First Data on the Age and Growth of Schmidt’s cod Lepidion schmidti (Moridae) from Waters of the Emperor Seamounts (Northwestern Pacific)

Abstract

This study presents the first data of growth and age of Schmidt’s cod Lepidion schmidti, a rare and poorly studied member of the Moridae family (Gadiformes, Teleostei). The research was focused on the Emperor Seamounts area with the aim of investigating the age, growth rates, and longevity of this species. The analysis involved examining annual growth increments on sagittal otoliths. Data were taken from longline catches in 2014 and 2016, resulting in the collection of 140 individuals and the use of 70 otoliths for age determination. The results revealed that Schmidt’s cod can live for up to 49 years, with a mean age of 31.5 years in the catches. The relationship between body weight and total length was described by a power function, indicating positive allometric growth. The most suitable growth model for this species was determined to be the Von Bertalanffy growth equation. These results provide valuable insights to add to the limited knowledge of growth and age in the Moridae family and emphasize the long lifespan and slow growth of Schmidt’s cod.

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

“…Our results and previous research have suggested possible seasonal movements of P. cynodon, its congener P. japonicus, and its relative Antimora rostrata [8,70], which may also contribute to variations in sex composition. The absence of males among larger specimens of P. cynodon has also been observed for other morids from the North Pacific, e.g., P. japonicus, Antimora microlepis, and Lepidion schmidti [8,47,49].…”

“…A widely employed method for estimating the age of fish using otoliths, which has demonstrated success in demersal (including deep-water) species inhabiting the waters along the west coast of the USA and Canada [40], is the "break and burn" technique. This method has also proven effective in studying the age of some morid species [41][42][43][44][45][46][47][48][49].…”

“…A comparison of the growth of males and females did not reveal significant differences, despite the average age disparity and absence of males in the older age classes. Growth characteristics not differing between males and females are common among deep-sea fish, such as other Moridae from the Emperor Seamounts, A. microlepis and L. schmidti [47,49].…”

“…In our sample from the Emperor Seamounts, the growth of P. cynodon is best described by a linear function (see Table 3). The linear function has also proven to be the most suitable for describing the growth of another morid from the same area, L. schmidti [49]. The linear growth of P. cynodon is supported by the values of the LWR equation coefficient b, which is close to 3 (where b = 3 represents isometric growth [79]).…”