Understanding catch and release

The fish you catch are perfectly adapted to living in an aquatic environment, so the second they leave the water you are responsible for their continued well-being.

To ensure a fish’s safe return and recovery we need to be aware of what changes occur when we take it out of water.

In this month’s Waterlife I’ll detail what happens when a fish is hooked, and show you how you should care for it and return it to fight another day.

How fish fight

Once hooked, a fish will try to escape, and its first reaction will be an instinctive dash away from the spot where it was hooked.

After this initial dash the fish tries to escape using pure swimming speed and strength, maybe trying to get to the safe haven of a nearby feature.

All this activity requires energy and, with fish, this comes from its muscles. Fish have a far greater muscle mass than we do, something that’s needed to move efficiently in water.

The main muscle used in this escape attempt is ‘white muscle’, which makes up the majority of the fish’s body mass.

It generates a huge amount of energy, which gives the fish its ability to accelerate. But white muscle isn’t very efficient, and runs out of fuel very quickly.

Different fish species have different levels of white muscle, and this affects their ability to fight.

Pike, for instance, have very high levels of white muscle to give them the blistering acceleration they need to catch other fish.

However, they haven’t got much of another muscle type – red muscle – which releases energy more slowly and delivers the ability to fight for longer.

Looking after your fish

During the successful capture and release of fish, scientific studies have shown that a number of factors are brought to bear. These include:

Hooks: Barbless or micro-barbed patterns are easiest to remove and cause the least trauma to the fish.

A scientific study showed that the survival of deeply hooked trout was far greater if the barbed hook wasn’t actually removed. The presence of the hook may prevent the fish from feeding in the short term, but modern high carbon hooks rust and break down quickly in water, so the fish can often shed them a short while after capture.

Line breaking strain: Low breaking strain lines mean fish are played more conservatively and so for longer, leading to a greater level of exhaustion. Be fair to the fish and use lines that are strong enough to land it promptly.

Landing nets: Netting a fish may be essential, but you must use a net with a mesh that minimises the potential to damage the fish’s skin by removing mucus and scales.

The old-style knotted mesh nets shouldn’t be used, because they can rub scales off fish. Instead, use one of the modern, softer mesh nets designed to wrap the fish in a soft, wet fabric.

Handling the fish: The fish should be unhooked in the water or placed on a soft, wet mat to minimise damage to the skin and mucus layer surrounding it. It is also important to use wet hands to hold a fish while restraining it to remove a hook, because dry hands or cloths suck moisture and mucus off the fish and can even remove scales.

Handling time: The time out of water is critical to survival for most fish. In average conditions, a fish shouldn’t be kept out of the water for more than 30 seconds. More tolerant fish like carp can survive longer, but don’t take advantage of this hardiness – they should still be returned to the water with all speed.

The time fish can spend out of water is much reduced under warm conditions, because the increased temperature means the fish is using more oxygen.

In extremely cold conditions don’t keep fish out of water very long, otherwise their gills can freeze solid.

Recovering the fish: One of the most important aspects of safely returning a fish is holding it in the water until it can swim off strongly.

If its breathing or swimming is erratic, hold it in a current or gently move it to generate a water flow over the gills. This will speed its recovery.

The fish should be released into an appropriate area, so avoid strong currents that may cause it to over-exert itself again. You should also avoid warm, shallow water where there is less oxygen for the fish to breath.

Keeping fish in keepnets can help the them to recover as long as they’re not going to get caught up, or damaged by, any lumps in the mesh.