Abstract
The deep ocean ecosystem hosts high biodiversity and plays a critical role for humans through the ecosystem services it provides, such as fisheries and climate regulation. However, high longevity, late reproduction, and low fecundity of many organisms living in the deep ocean make them particularly vulnerable to fishing and climate change. A better understanding of how exploitation and changing environmental conditions affect life-history parameters (e.g., growth) of commercially important fish species is crucial for their long-term sustainable management. To this end, we used otolith increment widths and a mixed-effects modeling approach to develop a 42-year growth chronology (1975–2016) of the commercially important deep-sea fish species blackspot seabream (Pagellus bogaraveo) among the three island groups of the Azores archipelago (Northeast Atlantic). Growth was related to intrinsic (age and age-at-capture) and extrinsic factors (capture location, temperature-at-depth, North Atlantic Oscillation (NAO), Eastern Atlantic Pattern (EAP), and proxy for exploitation (landings)). Over the four decades analyzed, annual growth patterns varied among the three island groups. Overall, temperature-at-depth was the best predictor of growth, with warmer water associated with slower growth, likely reflecting physiological conditions and food availability. Average population growth response to temperature was separated into among-individual variation and within-individual variation. The significant among-individual growth response to temperature was likely related to different individual-specific past experiences. Our results suggested that rising ocean temperature may have important repercussions on growth, and consequently on blackspot seabream fishery production. Identifying drivers of blackspot seabream growth variation can improve our understanding of past and present condition of the populations toward the sustainable management of the fishery.
Highlights
The deep ocean, below 200 m depth, hosts ecosystems of high biodiversity and plays a critical role for humans through the services it provides, such as fisheries (Van den Hove and Moreau, 2007; Thurber et al, 2014)
Using archived otoliths of adult blackspot seabream collected in the three island groups of the Azores archipelago, this study aimed to evaluate how growth is affected by intrinsic and extrinsic factors and to detect possible growth differences between island groups
Otolith chronologies from this study reconstructed fish growth over 40 years based on individuals ranging from 6 to 28 years of age
Summary
The deep ocean, below 200 m depth, hosts ecosystems of high biodiversity and plays a critical role for humans through the services it provides, such as fisheries (Van den Hove and Moreau, 2007; Thurber et al, 2014). For a better understanding of the fundamental mechanisms responsible for biological responses to environmental change, long-term biological data (continuous information, collected and archived over time) with the appropriate spatial-temporal resolution are needed Such data can provide valuable and robust information on marine ecosystem changes and allow exploring species growth responses to environmental changes and exploitation, concerning their habitat, life history, and potential of adaptation (Thresher et al, 2007; Shelton et al, 2013; Coulson et al, 2014; Martino et al, 2019). Since environmental variables generally play a key role in driving growth variation and population dynamics in aquatic organisms (Morrongiello et al, 2012), this biochronological approach allows the prediction of species’ responses to future climate change (Rountrey et al, 2014; Barrow et al, 2018)
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