Effectiveness of Relocation Trawling During Hopper Dredging for Reducing Incidental Take of Sea Turtles
Type:
Presented during:
WODCON XVIII - 2007 Orlando, Florida, USA
Authors:
Dickerson, et al
Abstract: Modified shrimp trawling equipment and techniques are used to capture and relocate threatened and endangered sea turtles from hopper dredging sites. This method of sea turtle protection was originally initiated in the early 1980s at Canaveral Harbor, Florida. In 1992, relocation trawling was implemented as a potential mitigation tool for incidental take (injury or mortality) of sea turtles for additional coastal hopper dredging projects in the southeastern United States. Although its effectiveness under various project conditions has been undocumented, this mitigation tool is now used extensively whenever sea turtles or Gulf sturgeon (Acipenser oxyrinchus desotoi) are potentially at risk for incidental take during hopper dredging projects. The National Marine Fisheries Service of the National Oceanic and Atmospheric Administration now recommends relocation trawling during many hopper projects throughout the southeastern United States and may recommend suspension of hopper dredging activities if weather or other conditions prevent trawling operations. This requirement impacts dredging schedules and inflates project costs. Relocation trawling is also a potentially hazardous undertaking for trawler crews and the species intended for protection. Other protected and non-protected organisms are also captured as by-catch and may be killed during the relocation trawling efforts. In light of the potential positive and negative impacts of relocation trawling during hopper dredging projects, it is crucial to evaluate the effectiveness of this technique as a mitigation option. Incidental take records from endangered species observer reports, relocation trawling reports, and hopper dredging project reports from 1995 through 2006 were analyzed to evaluate the effectiveness of relocation trawling for reducing incidental take of sea turtles. This study presents results related to sea turtles based upon: 1) analysis of species distribution; 2) analysis of catch per unit effort (CPUE) data; 3) spatial and temporal patterns of trawling captures and incidental takes; and 4) evaluation of effectiveness of trawling for reducing incidental takes.
Keywords: Endangered species, sturgeon, entrainment, mitigation, biological opinion