Similar changes have been observed in the Benguela system, with substantially less upwelling-favorable wind in the northern Benguela in recent years ( Lamont et al., 2018a), accompanied by positive trends in Sea Surface Temperatures (SSTs) ( Jarre et al., 2015). Recent studies have revealed that upwelling ecosystems globally are undergoing long-term change, marked by a poleward shift in upwelling, linked with poleward shifts in the atmospheric high pressure systems that drive upwelling-favorable winds ( Rykaczewski et al., 2015 Wang et al., 2015). The Benguela system is commonly described as two sub-systems separated by the Lüderitz upwelling cell ( Duncombe Rae, 2005), with the northern Benguela characterized by perennial upwelling, and the southern Benguela characterized by strongly seasonal upwelling ( Hardman-Mountford et al., 2003 Lamont et al., 2018a). The deepwater hake, Merluccius paradoxus, form an important component of these commercially valued species, with the total stocks in the Benguela system representing more than 33% of the global hake biomass ( Kathena et al., 2016). These results provide background ranges of growth variability and context for what will likely be negative impacts of predicted decreases in future upwelling.Īs one of the four major Eastern Boundary Upwelling Systems of the world, the Benguela Upwelling System, located along the west coast of southern Africa, supports a productive environment typified by a complex ecosystem structure that supports numerous species of substantial commercial value ( Hutchings et al., 2009 Verheye et al., 2016). As an upper-level demersal predator, this species integrates signals throughout the food web to provide a unique “view from the top” of long-term changes in the northern Benguela upwelling system. Annual growth rates calculated from the two methods (overlapping 2000–2013) were strongly positively correlated (ρ = 0.730, n = 14, p 300 m bottom depth, are thus strongly influenced by fisheries. paradoxus otoliths were compared with change in mean length at age 3 to age 4 determined from Namibian whole-otolith-read age-length keys (ALKs). Mean annual growth (mm) calculated from 140 thin-sectioned M. In this study we develop a 32-year (1982–2013) otolith biochronology of the commercially important deepwater hake Merluccius paradoxus in the northern Benguela, Namibia.
3Laboratory of Tree-Ring Research, University of Arizona, Tucson, AZ, United States.2Marine Science Institute, The University of Texas at Austin, Port Aransas, TX, United States.
1Department of Fisheries and Aquatic Sciences, University of Namibia, Henties Bay, Namibia.Paulus 6, Chris Bartholomae 6 and Deon C.