Scaling acoustic telemetry of bluefish in an estuarine observatory: Detection and habitat use patterns

We telemetered adult bluefish Pomatomus saltatrix via a fixed estuarine hydrophone array to assess estuarine habitat use and determine the feasibility of using this approach coastwide. Eighteen bluefish (286-622 mm fork length) were surgically implanted with ultrasonic tags transmitting at either 2-s or 5-s intervals. The fish were monitored during their stay within a temperate estuary by hydrophones and associated environmental data loggers at major bottlenecks. They moved quickly through the hydrophone detection ranges, with 3-100 acoustic contacts being recorded within 15-min intervals. Contacts per 15-min interval with fixed hydrophones were similar for fish with 2-s and 5-s transmission interval tags, but mobile tracking proved ineffectual. Bluefish preferred the shallow polyhaline portion of the estuary, but several moved upriver to a salinity as low as 12 parts per thousand. The latter occurred near the minimum (14 degrees C) of the temperature range utilized (11-27 degrees C). Residence times (0-55 d; mean = 15 d) indicated the importance of estuaries to bluefish during spring and fall. Residence time was unrelated to fish size. The success of a coastwide effort monitoring multiple estuaries for bluefish could be high and would be enhanced by proper configuration of the tags and hydrophone arrays, as outlined here.