GAP II: 2004–2006
GAP’s interrelated studies have focused on Steller sea lion concerns and also broadly assessed the degree of temporal variability and dietary overlap among Kodiak’s sympatric apex predators. The distinct but related hypothesis-driven research projects explore the processes that drive populations of their prey within a dynamic marine environment. These studies overlap spatially and temporally, allowing synchronous collection of environmental, predator, and prey data and synoptic assessment of their seasonal interactions. The continued decline of apex predator populations has illustrated the fundamental need to understand ecosystem mechanisms and processes at the organismal and population levels. After years of unprecedented and intensive research on Steller sea lions, there is still no clear evidence that nutritional stress, environmental change, or predation are individually linked to their continued declines. A primary stumbling block has been in determining what mechanisms are expected to control the population’s decline/lack of recovery at the ecosystem, population, individual, and cellular levels.
In GAP II, we continue to explore the structure of this system and monitor spatial and temporal changes in its biotic and abiotic components. We will take insights developed in the previous GAP efforts to explore the connections between these components from oceanographic, physiological, and ecological perspectives. While continuing to monitor the structure and variability of the system, we will begin to explore the physical processes, energetic pathways, and physiological mechanisms that link its components. This and future GAP research will explore the interfaces where physical oceanography drives primary productivity, where predators consume their prey, and where captive fish react to controlled environmental change.
Although originally addressing questions regarding Steller sea lion declines, our GAP questions have broader managerial relevance as well. Ecosystem-based marine resource management relies on understanding both the structural components of the system and the functional mechanisms of their interactions. By monitoring the seasonal distribution and abundance of predators and prey, we are defining their “habitats of particular concern.” By tracking oceanographic variability in relationship to zooplankton and fish populations we are exploring effects of environmental change on primary and secondary production. As a multiyear study, GAP is developing time-series needed to forecast and predict the effect of perturbations. Ultimately, by considering predators and prey in terms of energetic content and their interactions as energetic exchange, data collected in GAP will be used to develop a holistic model of the Kodiak area marine ecosystem.