Front pages with contents of No. 45, 1987

Front cover. Information for supporters of the Charles Darwin Foundation. Contents.

Back pages of No. 45, 1987

Map of Galápagos. Medium Ground Finch (Geospiza fortis), Drawing by Godfrey Merlen.

Histochemical data on the skin mucous cells during the development of the trout [Translation from: Bollettino della Societa Italiana di Biologia Sperimentale 45, 1273-1276, 1969]

In the skin of Salmo irideus the production of mucus is due to one type of cell specialized as a mucus cell. The histochemical research presented in this paper describes the mucous cells of Salmo irideus and demonstrates observable variation in such cells during the fish's development.

Avoided temperatures by young fish [Translation from: Informatsionnyi Byulleten Biologiya Vnutrennikh Vod No.50, 45-47, 1981]

Directed local changes of water temperature for the purpose of controlling the behaviour of fish are based on the knowledge of the characteristics of seasonal-age dynamics of their thermoadaptation possibilities. These possibilities are still inadequately studied especially in relation to avoided temperatures. By the authors the attempt was made to determine zones of avoided temperatures for the young of five species of fish (bream, roach, blue bream, perch, peled) in the summer period of the year, and also to assess the influence on them of additional factors, in particular mechanical driving. In parallel in two-fold repetition were conducted experiments on the determination of selected, shock and lethal temperatures of these fish. Experiments were conducted with fish, caught in the littoral of the Rybinsk reservoir.

Influence of starvation on selected temperatures in the young of bream, roach and perch [Translation from: Informatsionnyi Byulleten Biologiya Vnutrennikh Vod No.50, 45-47, 1981]

Works devoted to the influence of starvation on temperature selection by fishes are few and their conclusions are contradictory. This study determined the influence of brief, up to 14 days, starvation on temperature selection by young fishes. The experiments were carried out in August-September 1976 on fingerling bream (Abramis brama L.), roach (Rutilus rutilus L.) and perch (Perca fluviatilis L.) with body lengths of 3-5 cm and weight 0.5-1.2 g. The young fish were caught in the littoral by seine-nets or small drag-nets. Immediately after catching the fish they were put in acclimatization boxes. The period of acclimatization did not exceed 2 days for bream and roach at a temperature of 20 °C and 6 days for perch at 17 °C. Before the start of the experiment and for the first 10 days of the experiment the fish were fed with oligochaetes, earthworms and daphnia, after that feeding discontinued. At the end of a 10-14 day period the giving of food was resumed. The study concludes that the experiments have shown that in the summer season the factor of starvation significantly changes the reaction to the gradient of temperature in young cyprihids - roach and bream.

A note on fishery development on the Kafue Floodplain

The annual fish catch from the Kafue floodplain varies between 2,000 and 11,000 tons with a median of 5,500 tons valued at about K 500,000. It is believed that over 1,500 persons fish full time in the area. Fishermen's earnings can vary from a ew ngwee per day to a period in June 1970 when in one day four owners of drawnets in the Maala area, after hauling 13 times, caught 395 kg of fish valued at K 43.45 (i.e. about K 10 each per day). (I Kwacha=IOO Ngwee=US $1.40 Fresh fish is bought by traders with five to ten ton trucks more commonly in the upstream Namwala sector than in the central and downstream sectors of the floodplain (where consignments tend to weigh less than 125 kg). Over 25 tons (fresh weight equivalent) may pass through a fish market such as Busangu each month. Dried fish is destined for a greater range of towns than fresh fish.