Effect of diatom diets on the growth of juvenile sea cucumber holothuria scabra
Holothuria scabra, also known as sandfish, is a highly valued sea cucumber that is widely farmed in the Indo-Pacific region. However, farmed sandfish seeds were taken from the wild habitat, resulting in population depletion. As a result, production in hatcheries is being established to meet the need...
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| Format: | Thesis |
| Language: | English English |
| Published: |
2022
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| Subjects: | |
| Online Access: | https://eprints.ums.edu.my/id/eprint/40508/1/24%20PAGES.pdf https://eprints.ums.edu.my/id/eprint/40508/2/FULLTEXT.pdf |
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| Summary: | Holothuria scabra, also known as sandfish, is a highly valued sea cucumber that is widely farmed in the Indo-Pacific region. However, farmed sandfish seeds were taken from the wild habitat, resulting in population depletion. As a result, production in hatcheries is being established to meet the needs of aquaculture. While diatoms are widely cultured and used in bivalves and sea cucumber hatcheries. Adequate diet is critical for hatchery production because it has a direct impact on growth and survival. In this study, to achieve the aim of understanding the appropriate diet for sandfish juveniles, Chaetoceros gracilis were cultured using agricultural fertilizer (NPK) and harvested using chitosan through flocculation. Diatom Navicula sp. the microalgal flocs produced were fed to juvenile sandfish to determine the growth performance. In objective 1, the growth of C. gracilis was tested in different types of media consisting of 5 concentrations of fertilizer (NPK 10:8:6) and Walne’s Media as the control. Final cell densities (cells/mL), specific growth rate (cell/d), doubling time, and division rate (div/day) was determined. The findings revealed that liquid fertilizer at 0.5 mL/L has the highest final cell counts and relatively high specific growth rate (7.428±0.05 106 cells/mL and 1.201±0.05 cell/day respectively). For objective 2, determination of flocculation efficiency (%) of C. gracilis harvested using chitosan was done under different pH (7, 8, and 9), salinity (20, 25, 30, and 35 ppt), chitosan concentration (0 – 75 ppm) and cell density (0.5, 2, 4, and 6 cells/mL). Based on the findings, C. gracilis harvested in 20 ppt, pH 9, cell density of 4 x 106 cells/mL with chitosan concentration of 75 ppm showed the highest percentage of flocculation efficiency (89%). In objective 3, the growth performance of juvenile sandfish was determined by first testing the ingestion and digestion of 2 diatom diets (Navicula sp. and C. gracilis flocs) and a 2-week feeding trial of 6 experimental diets consist of combination of C. gracilis flocs and sea mud with different inclusion levels of microalgal flocs (N, CF0, CF10, CF20, CF30, CF100). Navicula sp. (diet N) was a control diet. Ingestion rates were determined by observing the faecal excretion time and cell wall digestion of microalgae was determined by viewing newly excreted faeces under a fluorescent microscope. While, for the feeding trials, approximately 1 cm juvenile sandfish were placed in small plastic containers with a stocking density of 0.01 juveniles/cm2. Initial and final weight was measured to determine the weight gain (%), specific growth rate (%/day), and condition factor (%). The findings showed that both Navicula sp. and C. gracilis were ingested by the juvenile sandfish. However, C. gracilis showed high cell wall digestion while Navicula sp. was observed to be indigestible. The feeding trial of experimental diets showed that juvenile sandfish fed with CF30 had higher weight gain and specific growth rate (59.20±27.25% & 3.25±1.22%/d respectively) followed by CF100 (35.17±10.32% & 1.83±0.83%/d) and CF20 (30.02±5.59% & 1.87±0.31%/d). However, there were no significant differences between diet CF20, CF30, and CF100 in weight gain (.244), specific growth rate (.451), or survival (.339). This study demonstrates the efficiency of chitosan as flocculant for flocculation harvesting of C. gracilis and the viability of using C. gracilis flocs as feed to juvenile sandfish to promote growth and survival. It is also advised to combine sea mud and C. gracilis flocs in a 70:30 ratio for improved growth performance and less diatom biomass required for diet preparation. |
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