Abstract
The development of the Fundy Ocean Research Centre for Energy (FORCE) in-stream tidal turbine test site in Minas Passage, Bay of Fundy has necessitated environmental monitoring of commercially and recreationally valuable species, including the American lobster (Homarus americanus) fishery. The upper Bay of Fundy commercial lobster fishery (lobster fishing area 35) is lucrative and supports 75 licensed fishers (Canadian Science Advisory Secretariat, 2013). Adult American lobsters are known to undergo seasonal migration of 10s to 100s of kilometres to avoid cold winter water temperatures (Estrella and Morrissey, 1997, Robichaud and Lawton, 1997); this is of particular importance to ovigerous or berried females (Campbell, 1986, Cowan et al. 2007).
Impacts on lobster migration from the testing of tidal energy technology are unknown. Preliminary studies completed in the Minas Passage (Lockhart-Bastian et al., 2009, Collins, 2011) confirmed the presence of lobsters in the area and the FORCE test site. Conventional tagging methods were used with limited success as they provided data only during the fishing season. In order to gain higher temporal resolution and more data on fine-scale movements in and around the FORCE test site, Minas Basin lobsters were tagged with VEMCO tracking technology in both 2011 and 2012.
Prior to lobster tracking, a field test to assess detection range of the technology used was conducted in the Minas Passage using three Vemco VR2w acoustic receivers and six Vemco V13 acoustic transmitters. Transmitters and receivers were mounted in lobster traps and deployed for a three-day period to monitor detection efficiency of bottom moored tags in the Minas Passage. All three receivers logged detections from all transmitters. However, detection of tag transmissions varied throughout the tidal cycle, with the majority of detections occurring at average water column currents speeds of <1.5 m/s. Transmission interference due to ambient environmental noise is considered the cause of reduced detection efficiency at high flow speeds.
In November 2011, 85 adult American lobsters sourced from the commercial catch in Minas Basin were weighed, sexed, measured, and fitted with a Vemco V13 acoustic transmitter and a numbered disc tag to facilitate fisher tag returns. Lobsters were released near their site of capture, several kilometers east of the innermost array of acoustic receivers in Minas Passage. A total of 29 acoustic receiver stations were deployed in three line arrays as “listening gates” spanning the Minas Passage and FORCE test site. Receivers were housed in moored sub buoys that were tethered approximately 3 m above the seafloor.