A Community and Forum For Aquaponic Gardeners
Humane Treatment of Fish
Every so often when I talk about aquaponics someone brings up issues around either the captive culture, or humane slaughter of fish. These are important, relevant questions that we are going to need to wrestle with in aquaponics.
Here is a link to a short PETA editorial that just came out in our local paper about this subject. Treehugger.com regularly brings this up.
How do you answer these questions? Are fish humanely treated in aquaponics? How do you humanely slaughter a fish?
Replies to This Discussion
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Permalink Reply by Carey Ma on
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Boy is this good reading. Everyone has a comment and they are all different. I like the general tone of this thread.
One thing I would like to mention though is in reply to a comment about fish not being able to feel happiness and its opposite, depression. I truly believe fish can process much more than we give them credit for. I believe fish have personality and character. (As with most hings I do; through observation). However, for the sake of production. I will accept that stress is a factor I would not like to see. For in my book, stress equals suffering.
Previously, I had written something in another thread along the same lines as this one so I won't reiterate. Instead,
I would like to ask if anyone transports live fish?
This year, I had the opportunity to work with three, one acre sized fish ponds totaling about 50,000 tail of fish. Here in China, most fish are sold live in supermarkets so have to be caught and transported. This process causes a lot of stress and damage to the fish. Would anyone like to help me figure a better way of transporting live fish?
There are two directions I would like to try. The first is to pass through an electrical field to stun them. The second method I'd like to experiment with is to stun them with gas. The first option that comes to mind is to use oxygen. Unfortunately, DO seems to max out at around 5ppm. So how about putting them to sleep with CO2? What do y'all think?
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Permalink Reply by RupertofOZ on
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Carey, I don't know what your local regulations might be concerning it...
But clove oil in small amounts will sedate fish.... slowing their metabolism, movement etc.... preventing transport stress/damage...
Indeed it's often used in general fish handling.. particularly during grading/weighing.. either for sampling or market selection..
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Yes Rupert, thank you. I am familiar with the use of clove oil but that is after they have been manhandled. I could see using it in tanks but I don't think I'd want to use it on the whole pond. I'd have to look up how long it remains effective in water. Thanks for your suggestion.
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Permalink Reply by TCLynx on
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I think most people will use the clove oil in the transport tank so yes, some handling has happened before the fish get there.
Hum, I wonder if one might set up a sort of cage/trap in a pond (and perhaps that could be a place where special food is provided to encourage the fish to like the shelter.) Anyway that trap would be kept there, Open, so the fish could become used to. And if it was set up right perhaps when harvest time comes you close the trap with whatever fish are in it then lift it out and into a hauling tank so that the handling stress to the fish might be minimized? Yea I know easier said than done, and it would definitely not be the way to harvest more than a small % of the fish at any one time.
Now if it was a really big and sealable container and a crane handy to lift it with fish and water out and directly onto the truck then the handling would really be minimized but the cost of those logistics are probably too much.
I try to keep handling of my fish to a minimum because it really does stress out the catfish badly and also net scrapes are prone to infection with catfish so I really try to make handling and moving of fish a rare event and when I do it. I try to do it as quickly as possible. Even so. Any time I dip a net into a catfish tank, they tend not to eat well for at least a day after which I usually take as a sign of stress and fright.
fish might not be into poetry or anything like that but they definitely respond to fear/stress like most all creatures with a drive of self preservation and instincts to preserve the species. We humans are not that special, we are not the only thinking/feeling creatures. It is just the idea that our pets actually like us that we need to avoid ascribing to our food animals. They just seem fond of us because they may have learned to recognize who brings the food or perhaps have even learned that if they act in a certain way, food seems to come quicker. I've watched tilapia train humans to feed them more than necessary that way before.
As to electricity to stun fish? Hum. I'm listening, not sure how practical it is or if it would work without causing other problems but I'm interested to hear what anyone might find out. I have heard that a leak of electrical current through a tank can cause damage to fish so even that sort of stunning I'm sure won't be totally free of stress even if it works but I've wondered about it as perhaps a more humane way to kill fish? (Big channel catfish have really hard skulls so the blade to the brain has been known to break a blade and even cutting the spine of a flopping fish can be hit and miss which is dangerous with a heavy blade and clobbering a big catfish with a heavy blunt object has it's dangers, but we refuse to simply leave the fish to suffocate in air because we believe a long drawn out painful death is terrible and we have tried dropping a catfish in ice water, they jump back out and that kind of frenzy definitely isn't caused by something humane.)
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Carey/TCL ....
Simply use a "car" ..... drag net the pond to one end, float the car.....drop the net, or fish into the "car"..... clove oil... and most importantly aerate....
