This study investigated the size, diversity, dominance
and trophic structures of the exploited inshore fish community of the
Sinazongwe area, Lake Kariba, Zambia, for the period 1980-1995. It was based
on fish records of scientific gillnet surveys and on data available in the
literature. The size and diversity spectra exhibited, like those of
exploited demersal marine fish communities, regular decreasing patterns,
indicative of high fish numbers and diversity in smaller sizes and vice
versa among larger sizes. The size spectra patterns were recurrent from year
to year and well fitted by quadratic functions. The diversity (Shannon
index) and dominance (J' index) decreased and increased linearly,
respectively, with fish length. Diversity for larger lengths has decreased
as evidenced by the annual variations of diversity spectra's slopes. The
abundance-biomass comparison plots indicated years of undisturbed, strongly
and moderately stressed fish community. The proportions of predators,
especially of Hydrocynus vittatus, and the mean trophic level decreased linearly over years.
The average diversity trophic spectra remained unchanged. The mean abundance
and biomass trophic spectra indicated a top-predator controlled community
over 1980-1984, and vice versa thereafter. The trophic structure descriptors
better captured the fish community changes under increasing fishing pressure
and revealed for the first time the “fishing down marine food webs”
effects for Lake Kariba. The community attributes studied are potentially
promising alternatives for the assessment and management of tropical
exploited freshwater fish communities.