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 degrees 48' N) grew significantly faster (0.16 +/- 0.005 mm day(-1)) than those at the warmer, more southern (21 degrees 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.

Automated summary

Growth patterns and hatch-date distributions of two mesopelagic Red Sea fishes were analyzed using otolith microstructure analysis. Lower growth rates were observed compared to other mesopelagic fish in similar latitudes, which may be due to low zooplankton concentrations and high water temperatures in the Red Sea. Maurolicus mucronatus grew faster than Vinciguerria mabahiss, and growth differences can be attributed to different vertical distributions and migration patterns. Significant differences in somatic growth between locations were also observed for V. mabahiss, with faster growth at the Kebrit location compared to the Atlantis II station. For V. mabahiss, otolith increment width at age remained similar throughout the hatching times, while for M. mucronatus, growth trajectories were dependent on hatch dates, with earlier cohorts showing higher maximum growth rates. This study provides essential baseline data for understanding the population dynamics of these fishes.