Effects of cultivation methods and types of Seabed on the growth of Kappaphycus striatus (F.Shmitz) Doty Ex P.C. Silva during the northeast monsoon season and its application as fish feed additive and binder

Kappaphycus striatus is one of the commonly cultivated red seaweed species in Malaysia. It contains high levels of kappa and iota carrageenan that are used in various industries such as food processing, agriculture, pharmaceutical and aquaculture. In the present study, K. striatus was cultivated using two methods namely the floating line and the fixed, off-bottom methods for 21 days. The results showed that there were no significant difference in terms of K. striatus growth performance. However, the daily growth rate (DGR) was higher when K. striatus was cultivated using the floating line method. Therefore, it was selected as the method used in the subsequent experiment where K. striatus was cultivated in three different seabeds which are the coral, sandy and seagrass seabeds from the intermonsoon to the Northeast monsoon season (September – April). It was found that K. striatus growth performance were significantly higher when cultivated in the coral and sandy seabeds with a DGR were 3.1 ± 0.26 % day-1 and 2.9 ± 0.45 % day-1 respectively. Meanwhile, K. striatus had a significantly higher growth performance from September to October with final wet biomass of 95.8 ± 5.21 % and DGR of 3.2 ± 0.10 % day-1. Their growth performance began to deteriorate in November to December recording a final wet biomass of and continued throughout January and February characterised by heavy rain, strong winds and waves which are not suitable for cultivation of K. striatus. There was an improvement in K. striatus growth performance in March to April but still unsatisfactory. All the K. striatus were harvested and dried before being processed into powder form to be incorporated in a fish feed formulation at 2 %, 4 %, 6 %, 8 % and 10 %. K. striatus performance as a binder was tested using the water stability test where the results showed that there were no significant difference in water stability for all the feed tested. Nonetheless, K. striatus inclusion at 4 % was the most stable at 60 minutes (74.1 ± 0.54 %). The Bicinchoninic acid (BCA) protein assay was carried out to test the ability of K. striatus as a feed additive. It was found that water soluble protein (WSP) levels increased with the increasing levels of K. striatus inclusion. However, there were no significant difference between the WSP content from 4 % to 10 % of K. striatus inclusion. In conclusion, the growth performance of K. striatus can be improved when using the floating long line method in the sandy seabed but not during the Northeast monsoon season. In addition, K. striatus can be included as a binder and feed additive at 4 % in fish feed.