Nocturnal surveys reveal novel insights into the community dynamics of an anchialine ecosystem from The Bahamas

O’Brien, Duncan A.; Masonjones, Heather D.; Bethel, Enrique; O’Shea, Owen R.

doi:10.1016/j.ecss.2021.107588

Cited by 1 publication

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References 80 publications

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“…Previous work included formal population sampling during the day (Masonjones et al, 2019) with animals observed engaging in cryptic behaviors in groups fewer than four seahorses (animals camouflage and tuck themselves away within the structure of the habitat) consistent with the behavior of other seahorse species (Freret‐Meurer et al, 2017). Both formal nocturnal fish census using baited remote underwater video (BRUV) and informal nighttime observations in Sweetings Pond suggest that this population of H. erectus may be nocturnal, engaging in noncryptic behaviors, including congregating in large social groups of up to 14 animals, perching on the top of vegetation, and performing courtship displays (Mason, unpublished data; O'Brien et al, 2021).…”

Section: Introductionmentioning

confidence: 99%

Nocturnal surveys of lined seahorses reveal increased densities and seasonal recruitment patterns

Masonjones

Rose

Gonzalez

et al. 2023

Ecology and Evolution

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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.

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Section: Introductionmentioning

confidence: 99%