Abstract
Although the nighttime ecology of organisms remains understudied, nocturnal surveys play an integral part in assessing fish assemblages and the selective forces shaping them. Eleuthera (Bahamas) contains an unusual population of lined seahorses (Hippocampus erectus) in an anchialine lake, possessing morphological characteristics distinct from those found in the ocean. Population surveys for seahorses and their potential predators were conducted at midnight and midday during wet and dry seasons, with belt transects perpendicular to the shoreline that increased in depth away from shore. Nocturnal surveys uncovered seahorse densities 259% higher than daytime transects on average. Sex ratios were consistently male-biased, and the frequency of animals from different reproductive categories varied significantly by time of day, with gravid males observed around the clock but females and nongravid males observed more often at night. Spatial and seasonal recruitment was detected for the first time in this species, with an increase in juveniles detected in the shallow ends of transects during dry season surveys. Juvenile recruitment is poorly understood across syngnathid fishes, so the detection of early recruits at night has broad implications for this fish family. Seahorses from all reproductive categories were perched significantly higher in the water column during the night regardless of their depth or season. Predator densities followed a similar pattern with higher densities observed at night, indicating that elevated nocturnal perch height may be a response to predator presence. However, the selective agents driving these nocturnal behaviors have yet to be identified. Considering H. erectus is listed on the IUCN Red List as “Vulnerable,” the increase in nocturnal population size and the detection of juveniles has crucial implications for understanding their ecology, recruitment, and conservation.
| Original language | English |
|---|---|
| Article number | e9573 |
| Pages (from-to) | 1-16 |
| Journal | Ecology and Evolution |
| Volume | 13 |
| Issue number | 1 |
| DOIs | |
| Publication status | Published - 11 Jan 2023 |
Bibliographical note
Funding Information:This work was supported by the University of Tampa Research Innovation and Scholarly Excellence (RISE) Grant (AWD‐00000036); the University of Tampa Office of Undergraduate Research and Inquiry Grant (awarded to H.D.M., E.R., and J.E.); and a University of Tampa International Programs Grant (to H.D.M.). Special thanks to the Center for Ocean Research and Education (CORE) for providing housing and lab space for the research project, and for allowing us to be the inaugural research team housed at the new field station. In‐kind support provided by the Leon Levy Native Plant Preserve and the Bahamas National Trust (staff, resources). Special thanks to Dr. Ethan Freid, who was the driving force in the initial discovery of nocturnal seahorses in the pond.
Funding Information:
This work was supported by the University of Tampa Research Innovation and Scholarly Excellence (RISE) Grant (AWD-00000036); the University of Tampa Office of Undergraduate Research and Inquiry Grant (awarded to H.D.M., E.R., and J.E.); and a University of Tampa International Programs Grant (to H.D.M.). Special thanks to the Center for Ocean Research and Education (CORE) for providing housing and lab space for the research project, and for allowing us to be the inaugural research team housed at the new field station. In-kind support provided by the Leon Levy Native Plant Preserve and the Bahamas National Trust (staff, resources). Special thanks to Dr. Ethan Freid, who was the driving force in the initial discovery of nocturnal seahorses in the pond.
Publisher Copyright:
© 2023 The Authors. Ecology and Evolution published by John Wiley & Sons Ltd.