| Author: | Zhong, Dan |
| Title: | A study on the relationships between water quality, production and food conversion ratio on channel catfish : Ictalurus punctatus |
| Degree: | M.Sc. |
| Year: | 2009 |
| Subject: | Hong Kong Polytechnic University -- Dissertations. Channel catfish -- Ecology. Channel catfish -- Effect of water quality on. Channel catfish -- Productivity. |
| Department: | Department of Civil and Structural Engineering |
| Pages: | x, 89, xi leaves : ill. (some col.) ; 30 cm. |
| Language: | English |
| Abstract: | This study was aimed at evaluating interactions between production, stocking density, food conversion ratio, and water quality on channel catfish (Ictalurus punctatus) . There has been little research about multiple-batch production method to define these interactions. A multiple-batch system involves multiple sizes and year classes of fish. Most farmers use a multiple batch production system where ponds contain both newly stocked fingerlings and carryover fish from the last production year. The channel catfish were stocked at four densities: 56, 117, 180 and 234 fingerlings/pond, along with 16.8 kg/pond of carryover fish, which ranged from 0.35-0.43 kg/fish. There were twelve ponds (6mx10m), with the depth of 1.2m, rectangular with silt of 15cm. Every treatment had three replications. Fish were fed daily satiation with a 36% floating commercial catfish feed. These fish were harvested after a 210d culture period. Water quality parameters were measured, including Nitrite-N, nitrate-N, chlorophyll a, total ammonia nitrogen, total nitrogen, total phosphorus, pH, total alkalinity, Secchi disk visibility and chemical oxygen demand. Growth rate and yield of each of the densities were also compared. ANOVA models applied to investigate these effects and interactions. The fish in this article were classified into fmgerling (<0.95kg), carryover (>0.95kg ), marketable (>0.5kg ), sub-marketable (<0.5kg ). Gross, net and net daily yields indicated some differences at four stocking densities. At the density of 234 fingerlings/pond, it had the lowest average weight gain of individual fish as compared with the other densities. The reason was water deterioration. Fingerlings mean survival rate was from 25% to 36%, whereas carryover survival rate was from 88% to 95%. The lowest survival rate and Secchi disk visibility occurred at the density of 234 fingerlings /pond. The highest value of TN, TP, chlorophyll a and chemical oxygen demand also occurred in this pond. This study found the individual fish growth was correlated with water quality. This study also suggests that managing water quality parameters and stocking density is the most important factor to overall production efficiency. The net yield was strongly correlated with mean daily feeding rate(r=0.96). Total ammonia nitrogen was moderately correlate with mean daily feeding rate (r=0.62). The FCR at 234 fingerlings/pond was 2, compared with other densities of 1.69, 1.65 and 1.60, respectively. As water quality index increased; the value of food conversion ratio also increased, but growth rate, survival rate, and individual mean weight at harvest all decreased. |
| Rights: | All rights reserved |
| Access: | restricted access |
Files in This Item:
| File | Description | Size | Format | |
|---|---|---|---|---|
| b23297591.pdf | For All Users (off-campus access for PolyU Staff & Students only) | 5 MB | Adobe PDF | View/Open |
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