Title page for ETD etd-04162010-101313


Type of Document Dissertation
Author Aronhime, Barry Richard
Author's Email Address baronh1@tigers.lsu.edu
URN etd-04162010-101313
Title Predator-prey Interaction in Estuarine Bivalves: Size Selection, Effects of Salinity, and Indirect Interactions
Degree Doctor of Philosophy (Ph.D.)
Department Biological Sciences
Advisory Committee
Advisor Name Title
Brown, Kenneth M Committee Chair
Fleeger, John W Committee Member
Melancon, Earl J Jr Committee Member
Stickle, William B Jr Committee Member
Kelso, William E Dean's Representative
Keywords
  • stress
  • oysters
  • blue crabs
  • stone crabs
  • estuaries
  • oyster drills
  • predator-prey interaction
Date of Defense 2010-03-29
Availability unrestricted
Abstract
High stress environments can reduce species diversity. How such stress-induced reduction in predator diversity impacts prey survival is less well studied. Brackish waters in estuaries are stressful, species depauperate areas, but also prime oyster habitat in Louisiana. Surveys revealed reduced bivalve predator diversity at the low salinity (high stress) site. Exclosure experiments indicated highest prey mortality at the high salinity (low stress) site. Predator enclosures corroborated the field study results, with reduced consumption rates at the low salinity site for both stone crabs, Menippe adina and oyster drills Stramonita haemastoma, but not blue crabs, Callinectes sapidus. Blue crab mortality in enclosures was relatively low at all sites, while stone crab and oyster drill mortality were higher at the medium and low salinity sites.

As predator diversity increases, interactions between predators can impact prey mortality. Therefore I studied how the bivalve predators interact, how interactions impact prey survival, and how interactions change with stress. Interactions between blue crabs and stone crabs had an additive effect on bivalve mortality. Videotaping suggested blue crabs fed longer than stone crabs, and that interactions did not impede feeding. Bivalve mortality was however lower than predicted in blue crab-oyster drill combinations, suggesting interference reduced feeding by oyster drills. Salinity did not affect multiple predator interactions or feeding times.

Prey preference by predators also affects prey mortality. Hooked mussels, Ischadium recurvum, had higher mortality than oysters, Crassostrea virginica, in field and laboratory experiments, possibly because the thinner-shelled mussels were easier to consume. Chapter 4 examined prey preference in two important predator species. Blue crabs preferred small hooked mussels. Because profit did not differ with mussel size, stone crabs because their stronger claws were less prone to damage showed no size preference, and large mussels required force generation near levels that can damage claws, I concluded blue crabs consumed small mussels to reduce risk of claw damage, or to minimize handling times to limit their own predation risk.

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