The use of data provided by fishers is a contentious topic in fishery management. We compare fisher local ecological knowledge, fisher catch data and scientific data for Murray crayfish (Euastacus armatus) size and sex ratios in the River Murray, Australia, to determine if these data are consistent and if fisher knowledge can be a reliable input into fisheries management. Data were obtained through field surveys of crayfish populations, face-to-face fisher interviews and catch cards completed by fishers. All data sources indicated that there were higher numbers of crayfish <90mmOCL compared to '90mmOCL and the sex ratio of larger crayfish ('90mmOCL) was skewed towards females. Fisher catch card and scientific survey data showed the size frequencies of male and female crayfish were significantly different. Study results suggest that fisher local ecological knowledge can be a reliable source of nformation to improve fisheries management.