Spatio-temporal distribution and acoustic characterization of haddock (Melanogrammus aeglefinus, Gadidae) calls in the Arctic fjord Kongsfjorden (Svalbard Islands)

Abstract

In this study we analysed the acoustic properties and presence of haddock calls in the Arctic fjord Kongsfjorden (79° N–12° E, Svalbard Islands, Norway) in one year. Data were collected with three autonomous acoustic recorders located in the inner, middle, and outer parts of the fjord. The fjord is characterized by a gradient of oceanographic conditions from the inner to the outer part, reflecting changes from Arctic to Atlantic waters. Haddock sounds were more abundant in the outer fjord than in the middle fjord, whereas they were absent at the inner site. Mainly at the open-water site, the call abundance exhibited strong periodicity and a correlation with the cycles of neap tide (15 days) in August, with a clear diel cycle (24 h) in September and October. This result suggests that in this extreme environment with 24 h of light during summer, haddock regulate their acoustic activity according to the main available oscillating external physical driver, such as tide during the polar summer, while when the alternation of light/dark starts, they shift the periodicity of their calls to a diel cycle. Calls were recorded outside the spawning period (from July to October), and their characteristics indicated non-reproductive communicative contests. By using a detailed sound analysis based on previous laboratory studies for the first time, we suggest that the monitored population contains mainly juveniles (44% compared to 41% females and only approximately 15% mature males), showing the predominance of females in the middle fjord and juveniles at the open-water site.

A pattern recognition approach to identify biological clusters acquired by acoustic multi-beam in Kongsfjorden

“…Although there appears to be an overlap in the distribution between Atlantic cod and haddock, the former, tolerating lower temperatures, typically expands further north than haddock [16], [4]. There seems to be no trace of the haddock both in the innermost part of the fjord [24] and in the proximity of the Kronebreen glacier [8].…”

Sound discrimination of two sympatric, threatened fish species allows for their in situ mapping

“…Monitoring the reproductive performance of wild, threatened populations is an essential requirement for their effective management as fishery resources. More recently, haddock behaviour and population characteristics have been inferred from their sounds recorded at 75 m depth in cold Arctic waters (Buscaino et al, 2020), giving gender and maturity information on an exploited fish species located in a habitat that is otherwise difficult to access and monitor. Such qualitative assessments could form the basis of local fisheries management and conservation strategies.…”