Growth patterns of two Red Sea mesopelagic fishes

Growth patterns and hatch-date distributions of two mesopelagic Red Sea fishes, Vinciguerria mabahiss and Maurolicus mucronatus, were inferred from otolith microstructure analysis. Estimated somatic growth rates were lower than other mesopelagic fish at similar tropical and subtropical latitudes. Low zooplankton concentrations and high Red Sea water temperatures may explain the low growth rates observed. Maurolicus mucronatus grew faster (0.15 ± 0.005 mm day−1) than V. mabahiss (0.13 ± 0.003 mm day−1). Growth differences could be attributed to different vertical distributions and migration patterns. Significant differences in somatic growth between locations were also observed for V. mabahiss. Individuals at Kebrit (24°48’ N) grew significantly faster (0.16 ± 0.005 mm day−1) than those at the warmer, more southern (21°27’ N) Atlantis II station (0.12 ± 0.003 mm day−1). For V. mabahiss, otolith increment width at age was similar at hatching times throughout the late spring/summer and autumn. However, for M. mucronatus, growth trajectories were hatch-date dependent, with the earliest cohorts displaying the highest maximum growth rates. This study provides baseline data which will be essential for a better understanding of their population dynamics.