Browsing College of Fisheries and Ocean Sciences by Author "Pirtle, Jodi L."
Habitat Function In Alaska Nearshore Marine EcosystemsPirtle, Jodi L.; Eckert, Ginny; Reynolds, Jennifer; Quinn, Terrance II; Tissot, Brian; Woodby, Doug (2010)This research demonstrates how habitat structures subtidal communities and supports individual species in Alaska nearshore marine ecosystems. This was accomplished through a case study of southeast Alaska coastal regions, and an in-depth investigation of red king crab Paralithodes camtschaticus early life stage ecology and nursery habitat. How subtidal communities reflect variation in the marine environment of southeast Alaska is poorly understood. The purpose of the first part of this body of research was to identify and compare patterns of community structure for macroalgae, invertebrate, and fish communities at shallow subtidal depths between inner coast and outer coast regions, and link patterns of community structure to environmental variability in southeast Alaska. The major hydrographic gradient of decreasing salinity and increasing temperature from the outer coast to the inner coast affected regional community structure, with greater species diversity at the outer coast. Species distribution for invertebrate communities was linked to variation in benthic habitat at local scales among sites within regions. This study improves understanding of processes that structure marine communities to better predict how environmental change will affect Alaska marine ecosystems. Many Alaska red king crab populations have collapsed and continue to experience little recovery, even for areas without a commercial fishery. Several aspects of red king crab early life stage ecology were investigated because reasons for the lack of recovery may be related to the early life history of this species. Field experiments were conducted in southeast Alaska. Settlement timing was consistent between study years (2008--09) and with historical data for this region. Local oceanographic processes that influence larval transport may be responsible for spatial variation in larval supply. In laboratory and field experiments, early juvenile crabs (age 0 and 1) demonstrated refuge response behavior to a predator threat that changed with crab ontogeny. When predators were absent, juvenile crabs preferred highly structured biogenic habitats due to foraging opportunities, and associated with any structural habitat to improve survival when predators were present. This research shows how availability of high quality nursery habitat affects red king crab early life stage success and potential for population recovery.