An estuarine observatory for real-time telemetry of migrant macrofauna: Design, performance, and constraints

Thomas M. Grothues, Kenneth W. Able, Janice McDonnell,Mitchell M. Sisak

Limnol. Oceanogr. Methods 3:275-289 (2005) | DOI: 10.4319/lom.2005.3.275

ABSTRACT: In 2002, we began tagging macrofauna and established an array of hydrophones in the Mullica River and Great Bay estuary in southern New Jersey, USA, as part of an observatory for the study of migration. The hydrophone array differs from other model telemetry programs in several aspects. The wireless radio-linked design provides the capability to couple observation in real time with reactive sampling schemes (including mobile tracking), provides for public interaction via frequent updates to a Worldwide Web–based distance learning program, and saves ship time. However, the wireless design is more amenable to a turnstile-like acoustic gate than to positioning, and strategic positioning of hydrophones at bottlenecks is favored over continuous contact of transmitters within the large study area. The hydrophone array is supplemented by infrastructure from two existing marine observatory programs focused on physical processes. These are the Long-term Ecosystem Observatory (LEO-15) outside the estuarine inlet and the System-Wide Monitoring Program of the Jacques Cousteau National Estuarine Research Reserve (JCNERR) within the river and estuary. This article outlines considerations in the design and implementation of the array from infrastructure, predeployment survey, and biological considerations through hydrophone placement, maintenance, calibration, and data collection. Further, it presents a comprehensive description of the observatory and study area for reference in works on the biology of those organisms under study. The hydrophone array serves as a unit intended for stepwise extension into other estuaries to assist in our understanding of habitat use and of those species that use estuarine habitat during coastal migration.