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Today on Animal Fact Files we’re discussing blacktail humbugs. You may be familiar with these fish because one individual (or two, if you want to get technical) played a role in Finding Nemo. Deb (and by extension her sister Flo) are blacktail humbugs, though they got a blue treatment to their black stripes. In nature, these fish are white with four black stripes, sometimes leading to the name zebra humbug or zebra damselfish. They have one key identifying factor and that's the black-colored two thirds of their tail, hence the common name. This feature is unique to this species and sets it apart from other similar-looking damselfish. While watching through the video, see if you can spot any of the imposters.

Blacktail humbugs live in reef habitats of western Pacific along Australian, Indonesia, and Philippine coasts among others. They're shallow water inhabitants, preferring to remain above depths of 33 feet (10 meters), though they can be found as deep as 223 feet (68m). They are commensal with coral, keeping the invertebrate clear of unwanted algae. Blacktail humbugs also eat planktonic organisms suspended in the water column such as fish and crustacean eggs and larvae as well as copecopes and more.

These fish don't migrate. They spend their days shoaling with other members of their species throughout the reef, sticking to their favorite kinds of corals. In fact, juveniles of this species may find places to disperse and join the adult population by sniffing the older fish out along with the best-smelling corals– at least to a blacktail humbug! Their groups range from a dozen or two members to over 100 individuals in areas where coral is alive and abundant. In studies, blacktail humbugs avoided degraded coral habitats, so this ongoing issue also threatens the fish that live among the reefs. Over-collecting also impacts these fish as they are part of some of the most traded aquarium species as of this recording.  

Blacktail humbugs can reach more than 3 inches (8 centimeters) in length, and they become reproductively mature at around half this size. Their eggs settle to the seafloor where they stick to substrate like coral formations or rocks. The males of this species protect the eggs and keep water flowing over them so they don't develop infections. Something to note, however, is that male blacktail humbugs don't start out as males. These fish are protogynous hermaphrodites meaning they begin their life as a female and are able to transition to male later in life. The males defend their group of females and juveniles and females transition to replace them if they perish. 

For more facts on blacktail humbugs, check out the links below. Give a thumbs up if you learned something new today. Thank you to our Patrons SpikeSpiegel93, Dad, and everyone else for their support of this channel! And thank you for watching Animal Fact Files!