The pathogenic organism (Ichthyophthirius multifiliis Fouguet, 1876) is widely distributed among freshwater fish. It was established that the disease was one of the most dangerous eel Anguilla anguilla diseases in Latvia. The bath of 0.9 % solution of sodium chloride was recommended as the most effective remedy against the disease. | Published | Not Known

Mainly large lakes - Raznas Lake (5596 ha), Usma Lake (3890 ha), Aluksnes Lake (1590 ha) were stocked with eel Anguilla anguilla in Latvia. Corresponding investigations showed that for the determination of age in eel it is necessary to account for both to its scales and otoliths. In eels of various water bodies the difference between the rings on the scales and otoliths can vary. The studies revealed that with increasing age in eel the weight increase surpasses its growth in length. It was established that in the Latvian water bodies eel has good fatness and its growth rate was comparable with eels in other countries. | Published | Not Known

In 1968-69 the basic part of bottom fauna of the Kegums Reservoir (Latvia) was composed of molluscs and oligochaetes. Both the qualitative and quantitative composition of benthic fauna considerably differed in various parts of the reservoir. The most and the least productive were the central and the lower parts, respectively. Only some species displayed a clear seasonal dynamics in biomass. This was mainly dependent on the regime of water level of the reservoir. The increase in diurnal fluctuations of the water level and changes in the flow rates in the Kegums Reservoir after the construction of the Plavinas hydro-electric power station lead to a decrease in the biomass of bottom animals compared to the period 1959-61. Since the 1959-61 the annual average biomass of benthic fauna had decreased 2-3 times. Also, the decrease of the biomass in 1969, compared to the 1968 level, was explained with sharp fluctuations in the water level. The biomass changes were the largest in the upper area whereas in the lower area they were the least. | Published | Not Known