A Deeper Look into Atlantic Salmon Smolt Predation Using Acoustic Telemetry

An effective and common application of acoustic telemetry investigations is characterizing fish behavior and assessing survival over various spatial and temporal scales. Results obtained from such studies provide researchers with a better understanding of population dynamics and allows managers to make informed decisions. In the Penobscot River, a network of stationary receivers has been used since 2005 to study the downstream migration of wild and hatchery origin Atlantic salmon smolts. This network has produced thousands of smolt movement tracks. Appropriate interpretation of these data, however, depends upon exclusion of any spurious or erroneous information. Some obvious specious track data can be readily excluded while other tracks that appear “abnormal” or “inconsistent” with previously observed patterns are problematic. These observations could be either novel information or unrepresentative data (indicative of mortality or a predation event). Analysis of individual smolt tracks has allowed us to infer when predation events occur.  Combining our knowledge of the system’s geography and suite of potential smolt predators (e.g. striped bass and cormorants) we have been able to assess predation on smolts through circumstantial evidence. Our findings indicate that between 5% and 20% of tagged smolts suffer predation mortality in the Penobscot River Estuary.