Mystery Fish


Just returned from a week at Cayo Ensenachos, Cuba. Spied this little guy or gal floating under a mass of sargassum that drifting in after two days of brisk winds. Any ideas? Looks to have a black dot below and to the rear of the dorsal fin adjacent to the tail. Possible butterfly pre-juevnile/larval, as we saw numerous juvenile spotfins and four-eyes? I'll be quite impressed if someone can offer something definitive. Many thans as always!! 

Mystery fish

Hey Jeff, this guy belongs to the jack family (Caranx, Carangoides, Seriola etc.). Great find!

Thx Carlos. I hope you don't

Thx Carlos. I hope you don't mind me asking, but what was it that pointed you in that direction? Fin structure, colouring, where it was spotted?

All the above

I've photographed very similar, if not identical, individuals and had those image reviewed by marine biologists and been told they are juvenile jacks but that at this stage of development making an ID to species is not practical. 

Edit: I tried uploading a similar photo for you to compare but without success.

PS. Go here and see the image

Thx Carlos, I definitely

Thx Carlos, I definitely will... I actually found a pic of a juvenile Jack Crevalle (though google) taken by a guy netting fish in the Lower New York Bay and it's extremely close. The title of the guys post was "the bay knows jack" and he writes a blog for Nature on the Edge of New York City. I couldn't find any of Bar or Yellow jacks pics, which is what we saw a ton of at the resort. I suppose though, the little fish could have drifted in from anywhere?


As you probably know the jack family is pelagic, open ocean, so finding juvis in flotsam or sargasso is common. 

I'm going to say this is probably not a Bar jack but could be a Yellow jack. The stripes resemble those of the amberjack family.

Good to know....I have to

Good to know....I have to credit my wife on this one, she spied it. She used to think I was silly, looking through the stuff...not now. I really appreciate your help and value your knowledge. Thx


I have spent entire dives drifting under Sargasso mats! There are endemic species to flotsam that you'll only find there such as Sargassumfish and Sargasso pipefish not to mention all the pelagic juveniles that love to hide in these mats. I look forward every year to the season when they float over the reef, you never know what you'll find in them.


Thank you both for this discussion.  This is the kind of conversation that benefits everyone.

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