Sampling Efficiency of the Moore Egg Collector

Abstract

Quantitative studies focusing on the collection of semibuoyant fish eggs, which are associated with a pelagic broadcast-spawning reproductive strategy, are often conducted to evaluate reproductive success. Many of the fishes in this reproductive guild have suffered significant reductions in range and abundance. However, the efficiency of the sampling gear used to evaluate reproduction is often unknown and renders interpretation of the data from these studies difficult. Our objective was to assess the efficiency of a modified Moore egg collector (MEC) using field and laboratory trials. Gear efficiency was assessed by releasing a known quantity of gellan beads with a specific gravity similar to that of eggs from representatives of this reproductive guild (e.g., the Arkansas River Shiner Notropis girardi) into an outdoor flume and recording recaptures. We also used field trials to determine how discharge and release location influenced gear efficiency given current methodological approaches. The flume trials indicated that gear efficiency ranged between 0.0% and 9.5% (n = 57) in a simple 1.83-m-wide channel and was positively related to discharge. Efficiency in the field trials was lower, ranging between 0.0% and 3.6%, and was negatively related to bead release distance from the MEC and discharge. The flume trials indicated that the gellan beads were not distributed uniformly across the channel, although aggregation was reduced at higher discharges. This clustering of passively drifting particles should be considered when selecting placement sites for an MEC; further, the use of multiple devices may be warranted in channels with multiple areas of concentrated flow.

Received August 8, 2012; accepted October 12, 2012

ACKNOWLEDGMENTS

This research is a contribution of the Oklahoma Cooperative Fish and Wildlife Research Unit (U.S. Geological Survey, Oklahoma Department of Wildlife Conservation, Oklahoma State University, and Wildlife Management Institute cooperating) with collaboration by the Texas Cooperative Fish and Wildlife Research Unit (U.S. Geological Survey, Texas Department of Parks and Wildlife, Texas Tech University, and Wildlife Management Institute cooperating). Funding was provided by the U.S. Fish and Wildlife Service, Great Plains Landscape Conservation Cooperative (U.S. Fish and Wildlife Service agreement F11AP00112). The use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government. We thank B. Brewer, S. Maichak, and J. Powers for field assistance; G. Fox and S. Lovern for technical support and equipment; G. Hanson, S. Hunt, K. Kadavy, T. Selvey, and B. Sappington of the U.S. Department of Agriculture–Agricultural Research Service National Hydraulic Engineering Research Unit and K. Graves and the staff of the U.S. Fish and Wildlife Service for logistical support; C. Jennings for providing gellan beads; and S. Platania and associates for technical and logistical assistance. This manuscript was improved by comments from P. Bettoli and three anonymous reviewers.