Líffræðifélag Íslands - biologia.is
Líffræðiráðstefnan 2025
Erindi/veggspjald / Talk/poster E37
Höfundar / Authors: Guðbjörg Ásta Ólafsdóttir, Anja K. Nickel
Starfsvettvangur / Affiliations: Háskóli Íslands, Rannsóknasetur á Vestfjörðum
Kynnir / Presenter: Guðbjörg Ásta Ólafsdóttir
Early juvenile stages are critical in determining recruitment success in marine fishes, yet the drivers of settlement progression and growth remain insufficiently resolved for many species, including gadids. We examined variation in settlement dynamics; timing, abundance, growth, condition, and signals of benthic settlement through stable isotope values, of 0-group Atlantic cod (Gadus morhua) and saithe (Pollachius virens) in shallow coastal nurseries of northwestern Iceland. Between 2015 and 2021, we sampled 3919 juveniles using beach-seining. Generalized additive models showed consistent positive effects of coastal summer temperature on juvenile length in both species, indicating that current coastal conditions remain within or near thermal optima for growth. In contrast, somatic condition declined at higher temperatures, suggesting potential trade-offs between rapid growth and energy reserves. Stable isotope analyses revealed divergent settlement trajectories of the two species: cod exhibited more abrupt δ¹³C and δ¹⁵N enrichment, consistent with a rapid shift into benthic niches and increasing residency, whereas saithe showed gradual isotopic changes indicating a more pelagic, mobile strategy. Therefore, despite a period of sympatry in shallow fucoid forests, cod and saithe partition nursery use through distinct timing of arrival and other settlement strategies.