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AB 30:1-18 (2021)  -  DOI: https://doi.org/10.3354/ab00736

Age determination in the icefish Pseudochaenichthys georgianus (Channichthyidae) based on multiple methods using otoliths

Ryszard Traczyk1, Victor Benno Meyer-Rochow2,3,*, Robert M. Hughes4,5

1University of Gdańsk, Department of Oceanography and Geography, 81-378 Gdynia, Poland
2Department of Ecology and Genetics, Oulu University, 90140 Oulu, Finland
3Agricultural Science and Technology Research Institute, Andong National University, Andong 36729, Republic of Korea
4Amnis Opes Institute, Corvallis, Oregon 97333, USA
5Department of Fisheries & Wildlife, Oregon State University, Corvallis, Oregon 97331, USA
*Corresponding author:

ABSTRACT: Aging Antarctic icefish is difficult because of their lack of scales and poorly calcified bones. Icefish ages must therefore be estimated from otoliths. We describe a method of reading daily micro-increments in connection with shape, size and mass analyses of the otoliths of the South Georgia icefish Pseudochaenichthys georgianus. Changes in otolith morphology and mass correlate with fish size and age group. The otolith micro-increment analysis is capable of establishing the age of an icefish by relating the daily micro-increment count to the life history of the fish. Micro-increment measurements and analyses are relatively simple to do by light and scanning electron microscopy and by using micro-densitometer and digitizing equipment. Drastic changes in the life history of an individual are reflected by measurable changes in its otolith micro-increment data as seen in our analyses of age groups 0-VI. The initial drastic change in daily micro-increment shapes and periodicities occur in connection with the hatching period of the icefish. The next drastic change in otolith shape and daily micro-increments occurs when ~7 cm long fish shift from pelagic to benthic habitats. As the fish age beyond group III, individual otolith variability lessens until they begin spawning. Our results indicate a single population of P. georgianus between the Antarctic Peninsula and South Georgia.


KEY WORDS: Southern Ocean · Daily micro-increments · Light microscopy · Scanning electron microscopy · Aging analyses


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Cite this article as: Traczyk R, Meyer-Rochow VB, Hughes RM (2021) Age determination in the icefish Pseudochaenichthys georgianus (Channichthyidae) based on multiple methods using otoliths. Aquat Biol 30:1-18. https://doi.org/10.3354/ab00736

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