This study delves into the fascinating morphological diversity and population groups of the Crucifix crab (Charybdis feriatus), a species steeped in the cultural and spiritual significance of recreational fisheries across East and Southeast Asia. It is known in the West as the “Crucifix crab” due to the distinct cross pattern on its shell. In this research, we collected 759 specimens from seven estuarine locations: Kyushu (Japan), Shanghai, Xiamen, Hong Kong (China), Yilan, Kaohsiung (Taiwan), and Singapore. Using advanced statistical methods, including canonical variate analysis (CVA) and hierarchical clustering, we identified three distinct population groups: the Northeast Asian group (NAG), the Kuroshio tributary group (KTG), and the Southeast Asian group (SAG). Significant morphological differences were found between these populations, suggesting that the crab’s adaptation to varying sea environments is as unique as its symbolic cross-shaped marking. The canonical variate analysis revealed that the first two eigenvalues explained 88% of the total variance (61% and 27%, respectively) in females and 80% in males (62% and 18%, respectively). The key morphometric traits CP1 (frontal teeth) and CP4 (posterior margin) showed the highest variability (correlation coefficients ranging from 0.76 to 0.82, p < 0.001). Interestingly, the traits CP1 (frontal teeth) and CP4 (posterior margin) emerged as key drivers of allometric growth variation, further enriching our understanding of this species.

Aquaculture lagoons must reconcile visitor access with biodiversity protection. This study integrates results of a large survey of the attitudes of tour operators with field observations of fish populations to test whether operator choices can align tourism and conservation. Using data from 801 guided-tour participants in Taiwan’s Cigu Lagoon, a sequential experience hierarchy was validated whereby environmental knowledge enhanced attitudes, strengthened perceived guide professionalism, induced flow, and ultimately increased conservation intention (R² = 0.523). Experiential service quality exerted stronger effects than functional quality (β = 0.287 vs. 0.156; both p < 0.001). Parallel underwater monitoring indicated that electric, low-vibration motors were associated with richer fish assemblages and larger fish body sizes; fish abundance is 61% higher and mean body length 38% greater, with community composition differing significantly by motor type (PERMANOVA, p < 0.001). Together, these results link training and technology adoption to measurable ecological gains and pro-conservation motivation, indicating that electrified propulsion and interpretive practice are mutually reinforcing levers for biodiversity-positive tourism. The framework offers directly actionable criteria—motor choice, guide development, and safety/facility context—for transitioning small-scale fisheries and recreation toward low-impact marine experiences.

Tainan’s Cigu, located on Taiwan’s southwestern coast, is a prominent aquaculture hub known for its extensive ponds, tidal flats, and lagoons. This study explored the novel integration of kayaking within aquavoltaic (APV) aquaculture ponds, creating a unique hybrid tourism landscape that merges industrial land use (aquaculture and energy production) with nature-based recreation. We investigated the relationships among facility maintenance and safety professionalism (FM), the perceived value of kayaking training (PV), and green energy and sustainable development recognition (GS) within these APV systems in Cigu, Taiwan. While integrating recreation with renewable energy and aquaculture is an emerging approach to multifunctional land use, the mechanisms influencing visitors’ sustainability perceptions remain underexplored. Using data from 613 kayaking participants and structural equation modeling, we tested a theoretical framework encompassing direct, mediated, and moderated relationships. Our findings reveal that FM significantly influences both PV (β = 0.68, p < 0.001) and GS (β = 0.29, p < 0.001). Furthermore, PV strongly affects GS (β = 0.56, p < 0.001). Importantly, PV partially mediates the relationship between FM and GS, with the indirect effect (0.38) accounting for 57% of the total effect. We also identified significant moderating effects of APV coverage, guide expertise, and operational visibility. Complementary observational data obtained with underwater cameras confirm that non-motorized kayaking causes minimal ecological disturbance to cultured species, exhibiting significantly lower behavioral impacts than motorized alternatives. These findings advance the theoretical understanding of experiential learning in novel technological landscapes and provide evidence-based guidelines for optimizing recreational integration within production environments.