Peri-urban fish farms with limited access to open natural water bodies draw fresh water from urban water supply and dug wells,which is unreliable and costly.Reuse of fish pond effluent is also limited by high ammonia ...Peri-urban fish farms with limited access to open natural water bodies draw fresh water from urban water supply and dug wells,which is unreliable and costly.Reuse of fish pond effluent is also limited by high ammonia concentration(>0.3 mg/L)that renders water toxic and is stressful to fish.Despite the existence of several fish effluent treatment methods,not all may be appropriate for a particular location.This review article therefore examines the various fish effluent treatment methods to aid selection of the most suitable one(s)for peri-urban areas.The key parameters considered in their comparison were:initial,operational and maintenance costs;ammonia removal efficiency;energy consumption and land requirement.The effluent treatment methods are both conventional and non-conventional.Despite a slight higher treatment efficiency and less space requirement by conventional methods,they mainly require reliable power supply for continuous running,highly skilled labor for operation and maintenance leading to high operational costs.In addition,their investment costs are higher than non-conventional methods,hence not widely applied in developing countries and majority have broken down.On the other hand,non-conventional methods such as constructed wetlands are widely in use for treating effluent mainly due to their cost effectiveness and no or little energy requirement.Constructed wetlands were found most suitable bio-filtration system for treating fish effluent because they are cost effective,require less skilled labor and still have better effluent treatment though space required is slightly more.Vegetables(lettuce,collards,etc.)have potential to grow in constructed wetlands thus form vegetable-based bio-filtration units which serve not only as bio-filters but also provide additional sources of nutrition and income.This review indicated limited information on the appropriate size and performance of vegetable-based bio-filtration unit utilizing indigenous vegetables and recommended further research to explore the idea.展开更多
Vertically-suspended environmental enrichment has been shown to produce improvements in fish growth during hatchery rearing in circular tanks. This study documented the effects of a novel suspended structure on the ve...Vertically-suspended environmental enrichment has been shown to produce improvements in fish growth during hatchery rearing in circular tanks. This study documented the effects of a novel suspended structure on the velocity profile of a 3.63-m diameter circular tank containing juvenile landlocked fall Chinook salmon (<em>Oncorhynchus tshawytscha</em>) at two different densities (9.0 and 34.3 kg/m<sup>3</sup>). The addition of vertically-suspended structure to the tank significantly decreased velocities at nearly every sampling point, with velocities typically dropping from 15 cm/s without structure to less than 6 cm/s when structure was present. Fish density also significantly impacted in-tank velocities, with an inverse relationship observed between the density of fish and water velocity. Significant interactions were present among the presence or absence of structure and fish density. When structure and fish were absent, the velocity at the edge of the tank was 15.63 cm/s, which was significantly higher than the 4.75 cm/s velocity when both structure and the lower fish density were added, which was in turn significantly higher than the 2.29 cm/s velocity observed with structure and higher fish density. Despite the potentially unique features of this study, vertically-suspended environmental enrichment and the presence of fish clearly alter circular tank water velocities, which may at least partially explain the improvements in fish rearing performance observed with the use of suspended structure.展开更多
Occupational noise is commonly encountered during aquaculture. This study documented noise levels in two buildings at a production fish hatchery, a tank room with 32, 1.8-m diameter tanks, and a rearing pavilion with ...Occupational noise is commonly encountered during aquaculture. This study documented noise levels in two buildings at a production fish hatchery, a tank room with 32, 1.8-m diameter tanks, and a rearing pavilion with 32, 6.1-m diameter tanks. With water flowing to all of the tanks in the tank room, mean noise levels were 68.4 dB, and significantly increased to 73.0 dB during tank cleaning and 73.2 dB when intermittent automatic feeders were running. The highest tank room values of 77.1 dB were recorded directly next to individual tanks during cleaning. With water flowing to all of the tanks in the rearing pavilion, mean noise levels were 70.2 dB. A significant increase to 76.1 dB was observed when the pavilion tanks were being power washed, with the highest value of 83.2 dB recorded immediately adjacent to the power washer. Although none of the noise levels exceeded regulatory limits, the use of techniques to reduce occupational noise in aquaculture environments is recommended.展开更多
