Modeling the Relative Importance of Near-bottom Temperature and Dissolved Oxygen to the Distribution of Adult Pacific Halibut (Hippoglossus stenolepis)

Earlier studies suggest that depth, temperature, and dissolved oxygen (DO) content all play a role in Pacific halibut (Hippoglossus stenolepis) distribution. Furthermore, the relative importance of temperature and DO may vary temporally, spatially, and by depth. The North American Pacific halibut fishery spans the area from northern California to the Bering Sea. This area supports a healthy, but fully utilized stock with harvests for commercial, sport, subsistence, and ceremonial uses. Data critical for the halibut stock assessment are collected through a coastwide setline survey that operates each summer and includes water column profiles coincident with fishing at each station. Understanding the underlying drivers to the distribution of halibut across their habitat ensures that the survey is interpreted correctly. In this study, catch and profiler information are coupled and analyzed using tree regression models to identify the driving environmental factors to halibut distribution and how those factors may vary in importance by area and depth.