Rather than post a whole heap of photos in here.... go to this thread for an example...
http://www.backyardaquaponics.com/forum/viewtopic.php?p=125747#p125747
TCLynx said:I think most people will use the clove oil in the transport tank so yes, some handling has happened before the fish get there.
Hum, I wonder if one might set up a sort of cage/trap in a pond (and perhaps that could be a place where special food is provided to encourage the fish to like the shelter.) Anyway that trap would be kept there, Open, so the fish could become used to. And if it was set up right perhaps when harvest time comes you close the trap with whatever fish are in it then lift it out and into a hauling tank so that the handling stress to the fish might be minimized? Yea I know easier said than done, and it would definitely not be the way to harvest more than a small % of the fish at any one time.
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Permalink Reply by David R. Russell on
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Aside from being humane, there is one good reason to quickly dispatch your fish with the least amount of pre-slaughter stress; it can make a big difference to flesh quality. This is particularly true for salmonids such as trout. High amounts of stress pre-slaughter, such as crowding in a seine net or being anesthetized in a tub with CO2 has been shown to have a measurable difference in the resting pH of filets (sometimes in excess of half a point lower on the pH scale). This corresponds to a softer, less firm flesh, and in salmonids it has also been linked to gaping (muscle separation), which is visually less appealing.
The Scottish, as the result of having animal welfare being forced upon them, had a side benefit. Their fish as an industry were generally slaughtered quick and humanly. The result was better quality flesh across the board and as a result “Scottish Quality Salmon” became a motto that resulted in better prices. Since then, the rest of the big salmon companies (industries) have caught on and most fish are harvested humanely.
One of the more popular methods for slaughter in the salmon industry is the use of pneumatic hammers that deliver a precise blow to the head. Gills are cut thru with a knife on the unconscious fish and then put into an ice slurry to bleed out and chill. There is an Australian company that makes equipment for this. Works well. There are automated devices and hand held.
Some Alaskans (a small few who have focused on producing the highest quality salmon) have used a hyper saline (concentrated salt water) chilled to several degrees below freezing for quick knock out (-5 C, I think). Fish dipped into this super-chilled solution will knock out in seconds! Fish are then treated as above (gills cut, etc…). For a small producer this method could work well. Typical chest freezers will chill to -20 C or so. Don’t forget to use a net to remove fish as you can get severe frost bite with super chilled brine.
Bleeding out fish in multiple species can make a difference to flesh quality and taste. Purging fish grown in RAS systems is important for taste. No feed, clean water, and normal rearing temperatures are important. Use of ozone will also help considerably (Keep ORP under 350 for health of the fish).
On clove oil- I have heard of people that have eaten such harvested fish complain about lip numbness (whole fish preparation as with tilapia). Make sure you rinse well post harvest. Check legality if you are in U.S.
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David R. Russell said:On clove oil- I have heard of people that have eaten such harvested fish complain about lip numbness (whole fish preparation as with tilapia). Make sure you rinse well post harvest. Check legality if you are in U.S.
The withholding period for clove oil use... is measured in hours.... but for safety is suggested at 24-48 hours
Fish respond instantly to fresh water... and NO clove oil residue has been found in fish flesh after (less than) 12 hours... at least not from any study I've been able to locate....
I'd be interested in any link regarding "lip numbness" from fish harvested after clove oil usage David....
Frankly... I just don't believe it... unless they were eating the fish raw... straight out of the clove oiled container...
The amount used to anaesthetise the fish.... is miniscule compared to water volume...
Perhaps it was benzicane used... not clove oil...
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I heard this from a reptubale Israeli fish farmer. If the fish is dead, how can it have with drawal time? The case sited by the farmer was a whole fish skin on, served on a plate. I assume not well washed. Like you- I doubt there would be any problems from eating a fillet of a fish harvested with clove oil.
RupertofOZ said:
David R. Russell said:On clove oil- I have heard of people that have eaten such harvested fish complain about lip numbness (whole fish preparation as with tilapia). Make sure you rinse well post harvest. Check legality if you are in U.S.
The withholding period for clove oil use... is measured in hours.... but for safety is suggested at 24-48 hours
Fish respond instantly to fresh water... and NO clove oil residue has been found in fish flesh after (less than) 12 hours... at least not from any study I've been able to locate....
I'd be interested in any link regarding "lip numbness" from fish harvested after clove oil usage David....
Frankly... I just don't believe it... unless they were eating the fish raw... straight out of the clove oiled container...
The amount used to anaesthetise the fish.... is miniscule compared to water volume...
Perhaps it was benzicane used... not clove oil...
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There's actually no withholding period here in OZ David.... and "dead" fish have usually been harvested and processed some time after any use of clove oil which might have been used to transport back to perhaps a purge tank...
Our Silver Perch are usually sold/transported "live" to Asian restaurants.... and might be sedated for transport, but then are usually placed into tanks at restaurants before consumption....
