Okay folks fish oil can be purchased from trapping supply houses easily,but for those do it yourselfers out there I'll go over this process of rendering fish oil, as most of us don't have the equipment for pressed fish oil which has a different fresher composition.

things you'll need---

- A larger container like a 5 or 7 gallon bucket with a lid that has the seal gasket
-a length of rubber or plastic tubing approx.2 or 3 foot long
-a empty 20 oz soda bottle
-a cup or cup and a half of vegtable oil
-lots of oily fleshed fish
-a clean quart jar with tight fitting lid
-a soup type ladel that you will never use for food again
-silicone sealant of some kind
Now we are going to render the actual fish oil,not the juice,though I save some of that also,you will end up witha clear to golden oil.

the oilier the fish used the more oil you will get per batch, this is NOT a process for those with weak stomaches or sensetive noses,lol.
Some of the best fish for this process is stuff like shad,carp,and even catfish scraps from cleaning catfish. Shad is my favorite around here,if you live somewhere where you can get oily saltwater baitish do so.

Getting set -up!
not much to do with the bucket itself,but you will need a shady cooler spot to put it far away from neighbors and in a place where critters like raccoons cant get at it. I like to dig a hole that is half to 3/4 deepness of the bucket to put the bucket into to slow and help the process.

-the lid
drill a hole into the lid of the bucket that will tightly accept the length of hose you found,insert the hose about two inches into the inside of the lid and silicone it tight so it is sealed well,while your at it drill a hole in the soda bottle lid that will accept the hose also,no need for sealant on this part.

the soda bottle
with a hole in the lid already, all you need to do is fill the clean empty soda bottle about halfway full of veggie oil. I use veggie oil because it doesn't evaporate like water will so I don't have to mess with it very much,and it can be used for multiple batches of oil making. Cut a small slit into the top of the bottle on one side,just poke your pocket knife through will do the job. make sure you do this well above the oil level!
The hose,soda bottle and oil will make for a bug and oxygen free atmoshpere in the bucket,while allowing the rendering process to vent off gasses from the decomposition process. If flys and bugs get into ths mess you won't get any oil as they will consume it and ruin the batch.

preparing the fish
On bigger fish like carp,etc I chop the fish up and toss the guts out,there is no oil in the guts you want,and they just take up space in your bucket.
On small fish like buckets full of small shad I don't bother with anything just load them into the bucket. If I have room left over and I have some leftovers from filetting catfish etc. I will toss those in too.

putting it all together
Now that your bucket is full of fish chunks and fish you need to get the lid on it,try to avoid letting flys etc. get to the fish in your bucket while the lid is off. Now you have your lid on and a hose running out of the lid and sealed tightly in place, it may help to take a rag and dip it in veggie oil and give the rubber lid gasket a quick wipe down before sealing the lid tight.
Next you need to get your homemade air trap put together,shove the hose through the top of the soda bottle lid till it is right near the bottom of the bottle and fully covered by the veggie oil. I like to duct tape the bottle right to the side of the bucket.
now as the fish in the bucket slowly decompose releasing the oils,juices,and gasses, the gasses will go through the hose,down into the oil "tank" and float up and escape through the slit in the side of the soda bottle, at the same time the decomposition process will eat all the available oxygen in the bucket and will not have access to anymore oxygen, also no flys or other bugs will be able to get into the soda bottle swim through the oil ,climb the hose and get at your oil. Having a oxygen free atmosphere helps give you more decomp and let rotting.
Now you can carry the bucket to your "safe place" and put it there. I put it in the hole and fill in some dirt around it them put an old tub over it and a couple concrete blocks on top to keep critters away.

Recovering the oil!!!
Okay this is gonna stink, by now about 45 days have gone by and the fish should be well broken down into some real nasty stuff. pick a windy day and get your bucket out gently, try not to disturb the contents,even so get it where you want to work on it and let it set for an hour. Now comes the nasty part, have your jar and ladle handy! stand upwind and remove the hose from the soda bottle to release any lightly trapped gasses. then gently take off the lid. this stuff is nasty,stay upwind! the oil floats to the surface,which is why we didn't want to disturb the bucket much! there should be a clearly visible oil layer on top,take your ladle and gently submerge it slowly into the bucket just enough for the oil layer to run into the ladle,go slow here as you want to keep as much fish "juice" out as possible,pour it into the jar and continue till you have recovered as much oil as possible. each batch and different fish types will produce different amounts of oil, seal your oil jar and put it someplace safe.

what to do with the "leftovers"
the juice and bones will be left in the bucket,some juice can be saved for fishing baits you want to stink of nasty fish,the rest I take away and dump far away from any dwellings,unless I want it for trapping bait.

How to use the oil
let your fish oil settle for a bit and any water/juice you got into the jar will seperate and you can remove it with a squeeze pump like a turkey baster. the oil itself really won't smell that bad. now this is some powerfull concentrated fishing scent,that can be mixed and experimented with in all types of homemade fishing baits, this stuff puts lots of fish pulling scent into the water system. doughs ,dips,soaks,punch baits,what have you,this will put the scent of fish in the water for you. Depending on how much bait your making,but this stuff will/should last along time for the average guy making bait for themselves.

good luck and any questions just pm me as always

Of couse I can't track a fish,but I have tracked coons in a light snow who picked up this scent from over 3/4 mile away with just 3 or 4 drops and made a beeline for the set in below freezing weather. fish love it too. I have even used some on cut bait and cut some up and put in a plastic baggie and added a shot of fish oil and it really seemed to increase the hits on those treated baits fished next to regular cutbait by about two to one, though it wasn't a careful study or experiment.