Is catch and release fishing haram?

It depends on the scholar and on how you do it. Fishing for food is clearly allowed, and no text bans catch and release by name. But some scholars say hooking an animal for fun and letting it go is not allowed, or at least disliked, while others allow it if the fish is handled gently, especially where the law requires release. The safest path is to keep what you'll eat.

Fishing for food is allowed

The Quran makes fishing lawful and describes fish as provision:

أُحِلَّ لَكُمْ صَيْدُ ٱلْبَحْرِ وَطَعَامُهُۥ مَتَـٰعًا لَّكُمْ وَلِلسَّيَّارَةِ "It is lawful for you to hunt and eat seafood, as a provision for you and for travellers." Quran 5:96

The purpose here is food. The question with catch and release is what happens when the aim is not food but fun. For fishing and hunting in general, see Can Muslims go hunting and fishing?

The concern: hurting an animal for sport

Islam teaches kindness to animals. The Prophet ﷺ said, "Allah has enjoined goodness to everything; so when you kill, kill in a good way and when you slaughter, slaughter in a good way" (Sahih Muslim 1955). He also said, "Do not make anything having life as a target" (Sahih Muslim 1957), a rule scholars apply to using animals for target practice or play.

Scholars who discourage catch and release argue that hooking a fish, fighting it and letting it go causes pain and stress for no benefit, so it is close to using a living creature for amusement. They add that fish can be injured by hooks or die later even after being released.

The case for allowing it

Scholars who allow it say the act of fishing is itself permitted, the catching is the aim and the fish is not being tortured or killed for fun. They point out that:

In many places the law requires anglers to release fish that are undersized, out of season or protected.
Releasing a fish gently can be an act of mercy, and it helps keep fish stocks healthy.
A fish handled quickly and carefully often swims away unharmed.

Both views are held by sincere scholars, so follow the one your trusted imam or scholar recommends. See What does the Quran say about animals?

If you do release fish, do it kindly

Use barbless or circle hooks where allowed, and play the fish quickly rather than tiring it out.
Wet your hands before handling it, and keep it in the water as much as possible.
Don't squeeze it, drop it or hold it up for long photos.
Release it promptly, and if it's badly injured, keep it for food rather than letting it suffer.

A simpler approach

You can avoid the debate by fishing for food:

Catch what you will eat or share with neighbours and family.
Kill the fish quickly and cleanly, which follows the Prophet's ﷺ rule of doing it well. Fish don't need ritual slaughter.
Check local licences, size limits and seasons, and release what the law requires.
Be careful with fishing competitions, where fish may be caught only to be weighed and photographed.

Key points

Fishing for food is clearly allowed.
Scholars differ on catch and release, and some say it is not allowed or disliked.
Cruelty and using living things for play are discouraged.
Safest: keep what you'll eat, and release gently only when required.

Tip: Read your local fishing regulations before you go. They will tell you which fish you must release, and you can plan a trip that follows both the law and your conscience.