I was involved in cruise in Indian ocean for hydrothermal vent areas and I was involved in chemical survey but there are also biology team so may be you can find them 

Just search for ISA-BGR INDEX CRUISE 2016.

you will find all data and staff that you can ask.

Regarda

Difficult to identify from a photograph. This may be a trachichthyid. The most recent revision of Indian Ocean species is by Kotlyar (1980), but none of the species in that paper matches your fish.

Kotlyar, A. N. 1980 (27 June) [ref. 8322]

Systematics and distribution of trachichthyid fishes (Trachichthyidae, Beryciformes) of the Indian Ocean. In: Deep sea fishes of the Indian Ocean. Trudy Instituta Okeanologii Imeni P.P. Shirshova v. 110: 177-224. [In Russian, English summary.]

Kotlyar had published "Beryciformes of the World Ocean" (Moscow, VNIRO Press, 1996, 368 pp.) in Russian. It can be useful for you.

But for me the photo looks more like Diretmidae species.

Good suggestion, Diretmidae seems probable to me. Relevant literature would be the following:

Kotlyar, A. N. 1987 [ref. 13522]

Classification and distribution of fishes of the family Diretmidae (Beryciformes). Voprosy Ikhtiologii v. 27 (no. 6): 883-897. [In Russian. English translation in Journal of Ichthyology 1988, v. 28 (no. 2):1-15.]

Kotlyar, A. N. 1990 [ref. 20897]

Diretmichthys, a new genus of Diretmidae (Beryciformes). Voprosy Ikhtiologii v. 30 (no. 1): 144-151. [In Russian. English translation in Journal of Ichthyology v. 30 (no. 2):153-162]

I have looked through the book of Kotlyar, it is definitely genus Diretmoides and very probably Diretmoides veriginae. See attached files. Of course it is in Russian, but the figures are very nice. Main visual difference between D.veriginae and D.pauciradiatus is that the first species have ventral fins reach origin of anal fin, while not in the second species.

Thanks Andrey V. Dolgov and Ronals Ricke, your views are most helpful

Andrey:

I agree with your identification. [Will try to get that excellent Kotlyar monograph as soon as possible.]

- Ron

Ron, we have got this book in our library. I scanned some pages (but not all). If you need I can send its to you.

Dear Andrey:

I would need the complete monograph. I could try to get it through ILL, but if it is not too much trouble to scan it I would be happy to receive it.

With best wishes,

Ron

Hi, personally I do not like to identify by photographs, but although in this case really seems to fit with Diretmoides veriginae … I would not totally rule out that it could be Diretmichthys. Really Is difficult to be appreciated in the photo, but it seems to have spines at the base of the anal fin... but it is unclear. In this genus the pelvic also reach the anal fin. Although  are usually darker in color, but I do not know if the specimen is damaged and has lost its color. In addition, we do not have information on the size of the specimen.

On the other hand, Andrey, I would also be interested in the monograph of Kotlyar, but for the moment, could you send the following pages on Diretmicthys, 233 and following? Thank you very much.

To Jose

Yes, you are right on length of pelvic fins length, but it is difficult to see other characteristics on the photo. You are also right concerning fish size and colouring, For me, D.veriginae has also got much longer caudal fin compared to Diretmichthys. The fish on your photo has got much shorter caudal fin compared to the photo for identification.

To Andrey

Ok, the caudal fin is typical of D. veriginae. But I always like to check all the details and sometimes in the photographs it is imposible … so I do not usually like to identify by those means. I need to have the fish in my hands !!!!

Best regards

To Jose

I am completely agree with you. Photo is not a reliable tool for species identification, live or preserve fish is much more preferable. But if such identification was requested only by photo (as in this case), we should help  even if we can use only photo.

To Andrey

Totally agree, in fact I think that is the purpose of this web .. help in everything that is possible.

Best regards

Thanks for your valuable observations

Sileesh Mullasseri