First Advisor

Catherine E. de Rivera

Term of Graduation

Winter 2022

Date of Publication


Document Type


Degree Name

Master of Science (M.S.) in Environmental Science and Management


Environmental Science and Management




Carcinus maenas -- Behavior -- Oregon, Carcinus maenas -- Effect of temperature on -- Oregon, Carcinus maenas -- Habitat, Predation (Biology)



Physical Description

1 online resource (viii, 80 pages)


The invasive green crab (Carcinus maenas) has increased in abundance and distribution among Oregon's estuaries. Its global success in establishing in new environments and tolerance for abiotic stressors, such as temperature, raises concern for C. maenas to negatively influence native crab species, especially given global climate change. To improve in predicting invasion impacts, this work analyzed the results from a controlled tank experiment at Portland State University and the field data on a population of C. maenas in South Slough National Estuarine Research Reserve (SSNERR). The aquarium experiment documented predation pressure on C. maenas across a range of temperatures (9° to 30°C) and predatory crabs Callinectes sapidus, Cancer productus, and, as a control C. maenas. The behavioral responses of prey C. maenas were observed across temperature and predator combinations. There were five categories of behavioral responses measured in time duration. The west Atlantic C. sapidus preyed heavily on C. maenas, especially at warmer water temperatures; however, east Pacific C. productus preyed much less on C. maenas and only at the cold temperatures, suggesting different trajectories of biotic resistance across the coasts as waters warm. Crab behavior aligned with the predation findings. For example, C. productus were most active at 9°C and all died at 27°C and higher. In tanks with C. productus, C. maenas were most aggressive at warm temperatures. In contrast C. maenas spent more time feeding at 9°C when in tanks with C. sapidus and, surprisingly, also with C. productus. Crab trap data from SSNERR was plotted on a map to identify surrounding habitat and bottom substrate of areas with high catch per unit effort (CPUE) of C. maenas in the last six years. Mean CPUE of C. maenas was below five throughout the SSNERR region with sites closest to the mouth of the estuary having the highest CPUE rates. Little structure was surrounding trapping sites; however, there was seagrass at sites with the highest CPUE of C. maenas. The mean CPUE difference of native species prior to (2002-2016) and following (2016-2021) C. maenas abundance increase in 2016 was compared to the mean CPUE of C. maenas in the last six years. Results indicated no correlation between the CPUE of C. maenas influencing the difference of CPUE of native crab species. The tolerance and predation avoidance demonstrated from prey C. maenas in warmer temperatures indicate their ability to acclimate and/or adapt in stressful climate change conditions of higher water temperatures. This is of concern due to the increasing potential to negatively affect Oregon native crab species, such as C. productus over time.


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