Abstract
This article presents the results of the study of ecological and biological characteristics of common carp (Cyprinus carpio Linnaeus, 1758) from Kapchagay Reservoir on the Ili River in Kazakhstan. We studied size-weight indices, body condition (Fulton condition factor), age structure, fecundity, and body length. We also determined the gonadosomatic index (GSI) during the spawning period. Fish samples were caught using fixed nets with mesh diameters ranging from 16 to 90 mm. Total body length (TL) in mm and total body weight (TW) of fish in grams were measured. A logistic regression model was used to determine body size at first maturity for females and males. Fecundity was determined in mature females (stage IV maturity). Calculation of the GSI made it possible to clarify the duration of the spawning period. This study provides important information about the troubling status of the population of C. carpio in the area of study and suggests effective approaches to regulate fisheries in the reservoir and other water bodies of Kazakhstan. There is clearly a need to limit IUU (illegal, unreported and unregulated) fishing and otherwise regulate over-fishing.