Geographic variability in lingcod Ophiodon elongatus life history and demography along the US West Coast: oceanographic drivers and management implications

Abstract

Understanding the environmental and anthropogenic drivers of spatial patterns in life history variation for exploited fish populations is important when making management decisions and designating stock boundaries. These considerations are especially germane for stocks that are overfished or recently rebuilt, such as lingcodOphiodon elongatus, a commercially and recreationally valuable species of groundfish along the West Coast of North America. Between 2015 and 2017, we collected 2189 lingcod from 24 port locations, spanning 28° of latitude from southeast Alaska (60°N) to southern California (32°N), to investigate latitudinal patterns in size- and age-structure, growth, timing of maturity, condition, and mortality, as well as to identify biologically relevant population breakpoints along the coast. We found strong latitudinal patterns in these life history and demographic traits consistent with Bergmann’s rule: lingcod from colder, northern waters were larger-at-age, lived longer, matured at larger sizes, and had lower natural mortality rates than lingcod from warmer, southern waters. Female lingcod were larger-at-age, lived longer, and matured at larger sizes compared to males within each examined region. In addition, we found evidence for strong associations between lingcod life history traits and the oceanographic variables of sea surface temperature and chlorophylla. Cluster analysis using life history traits indicated that central Oregon is a biologically relevant breakpoint for lingcod along the US West Coast. This breakpoint based on life history traits, in conjunction with a recently identified population genetic breakpoint between central and northern California, highlights the need for future lingcod stock assessments to consider multiple sources of information to best inform management of this trans-boundary stock.