Acoustic telemetry was used to assess riverine behavior and passage success for prespawn male adult Atlantic salmon Salmo salar in the lower Penobscot River, Maine, in 2005 (n = 10) and 2006 (n = 25). Only 3 of 10 (30%) and 2 of 25 (8%) tagged Atlantic salmon successfully passed all three dams between the head of tide and presumed spawning habitat in 2005 and 2006, respectively. Migrants that failed to pass the second upstream dam frequently fell back into the estuary (3 of 4 in 2005; 17 of 23 in 2006), and few successfully reascended Veazie Dam at the head of tide. Fallback behavior was associated with temperatures exceeding 22°C and may reflect a strategy for coping with thermal stress and migratory delays. Atlantic salmon were also observed to actively seek out thermal refuge near one of the dams. Passage data were compared with results from previous telemetry studies that used Carlin tags and radio telemetry from 1987–1990 and 1992, and passive integrated transponder tags from 2002–2004. For all 10 years of study combined, median passage success was 64, 72, and 93% for the three dams. While 2006 may represent an uncommonly poor year for upstream passage at these dams, median cumulative passage past two of these dams was only 71% and ranged from 8% to 87% among years. Study results indicate that poor upstream passage severely limits migratory success in this system, particularly during periods of high discharge. Planned removal of two of these lower river dams is expected to improve migratory success for adult Atlantic salmon in the Penobscot River system.
Freshwater ecosystems provide many ecosystem services; however, they are often degraded as a result of human activity. To address ecosystem degradation in the Laurentian Great Lakes, Canada and the United States of America established the Great Lakes Water Quality Agreement (GLWQA). In 1987, 43 highly polluted and impacted areas were identified under the GLWQA as having one or more of 14 Beneficial Use Impairments (BUIs) to the physical and chemical habitat for fish, wildlife and humans, and were designated as Areas of Concern (AOC). Subnational jurisdictions combined with local stakeholders, with support from federal governments, developed plans to remediate and restore these sites. Biotelemetry (the tracking of animals using electronic tags) provides information on the spatial ecology of fish in the wild relevant to habitat management and stock assessment. Here, seven case studies are presented where biotelemetry data were directly incorporated within the AOC Remedial Action Plan (RAP) process. Specific applications include determining seasonal fish-habitat associations to inform habitat restoration plans, identifying the distribution of pollutant-indicator species to identify exposure risk to contamination sources, informing the development of fish passage facilities to enable fish to access fragmented upstream habitats, and assessing fish use of created or restored habitats. With growing capacity for fish biotelemetry research in the Great Lakes, we discuss the strengths and weaknesses of incorporating biotelemetry into AOC RAP processes to improve the science and practice of restoration and to facilitate the delisting of AOCs.
Seasonal and daily vertical activity of lake whitefish Coregonus clupeaformis was studied in Clear Lake, Maine (253 ha), using acoustic telemetry from November 2004 to June 2009. Twenty adult lake whitefish were tagged with acoustic tags that had either a depth sensor or both depth and temperature sensors to assess vertical habitat use at a seasonal and daily resolution. Vertical habitat selection varied seasonally and was strongly influenced by temperature. Between December and April, when the lake was covered with ice, surface temperature was below 2°C and tagged individuals occupied deep areas of the lake (∼15 m). After ice‐out, fish ascended into shallow waters (∼5 m), responding to increased water temperature and possibly to greater foraging opportunity. When surface water temperatures exceeded 20°C, fish descended below the developing thermocline (∼9 m), where they remained until surface temperatures fell below 20°C; fish then ascended into shallower depths, presumably for feeding and spawning. Through the winter, fish remained in thermal habitats that were warmer than the surface temperatures; in the summer, they selected depths with thermal habitats below 15°C. Though the amplitude varied greatly across seasons, lake whitefish displayed a strong diurnal pattern of activity as measured by vertical velocities. Fish were twofold more active during spring, summer, and fall than during winter. Lake whitefish exhibited diel vertical migrations, rising in the water column during nighttime and occupying deeper waters during the day. This pattern was more pronounced in the spring and fall and far less prominent during winter and summer. The strong linkage between temperature and habitat use may limit the current range of lake whitefish and may be directly impacted by climatic change.
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