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Management Plan for Pacific Walrus (Odobenus rosmarus divergens) in Alaska, 2017-2027

Fri, 04/28/2017 - 18:06
Abstract: Pacific Walruses are social mammals and travel in herds. Most of the population spends the summer months in the ice pack of the Chukchi Sea; however, mostly adult males use coastal haulouts in the Bering Sea. Walruses use ice to rest between foraging trips, mate, care for their young, and defend themselves against predators. Climate reduced their ability to engage in these behaviors by eliminating the ice pack in their summer season. Walruses feed on bivalves on the sea bottom; however, because of climate change they no longer can reach the bottom. In response to the loss of ice, walruses are resting on land haulouts with as many as 20,000-40,000 individuals. This puts pressure on the benthic material supply. The swim from drifting ice to coastal haulouts can be hundreds of kilometers, which leads to the death of young walruses. Walruses are sensitive to sounds from ships, aircrafts, and tourist underwater and out of water. When walruses are disturbed by these events, they create stampedes by trying to dive into the water. The stampeding event ends in high mortality for calves. In 2007, more than 1,000 walruses were trampled to death in Chukotka, Russia. To prevent human disturbances, management at haulouts needs to occur for 10 years (2017-2027). The goals are to improve demographic knowledge of pacific walruses, minimize stampeding events, and grow and replace native bivalves near land haulouts. This could be accomplished by laws that require aircraft and vessels to maintain the appropriate distance. Creating artificial habitat would result in less use of coastal haulouts which would decrease mortality during stampeding events. It would also provide easier access to bivalves for foraging trips. Bivalves are depleting near land haulouts due to large demand from the high density of walruses, therefore aquaculture is needed to replace their food source. Harvesting more of the adult population would be essential to maintain the population from going over carrying capacity. If the adult population decreases then fewer calves will die in stampedes. These objectives are necessary to ensure the future of walruses and their new habitat.
Access: No
Literary Rights: On
Major: Fisheries and Wildlife Science
Year: 2017
File Attachments: The Author has selected not to publish this complete work.
Authors: Desiree Stumpf

Are Zooplankton As Patchy As Phytoplankton?

Mon, 05/01/2017 - 15:44
Abstract: Phytoplankton and zooplankton form the base of most lake food webs and are the primary sources of energy for higher trophic levels. Recent studies have shown that the horizontal distribution of phytoplankton is not even across the surface of lakes. While the vertical distribution of zooplankton has been well studied, little is known about the horizontal distribution of zooplankton in the surface waters of lakes or the spatial interactions among zooplankton and phytoplankton. The aim of this study was to quantify the spatial distribution of phytoplankton and zooplankton and determine if their spatial distributions are related. We sampled zooplankton and phytoplankton during the day and at night in a 24 point grid in Paul Lake, Michigan in the late spring and early summer of 2016. Phytoplankton and zooplankton were not uniformly distributed horizontally. Instead, there were high density patches of both zooplankton and phytoplankton, and in many instances there was positive autocorrelation. Additionally, zooplankton and phytoplankton concentrations were rarely correlated in space indicating that grazing is likely not a driver of zooplankton or phytoplankton spatial heterogeneity. If the goal of a study is to understand and characterize the entire population of either phytoplankton or zooplankton, we suggest taking multiple samples of the pelagic zone.
Access: No
Literary Rights: Off
Major: Fisheries and Wildlife Science
Year: 2017
File Attachments: The Author has selected not to publish this complete work.
Authors: Jonathan Stetler, Cal Buelo