Turbidity and plant growth in large slow-flowing lowland rivers. Progress Report: March 1989

The River Great Ouse is a highly managed large lowland river in eastern England. It drains rich arable land in the Midlands and Eastern England and over the years nutrient concentrations have increased and there is a general perception that the clarity of the water has decreased. The main river channels have been dredged a number of times partly for flood control reasons but also for recreational boating and navigation activities. The period covered by this first report has been used to develop specific methodology and instrumentation for measuring turbidity, suspended solids and underwater irradiance for conditions found in the middle abd lower reaches of the River Great Ouse. Sampling strategies have been developed and an extensive sampling programme is now underway covering phytoplankton, suspended solids and turbidity in relation to algal epiphyte growth on underwater macrophytes. Preliminary data are presented relating light levels on the river bed to the river bed profile, turbidity levels and phytoplankton chlorophyll a concentrations. Studies are underway concerning the extent of macrophyte cover and periphyton densities.

Back pages of No. 47, 1989

Back cover

Resultados da avaliação dos recursos de carapau e cavala nos bancos de Sofala e Boa Paz no período 1986-1989

Catch evolution, fish yield and specific composition of commercial catches as well as biomass reduction of the main species exploited were analysed and the stock assessments of horse and chub mackerels in the Sofala and Boa-Paz Banks were examined for the period 1986 to the first half of 1989.

Station hydrologique cotière d'Abidjan de 1966 à 1980

In this document the monthly T-S diagrams and the regression lines of the temperature and salinity two weeks mean values have been drawn for 0, 5, 10, 15, 20 and 25 meters of depth. The annual variations of the dynamic height anomaly are represented for every coastal station from 1966 to 1980.

Station hydrologique de Vridi et stations cotières de 1989 à 1991

In this report, accurate data from coastal stations and from the Vridi hydrological station were gathered. The used experiments took place from 1989 to 1991.

La pêche artisanale en lagune Aby (Côte d'Ivoire): analyse des captures en 1988 et 1989

The exploitation of fish stocks in Aby lagoon was marked by an increase of total fishing effort, yields and therefore by the increase of total production. Fishing effort evolution was due to: the increasing of the number of beach seines which has increased from 26 in 1987 to 32 in 1988, the reappearance of syndicat seines and finally the importance of fishing teams activity.