Backyard Aquaponics
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Can anyone point me to a table of average weight versus length for nile tilapia? I don't have a scale to weigh my fish and I'd rather not stress them, but I can measure them easily. I know it won't be highly accurate but I just want a rough estimate of their weight.

Sorry if this has already been posted somewhere but I searched and didn't find anything.

I've never come across a length to weight ratio chart for Tilapia on the internet. I even went to an old reliable site and found a good weight chart, no length conversion though.

From my experience so far, a 1.5 inch fish is about 2 grams, and a 3.5 inch fish is about 20 grams.

I can only speak in relation to perch - but once they get to a reasonable length they tend to do a lot of fattening out. I had perch that stayed at 23-25cm for months but got much bigger in girth.

W=BMI*(L^3)/100
Where:
W=Weight (g)
BMI=Body mass index
L=Length (cm)

Average BMI:
African Catfish 1,09 http://www.academicjournals.org/AJB/PDF ... Oluajo.pdf
American Eel 0,17 http://www.michigandnr.com/PUBLICATIONS ... pter17.pdf
Atlantic Cod 0,93 http://www.nefsc.noaa.gov/nefsc/publica ... /tm171.pdf
Atlantic Salmon 1,01 http://www.michigandnr.com/PUBLICATIONS ... pter17.pdf
Atlantic Sturgeon 0,27 http://www.nefsc.noaa.gov/nefsc/publica ... /tm171.pdf
Australian Bass 2,00 http://www.fish.wa.gov.au/docs/mp/mp174/fmp174.pdf
Barramundi 1,06 http://www.publish.csiro.au/paper/MF9820663.htm, "Barramundi - your questions answered", Allsop, de Lestang, Griffin, White 2006
Black Bream 1,69 http://www.cffr.murdoch.edu.au/frdc/FRDC_2000-180.pdf (average from 8 findings)
Black Sea Bass 1,38 http://www.nefsc.noaa.gov/nefsc/publica ... /tm171.pdf
Bluegill 2,00 http://www.michigandnr.com/PUBLICATIONS ... pter17.pdf
Brown Trout 1,19 http://www.trjfas.org/pdf/issue_4_1/45_47.pdf
Channel Catfish 0,75 http://www.michigandnr.com/PUBLICATIONS ... pter17.pdf
Common Carp 1,48 http://www.michigandnr.com/PUBLICATIONS ... pter17.pdf
Golden Perch 2,30 http://www.fish.wa.gov.au/docs/mp/mp174/fmp174.pdf
Goldfish 2,14 http://www.cffr.murdoch.edu.au/reports/ ... t_2006.pdf
Grouper 1,13 http://www.nobelonline.net/UserFiles/File/1.pdf (average of 2 different species)
Herring 0,70 http://www.michigandnr.com/PUBLICATIONS ... pter17.pdf
Jade Perch 2,58 Jaymie (average from 10 fish)
Koi Carp 1,70 http://pondlibrary.org/artikel/68/24/Ho ... jn-koi.htm
Lake Sturgeon 0,52 http://www.michigandnr.com/PUBLICATIONS ... pter17.pdf
Largemouth Bass 1,37 http://www.michigandnr.com/PUBLICATIONS ... pter17.pdf
Lizardfish 0,65 http://www.nobelonline.net/UserFiles/File/1.pdf
Murray Cod 1,80 http://www.fish.wa.gov.au/docs/mp/mp174/fmp174.pdf
Northern Pike 0,54 http://www.michigandnr.com/PUBLICATIONS ... pter17.pdf
Orfe 0,80 http://www.biolbull.org/cgi/reprint/99/2/213.pdf
Oscar 2,78 http://www.fishbase.se/PopDyn/LWRelatio ... tus&fc=349
Pacu 2,82 http://www.scielo.br/scielo.php?script= ... g=&nrm=iso
Pink Salmon 0,93 http://www.michigandnr.com/PUBLICATIONS ... pter17.pdf
Pirate Perch 2,05 http://www.michigandnr.com/PUBLICATIONS ... pter17.pdf
Rainbow Trout 0,95 http://www.michigandnr.com/PUBLICATIONS ... pter17.pdf
Rudd 1,35 http://www.iii.to.cnr.it/pesci/scardola.htm
Saratoga 0,59 http://books.google.nl/books?id=cDsRfy0 ... frontcover
Seabream 1,41 http://www.nobelonline.net/UserFiles/File/1.pdf (average of 5 different species)
Silver Perch 1,55 Nick and Troutman (average from 40 fish)
Sleepy Cod 1,02 http://www.ceps.com.tw/ec/ecjnlarticleV ... nliid=1690
Spanish Mackerel 0,95 http://www.nefsc.noaa.gov/nefsc/publica ... /tm171.pdf
Striped Bass 1,19 http://www.nefsc.noaa.gov/nefsc/publica ... /tm171.pdf
Tench 1,62 http://journals.tubitak.gov.tr/zoology/ ... -97075.pdf
Tilapia 3,67 http://www.fisheries.ubc.ca/members/dpa ... ybrids.pdf (average from over 100 fish from 4 different species and 24 different hybrids)
White Perch 1,38 http://www.michigandnr.com/PUBLICATIONS ... pter17.pdf
Yellow Perch 1,20 http://www.michigandnr.com/PUBLICATIONS ... pter17.pdf


