ðeɪ tɹˈævəl ˌʌpɹˈɪvɚ tə spˈɔːn, ænd mˌeɪk ˈɔːdᵻbəl ɡɹˈʌntɪŋ nˈɔɪzᵻz ðæt hɐvbɪn dᵻskɹˈaɪbd æz ɹᵻzˈɛmblɪŋ ðə sˈaʊnd əvə mˈoʊɾɚbˌaɪk.
They travel upriver to spawn, and make audible grunting noises that have been described as resembling the sound of a motorbike.