Spatial distributional shifts and associated body condition changes of haddock (<i>Melanogrammus aeglefinus</i>) following population expansion

Abstract Temperature fluctuations impact the distribution of various marine fish species and typically result in distributional changes, seeing either a geographical expansion or, possibly, retraction. Survival fitness new habitat depend, however, on species’ adaptability capacity. Here, we describe changes Icelandic haddock (Melanogrammus aeglefinus) based annual survey data for 38-year period, 1985–2022. Most stock is warm waters off south west coasts Iceland (south area), but small proportion colder water masses north east (north area). Due to high recruitment, density increased greatly both areas years 2001–2005. Haddock was usually higher area 1985–2004, 2005–2014, similar 2015–2022. condition found be influenced by temperature density. Density-dependent factors mean weight, which dropped considerable during times Capelin great importance as diet, especially south, where stomach fullness decreased considerably when capelin not part diet. Food availability seems highly variable between two more stable north, were small. Even though favourable environmental conditions may lower indicates that northern less suitable this species.