Superglue has been used in fish surgery
"Superglue in Surgery
Superglue has also proved to be a life-saver. During the Vietnam War soldiers were issued with tubes to seal stomach wounds in the battlefield.
A redefined formulation is now used to seal post-operative wounds worldwide.
It has also been used in veterinary care. A tortoise who cracked its shell after falling from a second floor window was successfully glued back together.
Racing pigeons have had their feathers superglued, fish have had their fins re-attached and horses have had their split hooves bonded together. "
Reefers superglue coral and polyps together and I found this reference too...
"I have used superglue to good effect on fish.
We used commercially available superglue (Loctite super glue gel) as an
alternative to suturing an incision (25-30 mm long) made to implant acoustic tags in European eels (Anguilla anguilla)- following Baras & Jeandrain (1998). Not surprisingly, we found that the key to successful adhesion was to ensure that the surface was blotted as dry as possible.
We recaptured one of the tagged eels ca. 3 months after release and the scar was only just visible. In fact if it had not have been pit-tagged we wouldn't have identified it as a acoustically-tagged fish (as the tag had died).
There are cyanoacrylate glues available for surgical usage which are far more expensive than the regular superglue you can buy in the shops, but are less aggressive to the fish's tissues. '