by Jimbo Roberts » May 8th, 2013, 8:36 am
There is really five major things that contribute to delayed mortality. The first two were mentioned: 1) time out of water, 2) loss of the protective slime coat, but also 3) lactic acid buildup from playing a fish too long, 4) damage to internal organs from squeezing them too hard during handling, and 5) wounds from their hooking.
When it comes to loss of the slime coat, anything touching the fish like; your hands, a net, the earth, rocks, or grass, anything, wet is far perferable to it being dry. The fish has evolved in liquid world and is use to bumping into things wet. The slime coat can handle things wet up to a point. That said even something wet can remove some slime coat. Just smell your hands after touching a fish, that is it's slime coat your smelling. Dry surfaces touching it's skin almost immediately removes all the slime coat. Their bodies react and try to produce additional slime to replace it. Sometimes the damage is done and a fungal infection sets in in that area. This fungal infection does not always kill the fish but it's survival is probably no better than a 75:25 chance.
I know we are in a blood sport even when we practice the best catch and release tactics. Studies estimate that even using the best catch and release tactics overall survival is around 96%, that is including all 5 factors. But laying a Trout on dry ground is terrible. If you are going to do such a thing at least wet the surface first, mud is better than dirt. Wet grass is far less damaging than mud or wet rocks.
I usually just leave them in the rubber net and take that shot, boring yes, but it does far less damage. Occasionally with a fish of unusual coloring or size I will take a hero shot. It is best to leave the fish in the net while you turn on the camera and get everything ready. This is also best as a two man operation, one on the fish, one on the camera. Wet your hands, first grab the tail firmly, but don't use all your strenght as it can lead to bruising of the muscles. Place your second hand underneat it's upper belly and beneath it's head. Lift the fish quickly from the water and take the shot. If it struggles violently, it is best to place it (or drop it) back in the water quickly in the net, allow a couple of seconds to calm down, and try again. This can be done in a matter of a couple of seconds. I have been told this analogy. Imagine yourself running a race the time it took to land the fish. Now hold your breath for as long as it takes to take the picture. That's what it's like for the fish and being cold blooded they recover even more slowly than a warm blooded animal like ourselves.
I see many anglers use one hand to hold the fish around it's belly to take a picture. This is not good for any fish that is bigger than about 12". Especially bad if that fish is 18" or bigger because you are no longer supporting it's weight naturally. Remember fish live in virtually a weightless world. Their internal organs are such that they are supported neutrally in the water, but not outside the water. The single handed method, can cause bruising and bleeding of the internal organs that increases delayed mortality.
These are some of the things I have learned over the years talking with biologists, hatchery employees, and reading publications on the matter. I do the best I can myself, but even using the best techniques, everyone is responsible for some delayed mortality including myself. Do the best you can, think before you act, and practice the best possible catch and release tactics for the future of the sport.
Jimbo