Lot's of fingerling stocks are lightly "oiled"... for bagging and freighting...
Any "withholding" period less than 24-48 hours... is essentially meaningless... and inconsequential...
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P.S ... I should probably place a cavaet on my remarks....
The use of clove oil... while common... is not actually "approved" in Australian aquaculture.... although an "approved" certified (and expensive) product is... and is actually just clove oil...
Check your local regulations with regards to use....
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The equivalent "approved" US product is "Finquel"....
And here's some "approved" methods ....
- Tricaine Methanesulfonate (TMS). This method is probably the most quoted by people with much experience in euthanizing fish humanely (i.e. for university experiments, etc.). TMS is also known as MS222 and commercially is known as Finquel. You can buy it from a pet supply store; Drs. Foster and Smith carry it; a bottle costs $24.99 plus shipping and handling. You can also buy this from PondRx ($14.99 plus shipping and handling for a 5 gram bottle) and Argent Labs. According to fish biologist Meyers' blog, simply by doubling the regular dose that you would use to anesthetize the fish will euthanize it. This substance is FDA approved for anesthetizing and euthanizing fish; it is the only product that is FDA approved to anesthetize fish.
- Benzocaine Hydrochloride is a drug requiring a veterinarian's prescription; you cannot buy it over the shelf for your fish. The AVMA advocates the use of Benzocaine hydrochloride but not straight Benzocaine. Benzocaine is not water soluble and must be mixed in water with acetone or ethanol, both can irritate fish tissue.
- Clove Oil/Vodka Method. Many fish keepers advocate using clove oil to anesthetize fish. You both anesthetize them first with the clover oil and dispatch the fish with another method or you give them such a strong concentration of clove oil that the clove oil alone will kill them. This article probably covers using the clove oil/vodka method is most detail: What is the Most Humane Way to Euthanize a Fish by wiseGeek.com. This process is not advocated by the AVMA in their 2000 report due to lack of research.
I've heard of the "vodka" method before... but it seems like a waste of perfectly good vodka to me...
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Thanks TC, you are always coming up with wonderful and helpful suggestions. This site couldn't run without you. And I always appreciate people willing to spend some time thinking and answering more than off the cuff comments.
China is definitely still very third world despite it's glamorous facade. A cage/ net trap would be better than netting fish individually. There is no way peasant farmers can afford to hire portable cranes however, I think you might be onto something. I can envision a specialized service. But in the end, they prob cab't afford that either.
Personally, I love using electronic technology, however, I was not gifted with the understanding necessary for this project. Therefore, I choose not to mess with electricity with water. I'll try to get one of the Unis to help at a later date.
I can envision how to apply it but not actuate a product. Maybe some of the scientist here would like to tackle this dilemma.
What they currently do isn't that bad or there wont be so many live fish at the markets. What they do is drive a net on parallel banks from one end to the other, where smaller nets are sectioned off and hauled to shore where fish are sorted and tossed into either storage tanks or the other side of the main net to live another cycle.
What I envision at the moment is replacing the small nets with a funnel net so fish are driven into a sluice trap device (like they have for salmon)connected to an underground spherical transportation container a little below the transport tube level to balance water pressure. We could have the electrical stunner fitted in the sluice part of the system. That way, fish are never hauled out of water but merely pass through an air zone for no more than a gulp or two and they are back in water. No bumps, no scrapes, no bruises and no chase. Transported fish can be further dosed with clove oil depending on the length of their trip. I further envision these tanks to be connected to an automated life support system ensuring temperature, oxygen/ CO2 and ammonia levels are stable and within comfort zones.
At the delivery site, I envision the bottom of the sphere to be connected to an equal depth reception tank where fish are "let out" at an equal pressure. Air is pumped into the top of the sphere to drive water out.When the tank is empty, the valve is closed and an air valve releases any pressure built inside.
Prob not feasible, but that's how I kind of envision how I would want to transport fish in bulk.
As for point of sale slaughter: well, I have to admit defeat. There is no way to catch fish individually without scaring the bajeeba's outta them before actual termination (fear doesn't taste too good). I could see a limited range stun stick, like a cattle prod but I don't like the idea of mixing water and electricity so that's prob not a good option. Continued use of love oil at this point would scare off too many customers even if it were OK to use, which I don't think I would use anyway, unless it was harmless, tasteless and quick acting. Ice water sounds like the best option so far to stun them before...?
We use a cone for chicken slaughter. How about fitting the fish in a cone and injection of compressed air to the brain? Or how about a water or light lazer-saw to zip their heads off (disconnect the vertebra)? Too fancy eh?Thanks Rupert. You are always a wealth of information. I am so glad you support this site. I'd love to buy you dinner one of these days.
Cheers all.
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