Distribution and abundance of two dipteran aquatic larvae in Northern Lake Victoria

Initial findings on the distribution and abundance of two dipteran larvae in an ecologically and environmentally changed northern Lake Victoria are presented Results suggest that density of Chironomid larvae seem to have gone up about four-fold since the pre-perch era and t hat of chaoborid larvae maintained at more or less the same level. Possible reasons for this increase are proposed. Inshore stations held higher densities of larvae when compared with the offshore station of Bugaia

Bagrus studies

The study covered aspects of the tagging programme and the biology of Bagrus docmac. During the course of the year the base of operations was transferred from Kisumu to Jinja due to practical considerations for this study. Following the collapse of the East African Community at the end of June study materials were collected only from the Uganda waters of l. Victoria. Future collection of data from the nonUganda part of the lake would be considered after consllttations and clarification with the relevant authoritie

Caridina nilotica in Lake Victoria: abundance, biomass, and diel vertical migration

Caridina nilotica (Decapoda: Atyidae) in offshore waters of Lake Victoria were investigated with both day and night sampling over a period of two years. Offshore populations are mainly planktonic rather than benthic, and the animals exhibit diel vertical migrations into near-surface waters at night. These changes in diel abundance as well as the size-frequency distribution of the migrating shrimp suggest that the migratory behavior is in response to visual planktivory, because only the very smallest individuals (2–4 mm) remain in surface waters during the day. During October 1992, abundances were estimated both by vertical net sampling and by underwater video transect methods. Concordance was established between abundances estimated by the two methods. Only about 9% (night) to 14% (day) of the Caridina population appeared to be epibenthic. We suggest that the behavior of the animal is consistent with the hypothesis that it is not a strict detritivore as previously reported; rather it may engage in facultative planktivory, especially at night.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/42890/1/10750_2004_Article_BF00036467.pd

Secondary production and energetics of the shrimp Caridina nilotica in Lake Victoria, East Africa: model development and application

Measurements of body mass, carbon content, respiration, growth, and egestion are combined in a model of secondary production by the tropical freshwater shrimp Caridina . The model is developed to permit its direct application to empirical data for abundances and size frequency distributions of field populations. Model calculations combined with population data for offshore Lake Victoria over a period of two years indicate that Caridina consume the equivalent of 2.2% of annual lake primary production. Present net annual secondary production by the shrimp is an order of magnitude greater than the present fishery yield of the lake. Detritus-fed experimental organisms evidently had assimilation efficiencies as low as 10% by model calculation.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/42892/1/10750_2004_Article_BF00031923.pd