Introduction.
The fresh water prawns of the genus Macrobrachium comprises 243 globally¹ but in Kenya it comprises of M. rude, M. dolichodactylus, M. equidens,,M. lepidactylus and M. niloticus species. The macrobrachium species is well known for its ecological role and for human consumption. However, there is limited information on their natural diet and feeding habits in Kenya limiting the aquaculture potential of some of these prawns.
Materials and methods .
Field sampling of prawns data was carried out in 7 selected sites along mid and downstream coastal estuaries/deltas of rivers Tana, Athi, Ramisi, Umba and Mkurumuji in both midstream and during the wet season/long rains (March-May 2021) and dry season (June-September 2021) in Kenya. Laboratory Microscopic work on stomach content analysis was carried out at both Kenya Marine Fisheries and Research Institute laboratory at Gazi-Bay station and National Museums of Kenya and stomach content data was analyzed using the percent frequency of occurrence of food items., using IBM SPSS 20software.
Results
A total of 343 specimen samples consisting of M. rude(220; 64.4%), M. lepidactylus (77; 21.9%) and M. dolichodactylus (46; 13.7%) per different sexes and size groups ranging from 20 to 231mm were analyzed. 80 different types of food items were identified. In terms of stomach fullness index, 70.2% of M. rude recorded &fraq14; full index while 29.4% of M. dolichodactylus and 33.3% of M.lepidactylus recorded full stomach indexes.The resultsrevealed significant differences in frequency occurrence of food items between different Macrobrachium species, sites, seasons, size lengths, sexes and stomach fullness index (P<0.05). The most dominant food items were sand particles (16%), unidentified plant materials (9.5%), animal materials (6.8%) and microplastics (4.3%) Figure 2). Combined algal species food items were the most frequent e,g. Ankistrodesmus sp (6%).
Discussions and Conclusions
The results of this study suggest that the three Macrobrachium spp are omnivorous in nature with a preference of algal species. This euryphagous feeding habit is important in the culture of these species. The presence of microplastics in the diet of most prawns suggest the dangers paused by these materials to both prawns health and human beings consuming them that need to be controlled. The nutritional information generated from this study on the prawns diet will allow formulating recommendations for artificial feeding of Macrobrachium spp. for the mass production in aquaculture to secure sustainable fishing and the success of aquaculture initiatives.