Usually, when the female shrimp enters maturity, there will be a lot of shrimp yellow on the head and neck, so crayfish with shrimp yellow must be female shrimp, but those without shrimp yellow are not necessarily male shrimp, because no mature female shrimp can see shrimp yellow.
The head of crayfish is a complicated part, which contains brain, stomach, heart, digestive gland, shrimp yolk and shrimp excrement, so the head can't just refer to shrimp yolk or shrimp excrement. Among them, shrimp yellow is the gland of shrimp, which is closely attached to the liver. Generally, it can be seen after the head is removed. This part is easily polluted by the garbage toxins handled by the shrimp itself, so it is not suitable to keep it. When handling the shrimp head, it should be cleaned together.