PS 15-142 - Measuring individual specialization through morphometric and stable isotope analysis of Greenland cod (Gadus ogac) in the western Canadian Arctic

Background/Question/Methods

Individual specialization can be driven by variation in feeding behaviors, resulting from environmental factors and/or individual preferences for resource use and may influence population resilience to environmental disturbances. Understanding variations in morphology potentially related to specialized feeding behaviors are useful for understanding the adaptive capacity of fish species in the context of a changing climate. Greenland cod (Gadus ogac) contribute to the functioning of coastal marine food webs and provide cultural and socioeconomic value across many Indigenous communities. However, knowledge pertaining to many Arctic fish species and the potential impacts of climate change remains poorly understood. The objective of this study was to measure individual specialization in an Arctic fish population. We estimated morphological variation of Greenland cod collected along the marine coast of Ulukhaktok, Northwest Territories (NWT) in the western Canadian Arctic (n=125). We used geometric morphometric analysis and compared individual morphology to habitat-trophic specialization via carbon and nitrogen stable isotope analysis from fast (plasma) and slow (red blood cells) turnover tissues to quantify temporal variability in feeding behavior.

Results/Conclusions

Results from principal component analysis (PCA) of linear morphometric measurements indicated significant variation in morphology of sampled cod, primarily in head shape and body depth posterior, with subsequent k-means clustering categorizing fish into two discrete morphological groups. Preliminary findings indicate minimal variation in δ13C and δ15N between morphologies, suggesting similar dietary patterns at the population level. Comparison of morphotypes showed statistical significance for each of the nine linear measurements, with stronger effects from head length and may suggest distinct feeding behaviors between groups. It is predicted that the effects of individual level variation are important and correlation between morphology and intra-individual variation in stable isotope signatures suggest that specific morphological traits are associated with dietary preference or specialization. Findings also signify the importance of carrying distinct morphological traits and flexible diets in order to maintain a high body condition. This integrated approach informs on our understanding of species’ flexibility to competition if resources become limited and range overlap occurs with closely-related sub-Arctic species. Given the potential impact of climate change on Arctic fish populations, understanding individual specialization is essential for informing fisheries co-management in the western Canadian Arctic.