Catfish fry grow better in total darkness

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bekateen
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Catfish fry grow better in total darkness

Post by bekateen »

Alsaqufi, A. S., Rahman, S. M., Mathew, R. T., Alkhamis, Y. A., Rahman, M. M., & Pathiri, M. A. (2021). Influence of Photoperiod and Shelter on Some Phenotypic Traits in African Catfish (Clarias gariepinus Burchell 1822) Larvae. Pakistan J. Zool., pp 1-15, 2021.

DOI: https://dx.doi.org/10.17582/journal.pjz/20200507220534
Abstract
Photoperiod and shelter have direct or indirect effects on phenotypic traits expression in different fish species. The present study was, therefore, intended to explore whether these light and shelter could influence some phenotypic traits of African catfish larvae under laboratory condition. Newly hatched larvae were stocked in plastic aquaria (10L) at a rate of 5 individuals/L and reared for one month under four treatments such as 24h light (24L), 24 h dark (24D), 12h light and 12h dark with PVC (12DL_PVC), and 12h light and 12h dark without PVC (12DL) conditions. A total of 108 larvae were sampled for phenotypic traits analysis. The results revealed that complete darkness (24D) significantly improved the overall growth parameters (total length, standard length, caudal peduncle length, anal fin length, caudal fin length, total body depth, dorsal fin length, pre dorsal distance, pre anal distance, pre ventral distance, head width, head length, eye diameter, maxillary barbell length, inter orbital length, and specific growth rate) than all other treatments, while no significant variation was found among other treatments. Although shelter did not show any significant role in the overall growth, it significantly reduced the larval mortality than those reared without shelter. The survival rates were also significantly different among various light regimes in which the highest was found in 24D (86%) followed by 12DL_PVC (74%), 24L (71%), and 12DL (60%). The study also revealed that larvae reared in 24D exhibited maximum dark brown body colouration (63%), while in 24L showed maximum light brown colouration (96%). On the other hand, maximum larvae were appeared as medium brown color (76%) in tanks having PVC, whereas many of them were light brown (61%) in non-PVC tanks. Taken together, the study suggests that C. gariepinus larvae should be reared in completely dark condition to enhance their overall production.
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Re: Catfish fry grow better in total darkness

Post by dw1305 »

Hi all,
....... Although shelter did not show any significant role in the overall growth, it significantly reduced the larval mortality than those reared without shelter......
My take home from that is the shelter aspect, rather than the darkness.

cheers Darrel
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Re: Catfish fry grow better in total darkness

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Indeed. Darkness is just one big shelter but not the best one? I do remember commercial pleco breeders talking about spawning species and rearing them in darkness - but those had plenty of shelter too.

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Re: Catfish fry grow better in total darkness

Post by dw1305 »

Hi all,
Jools wrote: Sun Nov 29, 2020 11:46 amIndeed. Darkness is just one big shelter but not the best one? I do remember commercial pleco breeders talking about spawning species and rearing them in darkness - but those had plenty of shelter too.
My guess would be that for, non aufwuchs eating, plecs darkness probably is optimal. I think the only provisos are that they would still do better with some cover and you would need a mechanisms to maintain high water quality.

In terms of maintenance of water quality I prefer plant/microbe biofiltration, but if you had a sumped system you could place the plants in the sump.

I'm going to take both water changes and high levels of dissolved oxygen as a given in any set-up.

cheers Darrel
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Re: Catfish fry grow better in total darkness

Post by Shane »

Nocturnal fish spp. fry will eat more and grow faster in the dark. Diurnal spp. fry can be growth "boosted" the same way by leaving the lights on 24 hours a day. Not to knock the study (good paper), but aquaculture studies have looked at this in the past.
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Re: Catfish fry grow better in total darkness

Post by bekateen »

Shane wrote: Sun Nov 29, 2020 10:19 pmNot to knock the study (good paper), but aquaculture studies have looked at this in the past.
Agreed, there's no need to insult people who are learning something new to them, even if it's not new to others, but I felt the same as you here - this didn't seem to be an epiphany moment. That said, while it might be stating what was obvious to experienced keepers and breeders, I did appreciate their efforts to document/quantify the differential effect.

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