Does the rope harm the fish in any way ?
Will someone answer this please?
A few things one should keep in mind:
1) After a tough fight, no fish should be simply plopped back into the water. Understand that the fish is fatigued and needs time to recover. If recovery is not done, the fish will float belly up and asphyxiate. Recovery methods vary from species to species. Some such as sharks have to be 'swum' in the water, fish such as carps and catfish (depending on their size) can be kept in a keep net and released. Most mahseer caught are however are so called 'gill strung' simply because their sizes do not allow them to be put in a regular keep net.
2) Gill Stringing: Gill stringing is tricky and is as much a science as it is an art form. Like pointed out earlier, only certain kinds of cords should be used. Jute, cotton threads are fine, nylon cloths line is a big no no. The thickness of the cord is dependent on the strength of the cord. Jute and cotton have a tendency to loosen up the ply when soaked therefore, you should use an adequately strong cord. You don't want a fish taking off with a knot around its gills.
Furthermore, while tying up the fish, one should be careful not to pinch the gills. the threading is done through the mouth and then the operculum. If th gill is damaged in any way, the fish will not survive. Its similar to a lung wound.
3) If a fish is to be released back into the waters, one should also handle the fish properly in terms of the fish scales, body etc. All fish are covered by a protective coat of mucous. Damage to the mucous layer can lead to complications such as velvet (fungal) or bacterial infections. Some anglers does their fish with iodine before releasing, however I'm skeptical about this practice. Iodine does as much harm as good.
I hope this answers your query. If you have further questions, please feel free to ask.