Growth rate extremes of a Sciaenid in an ocean-warming hotspot

Abstract

Argyrosomus inodorus is a cool water Sciaenid, important to the recreational and commercial coastal fishery in Namibia, the northern Benguela. Given recent findings on the northern Benguela as an ocean-warming hotspot and A. inodorus being more sensitive to warm temperatures than its congeneric A. coronus, it is important to study long-term growth responses of this Sciaenid. We developed a 34-year otolith biochronology for A. inodorus. The linear mixed-effects models fitted to A. inodorus’ otolith biochronology indicated that the best linear unbiased predictor of growth was significantly positively correlated with mean sea surface temperatures (SSTs) in September of the year of formation and significantly negatively correlated with mean summer SSTs (November y-1), in the central Namibian area (20–24^◦S, 12–14^◦E). Thus, faster annual growth was observed during warmer winter/spring temperatures (up to 16℃) and slower growth was noted during warmer summer temperatures (> 16℃). These results indicate that the species has a narrow range of thermal plasticity, and highlight the recent reductions in growth of this species in response to rapid thermal change observed in the ocean warming hotspot. Our findings suggest that A. inodorus would not be able to adapt readily with future climate warming predicted to happen and already happening along the northernmost part of the Namibian coast.