Introduction & Objectives

This telemetry monitoring study was initiated in May 2021 to collect year-round occurrence data for Atlantic and shortnose sturgeon in the lower Kennebec River (including Bath Iron Works) and also to collect data during recurrent Naval activities. This study will also implement monitoring stations offshore of Popham Beach to capture coastal movements of sturgeon and other species, including white sharks. This area encompasses a curtain between Fox-Seguin Islands and the Jack Knife Ledge Dredge Disposal area. Additionally, an additional 55 total Atlantic and shortnose sturgeon will be tagged in the Kennebec River to increase the population of tagged fish.

Project objectives are: 1) monitor sturgeon activity in the proximity of Bath Iron Works; 2) Document coastal movements of fish offshore from Popham Beach: ESA sturgeon species, striped bass, white sharks, and other highly migratory species; 3) Monitoring year-round presence and migration of Atlantic sturgeon in the lower Kennebec River; 4) Monitoring year-round presence and migration of shortnose sturgeon in the lower Kennebec River; and 5) add additional acoustically tagged species to the Kennebec River system. Collaborators on this project include State of Maine Department of Marine Resources, University of Maine, U.S. Geological Survey, Portsmouth Navy Yard, University of Maryland (data analytics).

Technical Approach

The technical approach is to deploy year-round telemetry monitoring stations in the Lower Kennebec River including Bath Iron Works area to capture timing and movement through these areas, and also offshore stations to assess movements of ESA-listed sturgeon between river systems.  Locations and habitat of deployments are chosen carefully to maximize detection of sturgeon and also to minimize potential loss of equipment.  Data analysis will include summaries of number of unique sturgeon detected at each station for each month, and number of days per month sturgeon detected.  Also, finer scale telemetry data for the array will be reviewed for metrics such as likelihood of detection for different areas across seasons, and comparative rates of movement. 

With many previously deployed sturgeon tags expiring, the approach is also to surgically tag a minimum of 55 new Atlantic and shortnose sturgeon.  Biometrics are collected during tagging including inter-orbital and mouth width, a PIT tag inserted, and a fin clip collected for DNA analysis.

Progress & Results

In May 2021, 8 telemetry stations were deployed in the river to supplement MEDMR existing 3, and an additional six were deployed offshore. The array configuration was updated in 2022 to consists of 12 stations in the river in coordination with MEDMR, and 5 offshore. As of December 2023, there are 15 year-round telemetry monitoring stations from Courthouse Point in Dresden to Fort Popham (including one in the Eastern River offshoot), and 5 stations offshore. Downloads of telemetry stations occur twice a year. In the river, the array has detected both species of sturgeon, American shad (Alosa sapidissima), and striped bass (Morone saxatilis). Offshore data includes detects for species of sturgeon, striped bass, American shad, white sharks, and Atlantic bluefin tuna (Thunnus thynnus), with several unknown tag IDs still pending.

There were 63 total sturgeon tagged in 2022, consisting of 40 Atlantic and 23 shortnose sturgeon. For the time period representing the last 2 download cycles (November 2022 – October 2023), 779,984 detections were recorded across all species and stations. The addition of new-tagged fish to the system significantly increased the dataset in river. Of those detections, the vast majority (river: 731,770) were Atlantic sturgeon, followed by shortnose sturgeon (river: 24,924), striped bass (river: 2,565), and white shark (ocean: 849). However, the frequency of tag observations should not be interpreted as a proxy for population distribution or abundance, as the proportion of tagged individuals for each species is not equivalent. For example, an increasingly high percentage of Atlantic sturgeon are tagged in the Gulf of Maine region, as compared with shortnose sturgeon.

Total detections for shortnose sturgeon were much lower than Atlantic sturgeon, although differences are reflective of current active tags in the region. Shortnose were not detected on stations in the lower Kennebec outside of April to August. The additional 23 tagged shortnose sturgeon in 2022 have provided insights on the important movements during the warmer months but also increased prevalence mid‐river as compared to Atlantic sturgeon. Overall counts and frequency of Atlantic sturgeon at offshore stations are unsurprisingly lower, with highest counts at these stations occurring June through September with notable detections also recorded in April. Offshore detections likely represent data for fish moving in and out of the system during those months. No sturgeon were detected on any station offshore in November and March.