Minas Passage Research Articles

Improved Modelling of Vertical Velocity Profiles at a Tidal Energy Site

The Minas Passage, one of the Bay of Fundy’s tidal channels, located in Nova Scotia, Canada, presents significant potential for tidal energy development because of its highly energetic flows. As development in the region gains traction, the implementation of floating tidal energy platforms is a topic of growing interest. Tidal energy deployments in Minas Passage have historically been bottom-mounted and stationary, and the transition to arrays of floating turbines requires additional considerations. Particularly, this new application demands characterization of flow over the entire water column, including near the free surface. Complete vertical velocity profiles are essential for the successful deployment of floating tidal turbines, allowing for the estimation of key metrics such as tidal power and shear across turbine blades. Here we explore adaptations to the well-established logarithmic law of the wall with the goal of extending the vertical range over which a fitting regime based in classical turbulence theory can capture the observational records of flow in Minas Passage.
 Observational site characterization efforts in Minas Passage have primarily consisted of stationary, bottom mounted Acoustic Doppler Current Profiler (ADCP) deployments. Using historical ADCP records collected in Minas Passage between 2008 and 2021, we fit the vertical profiles of velocity using three methods: logarithmic law of the wall, power law, and an adapted logarithmic law of the wall which includes a “wake function” to improve fits in the upper water column. We find that although the law of the wall results in well-fitted estimations of the vertical velocity profiles near the seabed, observational profiles consistently deviate from the fitted curves in the middle and upper water column, recording significantly faster flow speeds than predicted by the law of the wall. The adapted model, which is rooted in turbulence theory and includes a wake term, is successful in capturing flow in the outer layer of the water column and allows for reverse shear to be captured in the profile. The resulting fits show a sizeable reduction in error throughout the entirety of the water column compared to the law of the wall profiles, and consistently reduce the error in the vertical profile fits when compared to power law fits. In addition to resulting in low error for both individual and averaged vertical profiles of flow, the physical quantities estimated from the adapted model, including drag coefficient, agree well with those computed from the law of the wall, demonstrating the physical usefulness of the adapted model.

Towards Estimating Probability of Fish–Turbine Encounter: Using Drifters Equipped with Acoustic Tags to Verify the Efficacy of an Array of Acoustic Receivers

An area has been designated for demonstrating the utility of marine hydrokinetic turbines in Minas Passage, Bay of Fundy. Marine renewable energy may be useful for the transition from carbon-based energy sources, but there is concern for the safety of fish that might encounter turbines. Acoustic receivers that detect signals from acoustically tagged fish that pass through the tidal demonstration area and the detection efficiency of tag signals might be used to estimate the likelihood of fish encountering marine hydrokinetic turbines. The method requires that tagged fish passing through the development area will be reliably detected by a receiver array. The present research tests the reliability with which passing tags are detected by suspending tags beneath GPS-tracked drifters. Drifters carrying high residency Innovasea tags that transmitted every 2 s were usually detected by the receiver array even in fast currents during spring tides but pulse-position modulation tags were inadequate. Sometimes very few high residency tag signals were detected when fast tidal currents swept a drifter through the receiver array, so increasing the transmission interval degrades performance at the tidal energy development area. High residency tags suspended close to the sea surface were slightly less likely to be detected if they passed by during calm conditions. Previously measured detection efficiencies were found to slightly overestimate the chances of a high residency tag carried by a drifter being detected as it passed by a receiver. This works elucidates the effectiveness with which acoustically tagged fish are detected in fast, highly turbulent tidal currents and informs the application of detection efficiency measurements to calculate the probability that fish encounter a marine hydrokinetic turbine.

