Effect of Feeding Frequencies on Growth and Profit of Asian Seabass (Lates calcarifer) in Cage Culture Systems

Cage culture is one of the most advanced aquaculture production systems where fishes are held in floating enclosures like net cages, moored in the open water systems, and allow free water flow. The open water cages developed by Central Marine Fisheries Research Institute (CMFRI) during the last decade are becoming very popular in coastal waters. One of the major problems faced by farmers at all stages of culture is fish feed and feeding. A suitable feeding strategy is important to improve fish growth and reduce feed costs and environmental pollution. The study was conducted to investigate the effect of feeding frequency from sea bass cultured in cages on water quality, growth parameters, survival rate, economic return and bottom characters in Moothakunnam (N10011.478’ E076011.901’+ 4m) in Ernakulam district. Water and sediment samples and growth parameters were collected and analyzed monthly from inside and outside of the cages for a period of one year. Significant differences were found in growth parameters like weight gain (1.04±0.03-1.78±0.008), Specific growth rate (1.2±0.03-1.48±0.005), Survival rate (40%-61.53%) and FCR (4.3-4.56). The water quality parameters DO, Nitrate, Nitrite, Ammonia and Orthophosphate in the cage and reference sites did not show many significant variations indicating a healthy growth condition in the cages. Therefore it could be concluded that the growth performance of sea bass is increasing by feeding frequency, but the economic analysis indicated that net profit is negatively related to feeding frequency

Studies on the diversity and impact of macro biofouling organisms in brackish water finfish cage

Biofouling refers to accumulation of organisms on submerged surfaces. In case of open water cage culture, fouling organisms attached to cage nets block water flow and reduces waste removal resulting in increased stress levels on stocked fishes and reduces the rate of intake of feed and growth. It also increases weight of the nets leading to its damage. The quantity and diversity of biofouling organisms and their effects on the growth and survival of stocked fishes were studied

Impact of the invasive mussel, Mytella strigata (hanley, 1843) on fisheries and farming

Rapid surveys were conducted during periods from May to August 2020 in estuaries along Central Kerala (Chettuva, Vembanad, Ashtamudi estuaries),South Kerala(Kayamkulam Lake, Poovar lake, Anchuthengu Lake, Kadinamkulam Lake) and North Kerala(Kavai backwaters, Kallai estuary, Puthiappa fishing harbour, Kadalundi estuary) to assess the extent of invasion of the species, the influence of physico-chemical parameters on its abundance, the impact of bioinvasion of this species on economically important native fauna and aquaculture activities. Settlement density of M. strigata in Chettuva Estuary, Vembanad Lake and Ashtamudi Lake was estimated as 32-12,400 nos/sq.m. Physical and chemical parameters of water and sediment characteristics were also analysed. M. strigata was found to be highly euryhaline and adaptive to anoxic conditions. In all three estuaries of Central Kerala, there was spat settlement of the species on bottom, cage ropes, cages nets etc. In Chettuva estuary, P. viridis and M. strigata population in the fishing ground necessitated additional 3 h/fishing day/boat/person for segregating P. viridis from M. strigata. As per the fishermen’s perception, the fouling on cages increased the frequency of net exchange, interferes with harvesting activities and mortality of fish in cages . In Vembanad Lake, there was heavy infestation of the species on oyster rens suspended in oyster farms. There was a reduction in edible oyster spat settlement by 38% in oyster farms. More than 60% of the M. strigata settlement was observed on shells near the surface of the oyster rens. The potential threat of the species to bivalve farming, bivalve fisheries and finfish cage farming demands the formulation of management strategies for preventing the establishment of this non-native species that may cause ecological and economic havoc

Comparative study on pre-treatment methods for enhanced saccharification from tropical seaweeds to aid in bioethanol production

The selection of suitable pretreatment strategy that facilitates saccharification is the most critical step in the valorisation of seaweed biomass into bioethanol. Considering the scarcity of data on the comparative efficacy of different pretreatments particularly in tropical seaweed species, 50 pretreatment strategies were analysed on three major species representing all the three broad seaweed categories, viz. Ulva fasciata (green algae), Sargassum wightii (brown algae), and Gracilaria corticata (red algae). An improved release of reducing sugars was observed in all the tested pretreatments, with different conversion ratios for different species in each pretreatment. Ultrasonication and magnetic stirring showed maximum yield among physical pretreatments. In thermal methods, microwave oven incubation resulted in maximum yield from both U. fasciata and S. wightii, while it was autoclaving for G. corticata. Sulphuric acid was the best chemical for U. fasciata and G. corticata, while it was orthophosphoric acid for S. wightii. Hydrochloric acid was the best chemical for physicothermochemical pretreatment in all species. Maximum conversion ratios of 2.58, 2.11, and 2.0 were recorded in U. fasciata, G. corticata, and S. wightii respectively. In short, the paper sketches the best pretreatment method for three major tropical seaweeds along with their proximate composition. The results can be applied for aiding the valorisation of biomass of these seaweeds through a cost-effective manner