Want fry to grow fast with better survival? Use circular or ellipsoid tanks, not square

[bekateen]

Amponsah, S. K., Agodzo, S., Agbeko, E., & Osei, E. A. (2021). Impact of tank geometry on production of African Catfish (Clarias gariepinus). African Journal of Agricultural Research, 17(1), 165-172. https://doi.org/10.5897/AJAR2020.15239

https://academicjournals.org/journal/AJ ... 3FCDE65904
PDF: https://academicjournals.org/journal/AJ ... 3FCDE65904

Abstract

Geometry of fish tanks tends to affect the growth and yield of fish. The impact of tank geometry on the production of

Clarias gariepinus

was evaluated. Circular, rectangular and ellipsoid tanks were used to test the variation of water temperature, pH, dissolved oxygen and total suspended solids on African catfish growth performance. Results on water temperature, pH, DO, were within the acceptable ranges of 24.9-25.9°C, 6.39-7.52 and 5.81-8.32 mg/l, for circular tank; 25.1-26.1˚C, 6.49-7.53 and 3.96-8.53 mg/l, for rectangular tank; and 24.5-26.2°C, 6.49-7.50 and 5.08-8.43 mg/l, for ellipsoid tank; respectively. Weight gain ranged from 14 to 576 g, 13 to 330 g and 14 to 557 g; feed conversion ratio (FCR) ranged from 1.11-1.33, 1.23-1.54 and 1.22-1.34; specific growth rate (SGR) ranged from 0.40 g/day to 3.64 g/day, 0.11 to 2.27 g/day and 0.79 to 3.12 g/day; survival rate were >88, >84 and >92% for circular, rectangular and ellipsoid tanks, respectively. Except for weight gain and FCR, all other parameters (length increment, SGR and survival rate) showed no significant difference (P = .05) among the 3 tank geometries. Benefit cost ratio (BCR) for the circular, ellipsoid and rectangular tank was 1.12, 1.13 and 0.79, respectively.

• Key words: Aquatic system, benefit-cost, ellipsoid tank, growth performance, mudfish.

[Horlack]

very strange result.
I am not convinced of the result. I don't see any logical reason, from an evolutionary point of view (Darwin evolution), why a fish would grow faster in an elliptical aquarium. For me, this result should be taken with great care, there are surely some biases.

Because for example, I know that the elliptical shape of aquariums has a negative impact on the vision of goldfish. But I also know that the more a goldfish exercises, the faster it grows.
So by cumulating these 2, we could have: fish very stressed because of the distortion of the sight, which produced an overactivity. Thus, he did not grow because of an elliptical aquarium, but because of the physical activity caused by stress, or the physical activity to seek twice as much for their food because they could see badly.

For example :
Title: The effect of training on the swimming muscles of the goldfish (Carassius auratus)
Journal of Experimental Biology, 22 Juil. 1978 : Bill Davison - l'University of Canterbury
& Geoffrey Goldspink - University of London
HTML : https://www.researchgate.net/publicatio ... us_auratus
PDF : https://www.researchgate.net/profile/Bi ... 000000.pdf

It is an impact study on swimming training, to estimate muscle growth. On the 3rd page, after 28 days of swimming effort, at 28 ° C, the fish gained up to + 1.4% in length and + 5.8% in weight. Large swimming areas have a positive impact on his growth, provided he can exercise himself physically.

[Bas Pels]

Contrarily to Horlack, I think the results are quite logical.

Clarias is quite an agressive species, and in a rectangular tank, there are corners where fish can be cought. Being cornered like this could raise stress levels and stress prevents growht, amongst others. And around the end of the experiment, the fish of 300, 500 grams will certainly display agressivity.

Holack wrote "I know that the elliptical shape of aquariums has a negative impact on the vision of goldfish." and I think this refers to aquariums made from transparant material, such as glass. It is rather well known many catfish grow better in the dark, and therefore I would expoect the Clarias experiment te be done in tanks made from not trasparant material, which will not have any impact on visibility.

So, basically, I think that it is not correct to compare goldfish with Clarias.

[TwoTankAmin]

The tanks were not glass. However, they did not use the tank design which would have offered the most effective swimming potential. A donut shaped tank. This creates the ability for fish to swim continuously without bumping into any walls.I have seen one of these at a local pet store which does big fish rescues. Whenever I went in there it was to with the fish swimming in that tank. It was cement and filled with big fish swimming in circles. It was mesemerizing to watch.

While I am not trained in biology, chemistry etc. I was a psych major in college. Part of that involved experimental psychology and this stressed experimental design. I am pretty decent at controlled and uncontrolled variables. And I see one big issue with the experimental design. That is the current in the different tanks. Yhey all use similar filtration but the all have different properties as to how current is produced in the different tanks and how that differs. So there is one uncontrolled variable.

I wonder who thinks current and flow has nothing to do with how fish evolve or live. It can effect how easily the find food, how much energy they must expend to swim. Both of these are variables that surely can affect the weight, growth etc. of the fish over time?

The way I would assess the research design is that if failed to eliminate or equalize the variables created by current and flow. This suggests tank shape may not have had anything to do with the results but that something else not controlled for did.

Next, they sampled water every 30 days "Water quality assessment for each tank was carried out every 30
days before 9:00 hours. Parameters monitored included dissolved oxygen (DO), pH, water temperature and total suspended solids (TSS) using the Hanna multi-parameter water quality meter (HI9829)."

This suggest they have no idea of water quality the other 28 days or how that might be affecting things. Moreove,r they speculate that the parameters in the rectangular tanks for lower DO and higher TSS were likely due to a build up of gunk in the corners. Well maybe a different circulation pattern would have prevented that. To paraphrase Yoda, "Back to variables uncontrolled we are."

Also, they did state the tanks were open to the sun. Do we know all the tanks got equal exposure.

So, I look at this paper and I think it cannot make the conclusions it does based on the experimental design. And I can think of even more variables they failed to control. Not all fish grow at identical rates, not all fish do as well on the same mix or types of food. Some fish do not compete as aggressively for food as a way to avoid being beaten up. (This is my unproven theory based on growing out large numbers of bn plecos in tanks that should have been bigger. When the largest fish were sold, the runts began to equalize sizewise. They got more food when the bully sized fish were removed.)

We must also remember this was an aquaculture related experiment. The goal is to make more profit for fish farms. This may have biased the researchers to want to find a way to come up with an explanation despite the lack of controls and thus certainty re the conclusion. I wonder if there is a cost difference in building the 3 types of tanks which might balance out any discrepancies in ultimate fish size and added cost from a more expensive tank?