Lampetra fluviatilis (the lampern or river lamprey) undergoes a spawning migration in British rivers during the period between November and February, after which the animals spend from 4 to 6 months in fresh water prior to spawning.
the european river lamprey, lampetra fluviatilis
الواصلة
the Eu·ro·pe·an ri·ver lamprey, lampetra fluviatilis