Photo Credit: Steve Hughes

Integrated Biophysical Models

Overview

Ecosystem modeling is being used to determine which environmental conditions have the greatest effect on the survival of the five groundfish species that are the focus of this study (walleye pollock, Pacific cod, Pacific ocean perch, sablefish and arrowtooth flounder). A series of models is used to examine the effects of oceanography, current patterns, nutrient availability, food availability, predator interactions, and various combinations of these factors on how these fish survive under different conditions. This information will help managers to predict fish survival and therefore predict more accurately the number of fish that should be available to support the ecosystem and commercial fisheries in the future. Historic data is used to develop the models and field data provides information about current conditions and is used to test the predictive power of the models.

Oceanographic Models

Regional Oceanographic Modeling Systems (ROMS) is used to model the oceanography that transports larval fish from areas offshore where they were spawned to nearshore nursery areas. Factors like water temperature, salinity, wind, and current patterns determine if fish are transported to appropriate nursery areas and how they grow and survive.

Nutrient Phytoplankton Zooplankton (NPZ) Models

Nutrient Phytoplankton Zooplankton (NPZ) models examine the effects of varying levels of nutrients, phytoplankton, and zooplankton in the water column, which provides information on the productivity of the system, and the availability of prey, under different environmental conditions.

Individual Based Models (IBM)

Individual Based Models (IBM) developed for each of the five focal groundfish species provide information about the basic life history and behavior of these fish as they grow from eggs to larvae and juveniles and are transported from spawning to nursery areas. Information about the typical depth at which the fish spend time during a given life stage, and the time that elapses between stages, is included the models. The IBM, NPZ, and ROMS models are nested so that the oceanography determines the location of a given fish at a particular time, the NPZ model determines the productivity at that location, and the IBM determines if the habitat is suitable for the fish during that stage of its life cycle. The combination of these environmental conditions determines fish survival.

Photo Credit: Merrill Jensen