Measuring Detection Efficiency of High-Residency Acoustic Signals for Estimating Probability of Fish–Turbine Encounter in a Fast-Flowing Tidal Passage

Semidiurnal tidal currents can exceed 5 ms−1 in Minas Passage, Bay of Fundy, where a tidal energy demonstration area has been designated to generate electricity using marine hydrokinetic turbines. The risk of harmful fish–turbine interaction cannot be dismissed for either migratory or local fish populations. Individuals belonging to several fish populations were acoustically tagged and monitored by using acoustic receivers moored within the Minas Passage. Detection efficiency ρ is required as the first step to estimate the probability of fish–turbine encounter. Moored Innovasea HR2 receivers and high-residency (HR) tags were used to obtain detection efficiency ρ as a function of range and current speed, for near-seafloor signal paths within the tidal energy development area. Strong tidal currents moved moorings, so HR tag signals and their reflections from the sea surface were used to measure ranges from tags to receivers. HR2 self-signals that reflected off the sea surface showed which moorings were displaced to lower and higher levels on the seafloor. Some of the range testing paths had anomalously low ρ, which might be attributed to variable bathymetry blocking the line-of-sight signal path. Clear and blocked signal paths accord with mooring levels. The application of ρ is demonstrated for the calculation of abundance, effective detection range, and detection-positive intervals. High-residency signals were better detected than pulse position modulation (PPM) signals. Providing that the presently obtained ρ applies to tagged fish that swim higher in the water column, there is a reasonable prospect that probability of fish–turbine encounter can be estimated by monitoring fish that carry HR tags.

Probability of Atlantic Salmon Post-Smolts Encountering a Tidal Turbine Installation in Minas Passage, Bay of Fundy

Tidal stream energy is a renewable energy resource that might be developed to offset carbon emissions. A tidal energy demonstration (TED) area has been designated in Minas Passage, Bay of Fundy, for testing and installing marine hydrokinetic (MHK) turbines. Regulations require quantification of the potential for MHK turbine installations to harm local populations of marine animals. Here, we use acoustic telemetry to quantify the probability that post-smolt inner Bay of Fundy salmon encounter a turbine installation at the TED area. Previous work has quantified the detection efficiency of Innovasea HR acoustic tags as a function of the current speed and range from a moored HR2 receiver and also demonstrated that drifters carrying HR tags will be effectively detected when the drifter track crosses the array of HR2 receivers in Minas Passage. Salmon smolts were tagged and released in Gaspereau and Stewiacke Rivers, Nova Scotia, in order that the HR2 receiver array could monitor seaward migration of the post-smolts through Minas Passage and particularly through the TED area. Presently, we formulate and apply a method by which tag signals detected by the HR2 array can be used to estimate the expected number of times that a post-smolt would encounter a single near-surface MHK turbine installation during its seaward migration.

Modeling the Probability of Overlap Between Marine Fish Distributions and Marine Renewable Energy Infrastructure Using Acoustic Telemetry Data

Understanding the spatiotemporal distributions of migratory marine species at marine renewable energy sites is a crucial step towards assessing the potential impacts of tidal stream turbines and related infrastructure upon these species. However, the dynamic marine conditions that make tidal channels attractive for marine renewable power development also make it difficult to identify and follow species of marine fishes with existing technologies such as hydroacoustics and optical cameras. Acoustic telemetry can resolve some of these problems. Acoustic tags provide unique individual ID codes at an ultrasonic frequency, which are then detected and recorded by acoustic receivers deployed in the area of interest. By matching detection locations of fish species with environmental conditions at proposed sites for tidal energy infrastructure, species distribution models can be developed to predict the probability of species occurrence at sites of current and planned tidal power development. This information can be used to develop statistically robust encounter rate models to aid in quantifying the risk of tidal power development to migratory fish species. We used this approach to develop a predictive model of striped bass (Morone saxatilis) distribution within Minas Passage in the upper Bay of Fundy, Nova Scotia. Model results suggested increased probability of striped bass presence in Minas Passage during late ebb tide conditions and at relatively high water temperatures. We demonstrate the potential utility of species distribution modeling of acoustic tag detections in predicting interactions with renewable energy infrastructure, and show the importance of physical oceanographic variables influencing species distributions in a highly dynamic marine environment.

