Peter A. Cott

Effects of exposure to seismic airgun use on hearing of three fish species

Seismic airguns produce considerable amounts of acoustic energy that have the potential to affect marine life. This study investigates the effects of exposure to a 730 in.3 airgun array on hearing of three fish species in the Mackenzie River Delta, the northern pike (Esox lucius), broad whitefish (Coregonus nasus), and lake chub (Couesius plumbeus). Fish were placed in cages in the 1.9 m of water and exposed to five or 20 airgun shots, while controls were placed in the same cage but without airgun exposure. Hearing in both exposed and control fish were then tested using the auditory brainstem response (ABR). Threshold shifts were found for exposed fish as compared to controls in the northern pike and lake chub, with recovery within 24 hours of exposure, while there was no threshold shift in the broad whitefish. It is concluded that these three species are not likely to be substantially impacted by exposure to an airgun array used in a river seismic survey. Care must be taken, however, in extrapolation to other species and to fishes exposed to airguns in deeper water or where the animals are exposed to a larger number of airgun shots over a longer period of time.

Stability in Life History Characteristics among Burbot Populations across Environmental Gradients

Abstract We examined the variation in the growth, morphometry, life history, and reproductive traits of 24 lake-dwelling populations of Burbot Lota lota from across Canada with respect to latitude and lake characteristics as well as the differences in these traits between the sexes across populations. Overall, there was stability in most of the life history traits examined vis-a-vis the environmental gradients tested (latitude, Secchi depth, lake area, and maximum lake depth). Among populations, spawning dates ranged from the last week of January to mid-March (most commonly within the first three weeks of February), and date of spawning was not strongly related to latitude or lake characteristics. Liver size and gonad size did not vary significantly with latitude or other lake characteristics, and neither gonad size nor egg size were strongly related to maternal size. However, egg size decreased with latitude and increased with lake area. The proportion of females in nonspawning condition within populatio...

Hearing Sensitivity of the Burbot

Abstract Acoustic communication is central to the reproductive ecology of many fish species, particularly when conditions prevent the use of visual mating cues. The Burbot Lota lota is a freshwater codfish that spawns in a light-limited, under-ice environment. Both sexes possess swim bladder muscles, suggesting that both sexes engage in vocalization and that auditory cues are important to their mating system, but research on acoustic communication has been very limited in this species. In the current study we assessed the hearing sensitivity of Burbot from different size-classes. Burbot hearing was found to be more sensitive in juveniles than in adults, but across size-classes it was most sensitive at lower frequencies, which is similar to results with other codfishes and corresponds to the sounds produced by gadoids. Anthropogenic noise has the potential to disturb fish. The information gained in this study can be useful in assessing the impact of such noise, particularly under ice cover when Burbot are ...

Impacts of river-based air gun seismic activity on northern fishes.

Air guns are an energy source commonly used by the oil and gas industry for seismic exploration, particularly in marine environments. Exposure to air gun noise has been shown to negatively impact marine fishes (e.g., McCauley et al. 2003); however, little is known about the potential impacts on fishes in freshwater systems. A proposal to use air guns for a seismic survey along the Mackenzie and Liard Rivers (∼1,200 km) in the Northwest Territories (NWT) led to considerable public and regulatory concern. As a result, the Canadian Department of Fisheries and Oceans (DFO) required the proponent to validate their prediction that the project will have no impacts on fish. The proponent conducted a study that showed no acute mortality associated with air gun use, although some stunning was observed in caged fish closest (2 m) to the air gun blasts (Cott et al. 2003). Outstanding data gaps associated with sublethal impacts of air gun noise (e.g., physical damage, stress, herding, and hearing loss) prompted the DFO to initiate a study, in collaboration with academic partners, to assess these impacts on northern fish in a riverine setting. The project was split into two components: 1) physiological impacts on fish hearing and ear damage and 2) behavioral impacts on free-swimming fishes.

Assessing disturbance from under-ice noise on fishes in boreal lakes.

There are many potential sources of anthropogenic noise that can manifest under ice in boreal lakes that are within the hearing ranges of northern boreal fishes. Impacts of noise on fish can be correlated to the fishs hearing sensitivity. In general, boreal fishes have most sensitive hearing <400 Hz,but this varies by species and life stage. By assessing the hearing capabilities and vocalizations of fish species and sound signatures from development activities, it may be possible to forecast potential impacts resulting from expected under-ice noise exposure.There is still the need for basic information to facilitate the assessment and identification of potential impacts (e.g., the hearing capabilities of many species of boreal fishes at different life stages and the sound signatures of various anthropogenic noise sources). Additionally, the impacts to fish from a particular noise source (e.g., pile driving) or the potential for a sound-related disturbance ata particular time in a species life history, such as courtship or spawning, warrants further study.

