Changes in crayfish populations within streams can indicate shifts in habitat preferences, which often reflect environmental conditions such as shelter availability and food resources. Variations in crayfish measurements, such as body size, can signal differences in habitat quality. Streams that offer diverse substrates, ample hiding spots, and abundant food sources typically support larger and healthier crayfish populations. This field lesson combines habitat observations with crayfish sampling to investigate how different habitat characteristics influence crayfish distribution and abundance. Designed for upper undergraduate students, the lesson includes the collection of habitat data (water quality parameters, substrate type, vegetation cover) and crayfish data (including body measurements and species identification). An optional Excel sheet is provided for students to formulate predictions about expected habitat preferences and then analyze the collected data. Students are encouraged to reflect on their observations and initial predictions regarding how various habitat features affect crayfish populations.