hippoeampus zosterae, were observed at high frequencies. For these two species, body size decreased across the study period, but while S. scovelli＇s population density decreased, H. zosterae＇s increased. Across six of the seven species, population size declined over the course of this preliminary study; however, seasonal shifts were impossible to distinguish from potential anthropogenic effects of construction [Current Zoology 56 （1）： 118-133, 2010].