When you are in scuba diving training you learn that every 33 feet has a pressure increase of one atmosphere. Therefore, that is why no, or little decompression time is necessary for fish collected above 20 feet. Even so, for fish we do catch above 25 feet, we still hung them on our decompression line at about six feet to give them some adjustment time as a precaution. Many of you will be collecting with scuba gear. If you are, you will have to be concerned about decompressing the fish.
Some fish decompress well, while others really don't at all. As a rule Butterflies, Angels and Wrasses do not decompress well if caught below 30 feet, unless you spend a lot of time doing it. We're not talking about a few minutes decompression time here, we're talking hours sometimes. Tangs/Surgeons are a bit easier. A few exceptions are Kole and Orange-Shoulder (Band) Tangs. These are best caught and more easily decompressed from above 30-35 feet. Generally, the smaller the fish the faster they decompress.
For example; a three inch Yellow Tang will decompress well from 40 feet in an hour, whereas a four inch Yellow Tang will have more difficulties. The deeper you collect the fish, the longer the decompression time.
For our work we used a 30 foot decompression line. This is a 30 foot rope tied to a floater (a 1 gallon Clorox jug works well) with a knot tied every 6 feet, and a weight (about 5 lbs.) at the bottom. This line is tied with a 10 foot leader to the boat. When we are sitting on the boat decompressing fish this arrangement allows the catch bucket to rise and fall with the waves, in a relatively gentle manner. If it were tied off "hard and fast" to the boat, every wave would be jerking the decompression line, bucket and fish up and down with every wave. This is extremely hard on your catch buckets and the fish.
When we were collecting at depths to 50 feet, we tried to catch the tough decompressers only on the first dive. When we came up to re-bottle we attached these fish to the bottom of the decompression line knots, got in the boat, took a short 20 minute break, then re-bottled and hit the water again. When we would go down on the second dive, we would take the empty buckets off the decompression line, bring the buckets that we previously attached with the fish in them from the first dive and move them up to the next knot level (6 feet). At the end of the second dive we attached the new filled catch buckets at the bottom knot, and move the first catch buckets up another knot, then get into the boat.
When we were back on the boat, we would de-gear and start timing the decompression. We bring the fish up six feet every 20 minutes for the easy decompressers, longer for the toughies. By toughies we mean Raccoon, Auriga, Teardrop, Pebbled and Longnose Butterflies. Matter of fact, after a while we didn't even bother to collect these fish, especially large specimens from below 30 feet. This applied to large or extra large sized Orange Shoulder, Kole, Naso and Yellow Tangs past 40 feet as well.
Whenever collecting, as a rule we tried not to exceed going past 55 feet to collect anything. It was just too hard on the fish, and ourselves when we had to release fish because they did not decompress well. On a rare occasion we would dive a particular spot at about 90 feet and collect a few Black and White Banded Angels and Pyramid Butterflies, but we would spend up to four hours sitting on the boat decompressing them to insure they are going to do OK. They may have some minor residual effects of decompression after we bring them up, but they are fine by the next morning. If not, we would take them back and release them where we found them, because back at depth the decompression sickness subsides and the fish can recover quickly.
There is another method for ridding the fish of decompression sickness. It's called "needling", which is a process of inserting a syringe needle along the fish's lateral line and into the swim bladder, venting the expanded nitrogen gas. If done properly the fish should have no ill effects. However, if done improperly you can puncture a hole in the bladder wall or poke a pinpoint hole along the entry area that may result in an internal bacterial infection down the road. We can be honest and tell you that when we started our business, someone told us about this method and we tried it. Once was enough for us and we NEVER tried it again.
When purchasing deep water fish, make sure you observe the fish and look to see if there are any signs of possible internal infections. It is most likely seen as the fish not being able to swim level and its stomach may be bloated. Sometimes Wrasses have these signs, but this is not usually from needling. Its because they are sand dwellers and tend to pick up internal infections from living in unclean or dirty filter beds or substrate.
There you have it. We have covered all the things you need to know about collecting fish. You are now all set to go out and start collecting your own fish. Have fun and good luck. You will quickly find that the first fish in your tank that you brag to all of your friends about is that little Damsel you caught on your first collecting trip. Too bad the rest of your fish are all ripped to shreds. Maybe no one will notice. LOL
