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For Anyone Feeding/raising Fry


Chrissy_Bee

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So a while back I mentioned that I did a brief literature search at my lab for goldfish related research. Here?s a (very) brief summary of one paper I found. I have a few more and I?ll post them when I get the time. Most of what?s out there is on celluar stuff and eye physiology, I?m hoping to find more on disease soon. I have to admit, this was pretty fun for a geeky science fan like me :P

The authors wanted to see what combination of live and dry food provided the most benefits to young fish. 3-4 day old comets were kept in groups of 84 in 13L tanks (they used crushed oyster shells to stabilize pH and shredded plastic as biological filter media...thought that was an interesting side note). The temp was maintained at 24 degrees Celsius. There are more details, basically they kept the tanks clean by siphoning and keeping filtration high, and tested for ammonia and pH.

Live food consisted of Artemia (brine shrimp) and Daphnia. Dry food was AquaNutro Goldfish Food and was ground up for the fry. It has 45% crude protein. In all experiments fish were fed 5x a day until day 6, and then 3x a day.

Experiment 1: 20 days, 4 groups of fish. Group 1 got dry food in excess of what they could eat. Group 2 got Artemia. Group 3 got dry food supplemented with Artemia (600 per L per day). And group 4 got Artermia for the first 10 days and then Daphnia combined with dry food for the last 10 days.

Results: Fish length was significantly affected by diet. Group 1 (dry food) had lengths that were 36% less than the average of all other treatments. Group 3 showed reduced group when compared to group 2 when dry food was added to their diet. Survival of fish was lowest when they were fed dry food.

Experiment 2: 30 days. 1 control food got dry food only, the other got Artemia only. For the three experimental groups, they were weaned onto dry food at 24, 12 and 6 days. The weaning was gradual, with the proportion of Artemia to dry food gradually going down until only dry food was fed.

Results: Average survival didn?t differ between groups. The weaning method did significantly affect the fish length. The fish weaned at 24 days were the largest (surprise surprise!)

Experiment 3: 10 days. Three groups of fish. One was fed Artemia and dryfood, another got just Artemia and the third got decapsulated Artemia cysts only.

Results: The fish fed cysts grew at the fastest rate, those fed just Aertemia had the slowest.

Experiment 4: Fish were fed different amounts of decapsulated Atermia cysts 3-5x per day.

Results: Growth and total length was significantly affected by the amount of food. Growth was consistently faster with the increase in number of cysts fed. The amount of cysts available to the fish became limiting after 14 days of feeding.

Discussion (moral of the story):

They admit that the experimental design and sampling methods can influence how results are seen.

In short, live food provides greater survival and growth of young fish (21-30 days). They suggest that the replacement of Artemia by Daphnia after day 10 is acceptable as it didn?t cause a reduction in growth where no dry food was used. Weaning from Artemia shouldn?t be done until about day 24. Decapsulated Artemia cysts are a good alternative to live Artemia. During the first 14 days the fish need at least 93 cysts per day.

The authors admit that their stats aren?t great in this study, so I guess you should be cautious about the results. Good evidence for the benifits of feeding fry live food though!

Reference:

Kaiser, H; Endermann, F; Paulet, TG. (2003) A comparison of artificial and natural foods and their combinations in the rearing of goldfish, Carassius auratus. Aquaculture research. 34: 943-950.

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