Influence of oceanographic conditions on the body shape variability of Scomber japonicus larvae from the western coast of the Baja California Peninsula

Pacific chub mackerel (Scomber japonicus) is a relevant fishery resource shared among three countries in the northeastern Pacific. The spatiotemporal distribution of larvae has been related to the convergence of oceanographic mesoscale structures, which can generate considerable variability in the morphology of fish larvae. The main goal of this work was to describe the shape changes of larval S. japonicus and their relationship with oceanographic variability, through geometric morphometric analysis to assess the seasonal variability of 10 homologous landmarks distributed on the pre-anal section of 331 larvae from off the western coast of the Baja California Peninsula (WCBCP), Mexico (2006-2008). The results showed two principal morphotypes in Pacific chub mackerel larvae: The first morphotype had a more hydrodynamic body (longer and shallower head), influenced by increased sea surface flow and colder sea surface temperatures mainly during spring, and the second morphotype had robust larvae (shorter and deeper head) under slower current flow and warmer sea surface temperatures during winter and summer. We concluded that changes in larval body shape are influenced mainly by sea surface flow and sea temperatures, probably associated with the ability to reach higher swimming speeds during feeding success.

Automated summary

Through geometric morphometric analysis, this study explores the relationship between the shape changes of Pacific chub mackerel larvae and oceanographic variability. The results show that the body shape of the larvae is mainly influenced by sea surface flow and sea temperatures. The larvae can be classified into two main morphotypes, with one morphotype being more hydrodynamic in response to increased sea surface flow and colder sea surface temperatures during spring, and the other morphotype being more robust in response to slower current flow and warmer sea surface temperatures during winter and summer.