Spatial and Temporal Variation in length-at-Age in Northeast Arctic haddock (Melanogrammus aeglefinus)

Abstract

Summary: The growth of fish is one of the most important factors in fisheries management. As fish grow, their lifestyles often change considerably including their food sources and the species that prey on them. Growth is affected by several processes, both spatial and temporal. Northeast Arctic haddock (Melanogrammus aeglefinus) is the second most important demersal fish species in Norwegian fisheries, second only to Cod (Gadus morhua). Haddock is distributed on both sides of the Northern Atlantic. In this thesis I studied data from IMR’s Coastal Survey on NEA haddock, which has never before been analyzed. I examined how the growth of haddock varies along the Northern Norwegian coast. Additionally, I investigated the relationship between length-at-age and both spatial and temporal factors on haddock for three age groups: ages 1 to 3. For spatial factors temperature and density of individuals of similar size were analyzed, and for temporal I looked at cohort and age 3 recruitment. Density was used as a proxy for competition. The analysis of areas, mega-strata, along the coast with the von Bertalanffy growth function revealed spatial variations in growth. Mega-strata further Northeast were found to have reduced growth, K, and higher maximum average length, L∞. Temperature and density were found to significantly influence individual length of haddock aged 1-3, with increased temperature being positively correlated with length and high density negatively affecting length. An analysis of cohort and recruitment revealed that some year classes consistently have higher and lower length-at-age, after accounting for temperature and density. Strong recruitment was found to negatively affect the length of cohorts born after the peak. The findings in this thesis show that there are intricate interactions between spatial and temporal factors in the growth of haddock.