Cod Morphometric Analysis Reveals Physical Differences Among Sub-populations in the Georges Bank Fisheries Stock, Northwest Atlantic
Abstract
The Atlantic cod is an important species because it is a valuable food and economic resource, a key part of the fishing culture of New England, and an integral part of the food web. Currently there are two managed cod stocks in US waters: The Gulf of Maine stock and the Georges Bank (GB) stock, which includes the Southern New England (SNE) subpopulation. In recent decades, the GB cod stock has declined due to overfishing and rapid ocean warming, meanwhile, the abundance of SNE cod has increased. Our study sought to address two questions: 1) What are the characteristics of SNE cod? and 2) Do SNE cod look different from GB cod? We analyzed the morphology of both regions through morphometric analyses on images of Atlantic cod from the Fisheries Observer Program in Fall 2018/Spring 2019. By analyzing morphology, we searched for key physical differences among cod, determined the patterns of variability in morphological traits, and developed hypotheses to explain these morphological changes within and among regional sub-populations. Images were processed with the image analyzing software ImageJ, utilizing the box-truss network technique and established landmarks on the fish to measure ecologically relevant physical characteristics of body shape and size. Measurements were analyzed using principal component analysis and logistic regressions. Results showed that GB cod have larger heads, are wider from the belly to the second dorsal fin, and exhibit longer distances between the first and second dorsal fin, from the bottom to the top of the caudal fin and from the second anal fin to the caudal fin. Our generalized linear model (GLM) was able to correctly classify fish to their regional groups 83% of the time. Real and important ecological differences exist between these subpopulations of cod that are currently managed as one GB stock. Our results add further scientific support the growing idea that these subpopulations may need to be managed separately to promote sustainable harvest levels in U.S waters.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2020
- Bibcode:
- 2020AGUFMED0040016R
- Keywords:
-
- 0810 Post-secondary education;
- EDUCATION;
- 0855 Diversity;
- EDUCATION