Особливості плавальної здатності ранньої молоді коропових риб у зв'язку з формою їх тіла

Abstract

Встановлено, що ранні личинки коропових риб (плітка, Rutilus rutilus (L.); краснопірка, Scardinius erythrophthalmus (L.); верховодка, Alburnus alburnus (L.); плоскирка, Blicca bjoerkna (L.); гірчак, Rhodeus amаrus (Bloch); короп, Cyprinus carpio L.) характеризуються близькими показниками максимальної швидкості плавання, що пов’язано зі схожістю форми їх тіла. У процесі перетворення у мальків молодь набуває характерних для свого виду пропорцій, що обумовлює різницю у їх максимальній швидкості плавання: швидшою є молодь з видовженою формою тіла (верховодка, плітка), повільнішою – округла молодь коропа та гірчака.

Особенности плавательной способности ранней молоди карповых рыб в связи с формой их тела Установлено, что ранние личинки карповых рыб – плотвы Rutilus rutilus (L.), красноперки Scardinius erythrophthalmus (L.), уклеи Alburnus alburnus (L.), густеры Blicca bjoerkna (L.), горчака Rhodeus amаrus (Bloch) и карпа Cyprinus carpio L. – характеризуются близкими показателями максимальной скорости плавания, что связано со сходством формы их тела. В процессе преобразования в мальков молодь приобретает характерные для своего вида пропорции, что обуславливает разницу в их максимальной скорости плавания: быстрее оказалась молодь с удлиненной формой тела (уклея, плотва), медленнее – более округлая молодь (карп, горчак).

The paper presents the results of experimental studies to determine the critical swimming speed (CSS), one of the most important indicators of swimming performance of fish. The early young fishes (age 0+) of Cyprinidae family have been studied: roach Rutilus rutilus (L.), rudd Scardinius erythrophthalmus (L.), bleak Alburnus alburnus (L.), silver bream Blicca bjoerkna (L.), bitterling Rhodeus amarus (Bloch) and carp Cyprinus carpio L. The larvae and juveniles of most fish were caught in nature with a sweep net in May-August in the Dnipro and its tributary the Vita. The carp larvae were derived in laboratory by incubating the artificially fertilized eggs in Weiss's apparatus. Experiments were carried out in a special elongated aquarium, where a flow was created with the help of a regulated power pump. The CSS was regarded as the moment of fish being swept by flow or its transition to the burst speed mode. For the young bleak of 5.5-17.5 mm length, the CSS ranged from 6.7 to 38.4 cm/sec. For the young roach of 6.5-18.0 mm, the CSS fluctuated within the range of 5.8-32.7 cm/sec. For the larvae and juveniles of rudd sized from 5.0 to 19.5 mm, the CSS ranged from 4.2 to 26.3 cm/sec. The young silver bream of 5,0-17,0 mm reached the CSS of 7,0-26,1 cm/sec. The carp larvae and juveniles of 6.0-30.0 mm length reached the CSS of 4.6-31.9 cm/sec. For the young bitterling with the length 7.5-17.5 mm the CSS ranged from 8.9 to 22.6 cm/sec. The graph analysis of the results has shown that at small sizes (5-7 mm), all studied fishes are characterized by close values of CSS, due to the similarity of their body shape. In the process of transformation into juveniles, the young fishes acquire the proportions that are characteristic for the adults, which causes the difference in their CSS. The bleak, which turned out to be the fastest in comparison to other species, is characterized by the most elongated body shape, which increases its streamlining, reducing hydrodynamic resistance and allowing the larvae to achieve higher swimming speeds. The bleak was followed by the roach, the shape of which is quite elongated, but to a less extent compared to the bleak. Indicators of swimming activity of the young rudd and silver bream were close, which can be explained by high similarity of their body shape, which is more rounded and short compared to bleak and roach. The young carp and bitterling in the process of development acquire more rounded shapes, due to which the hydrodynamic resistance of their bodies is rather high, which prevents fast swimming, hence their critical speed was the lowest. The highest rates of relative swimming speed (body length per second, RSS) in all size groups were observed in bleak. Other species in order of decreasing the RSS have allocated differently depending on the size group. For example, the 6.5 mm size roach had the lowest RSS, but already at 12.0 mm it prevailed other species by this indicator. All studied species were divided into two categories: in the first one, with an increase in the body length, the RSS also increased, in the second group, it decreased. The first one combined bleak, roach and rudd, the species that keep relatively constant body height while its length increases, the second one included silver bream, carp and bitterling, the species that become noticeably rounded in the development process. Therefore, the body shape can be considered as one of the main hydrodynamic factors that determines the swimming performance of fish. The results obtained may have practical application in protection of young fish from entering the water intakes.