The Ups and Downs of Using Active Acoustic Technologies to Study Fish at Tidal Energy Sites

Active acoustic instruments (echosounders) are well-suited for collecting high-resolution information on fish abundance and distribution in the areas targeted for tidal energy development, which is necessary for understanding the potential risks tidal energy devices pose to fish. However, a large proportion of echosounder data must often be omitted due to high levels of backscatter from air entrained into the water column. To effectively use these instruments at tidal energy sites, we need a better understanding of this data loss and how it may affect estimates of fish abundance and vertical distribution. We examined entrained air contamination in echosounder data from the Fundy Ocean Research Center for Energy (FORCE) tidal energy test site in Minas Passage, Nova Scotia, where current speeds can exceed 5 m·s-1. Entrained air depth was highly variable and increased with current speed, and contamination was lowest during neap tides. The lower 70% of the water column and current speeds <3 m·s-1 were generally well-represented in the dataset. However, under-sampling of the upper water column and faster speeds strongly affected simulated fish abundance estimates, with error highly dependent on the underlying vertical distribution of fish. Complementary sensing technologies, such as acoustic telemetry and optical instruments, could be used concurrently with echosounders to fill gaps in active acoustic datasets and to maximize what can be learned about fish abundance and distribution at tidal energy sites.

Migration and apparent survival of post-spawning alewife (Alosa pseudoharengus) in Minas Basin, Bay of Fundy

The anadromous alewife is a commercially fished clupeid in Atlantic Canada, whose oceanic migration is poorly understood. Migration of alewives is presently investigated from the lower reaches of Gaspereau River into Minas Basin, Bay of Fundy. Seventy-five post-spawning adults were tagged on their downstream migration; within two days of being tagged, most alewives had left Gaspereau River and 57 entered into the Southern Bight of Minas Basin. Thirty-one alewives were detected in Minas Passage and their average time from tagging to final detection was 28 days with standard deviation of 11 days. None of the alewives were detected in Minas Passage until day 20 after the start of tagging. After day 20, the residence timescale in Minas Basin was only 8.8 days with 95% CI of 8.4–9.3 days. Fast tidal currents prevail in much of the study area, and alewives travelled many large tidal excursions in Minas Basin and Minas Passage. Separation distances between pairs of alewives increased greatly after day 20, indicating tidal mixing over large distances within the study area. Offshore movement was associated with seasonal warming, with alewives moving down the spatial temperature gradient and into deeper waters. Offshore, larger tidal displacements widely dispersed tagged alewives through Minas Basin and to Minas Passage. During transit of Gaspereau River, 18 ± 2 alewives were lost with corroborating evidence of mortality for 4 of these. By day 20, the apparent mortality within Minas Basin was ≤ 10 alewives. Individual alewives were observed to make many transits through Minas Passage during their migration, where they may become exposed to in-stream tidal turbines.

Atlantic sturgeon presence in a designated marine hydrokinetic test site prior to turbine deployment: A baseline study

