Studies on the population biology of helminth parasites of fish species from the Caspian Sea drainage basin

Abstract The northern section of the Caspian Sea and lower reaches Zhaiyk (Ural) River is an important fishery for Kazakhstan. In present study, a total 1597 individuals ten fish species were analysed. caught over three years, from 2018 to 2020. For each studied – Abramis brama , Alosa saposchnikowii Atherina boyeri caspia Carassius gibelio Chelon auratus Cyprinus carpio Leuciscus aspius Rutilus caspius Sander marinus volgensis between 100 200 examined. A series generalized linear models (GLMs) used examine association individual parasite intensity infection Fulton index, age, year was captured, where captured (northern or River) sex. GLM, best-fitting probability distribution –either Poisson, zero-inflated negative binomial binomial. some fish/parasite species, increased index associated with higher intensities infection, whilst, others, decreased infection. This also true age-related parasites having age whilst others had age. There evidence variation in different years when caught. that are endemic both fresh waters low-saline Caspian, there variations two environments. gave information about dynamics No Poisson parasites, which consistent entirely random process, all being potentially exposed. either exposed not; and, if exposed, process. Other distribution, entire population but process clumped susceptibility fish. Finally, can be interpreted as part not remainder aggregated and/or