## 4 Discussion  
The study on _Callinectes sapidus_ populations in the Palud-Palu salty swamp provides an insight into the relationships between abiotic environmental conditions, morphometric characteristics, sexual dimorphism, and temporal variations in growth patterns. The findings highlight the influence of environmental factors and sex-specific differences on crab morphology and condition, with implications for ecological understanding and fisheries management. Across the sampling years, a variation in the size distribution of the individuals was noted. In 2022, most specimens were larger in size and mass compared to those collected in 2023 and 2024, where smaller and younger crabs were more frequently recorded. This trend suggests the possibility of different recruitment events or seasonal variability in population structure over the years. The overall dataset provides valuable insight into the population structure and size distribution of _C. sapidus_ in the studied areas, reflecting the continued presence and spread of this non-native species in the region. Our findings reveal pronounced seasonal and spatial differences in key abiotic parameters, particularly temperature, salinity, and oxygen saturation. The marsh exhibited extreme salinities and temperatures during summer months, coupled with lower oxygen saturation and pH compared to the more stable adjacent coastal environment. These abiotic stresses likely impose physiological challenges that constrain crab growth and condition. Furthermore, salinity fluctuations can impact osmoregulatory energetics, potentially reducing the energy available for somatic growth [37]. This is consistent with prior research indicating that temperature influences metabolic rates and growth in crustaceans, while low oxygen levels can constrain energy allocation for growth [38]. High salinity, as observed in the marsh, may also affect osmoregulation, potentially diverting energy from growth to physiological maintenance [39]. _C. sapidus_ showed a significant osmoregulatory capability, facilitating its invasive success in various aquatic habitats. Gender differences are evident in osmoregulation, with females showing greater sensitivity to osmotic stress compared to males, which presented a more consistent response across different salinity levels. In general, the hydrographic conditions of the swamp, although oscillating within the ecological valence for _C. sapidus_ (0 to 40 \({}^{\circ}\)C for temperatures and 0-64 PSU for salinities) [40], were far away from the optimal salinity conditions (18 PSU) and close to the upper temperatures that allow the crab's growth (30 \({}^{\circ}\)C). On the other hand, swamp waters had oxygen levels which were well above the threshold of 0.6 mg/L (approximately 9% saturation) at 24 \({}^{\circ}\)C, which in laboratory conditions cause specimen mortality within 24 h [41]. The reason that the swamp can maintain tolerable summer conditions for _C. sapidus_ can be ascribed to the periodic tidal exchanges which lower T and S every six hours, bring oxygen to the system and prevent pH from decreasing excessively. During low tides, bottom waters in the inner parts of the swamp become very hypoxic (6-8% O\({}_{2}\) [%]), hypersaline (60 PSU) and can reach 37 \({}^{\circ}\)C (pers. observations [PERSON]), and this is why the majority of the specimens is concentrated in the channel and the adjacent portion of the swamp, where tidal influence is strongest. In addition to salinity, temperature, and oxygen, pH represents an important abiotic stressor shaping blue crab ecology in the swamp environment. Our measurements show that swamp waters exhibit lower and more variable pH values than adjacent coastal zones, particularly during summer stagnation and low-tide periods, when tidal flushing is limited. Such episodes of local acidification are common in shallow estuarine wetlands and result from high rates of organic matter decomposition and CO\({}_{2}\) accumulation [42; 43]. Although _C.