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Ukiel Lake (surface area 412 ha, maximum depth 43 m), the largest of the eleven lakes in Olsztyn, consists of four distinct basins, each with different environmental features. The presence of urban infrastructure, including a grid of streets, in the nearest proximity of the lake arises much interest in the recreational use of the lake. The present description of how the lake's shore zone around each basin is developed and managed relies on some observations gathered from monitoring the nature in the shore zone and access to the lake's water. The analysis of the actual use of the lake's tourist space was conducted on the basis of direct observations, including our assessment of the recreational pressure on the beaches, baths and near the water table. The results suggest that Ukiel Lake, owing to its size and diverse character, can be used for many different forms of recreation. Among the four basins, the most intensively developed and subjected to the highest recreational impact is Olsztyńskie Basin.
Angling is one of the most popular forms of recreation in Poland. The aim of the present work was an evaluation of angling potential of chosen lakes in the Olsztyńskie Lake District. Multidimensional comparative analysis was applied in this study. The study included 19 lakes. In the final assessment lakes Tejstymy, Tumiańskie and Dadaj achieved the highest potential for angling with values of synthetic measure over 0.5. The lowest values were achieved by lakes Rzeckie, Rasząg and Kraksy Małe (under 0.2). The best rated lakes were characterized by high values of synthetic measures in both studied groups of features. It was reassumed, that the lakes with low synthetic measure of the group of natural determinants were not worth to be invested. The lakes with not fully utilized natural potential and the lakes with unutilized natural potential (especially worth to beinvested) were indicated
An experiment was carried out concerning the effect of the initial stocking density per area unit on the growth and survival of the common barbel, Barbus barbus, larvae under controlled conditions. During the 21 days of rearing, the effect of fish stocking density between 2500 and 6250 individuals m⁻² was determined. Water temperature was 25oC throughout the experimental period. Fish were fed on live Artemia sp. nauplii. During the experiment, the mean total length (TL) of larvae as well as their weight (W) and survival were measured. On the basis of the obtained data, specific growth rate (SGR), Fulton condition coefficient (K) and fish biomass per area unit were calculated. The developmental stage of larvae was also determined. This study proved that initial stocking density of larvae does not affect survival, developmental stage or growth parameters. In all experimental treatments survival rate exceeded 98%. On the last day of rearing, all fish reached juvenile stage and TL of 28.5–30.2 mm. SGR ranged from 14.2 to 15% day⁻¹. The analysis of variance did not reveal statistical differences between the groups (P>0.05) for each measured parameter. The results obtained in this study indicate the possibility of a significant increase in the production intensity of fry-stocking material of the common barbel under controlled conditions, which should positively affect the economic effectiveness of rearing.
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