Structure of Danube shad (Alosa pontica Eichwald, 1838) spawner flocks migrating for reproduction in Danube river (Migration of fishes in Romanian Danube River № 2)

摘要

The main purpose of this paper is to actualize last data on Danube shad (Alosa pontica Eichwald,1838) migration process in Danube River. This species was widely studied last time in Danube River, butthere are still some biological and ecological aspects to be revealed. Study of periodical changes in thetotal amount of capture and spawners structure could bring more and relevant information on presumedcyclic decrease and increase of stocks and also about the main causes of their interesting populationdynamics. We try to examine some other aspects related to the spawning biology as well as to the biome-try of different age-classes and also to link these issues to the last changes in environment conditions