Movement Patterns of Brook Trout (Salvelinus fontinalis) Inhabiting a Restored Coastal Stream in Massachusetts: Preliminary Evidence of Anadromy

Although there is a growing movement to remove physical barriers as part of restoration efforts for small coastal streams in New England, it is unclear whether restoring connectivity alone will be sufficient to promote anadromy in resident brook trout (Salvelinus fontinalis) populations.  Capitalizing on restoration efforts of Red Brook (Plymouth/Wareham/Bourne, MA) that included habitat improvements and the removal of physical barriers that fragmented the stream, we are using acoustic telemetry to quantify the movement patterns of brook trout between the lower freshwater reach and the coastal waters of Buttermilk Bay.  Two fixed acoustic receivers were deployed in series in the lower reach and estuarine portion of the stream, while seven receivers were deployed as nodes along the coastline of Buttermilk Bay.  To date, two batches of brook trout have been surgically implanted with acoustic transmitters; 10 in June 2010 (mean FL 218 ± 34 mm SD) and 20 in September 2010 (mean FL, 209 ± 21 mm SD).  As of February 2011, 14 (47%) of the transmitter-implanted brook trout have generated a total of 4784 reliable detections on 76 different days.  Although 75% of the detections have been recorded on the receiver positioned in the lower freshwater reach, four individuals have been detected moving into the estuarine portion of the stream.  Of these individuals, three have also been detected on multiple receivers in Buttermilk Bay, including the most distant receiver 2.75 km from the mouth of Red Brook at the transition point to Buzzards Bay.  One individual (275 mm FL) was detected in Buttermilk Bay between August-September but has not been detected since, while the other fish (200-219 mm FL) were detected in the estuarine portion of Red Brook beginning in early November and in Buttermilk Bay from late November through January 2011.  These results underscore the need for connectivity between coastal and river habitats for the full expression of life history tactics in brook trout.  The small sample size of fish using Buttermilk Bay precludes any analyses to determine whether individual traits (e.g., body size) are associated with anadromy, however additional acoustic tagging in 2011 in combination with PIT tagging to monitor in-stream movements and growth may lead to a better understanding of the mechanisms behind the use of the coastal zone by brook trout.