Nanahara Takeshi had just started analyzing the Volume of Summer when he glanced at it and said indifferently, "This part describes the islanders' practice of catching sakura shrimp at night. It must have been the traditional shrimping season, which is the current eleventh month of the Gregorian calendar. That's when sakura shrimp are at their fattest and most valuable. Soon after, the sakura shrimp will enter the deep sea to avoid the cold and forage for food. They won't re-enter the ancient fishing boats' range until next March, and by then the quality won't be as good, so these ancient folks could only fish overnight during this period. The drawing is accurate; it's very realistic."
Oh, so that's how it is. Ancient shrimping isn't the same as the modern method; it's not something you can do anytime.