Do fish sleep at night like we do?
Yes, there are many species of fish that sleep at night (diurnal) as well as plenty of fish that sleep during the day (nocturnal). By snorkeling through a reef in the Florida keys called Hens and Chickens, we could see many species of fish swimming around during the daytime. Not only were there many species that were seen, but most of them were in large schools consisting of many more fish of the same species. Some of the species that were most abundant included the yellowtail snapper, sergeant major, and Bermuda chub.
However, when we went night snorkeling at the same location, it was very different. There were much fewer fish swimming around than there were during the day. The schools of fish that were observed were smaller and less abundant than they previously were. Out of the fish seen, a lot of them were either yellowtail snapper or Bermuda chubs. Multiple porkfish were also seen swimming in this location at night, while not many were seen here during the day. This is because porkfish are nocturnal, rather than diurnal like us.
When researched, it was found that porkfish as well as yellowtail snappers were nocturnal fish. Which leads to the question: Why were the yellowtail snappers one of the most commonly seen fish species in this location during the daytime?
There could be many reasons behind why these yellowtail snappers were swimming around during the day. One of these explanations could be that there's a better feeding opportunity during the daytime in this area. Another possibility is that it may have something to do with the water temperature. The water is warmer during the day and colder at night, so there's a chance that this has something to do with their sleeping habits.
In contrast, both Bermuda chubs and sergeant majors are diurnal, meaning they are awake during the day and sleep at night. This makes sense since many of these fish were seen swimming around this reef during the daytime. It also makes sense that the porkfish was mainly seen during the nighttime snorkel, due to that species of fish being nocturnal. The thing that varies from what research I found is that the yellowtail snappers were awake and swimming around the reef during the day. There are a plethora of reasons for why this could be, and future research could be done to look into this.
Hi Rachel! cool title to reel me in (Get it haha). I found it very interesting we saw a different variety of reef fish based on the time of day! The porkfish was one of my favorites to view while snorkeling and now that you mention it is a nocturnal fish, makes sense why I did not see it in our afternoon dive. The yellowtail snapper's habits do make sense in terms of your thought process on why they are out during the day, which could mean that the past knowledge made about this species has changed evolutionarily towards the future.
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