In 2009, the Fundy Ocean Research Centre for Energy (FORCE) developed a 1.6 x 1.0 km Crown Lease Area (CLA) to test Marine Hydrokinetic devices (MHKs) in Minas Passage (MP), a strait that connects the Bay of Fundy to Minas Basin (MB), Nova Scotia. Minas Basin is an important summer feeding aggregation site for numerous fishes including Atlantic sturgeon (Acipenser oxyrinchus Mitchill, 1815) stocks from Canada and the US. In this study, acoustic tagging technology was used to describe sturgeon presence in the CLA, as well as an adjacent site proposed for MHKs deployment. During 2018 and 2019, 33.9% (n = 19/56 Atlantic sturgeon tagged) and 29.9% (n = 23/77 Atlantic sturgeon tagged) respectively, of sturgeon acoustically tagged in MB during 2014–2019 were detected in these two FORCE sites. Binomial General Linear Models (GLMs) were fit to determine if environmental parameters influenced the presence, or depth of Atlantic sturgeon in the FORCE sites. The only significant predictor of Atlantic sturgeon depth and presence at the FORCE sites was tide type. Atlantic sturgeon was found to have a higher likelihood of being detected during ebb tide (12%) as opposed to flood tide (3%). Apparent decline in the presence of sturgeon during flood tide was probably due to poor signal reception caused by turbulence from higher current speeds. Tagged sturgeon travelled through the FORCE sites pelagically at similar depths (27.5 ± 14.57 m) to those proposed for seabed mounted MHKs (~30 m), travelling deeper during flood tide than ebb, suggesting they may be at risk of spatial overlap with MHKs. While this study indicated that the duration Atlantic sturgeon utilized the FORCE sites throughout the summer appeared to be low, sturgeon from both endangered and threatened stocks migrated through this region during their yearly entry and exit to MB and were present for approximately 12% of the days assessed in this study.

Seasonal occurrence of waterbirds in Minas Passage, Bay of Fundy, Nova Scotia, Canada, 2010 to 2012

We determined patterns of seasonal abundance and diversity of seabirds and coastal waterfowl in Minas Passage, Bay of Fundy, Nova Scotia, Canada using quantitative, shore-based point surveys from mid-March to late August and mid-October to December 2010 to 2012. This area experiences the world’s highest tides and greatest tidal currents. We showed that species and seasonal cycles of waterbirds in Minas Passage reflect patterns typical of the inner Bay of Fundy and the northeast Atlantic coast of North America. The study highlights the importance of Minas Passage as an important local migration pathway for waterbirds including Black Scoter (Melanitta americana) and Red-throated Loon (Gavia stellata) passing through the Bay of Fundy. Large numbers of sea ducks (Black Scoter, Surf Scoter [Melanitta perspicillata], White-winged Scoter (Melanitta fusca), and Long-tailed Duck [Clangula hyemalis]), and Red-throated Loon were observed at the site in spring and fall, corresponding to known peak movements elsewhere in the Bay of Fundy. Fewest species and smallest abundances of waterbirds overall occurred in summer and early winter, while most species and largest abundances occurred in April-May and early November. Of the 46 species observed, resident breeders such as Herring Gull (Larus argentatus), Great Black-backed Gull (Larus marinus), Common Eider (Somateria mollissima), Black Guillemot (Cepphus grylle), and Double-crested Cormorant (Phalacrocorax auritus), were most abundant in spring to early summer during breeding and migrants including Red-throated Loon, Black Scoter, Ring-billed Gull (Larus delawarensis), Surf Scoter, and Northern Gannet (Morus bassanus) occurred in moderate numbers during migration periods.

FindPorpoises: Deep learning for detection of harbor porpoise echolocation clicks

Tom Norris expressed conservation concern for the vaquita, a close relative of harbor porpoises; here we report on a harbor porpoise (Phocoena phocoena) conservation effort. Tidal energy devices are installed in high-flow estuaries that are also prime harbor porpoise habitat. To study tidal energy device impacts on porpoises, sound was recorded in Minas Passage, Bay of Fundy, Canada. Analysis aimed to distinguish harbor porpoises from noise sources. “Click candidate” sounds were detected using the ratio between the harbor porpoise frequency band and lower guard band, then reviewed by humans to label which were correct. Because more “correct” instances were needed, data were augmented by mixing porpoise clicks with known noise, producing 20,000 “click present” labeled instances. Additionally, 20 000 “non-click” instances were extracted from noise recordings. Labeled instances were made into a 0.5-s equalized spectrograms for training deep-learning networks. Of the network architectures tried, the best was a convolutional neural network with pooling and fully connected layers, achieving 99.1% accuracy. User-friendly “FindPorpoises” software was made to pre-process raw files, detect candidate clicks, use the trained network to sort candidate clicks into correct and incorrect instances, and plot and tabulate the results by time of day, tide cycle, and month. [Work supported by OERA.]

