FISH GRADING/SORTING MANEGEMENT.
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| Catfish grading |
BENIFIT OF FISH SORTING AND GRADING.
1. To ascertain the present population of fishes present in your ponds.
2.To determine the average weight of fishes at every point in time so as to know if you're on key
3. Reducing fish losses that occur through cannibalism
4. Reducing proportion of small sized fishes at harvest.
5. It helps the farmer to determine what sizes of feed will be suitable for different sizes of fish
6. Its useful for separating fishes based in sex; either male or female for breeding purposes.
7. Its in the process of sorting that a farmer can ascertain whether a particular set of fishes are doing fine or not.
8. It helps to know what prices various sizes of fish will go for since different buyers have their choice of size, sorting will make sales easy
9. It exposes your fishes to a form of exercise which makes them more resistant to stress at the pont of harvesting.
Fishes not exposed to this may suffer more stress during transportation by buyers after harvesting & die in transit.
Some farmers complain that despite the fact that they feed their fishes well, they still experience high level of mortality. Many at times, even experienced farmers may not be able to tell the true state of their fishes in terms of sizes & weight until they sort. At the hatchery stage, its the bigger fishes that cannibalize on the smaller ones when not sorted on time, in the grow-out stage, the reverse is the case. Apart from overstocking, not sorting can also bring about such incidence since the fishes don't grow equally. When you also sort regularly, you can also be able to tell what adjustment you may need to make on your fish diet. For grow-out production (raising fishes from fingerlings to table size), its required that the first sorting be done after 2 weeks of stocking & the next one be done after another 2 weeks which is a month after stocking. Subsequent sorting can be done every month or as seen necessary when rapid size differences occur.
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| Catfish seeds grading |
.MATERIALS REQUIRED FOR SORTING.
1. Weighing scale (Analogue or digital) 50 kg & above for grow-out
2. Scooping net or an improvised net using the popular window net material
3.Demarcation board
4.Large bowls
5. Plastic sieves
6.Grader (Adjustable grader for hatchery use and Locally fabricated fixed grader)
7.Counting table ( for hatchery use; Formica or ARCO board
8.Ruler (hatchery use)
9. Salt
10. Anti stress drugs
11.record book
Before sorting/grading can be done, one needs to be aware of the various fish sizes
.FOR HATCHERY.
Going by some authorities in fish farming, the following are their recommendations; fingerlings 5cm-6cm, advance fingerlings (post fingerlings) 7cm-9cm, juveniles- 10cm-12cm. Standard sizes are as follows:
Fry 0.5g
Fingerlings 1g
Post fingerlings 3-5g
Juveniles 10g
Different people have different yardsticks as it relates to standard. People sell 3-5g as juveniles which shouldn't be.
GROW-OUT IN CATFISH.
Below 500grams- melange (smoking sizes)
Table size - 500grams to 1.2kg. Fish mongers also have range of sizes each individual buys.
Things to note when planning to sort
Sorting should be done when the weather is cool, preferably very early in the morning.
I enjoy doing this when there are light rain showers.
Doing this very early in the morning when the sun isn't out will prevent both the fish & the farmer from experiencing heat stress
Another advantage is that it gives you enough time to sort unlike doing It in the evening when it can go dark before you finish.
Feed type mustn't be changed immediately after sorting because fishes that are stressed may not easily adapt to new feeds.
On the day preceding when you want to sort, don't feed your fishes too late so that they'd have digested their feed well before you sort
Don't sort older fish with younger fishes to avoid disease transference & also to maintain uniformity in growth rate as a result of age.
There's also need to get additional hands because fish sorting is one of the most tasking aspect of fish farming.
Yesterday, We were able to establish the sizes of fishes in that category.
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| Grading size table. |
USING THE SORTING TABLE MANEGEMENT.
When using the sorting table, you should try to keep the fish in good condition. Proceed as follows.
(1) Set up the sorting table close to the hatchery site, under the shade.
(2) Before starting, wet its surface well with clean water.
(3) Under each opening of the table, place a container with clean, fresh water, such as buckets, plastic basins or half metal drums which can be used to transport the fish
(4) Use good handling nets with no rough or torn edges.
