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Optimization of the larviculture of the tropical fish cobia Rachycentron canadum in Vietnam

Van Can Nhu (UGent)
(2009)
Author
Promoter
(UGent) , Mai Thien Tran and Thanh Lu Le
Organization
Abstract
Cobia is a potential fish species for marine aquaculture due to its rapid growth and succulent flesh. However, shortage of high quality fingerlings remains a bottle neck for further propagation of the species. This PhD thesis aimed to study the effects of feeds, feeding frequency and rearing density on the performance of cobia larvae and early juveniles, with focus on the co-feeding and weaning stage. During weaning, growth and survival of cobia juveniles were affected by the rearing density, but not by the feeding frequency. A commercial dry feed (NRD®, INVE Aquaculture SA) showed its advantages in comparison with the use of the home-made moist diet or minced trash fish in terms of growth and survival improvement. The study results also revealed the acceptance of the dry diet of cobia juveniles during weaning stage. Cobia larvae grow very fast and they may need high amounts of nutrition from the onset of exogenous feeding onwards. Use of umbrella-stage of Artemia franciscana (UAF) revealed that cobia larvae are able to ingest and digest UAF since the first feeding. Replacing enriched rotifers by UAF as starter food for cobia larvae had very little effect on larval growth by 8 dph and appeared to have no significant negative effect on larval quality, growth or survival by 18 dph. In order to balance and improve the nutritional condition of the larvae, early co-feeding of Proton® from 8 dph was conducted and resulted in better growth. The use of the experimental diet with a higher n-3HUFA content and DHA/EPA ratio, compared to Proton® or NRD®, significantly improved growth and survival of cobia at the stage of 20-38 dph, but was not appropriate for early co-feeding at the stage 8-23 dph. Cobia larvae retain DHA rather than other fatty acids in their body: the content of DHA and other fatty acids in the larval tissues decreased according to their age (0-12 dph), but the DHA/EPA ratio increased. Higher levels of dietary DHA and DHA/EPA ratios resulted in a better growth and survival of cobia juveniles (12-30 dph). Levels of DHA and DHA/EPA ratio in the juvenile tissues and in the diets could not be correlated, but the best survival in the transportation test was recorded in the treatments fed high dietary DHA content and DHA/EA ratio. In conclusion, our study revealed that cobia larvae are able to ingest and digest UAF from first feeding onwards. Growth, survival and quality of cobia juveniles can be improved by manipulation of early co-feeding of formulated diets, appropriate rearing density and feeding frequency as well as appropriate dietary DHA and DHA/EPA ratio. More researches for further improvement of UAF and formulation of the appropriate weaning diets were suggested.
Keywords
larviculture, Vietnam, Cobia, Rachycentron canadum

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Citation

Please use this url to cite or link to this publication:

Chicago
Nhu, Van Can. 2009. “Optimization of the Larviculture of the Tropical Fish Cobia Rachycentron Canadum in Vietnam”. Ghent, Belgium: Ghent University. Faculty of Bioscience Engineering.
APA
Nhu, V. C. (2009). Optimization of the larviculture of the tropical fish cobia Rachycentron canadum in Vietnam. Ghent University. Faculty of Bioscience Engineering, Ghent, Belgium.
Vancouver
1.
Nhu VC. Optimization of the larviculture of the tropical fish cobia Rachycentron canadum in Vietnam. [Ghent, Belgium]: Ghent University. Faculty of Bioscience Engineering; 2009.
MLA
Nhu, Van Can. “Optimization of the Larviculture of the Tropical Fish Cobia Rachycentron Canadum in Vietnam.” 2009 : n. pag. Print.
@phdthesis{2060878,
  abstract     = {Cobia is a potential fish species for marine aquaculture due to its rapid growth and succulent flesh. However, shortage of high quality fingerlings remains a bottle neck for further propagation of the species. This PhD thesis aimed to study the effects of feeds, feeding frequency and rearing density on the performance of cobia larvae and early juveniles, with focus on the co-feeding and weaning stage. During weaning, growth and survival of cobia juveniles were affected by the rearing density, but not by the feeding frequency. A commercial dry feed (NRD{\textregistered}, INVE Aquaculture SA) showed its advantages in comparison with the use of the home-made moist diet or minced trash fish in terms of growth and survival improvement. The study results also revealed the acceptance of the dry diet of cobia juveniles during weaning stage. Cobia larvae grow very fast and they may need high amounts of nutrition from the onset of exogenous feeding onwards. Use of umbrella-stage of Artemia franciscana (UAF) revealed that cobia larvae are able to ingest and digest UAF since the first feeding. Replacing enriched rotifers by UAF as starter food for cobia larvae had very little effect on larval growth by 8 dph and appeared to have no significant negative effect on larval quality, growth or survival by 18 dph. In order to balance and improve the nutritional condition of the larvae, early co-feeding of Proton{\textregistered} from 8 dph was conducted and resulted in better growth. The use of the experimental diet with a higher n-3HUFA content and DHA/EPA ratio, compared to Proton{\textregistered} or NRD{\textregistered}, significantly improved growth and survival of cobia at the stage of 20-38 dph, but was not appropriate for early co-feeding at the stage 8-23 dph. Cobia larvae retain DHA rather than other fatty acids in their body: the content of DHA and other fatty acids in the larval tissues decreased according to their age (0-12 dph), but the DHA/EPA ratio increased. Higher levels of dietary DHA and DHA/EPA ratios resulted in a better growth and survival of cobia juveniles (12-30 dph). Levels of DHA and DHA/EPA ratio in the juvenile tissues and in the diets could not be correlated, but the best survival in the transportation test was recorded in the treatments fed high dietary DHA content and DHA/EA ratio. In conclusion, our study revealed that cobia larvae are able to ingest and digest UAF from first feeding onwards. Growth, survival and quality of cobia juveniles can be improved by manipulation of early co-feeding of formulated diets, appropriate rearing density and feeding frequency as well as appropriate dietary DHA and DHA/EPA ratio. More researches for further improvement of UAF and formulation of the appropriate weaning diets were suggested.},
  author       = {Nhu, Van Can},
  isbn         = {9789059893412},
  keyword      = {larviculture,Vietnam,Cobia,Rachycentron canadum},
  language     = {eng},
  pages        = {VIII, 200},
  publisher    = {Ghent University. Faculty of Bioscience Engineering},
  school       = {Ghent University},
  title        = {Optimization of the larviculture of the tropical fish cobia Rachycentron canadum in Vietnam},
  year         = {2009},
}