Arctic char are cold water members of the Salmonid family that produce underwater sounds associated with internal air movement, as well as gravel displacement during spawning. Image credit: Department of Fisheries and Oceans, Canada.
Arctic char (Salvelinus alpinus) are members of the salmon family (Salmonidae) with a circumpolar distribution throughout northern Canada, Greenland, Iceland, northern Europe, Asia, and Alaska. The fish occur in anadromous and resident (freshwater) populations. Many populations of Arctic char are declining, particularly in Europe. A better understanding of the presence and timing of Arctic char spawning activities is critical to improved species management. Sounds associated with spawning and incidental body noises may be useful for population monitoring via passive acoustics.
Arctic char exhibit the same mating patterns as other Salmonids. Spawning takes place in the fall. Most courtship actions take place near the rocky bottom. Spawning activity produces broadband sounds associated with gravel displacement (150 Hz to 8 kHz). Females select areas for their nests, digging multiple depressions (“redds”) where they deposit their eggs. Males court nesting females and compete with other males for spawning access.
Arctic char also produce sounds associated with air movement. These sounds are described as ticks, air gulps, and snaps. Ticks occur in a quick repeated pattern, with a mean peak frequency of 1114 Hz and duration of 338 ms. Air gulps are high frequency, broadband burst sounds, with a mean peak frequency of 2003 Hz, and duration of 171 ms. Snaps are very short, broadband, high frequency sounds with a mean peak frequency of 2130 Hz and duration of 26 ms. Although air passage sounds are common with other members of the salmon family, little is known about their occurrence and significance. Based on limited data describing Salmonid hearing sensitivities, it is unlikely that these air passage sounds are audible to these species.