Sex Ratio Variation and Environmental Correlates in Aphaniops spp. Across the Wadi Systems of Northern Oman: A Preliminary Conservation Assessment
Aziza S. Al Adhoobi, Saud M. Al Jufaili, Said M. Al Barwani, Syed Ariful Haque, Alyasa N. Al-Hasni, Waheeb A. Al Waheibi, Alhussain M. Alhussaini, Abdullah N. Al-Hinai, Mohammed S. Al-Shehhi, Humaid D. Al MamariSex ratio skew in wild fish populations may indicate environmental stress; however, this remains poorly understood in Omani wadi-endemic killifish. This study investigates sex ratio variation, environmental correlates, sexual dimorphism, and conservation implications in Aphaniops spp. across seven wadi sites in northern Oman. A total of 1417 individuals were collected in spring 2023, while 30 physicochemical variables were recorded over five seasons from spring 2022 to spring 2023. The pooled sex ratio was strongly female-biased (73.4% female; χ2 = 310.21, p < 0.001), with six sites deviating significantly from 1:1. Males were longer than females (t = 3.94, p < 0.001). Dissolved potassium was the strongest negative associate of the proportion of males (β = −0.455, OR = 0.635, p < 0.001), followed by turbidity (β = +0.232, p = 0.005) and depth (β = +0.244, p = 0.006); all associations are exploratory and do not establish causation. These findings suggest that dissolved potassium is associated with sex ratio variation in Aphaniops spp., and highlight Wadi Al Amirat as a priority site, five wadis as watch sites, and Wadi Surur as a baseline site (non-significant sex ratio only; not indicative of undisturbed reference conditions) for conservation.