A fishway can assist fish species in overcoming barriers to migration, which depends on the eco-hydraulic characteristics of the fishway. Based on the tail fish benefiting when at the rear of a school than when at the front, and taking into account most anadromous fish species being characterized by egg-shaped morphology, the turbulent characteristics of an egg-shaped orifice fishway were experimentally studied in a fishway flume, a comparison with a rectangular orifice fishway with the same aspect ratio was made. The results showed that the maximum longitudinal velocity for the egg-shaped orifice decays faster than that for the rectangular one, the longitudinal velocity profile exhibits two peak values, while the corresponding velocity distribution for the rectangular orifice only reveals one peak, peak values of turbulence intensity on the different horizontal plane of egg-shaped orifice occur in the orifice edges, the larger turbulence intensities still exists in the central besides the edges for the rectangular orifice, Reynolds stress reaches peak value at the orifice edges, Auto-correlation coefficient of longitudinal velocity within orifice region is of small amplitude and short period relative to the outside the orifice region, microscale eddies within the orifice region were larger than those outside, mean scale of eddy is of larger variation and shorter period, and develops outside the orifice region, frequency-spectrum of velocity fluctuation exhibits dominant frequency in the low-frequency domain.
Sustainable management of marine and coastal systems depends not only on ecological dynamics but also on the ways stakeholders perceive and interpret them. This study investigates how fishers, scientists, and government officials understand and frame the management of the Indo-Pacific pearl oyster Pinctada radiata, a non-native yet economically valuable species established around Evia Island, Greece. Using a mixed-methods approach (N = 80), we combined an eleven-item Hydro-ecological Governance Perception Scale (HGPS) with open-ended responses to explore cognitive patterns and governance perspectives. Sampling adequacy was satisfactory (KMO = 0.74; Bartlett’s χ2(55) = 350.41, p < 0.001) and factor analysis revealed two interrelated dimensions explaining 67.8% of total variance (α = 0.84; ω = 0.86; CR = 0.82). Although Kruskal–Wallis tests showed no statistically significant differences among groups (p > 0.05), hierarchical clustering distinguished three partially overlapping cognitive profiles: Ecological Pragmatists, Institutional Collaborators, and Adaptive Stewards (Silhouette = 0.45; CH = 150.23; DBI = 0.75). Thematic and sentiment analyses underscored the importance of collaboration, transparency, and education (mean sentiment = 0.58). The findings demonstrate how cognitive diversity can improve hydro-ecological resilience and the sustainability of coastal governance when it is mobilized through co-management and participatory monitoring.
