How different life-history strategies respond to changing environments: a multi-decadal study of groundfish...

In recent decades, climate variability has led to significant shifts in the distribution and prevalence of various fish species in the North Atlantic. These changes are well documented for several groundfish species within the zoogeographical transition waters surrounding Iceland, coinciding with variations in seawater temperature. This study analyses groundfish assemblage structure through the frameworks of life-history theory and biogeography. Utilizing annual bottom trawl survey data from 1987 to 2024, groundfish species in the continental shelf waters around Iceland were categorized into three primary life-history strategies: periodic, opportunistic, and equilibrium, based on their life-history traits. Over the study period, these strategies demonstrated distinct responses to environmental changes, influenced by the biogeography of the species. Increased water temperatures were accompanied by an influx of Atlantic and Boreal species, while species richness for Arctic fish remained similar or decreased. Boreal periodic species emerged as the most prominent in Icelandic waters, maintaining long-term stability in abundance and distribution. However, environmental conditions in recent decades have favoured southerly warmer-water (Atlantic) species across life-history strategies, while most Arctic species have experienced declining abundance trends. Opportunistic strategists exhibited the most pronounced temporal changes during the warming period.