The Fishroom Diaries-Culling fry
December 16th, 2016
By Rob Crosby
In this episode, I would like to discuss the reasons and early criteria for culling baby goldfish. First off, it is important to realize that the fanciest goldfish varieties are not so easy to produce in great quantities, simply because the characteristic trait combinations will only occur in a small fraction of the fry. The greater the number of breed-specific characteristics desired, the rarer the ideal specimens will be. For example, a good blue-calico broadtail telescope will be much harder to produce than a red comet. By breeding mature fish (preferably in their third year), the breeder is more likely to see large spawns with strong, viable fry. Once a large healthy spawn is achieved, the next challenge is how to most efficiently reduce the number of fry to a manageable number. Certainly taking a random “scoop” is an option, however, the real goal is to enrich the reserved population with the most desirable fry and remove those fry that have obvious faults. The objective is to identify those more desirable fry at the earliest opportunity so that they can be grown up in uncrowded conditions with plenty of food. In some cases, it is impossible to make any early distinctions, and if space is very limited, it may be best to randomly reduce the population just to ensure that the fry will not be stunted by overcrowded conditions.
Unculled 2 week old fry
eye deformities are obvious in very young fry
I generally do not like to handle fry less than about ten days old. Young fry are very fragile and injuries sustained from netting could affect their development. At about ten days old, it is safe to net the spawn in a large net and corral them into a bowl. If at all possible, the maneuver should be done under water to prevent the fry from piling up when the net is lifted. From the sample of 10 day old fry, I first like to assess the overall quality. Sometimes they are very uniform and there isn’t much basis for selection, but at other times, there are obvious differences in size, swimming ability, and spinal deformities. The very undersized fry, bottom sitters, and those with bent spines or asymmetrical eyes are the first to go; be sure to have a strong light source, magnifiers and a culling net for this process. Two bowls are set side by side, and the culls are moved to the “discard” bowl. At this stage for me, these culls are offered to larger fish as food, and nothing is wasted. It’s a good idea to keep one or two carnivorous fish (like most cichlids) for this purpose. As the fry grow, successive rounds of both negative and positive culling are done. Please visit again for specific tips on culling in my next episode.
poor tail shape for a TVR
Nice tail shape and good overall conformation for a TVR
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