A review of the fishes and fisheries of Minas Basin and Minas Passage, Nova Scotia, and their potential risk from tidal power development

A total of 85 species of fish are known or suspected from Minas Basin and Minas Passage, Nova Scotia, Canada. This systematic review details their seasonal occurrence, habitat, abundance, migratory behavior, fisheries and potential impact from tidal power development. The fish assemblage is a mixture of species common to the Bay of Fundy and the Atlantic coast of Nova Scotia as well as numerous warm- and cold-water visitors seldom found elsewhere in Canada. Minas Basin fisheries exploit some species especially those that migrate through the Basin during summer. Fishes were captured or observed using angling, seines, benthic long lines, drift and fixed gill nets, intertidal fish weirs, bottom trawls and sightings while on vessels. Fishes are categorized with respect to their taxonomic diversity, seasonal occurrence, status, fisheries and the potential impact from tidal lagoons and propeller turbines resulting from development of tidal power in Minas Basin and Minas Passage. Keywords: Bay of Fundy, habitat, species status, propeller turbines, taxonomic relationship, tidal lagoons.

Performance of a Passive Acoustic Linear Array in a Tidal Channel

Baseline ambient sound level assessment is important in quantifying anthropogenic noise contributions. Static acoustical sensing in high-flow conditions is complicated by pseudosound, or flow noise, caused by turbulent flow on the surface of a hydrophone. Signal processing methods are used to identify and suppress flow noise at low frequencies (<; 500 Hz) in data collected on a four-element horizontal hydrophone array in Minas Passage, a tidal channel in the Bay of Fundy, in October 2016. Spectral slope analysis is used to identify the frequencies at which the flow noise and ambient noise contributions to the recorded signal are equal, between 180 and 275 Hz for current speeds of 0.1 to 2.6 m/s, respectively. The maximum frequencies at which flow noise is observed, between 100 and 125 Hz over the same current speed range, are determined using analysis of the spatial coherence. The array's performance in the Minas Passage is quantified by an empirical relationship between flow speed and the spectral critical frequencies of the coherent output from the linear array. Coherent averaging (broadside beamforming) is demonstrated as a potential flow noise suppression technique, improving low-frequency passive acoustic monitoring in a high-energy tidal channel.

Encounters in the ebb and flood: Knowing marine ecologies in the intertidal contact zone

Shifting rhythmically between land and sea with the ebb and flood tides, shores are places where humans and nonhumans encounter one another in ambivalent relations of deep familiarity and enduring strangeness. In this article, I use the space of the intertidal contact zone to think through a series of uneven encounters between humans and marine wildlife that populate a dispute over tidal energy testing in the Bay of Fundy's Minas Passage. I trace two contact zones through which knowledge about marine wildlife in the Bay of Fundy is generated: first, the contact zone continually (re-)assembled through the encounters of small-scale and traditional fishers with marine wildlife, and second, the contact zone staged in remote encounters between marine scientists and marine wildlife. The article reflects on the role of bodies in and out of encounter in the different ways of knowing about marine wildlife in this case and considers ethical possibilities and limits of knowing through, versus without, contact with nonhuman animals in the intertidal contact zone.

The impacts of tidal energy development and sea-level rise in the Gulf of Maine

In this study, we employed a 3-D and two-way nested Regional Ocean Modeling System (ROMS) to address several important outstanding issues regarding tidal energy development in the Gulf of Maine. We investigated the impact of projected sea-level rise (SLR) on the energy resources of the region, and examined how tidal dynamics will be influenced by energy extraction and/or SLR. Further, we assessed whether the effect of SLR on the generation of tides in the ocean (hence at the boundary of the region) is significant in these assessments. We find that the impact of SLR exceeds the impact due to energy extraction in the Gulf of Maine - even when considering very large energy extraction, of order 3.0 GW, in the Minas Passage. Although results showed that energy extraction does not significantly increase the amplitude of the tides in the far-field, a drastic change in the Bay of Fundy (e.g. full blockage) can lead to considerably higher amplitudes of tides (around 35 cm, or 12%) in the western Gulf of Maine. As a result of 1 m SLR, the theoretical tidal energy resources in some areas, including the Bay of Fundy can increase noticeably while any significant change in extracted energy highly depends on the turbine technology.

