they become darkly pigmented and absorb their yolk sacs (about three to four days after hatching). Rearing tanks must have clean, well-aerated running water and should be scrubbed and sterilized with a mild chlorine (1 tea- spoon of household bleach per gallon of water for five minutes) or formalin (1 part: 4000 parts water) solution between each crop of fry. Be sure to thoroughly wash chlorine or other antiseptics off equipment with three or more rinses in fresh water. Keep young fry away from bright lights to reduce stress. Counting Fry The number of fry transferred from hatching troughs to temporary rearing chambers can be estimated using volumetric or gravimetric methods. It is best to combine clutches of fry that are about the same age in order to facilitate counting and to keep equally-sized individuals together. Estimate the number of fry by water displace- ment in a household measuring cup or graduated cylinder prior to introducing them into rearing tanks. A rough estimate is that about 1,000 one-day-old fry will displace one ounce of water. A more accurate approximation can be obtained by counting a small sample of 200-300 fry, measuring the amount of water that they displace, and then recording the water level change for all fry. The total Counting fry by water displacement in a graduated cylinder. number of fry can then be estimated by the following formula: Total Number = of Fry Total number in sample X change in water level with all fry Change in water level of sample EXAMPLE: (1) A sample of 300 fry displaces water level in a 100 ml graduated cylinder from 50 to 62 ml. (2) The entire clutch of fry displaces the water level in a larger container from 500 to 900 ml. (3) The total number of fry can then be calculated: TotalNumber = 300 x (900 500) 62 50 = 10,000 Estimating fry number by weight is similar to the above method. Water in a container is weighed, a sample of fry is counted and then added to the water, and the increase in weight is recorded. The total weight of all fry is then measured and the total number of fry can be approx- imated using the same general formula as that for volumetric counting. Estimating the number of fry by these methods allows the producer to determine ap- propriate stocking densities and feed allotments when moving fry to facilities for growing fingerlings. In addi- tion, the number of fingerlings graded into various size classes must be counted when sold or transported to markets (see "Grading Fingerlings"). Feeding Fry Fry begin swimming up to the surface of the water and around the edges of the tank when they are ready to feed. Small ground pellets, "crumbles," and granules ("fry starter") are typically used for feeding fry. A nutritionally-complete, high protein diet is recommended for maximum growth (ideal feed contains at least 45-50% crude protein, of which 60% of the protein should be fish meal). Initial food particles should be 0.35-0.60 mm (standard seive gauge 30-40). Small particle feeds have greater surface areas and may lose valuable nutrients by leaching and erosion during processing or storage. Sup- plemental vitamins, minerals, or other nutrients may be required to fortify the diet. Young fry should be fed often with enough meal that will be eaten in 15 to 20 minutes. Avoid overfeeding and distribute meal over the water surface using a screen or fine strainer. Since fry grow rapidly the pellet size and amount of food must be gradually increased (Table 3).