“Firefly” of the Submarine Mountains: New Data on Physiculus cynodon (Moridae, Teleostei) from Emperor Seamounts and Northwestern Hawaiian Ridge

Abstract

Physiculus cynodon is a member of the Moridae family and possesses a ventral bioluminescent organ. Although it has been captured by commercial vessels for decades, our understanding of its biology and ecology remains fragmented. This paper provides data on the species’ spatial and vertical distributions; age and growth; size, age, sex compositions; and sex ratio in the waters around the Emperor Seamounts and the northwestern Hawaiian Ridge. This information is based on the analysis of multi-year Russian data obtained from scientific surveys and observations on commercial fishing vessels. The northernmost capture of this species has been recorded at Nintoku Seamount. Additionally, this species was regularly encountered at depths ranging from 53 to 900 m on seamounts such as Lira (Annei), Koko, Milwaukee (Yuryaku and Kammu), Colahan, and C-H of the Emperor Seamounts and Hancock, Zapadnaya, and Academician Berg of the northwestern Hawaiian Ridge. Catch rates of P. cynodon gradually decreased in a southeastern direction. Notably, the relative abundance of this species in bottom trawl catches significantly surpasses that in pelagic catches. The age of the fish in the catch varied from 9 to 37 years, and its growth is described by the VBGF equation with the following coefficients: L∞ = 858.6, k = 0.030, t0 = 3.5. While the growth patterns for males and females were similar, it is worth mentioning that males rarely survive beyond the age of 25 years.