文摘Peri-urban fish farms with limited access to open natural water bodies draw fresh water from urban water supply and dug wells,which is unreliable and costly.Reuse of fish pond effluent is also limited by high ammonia concentration(>0.3 mg/L)that renders water toxic and is stressful to fish.Despite the existence of several fish effluent treatment methods,not all may be appropriate for a particular location.This review article therefore examines the various fish effluent treatment methods to aid selection of the most suitable one(s)for peri-urban areas.The key parameters considered in their comparison were:initial,operational and maintenance costs;ammonia removal efficiency;energy consumption and land requirement.The effluent treatment methods are both conventional and non-conventional.Despite a slight higher treatment efficiency and less space requirement by conventional methods,they mainly require reliable power supply for continuous running,highly skilled labor for operation and maintenance leading to high operational costs.In addition,their investment costs are higher than non-conventional methods,hence not widely applied in developing countries and majority have broken down.On the other hand,non-conventional methods such as constructed wetlands are widely in use for treating effluent mainly due to their cost effectiveness and no or little energy requirement.Constructed wetlands were found most suitable bio-filtration system for treating fish effluent because they are cost effective,require less skilled labor and still have better effluent treatment though space required is slightly more.Vegetables(lettuce,collards,etc.)have potential to grow in constructed wetlands thus form vegetable-based bio-filtration units which serve not only as bio-filters but also provide additional sources of nutrition and income.This review indicated limited information on the appropriate size and performance of vegetable-based bio-filtration unit utilizing indigenous vegetables and recommended further research to explore the idea.
文摘Vertically-suspended environmental enrichment has been shown to produce improvements in fish growth during hatchery rearing in circular tanks. This study documented the effects of a novel suspended structure on the velocity profile of a 3.63-m diameter circular tank containing juvenile landlocked fall Chinook salmon (<em>Oncorhynchus tshawytscha</em>) at two different densities (9.0 and 34.3 kg/m<sup>3</sup>). The addition of vertically-suspended structure to the tank significantly decreased velocities at nearly every sampling point, with velocities typically dropping from 15 cm/s without structure to less than 6 cm/s when structure was present. Fish density also significantly impacted in-tank velocities, with an inverse relationship observed between the density of fish and water velocity. Significant interactions were present among the presence or absence of structure and fish density. When structure and fish were absent, the velocity at the edge of the tank was 15.63 cm/s, which was significantly higher than the 4.75 cm/s velocity when both structure and the lower fish density were added, which was in turn significantly higher than the 2.29 cm/s velocity observed with structure and higher fish density. Despite the potentially unique features of this study, vertically-suspended environmental enrichment and the presence of fish clearly alter circular tank water velocities, which may at least partially explain the improvements in fish rearing performance observed with the use of suspended structure.
文摘Occupational noise is commonly encountered during aquaculture. This study documented noise levels in two buildings at a production fish hatchery, a tank room with 32, 1.8-m diameter tanks, and a rearing pavilion with 32, 6.1-m diameter tanks. With water flowing to all of the tanks in the tank room, mean noise levels were 68.4 dB, and significantly increased to 73.0 dB during tank cleaning and 73.2 dB when intermittent automatic feeders were running. The highest tank room values of 77.1 dB were recorded directly next to individual tanks during cleaning. With water flowing to all of the tanks in the rearing pavilion, mean noise levels were 70.2 dB. A significant increase to 76.1 dB was observed when the pavilion tanks were being power washed, with the highest value of 83.2 dB recorded immediately adjacent to the power washer. Although none of the noise levels exceeded regulatory limits, the use of techniques to reduce occupational noise in aquaculture environments is recommended.