These values took ages to find and calculate, and they could be way off. I appreciate it if I get told if they're right or not.
I hope somebody can use this.

Wow, haven't you been busy! I'll have to let you know--I think we'll have tilapia for dinner this weekend. I do find the tilapia number to be something of an oddball. Seems high.

It does, doesn't it! Certainly the fattest fish on the list..

Using this pdf: http://hrcak.srce.hr/file/27562 and this word file: http://ag.arizona.edu/azaqua/ista/ISTA8 ... _India.doc
I found that Nile tilapia should be around 1,07 and other tilapia around 1,88, so I was way off. The values I used must've been without the tailfin. Thanks, Janet!

Put this on the wiki?

Janet, any recollection about how much some of the other sizes weigh? Like a 2" tilapia or a 5" tilapia?

I should probably at least do a guesstimate about the weight of my fish so I can pick a starting point for feed weight.

Tilapia very widely in weight versus length depending on variety.
The word "Tilapia" cover numerous breeds and cross-breeds.

To get things going correctly ,, it's vital to regularly monitor fish weight ....., grab a scoop full ,, randomly select 10 , weigh them , divide by 10 and multiply by number of fish.
Then you can accurately estimate total fish weight and feed the correct amounts.
Not so important in small systems ,, but food is actually the single largest cost on a large system ,, so good habits begun early is nice.

Grading them will be next , if you want an efficient food source.

Get a container with an overflow at a set level.
Fill to this level with water.
Put pre-weighed catch cup under overflow.
add Tilapia
Weigh the catch cup again with the water they displace.
The difference between the weights is the weight of the fish (providing the fish are at neutral buoyancy, not sitting on the bottom of the container)

Return fish to tank.

Not as easy as measuring length but it should work with minimal stress to the fish.

Regards,
Tony

HA????????????

Ok , I get it . water displaced into cup equals fish weight ,, AHHH in your dreams ,, ROFLMAO ,, fish get cranky and splash around like the begeezers. 400 grammes water dispersed by 100 grammes fish. Get them REALLY angry and it could be a lot more.

Get a largish bucket , set to exact weight ,, add fish , re-weigh ,, that may work ,, best have a good scale and a good cover.

At our farm its ..... net fish by 100 ,, ,,put fish into weigh station , weigh and quickly release fish ..... we don't lose many.

Luckily Tilapia seem far more tolerant of handling than some other fish I know. If I try to net any catfish, it tends to put not only the ones netted but all the rest off their feed for a day. So far in my short experience with Blue Tilapia, only the large female seems to get very stressed by handling. The rest of them would probably eat happily in a net.

OK, data points for you. I was not worried about stressing the fish since they are filleted and in the refrigerator now.

These are Rocky Mountain White Tilapia, a blend of Nile, Blue, and goodness knows what else.

420g, 27.5cm
340g, 25cm
410g 26.5cm

I'm having problems with the formula Xzorby--do you want to test the numbers and see what BMI you get?

TC, check my April 3 post on this thread for smaller weights.

Janet, these values give a BMI of 2,0 to 2,2 - average 2,13. Your April 3 values give a BMI of about 3, but fingerlings are always relatively fat for their length.
The BMI value I found for rainbow trout is probably for wild fish - c1's trout were much fatter.


Updated values (mods can change the old list):
Tilapia (Rocky Mountain White Tilapia) 2,13 (values from janetpelletier in this thread)
Rainbow trout 1,30 (values from creative1's deceased trout viewtopic.php?f=18&t=3473&st=0&sk=t&sd=a&hilit=trout&start=375 )