(5) Bring only small batches of fish to the table at a time. Put them in suitable temporary holding containers, with a regular change of clean water. This also helps to rinse them clean of mud, algae and plants.
(6) Transfer the fish gently on to the top of the sorting table.
(7) Have 1 or 2 qualified persons working around the table. The fish should be handled as little as possible and sorted quickly.
(8) Start sorting:
first the large fish, if any, placing them directly in a dip net and into water;
then the fish which are in the smallest number, sliding them towards one of the corner openings into a container and water;
Then The Remaining Group(s).
(9) After having sorted or graded this batch of fish, rinse the table well, with plenty of clean water.
(10) Place another batch of clean fish on the table and continue sorting or grading.
(11) Move the sorted fish as soon as possible to their recovery or destination areas.
At the end of the working day, clean the table well, dry it and store it in a protected place.
Note: the surface of the sorting table should always be perfectly smooth to avoid bruising the skin of fish. Regularly check your table surface and, it necessary, smooth it well with sandpaper and repaint it.
If its an ARCO board (The material used by aluminium fabricators), the troubles will be minimal.
HOW TO GRADE FISH WITH A CALIBRATED CONTAINER.
1. This method is particularly useful for smaller fish, which are more sensitive and more difficult to handle than larger fish. The basic idea is to place a group of fish in a container held in water, from which the smaller ones can drop through or swim away through holes of a specific size made in the bottom and in the walls of the container. If possible, the container should be held in flowing water.
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| FISH GRADING/SORTING 2 different size trays |
2. You may use one of the following:
specially woven baskets, each of them for fish of a certain size.
Plastic basins with holes of a uniform size drilled in the bottom and the lower 10 cm of the sides, for example from 0.3 to 10 mm in diameter;
wooden boxes with holes drilled as above; meshed boxes made from a wooden frame and material with a specific mesh size such as netting, plastic or metal mesh
PROCESSES OF SORTING FISHES IN GROW OUT CATEGORY (FROM FINGERLINGS TO TABLE SIZE).
1. Drain out the water from your pond completely to enable you bring out the fishes easily for sorting.
2. If they're fishes below 300grams, use net to bring them out in small batches & put them in large bowls. The net must be a clean one which you must have sterilized using salt to prevent disease incidence if you've used it for older fishes before.
3. Don't bring out too many fishes at a time until you're ready to sort them so that they won't become too stressed as a result of being in bowls on top of each other for too long.
4. After bringing them out, use the sieve to scoop & sort them into required sizes which most times is into minimum of 3 sizes.
Adequate provision must have been made for ponds that will be enough to take the available fish population to prevent overstocking.
5. Temporary demarcations can be done in ponds using the demarcation board so that as you sort, you can have someone move them almost immediately to reduce level of stress on them.
6. The ponds into which you want to pour the sorted fish must not have water in it.
The reason is to enable for the use of anti stress when you first keep the water at a low level & majorly to prevent cannibalism.
If there are some fishes in a pond filled with water,they'd go on to hold territories & likely perceive those being brought in later as intruders & feed on them.
6b. In sorting out bigger fishes of over 500grams size, they're more handy & can easily be picked & thrown behind the demarcation board for those that will remain in that particular pond. For other sizes, you'd put them in bowls & transfer them into other ponds.
7. In the process of sorting as you distribute the fishes based on physical observation of the sizes, count & record their number.
8. After you must have grouped them into sizes, take sample weight of fishes in each pond to know their average weight.
To do this, place w bowl on your scale & set it to zero.
Pick about 10 fishes randomly & divide their number by the weight obtained.
If 10 fishes weigh 5kg, it means your fishes have an average weight of 500grams.
8b. You can repeat the process for each pond a few more times & record it.
9. After sorting, pump in little water into the ponds containing the fish & add anti stress drugs.
10. Salt works fine in easing stress on them.
After about 30 minutes, raise their water & feed them once they show signs of recovery. Note
Don't change their feed type or sizes immediately at this point because they'd find it harder to adjust after the stress they must have been through.
Days after they must have adjusted, you can change the feed sizes into bigger sizes based on the fish size.
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| Fish grading tray |
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