Aquaculture parameters for Hypancistrus zebra

[bekateen]

Menezes Ramos, F., Abe, H. A., Martins Cordeiro, C. A., Barbas, L. A. L., Carneiro, P. C. F., Maria, A. N., & Fujimoto, R. Y. (2019). Feed management and stocking density of the endangered wild zebra pleco: Implications for captive breeding. Aquaculture Research. First published: 01 June 2019

https://onlinelibrary.wiley.com/doi/ful ... /are.14197
https://doi.org/10.1111/are.14197

ABSTRACT
Due to the economic potential of

Hypancistrus zebra

in the ornamental fish market and its current classification as an endangered species in its natural occurrence sites, the present study sought to determine a suitable feed management strategy and stocking density to allow for an adequate captivity maintenance of this fish species. Three experiments were conducted as follows: (1) feed preference (artemia Artemia sp., shrimp Litopenaeus vannamei, fish Cynoscion spp. or mussel Perna perna); (2) determination of feeding rate (5% and 10% live weight day−1) and frequency (1, 2 or 3 meals. Day−1); and (3) evaluation of stocking density (0.25, 0.50, 1.00 and 2.00 g/L). Zebra pleco did not present the characteristic buccal scraping behaviour on the feed, commonly seen in other Loricariids. Artemia was the preferred diet followed by fish, shrimp and mussels. The frequency of two daily meals and the feeding rate of 10% live weight day−1 allowed for an improved zootechnical performance. Zebra pleco showed enhanced specific growth rate at the density of 2 g/L. Our results suggest that, to improve the zebra pleco rearing conditions, it should be maintained at a density of 2 g/L, fed two daily meals at a feeding rate of 10% live weight day−1. These findings correspond to useful information for an adequate management of this species and could assist in the supply of healthy specimens to the ornamental fish market as well for the restocking of declining wild populations.

[TwoTankAmin]

Another interesting paper I cannot read I would love to see their design, methods and time frames.

However, I think it would only be of real interest to a professional aquaculture operations. Based on the abstract I have a bunch of questions as to how the information might benefit hobby/home breeders (HMB).

1. How many HMB can actually weigh their fish and food per feeding? How often must this be repeated to insure the proper"balance?" What is the Day-1 all about? And how did they know every fish ate the same amount?
2. What about some of the other foods many folks use that were not investigated?
3. To what does the 2g/l stocking density refer? Does it mean 2 grams of fish weight/liter of water?

One more big Q. There are 4 foods, 2 feed weights and 3 feeding frequencies. Doesn't that compute to 24 potential configurations? How many fish were used. If it is just 10 fish per configuration, that is 240 subjects. Is that sufficient numbers from which to generalize?

My limited experience in experimental design from my days as a psych major made me wonder about controlling variables and population sample sizes.

[Narwhal72]

Curious to read this paper too.
It does say that it was 3 experiments. So it could be a smaller number of sample individuals and the paper is summarizing the results of 3 different individual experiments. Same set of samples. Just tested three times looking at different variables.

IME tests like this with loricariids are very difficult to perform. The fish are very small and sample size is small so the error in measured weight of the fish is very high. The water clinging to the fish when weighing can significantly alter weights. Add in the fact that the fish grow quite slowly (in comparison to something like a Tilapia or salmonid) so the difference in weight between two time periods can often be within the margin of error caused by the excess water weight.

Another interesting aspect would be if they did any cost analysis of the different diets. Feeding the zebras shrimp, fish, and mussel may be great for growth. But these premium feeds have a high cost, zebras have low fecundity (relative to other ornamental species), and a slow growth rate. The overhead of rearing the fry may outweigh their market price.

[TwoTankAmin]

I was sent a copy of the paper. I came to many of the same conclusions as @Narwhal72 above.

In one experiment they use 180 zebras. In another they used 108. Aall were juveniles. So they could have overlapped. In the third experiment, to determine food preferences, they used 8 adults.

Cost of diet really doesn't matter. Density doesn't matter either unless it is causing health issues. Lets assume it takes 6-7 months to raise a zebra to sellable size (1.5 in. TL). The paper did not specify TL or SL (unless I missed it/). A 1.5 inch TL zebra would be about 1/4 inch smaller than a 1.5 inch SL.

How much food does 1 zebra need for this? All of the other costs to raise that zebra: labor, electricity, water, space to house etc. will relatively be much more of the cost than the food. In light of what a zebra sells for, food cost control means, don't let it spoil.

Finally, the researchers were working mostly with sub-adults in the 2 inch range +/- .25 inch. My bet is a zebra aquaculture operation would be moving them out the door at more like 1.5 inches.