Table of Contents

• Coverage
• Dataset Description
  • Methods & Sampling
  • Data Processing Description
• Data Files
• Related Publications
• Parameters
• Deployments
• Project Information
• Funding

Mud crab predation on oyster spat in the presence of caged blue crab predators placed various distances away from mud crab refuge. Field experiments were conducted at two different sites on Skidaway Island, GA during two different tidal types to determine the effect of current speed and turbulence on mud crab perceptive range.

These data were published in Pruett and Weissburg, 2018.

Mud crab perceptive range trials were performed in enclosures (2.2 m by 0.75 m by 0.3 m) that contained an oyster reef as a refuge for mud crabs at one end. Oyster shells were glued together to create artificial oyster clusters that were used to manipulate the placement of oyster spat within the enclosure. Four oyster spat (10-16 mm) were epoxied to the artificial oyster clusters and 4 clusters were placed within the constructed oyster reef and 4 clusters outside the reef. Fifteen mud crabs (8 crabs 15-20 mm CW, 4 mud crabs 20-25 mm CW, and 3 mud crabs 25-30 mm CW) were added to the oyster reef in the enclosure. Caged blue crabs (12-16 cm CW) were placed either 0.25, 0.5, 1.0, 1.5, or 2.0 m away from the center of the oyster reef. A caged blue crab was placed on both sides of the oyster reef in the direction of tidal flow with one caged blue crab in the enclosure and the other outside the enclosure. Empty blue crab cages were used for the control treatment.

Enclosures were deployed on intertidal mudflats at either Priest Landing or Skidaway Narrows during either mean tide or spring tide. Flow parameters differed between sites and tidal types based on previous work (Wilson et al. 2013). The number of oyster spat eaten by mud crabs inside and outside the refuge was counted after 24 hours. See Pruett and Weissburg, 2018 for full methods. 

Data were statistically analyzed using R version 3.3.1.

BCO-DMO Processing Notes:
- added conventional header with dataset name, PI name, version date
- modified parameter names to conform with BCO-DMO naming conventions
- re-formatted date from m/d/yyyy to yyyy-mm-dd
- reduced number of significant digits of normalized_eaten and refuge_use from 9 to 2 places to meet sampling precision methods

Extracted from the NSF award abstract:

In this project, the investigators will examine the ability of top blue crab predators to indirectly benefit the abundance of basal oyster prey by reducing the density (consumptive effects, CEs) and suppressing foraging (non-consumptive effects, NCEs) of intermediate mud crab predators. These NCEs are mediated by chemical perception of aversive cues in blue crab urine and produce a behaviorally mediated trophic cascade. Through a series of manipulative experiments, the investigators will examine how the strength of this behaviorally-mediated trophic cascade is modulated and factors that influence perceptive range such as predator diet and intake rate, and the flow environment. The investigators will also determine the chemical identity, concentration and release rate of chemical cues.

Identifying the quantitative and molecular aspects of aversive cues, and linking them to behavioral responses that produce trophic cascades establishes the chemical basis of risk perception by prey and how this translates into cascading ecological effects. The use of perceptive range as a framework for evaluating the effects of both chemistry and environment provides an integrated view of processes affecting chemically-mediated NCEs. The use of a water borne predator-prey signaling system to test ideas on the strength of NCEs should have broad applications.