Environmental conditions and chemical contaminants present in natural environments influence the physiology and body condition of marine species (Lloret, Shulman et al. 2014, Champion, Hobday et al. 2020, Bolin, Schoeman et al. 2021, Butcherine, Kelaher et al. 2021). Understanding these relationships may enable fishers to avoid fishing at times or in locations when survival or resource quality are compromised. Assessing how extreme levels of environmental variation that prevail in estuarine systems, in conjunction with associated inputs of key agricultural chemicals affect the survival, physiology and flesh quality of the commercially valuable giant mud and blue swimmer crabs is required to develop this capacity. Further, netted gears (including gillnets, trawls and traps) are used to target (or incidentally catch) giant mud and blue swimmer crabs in NSW estuaries, but these are poorly selective for minimum legal sizes (Leland, Butcher et al. 2013), resulting in massive proportions of individuals (e.g. up to > 50 %) being discarded with at least some physical damage (typically missing appendages; Leland, Butcher et al. 2013). This project will integrate the effects of major rain fall events with associated inputs from agricultural run-off and simulated discarding to gain an in-depth understanding of how environmental change, land-use and discarding impacts the study species.