Distribution, age and growth of the translocated invasive northern pike (Esox lucius, L.) in the upper course of the Vrljika River in the Adriatic Basin.
The objective of this paper is to determine the distribution, age and growth the Northern pike (Esox lucius) in the upper course of the Vrljika river. Samples were collected for two consecutive days in February 2020. In total, 38 individuals of E. lucius were analysed. The age of E. lucius in the upper course of the Vrljika River is divided into six age classes, and the oldest individual belongs to the 9+ age class. The total length of E. lucius ranges from 17.8 to 90.0 cm, while the relative population density is two individuals per 100 m. The upper course of the Vrljika River is habitat to two invasive, and three endemic fish species.