Aquatic coleoptera and hemiptera taken at light in some Asian countries with a note on Sphaerodema (Hemiptera-Belostomatidae)

Aquatic insects are relatively common at artificial lights and are often taken in light traps operated for catching other insects. They are however seldom recorded. These records are however of importance in understanding their distribution and abundance. Aquatic Coleoptera and Hemiptera are of importance in fisheries because some of them are predators on small fish whilst others serve as food for fishes of all sizes. Some like the Corixidae are of special interest because they can utilize the bottom ooze which is abundant especially in small habitats. Fernando (1961a) gave a comprehensive bibliography of records at light. In the present paper a number of records are given from various parts of Asia, where in the past records were very few. They are based on collections made by the author and also on material in the Zoological Survey of India, Calcutta. Amongst specimens sent for study by the Bernice P. Bishop Museum, Honolulu, were a few specimens which had been recorded at light.

Optical learning in a smart spatial light modulator

A synaptic plane rendered by an array of smart pixels was described regarding its application as a complementary component for neural network implementation. The smart spatial light modulator featured auto-modification abilities. Thus, an optical system incorporating this device can show self-reliant optical learning. Furthermore, the optical system design, in the area of its optical interconnection scheme, is highly flexible since the independent weight-plane pixels eliminated the difficulty between weight update calculation and weight representation.

Influence of light on diurnal behaviour of Carangids in the Wadge Bank trawl fishery

Adequate data on the Wadge Bank fishery relating to several groups of fish, including Carangids, taken in bottom trawls are available for study. Analysis of this data indicated that the variation in Carangid catches was related to the time of day. In this paper, the available Wadge Bank fishery data is analysed and discussed to show the diurnal changes in Carangid catches and the probable influence of light in affecting these changes.

Purse seining for small pelagic fish around Sri Lanka

An attempt has been made to study skipjack (Katsuwonus pelamis) live bait availability and other small pelagic fish, their seasonal variations with respect to distribution, species and size composition. Exploratory surveys made use of echo sounding and lookout during the day, and light attraction at night. Percentage composition of spp caught at each station is tabulated. Seasonal variations are discussed and monthly variations in some important groups are plotted. Size composition, especially for Sardinella spp, is considered. The availability of 'red bait' would not be adequate to support an extended pole and line fishery for skipjack. The daytime fishing methods were not considered to have been especially successful, and the choice of gear and method of capture is discussed. It is suggested that the present fishery could be improved by the adoption of ring nets by local fishermen in place of the present purse seines when catching bait.

An analysis of the experimental pole and line fishery conducted around Sri Lanka by Nichiro Fishing Company of Japan

Under a joint agreement the Government of Sri Lanka and the Nichiro Fishing Company of Japan have undertaken an experimental pole and line fishery around Sri Lanka with a view to determining the feasibility of establishing a joint commercial venture. 3 Japanese vessels conducted trials during the period March 1973-October 1974. Details of the vessels and cruises are given. A variety of fish were tried as bait, and the selection of appropriate bait is discussed. Catches and catch and effort statistics are presented, with tables showing distribution of the tuna. The results of the trials were below expectations, and are in part attributed to bait availability, and unfavorable weather conditions. Seasonal variation of the type of fishery is suggested in order to take account of this, and it is concluded that a fishery based on 45/50 ft combined pole and line and drift net fishing vessels might prove feasible.

Management of the nile perch, Lates niloticus, fishery in Lake Victoria in light of the changes in its life history characteristics

Nile perch, Lates niloticus Linnaeus, 1758, is a predatory fish of high commercial and recreational value. It can grow to a length of 2 m and a weight of 200 kg. In Uganda, Nile perch was originally found only in Lake Albert and the River Nile below Murchison Falls. The species is, however, widely distributed in Africa, occurring in the Nile system below Murchison Falls, the Congo, Niger, Volta, Senegal and in Lakes Chad and Turkana (Greenwood 1966).