Assessment of tidal stream energy resources in a hypertidal estuary with highly irregular bathymetry using 3D numerical modelling

Owing to large currents generated by the strong tides coming from Ungava Bay, the hydrokinetic energy potential of the Koksoak River Estuary (KRE) Nunavik, Canada, is substantial. With a tidal range of more than 12 m, the KRE is classified as “hypertidal”, and with water depths ranging from 10 to 130 m and widths ranging from 700 to 4500 m, it could also be said that the KRE is “hyperbathymetric”. Even aside from the intense cold associated with its Arctic climate, this combination of hypertidal/hyperbathymetric makes the KRE possibly the most extreme estuary in the world. Using a 3D hydrodynamic finite-difference model to simulate the KRE’s velocities, the in-stream power densities were calculated over the entire domain. The resulting map pinpoints the energy sites available for the 3000 residents of Kuujjuaq, a town located 50 km from the estuary mouth. At optimal KRE sites, based on vertically averaged velocities, the available mean power density is 7.2 kW/m2. Near the surface, the available mean power density increases to 10.5 kW/m2. These values exceed that calculated (6.0 kW/m2) for the famous Bay of Fundy’s Minas Passage. This paper describes the nature of the estuary, introduces the modelling efforts, and quantifies the spatial–temporal variability of the available hydrokinetic power density.

Turbines for modular tidal current energy converters

The vast potential of ocean energies is of increasing interest. Harnessing marine currents driven by the tidal cycle have triggered the development of various power conversion systems. However, the comparably high levelized cost of electricity is still the main hindrance for a faster market penetration. The paper describes a novel strategy to decrease the cost: A number of small prefabricated turbines of low complexity form an arbitrary scalable array of turbines; a modular design of the key unit “turbine” allows an easy adaption to the tidal current velocity profile at a particular site; hydraulically optimized turbine blades ensure maximum annual energy production and minimum immersion depth. Results of the design efforts are a 4 m and a 6.3 m diameter horizontal axis free flow turbine with an identical drive train for a rated electrical power of 70 kW. Four turbines have been tested on a 30 m × 26 m trimaran placed for several months near the Falls of Lora in Scotland. The power yield fully confirmed the prediction. As an example, the annual electric energy production from such a turbine, placed in the Minas Passage area of the Bay of Fundy in Canada - an ideal site of harnessing tidal currents, is forecasted as 230 MWh.

Winter and summer differences in probability of fish encounter (spatial overlap) with MHK devices

The likelihood of fish encountering an MHK device, and therefore the risk posed to fish, depends largely on the natural distribution of fish at tidal energy development sites. In temperate locations, such as the Bay of Fundy, seasonal changes in the environment and fish assemblage may alter the likelihood of fish encounters with MHK devices. We examined two one-month hydroacoustic datasets collected in winter 2015 and summer 2016 by an upward-facing echosounder deployed at the Fundy Ocean Research Center for Energy test site in the Minas Passage. Fish density was higher and less variable in winter than in summer, likely due to the presence of migratory vs. overwintering fish. The vertical distribution of fish varied with sample period, diel stage, and tidal stage. The proportion of fish at MHK device depth was greater, but more variable, in summer than in winter. Encounter probability, or potential for spatial overlap of fish with an MHK device, was &lt; 0.002 for winter and summer vertical distributions. More information on the distribution of fish (horizontal and vertical), species present, fish sensory and locomotory abilities, and nearfield behaviours in response to MHK devices is needed to improve our understanding of likely device effects on fish.

