Factors influencing the growth rates of three commercial eucheumoids at coastal sites in Southern Kenya

As a possible means of improving the livelihoods of local villagers, off-bottom rope cultivation of commercial eucheumoids was investigated on the southern Kenyan coast at three sites, representative of the variety of environments. The morphotypes used were brown Eucheuma denticulatum and green and brown Kappaphycus alvarezii. The study was carried out over a 15 month period from August 2001 until October 2002. Relative growth rates were highest at a sandy flat in a mangrove system (Gazi; 5.6% d(-1)), and lowest in an intertidal reef flat (Kibuyuni; 3.2% d(-1)) with a lagoon being intermediate (Mkwiro; 4.8% d(-1)). The brown E. denticulatum had the highest growth rate of 4.7% d(-1) compared to the green and brown K. alvarezii which were 4.3% d(-1) and 4.2% d(-1), respectively. Growth was more variable at Kibuyuni and Mkwiro. The growth was higher during the southeast monsoon (4.7% d(-1)) than during the northeast monsoon (4.0% d(-1)). This is part of a larger study and the effects of water motion, salinity, temperature, thallus nitrogen, and 'ice-ice' syndrome on growth of morphotypes is discussed. The water motion was observed to increase thallus nitrogen and hence the growth of eucheumoids. The 'ice-ice' condition affected both brown E. denticulatum and brown K. alvarezii but not green K. alvarezii. The results suggest that commercial cultivation of eucheumoids in Kenya will be feasible.