Using Fin Development to Determine Morphological Milestones in Arctic Cod (Boreogadus saida)

Arctic Cod (Boreogadus saida) play a key role in the food web of the Arctic ecosystem by linking higher trophic levels (marine mammals and sea birds) with lower trophic levels (zooplankton). Fin development plays a key role in the early life history of early stage fishes as fins assist with increased swimming abilities, which are essential for survival due to enhanced prey capture and reduced predation. The goal of this study was to determine when B. saida undergoes juvenile transformation based on the progression of fin development. A developmental series of B. saida was built from specimens collected by NOAA Ecosystems and Fisheries-Oceanography Coordinated Investigations (EcoFOCI) in the Chukchi Sea. Fifty specimens, increasing in 1 mm increments from 5 mm to 55 mm standard length (SL), were cleared and stained using the Hanken method. Meristic and skeletal development data were collected for each individual using Image Pro Software and all data were analyzed in R. The dorsal, anal, pectoral, pelvic, and caudal fin ray counts and ossification patterns were compared at each standard length. Boreogadus saida reaches the juvenile stage between 30-44 mm SL, which is at a larger stage relative to other gadid species (Theragra chalcogramma). Future research can then use the data generated in this study to compare developmental milestones of B. saida to other gadid species such as Theragra chalcogramma, which is a commercially important sub-Arctic gadid species, to understand how different early life history strategies may respond to changing climatic conditions in the Arctic.