The Biology and Culture of Tilapias

together a definitive monograph on the tilapias. I see her herculean efforts at
first hand-I share her habitat among the tilapia bottles at the Natural
History Museum in London-and I have seen (and have benefited from) the
ever-ready help she has given so unstintingly to numerous biologists from all
over the world.
Second, we have the contribution on ecology and distribution prepared
by Dr. J-C1. Philippart with Professor J-C1. Ruwet, who is unable to attend
this meeting. They have selected certain areas of ecology, believing that
aspects such as growth and production would be treated in other papers.
They have considered the physicochemical factors involved in tilapia distri-
bution; feeding behavior, e.g., trophic spectra, variations in feeding regimes
and the periodicity of feeding activity (subjects which lead onto our later
discussions on physiological aspects of feeding); reproductive behavior,
comments on practical implications and the choice of microhabitats and
spatial segregation. They have then assessed the ecological consequences of
introductions and transfers of tilapias in Africa and elsewhere.
Dr. D.L.G. Noakes then presents a paper that he and Dr. E. Won, who
is also unable to be here, have prepared on life histories of tilapias. This
seems to be a rather theoretical paper but it leads up to a practical suggestion
of culture methods which might help to produce the large fish with late
onset of breeding and fast growth rates that we all desire.
Lastly, the paper which I was asked to prepare on tilapias in fish com-
munities was originally aimed to look at the partitioning of resources among
sympatric tilapias and at some of the factors controlling tilapia numbers in
nature (with special attention to the switch from growth to reproduction in
Sarotherodon niloticus). It became clear, however, that much of what I had
written had considerable overlap with other manuscripts, so I have attempted,
at very short notice, to fill in some gaps by collating information on tilapia
growth rates, production and yields under natural conditions.