AGE-RELATED DYNAMICS OF INFESTING GOBIIDAE FAMILY FISH WITH CRYPTOKOTYLE LÜHE, 1899 (TREMATODA: HETEROPHYIDAE) IN THE ESTUARIES OF THE BLACK SEA IN THE SOUTHERN UKRAINE

Abstract

The research is devoted to the relation between the level of the invasion of the Gobiidae fish with the metacercaria from the Heterophyidae bloodline and the age of the fish. To be specific, the researched fish are Mesogobius batrachocephalus Pallas, 1814, Neogobius melanostomum Pallas, 1814, and Neogobius fluviatialis Pallas, 1814, caught in the waters of the Dnipro-Buh estuary and the Black Sea near Mykolaiiv and Odessa regions. It has been shown that the level of invasion grows proportionally to the age of the sam-pled fish. However, the index of abundance has not always been increasing with the age of the researched fish. It has been established that the oldest age groups – 6+ – 7+ – have been characterized by the highest level of the cryptocotyle invasion. In part, among the M. batrachocephalus fish the level of invasion in this age group made 46.6 %. The index of abundance reached its peak in this age group as well, counting 24.08 samples. The lowest invasion rates for the fish of this species were registered in the age group 2+ – 3+ – 18.1 %, the index of abundance for this age group counted 9.88 samples. N. melanostomum fish from the age group 6+ – 7+ were characterized as having the highest invasion rates. The prevalence in this age category made 100 %, while in the age group 2+ – 3+ the trematode invasion rates were at the lowest point for this Gobiidae species, counting 50 %. The index or abundance for these fish reached its maximum in the age group 0+ – 1+, counting 35.7 samples, and the minimal rates for N. melanostomum were registered in the age group 2+ – 3+ – 28.8 parasitic samples. N. fluviatialis aged 6+ – 7+ were infested and the prevalence made 54.3 %. The lowest level of invasion for this Gobiidae species was noticed in the age group 0+ – 1+, counting 31.2 %. The index of abundance among the N. fluviatialis fish was the maximal in the age group 2+ – 3+ and counted 12.26 samples, and the minimal rates were registered among Gobiidae fish aged 4+ – 5+, they counted 10.35 samples. To sum up, it has been established that the prevalence rates rise propor-tionally to the age, but this relation is not registered when it comes to the index of abundance rates. It has been proven that the level of cryptocotyle invasion among Gobiidae fish reached its peak in the oldest age groups – 6+ – 7+.