Coastal retreat rates and sediment input to the Minas Basin, Nova Scotia

The strong tidal currents of the Minas Passage in the Bay of Fundy, Nova Scotia, have made this area an important site for testing and development of tidal power technologies. Understanding sediment processes in this area is essential for determining the impacts that large-scale tidal power extraction would have on the system. Previous estimates of sediment input to the Basin suggest that much more sediment enters the Basin than accumulates within it; therefore, the bottom sediment texture should be in hydrodynamic equilibrium with bottom currents. A recent study, however, showed that sediment texture is generally finer that what was expected based on current speeds. This paper uses geographic information systems methods to provide updated and more highly resolved measurements of the amount of sediment entering the Minas Basin from the dominant source, which is coastal erosion. Volumetric input from coastal erosion is 1.1 × 106 m3·a−1, which is more than two times smaller than previous estimates. This updated value makes input rates comparable to accumulation rates, and agrees with the hypothesis that bottom sediment texture is not in equilibrium with current speeds. Grain-size distributions also support the hypothesis that the Minas Basin acts as a sediment trap.

Winter presence and temperature-related diel vertical migration of striped bass (Morone saxatilis) in an extreme high-flow passage in the inner Bay of Fundy

During a multiyear fish tracking study, subadult and adult life stages of Shubenacadie River striped bass (Morone saxatilis) were detected throughout winter in the well-mixed, hypertidal waters of the Minas Passage, Bay of Fundy. Thirty-five percent of the striped bass tagged with Vemco V16 transmitters were detected by two Minas Passage receiver arrays. Transmissions were received on 82% of winter days (December to April) and by all receivers spanning the width of the passage. Tagged striped bass were detected largely within the top 20–40 m during the day. The extent of vertical migration to shallower waters at night showed a strong relationship with water temperature; however, there was no diel vertical movement pattern observed at water temperatures &lt;1 °C. Our results demonstrate overwintering of a portion of the Shubenacadie River striped bass population in high-flow inner Bay of Fundy waters, which extends the northern limit of this species’ winter marine range. This study is also the first to describe the relationship between daily vertical migration by striped bass and low water temperatures. Both findings suggest an elevated potential risk of interaction with an in-stream tidal turbine facility in Minas Passage.

Atlantic sturgeon Acipenser oxyrinchus Mitchill, 1815 seasonal marine depth and temperature occupancy and movement in the Bay of Fundy

Pop-up satellite archival tags were used to collect fisheries-independent data that characterized the seasonal habitat occupancy and movement of Atlantic sturgeon Acipenser oxyrinchus Mitchill, 1815 in the Bay of Fundy (BoF). Atlantic sturgeon from Canadian and United States stocks aggregate annually for feeding in Minas Basin, inner BoF (45.28N, 64.18W), during May to September but depart to other locations from October to April. Sixteen PSAT tags were applied to sturgeon ranging from 152 to 203 cm total length captured and released in Minas Basin during May to August. Ten of the tags were reported after 1 year at large and provided pop-off locations. Seven were recovered with archived data, or provided transmitted data sets, which were analyzed for depth and temperature occupancy from June 2011 to August 2013. During June to August while in the Minas Basin the sturgeon spent >90% of time at depths <10 m and temperatures of 16–22°C. Departure from Minas Basin through the Minas Passage was in September and October, when depth occupancy varied from <10 to 120 m. From November to April sturgeon were in the outer BoF, where mean depth occupancies ranged from 40 to 100 m at mean temperatures of 3–14°C. Deepest mean depth occupancy of 60 to 90 m was recorded during December 2011 and 2012, and coldest mean temperature occupancy of 0–4°C in March 2011 and 2012. During April and May mean depth and temperature occupancy ranges shallowed from 40 to <10 m and increased from 4 to 15°C, respectively. Tag pop-off locations indicated that sturgeon spent the winter season in the outer BoF but by June had either migrated back to the Minas Basin or off the mouth of the Saint John River, a known spawning location.