Effects of riverine seismic air‐gun exposure on fish hearing

Seismic airguns produce considerable amounts of acoustic energy that have the potential to affect marine life. This study investigated the effects of exposure to an airgun array in the Mackenzie River Delta on the hearing of three fish species: northern pike (Esox lucius), broad whitefish (Coregonus nasus), and lake chub (Couesius plumbeus). Fish were placed in cages in 1.9 m of water and exposed to 5 or 20 airgun shots, while controls were placed in the same cage but without airgun exposure. Hearing in both exposed and control fish were then tested using auditory evoked potentials (AEPs). Threshold shifts were found for exposed fish as compared to controls in the northern pike and lake chub, with recovery within 24 h of exposure, while there was no threshold shift in the broad whitefish. It is concluded that these three species are not likely to be substantially impacted by exposure to a 2D airgun array used in a river seismic survey. Care must be taken in extrapolation to other species in other environm...

What killed Frame Lake? A precautionary tale for urban planners

Frame Lake, located within the city of Yellowknife, Northwest Territories, Canada, has been identified as requiring significant remediation due to its steadily declining water quality and inability to support fish by the 1970s. Former gold mining operations and urbanization around the lake have been suspected as probable causes for the decline in water quality. While these land-use activities are well documented, little information is available regarding their impact on the lake itself. For this reason, Arcellinida, a group of shelled protozoans known to be reliable bioindicators of land-use change, were used to develop a hydroecological history of the lake. The purpose of this study was to use Arcellinida to: (1) document the contamination history of the lake, particularly related to arsenic (As) associated with aerial deposition from mine roaster stacks; (2) track the progress of water quality deterioration in Frame Lake related to mining, urbanization and other activities; and (3) identify any evidence of natural remediation within the lake. Arcellinida assemblages were assessed at 1-cm intervals through the upper 30 cm of a freeze core obtained from Frame Lake. The assemblages were statistically compared to geochemical and loss-on-ignition results from the core to document the contamination and degradation of conditions in the lake. The chronology of limnological changes recorded in the lake sediments were derived from 210Pb, 14C dating and known stratigraphic events. The progress of urbanization near the lake was tracked using aerial photography. Using Spearman correlations, the five most significant environmental variables impacting Arcellinida distribution were identified as minerogenics, organics, As, iron and mercury (p < 0.05; n = 30). Based on CONISS and ANOSIM analysis, three Arcellinida assemblages are identified. These include the Baseline Limnological Conditions Assemblage (BLCA), ranging from 17–30 cm and deposited in the early Holocene >7,000 years before present; the As Contamination Assemblage (ACA), ranging from 7–16 cm, deposited after ∼1962 when sedimentation began in the lake again following a long hiatus that spanned to the early Holocene; and the Eutrophication Assemblage (EA), ranging from 1–6 cm, comprised of sediments deposited after 1990 following the cessation of As and other metal contaminations. The EA developed in response to nutrient-rich waters entering the lake derived from the urbanization of the lake catchment and a reduction in lake circulation associated with the development at the lake outlet of a major road, later replaced by a causeway with rarely open sluiceways. The eutrophic condition currently charactering the lake—as evidenced by a population explosion of eutrophication indicator taxa Cucurbitella tricuspis—likely led to a massive increase in macrophyte growth and winter fish-kills. This ecological shift ultimately led to a system dominated by Hirudinea (leeches) and cessation of the lake as a recreational area.

Can traditional methods of selecting food accurately assess fish health

Indigenous peoples living in Canada’s north have long-valued the livers of Burbot (Lota lota) as a traditional food source; however, there has been concern relating to liver quality and potential contaminants. In this study, livers of Burbot collected in lower Mackenzie River were ranked using a traditional appearance-based assessment. These rankings were compared to a variety of biological and contaminant metrics. Livers ranked “most palatable” had a significantly higher mass and lipid content and were from younger fish with greater hepatosomatic index and total mass and had lower parasite intensities. There were no differences in the concentrations of persistent organic pollutants or metals, except copper, which although still well below consumption guidelines, was significantly higher in fish with livers that appeared most palatable. The results of this study demonstrated that traditional methods effectively assessed the quality of livers by selecting for the most nutritious (high lipid levels) and saf...

Managing anthropogenic underwater noise in the Northwest Territories, Canada.

Potential impacts on aquatic life associated with anthropogenic underwater noise are an emerging concern worldwide (Popper et al. 2005). In the Northwest Territories (NWT), Canada, there has been an increased interest in natural resources development and the potential for impacts to both marine and freshwater areas. Fish (including marine mammals and other aquatic life) and their habitats are managed by Canada’s Department of Fisheries and Oceans (DFO) under the federal Fisheries Act and the Oceans Act. The DFO reviews project proposals, assesses potential impacts, provides scientific and regulatory advice based on the current state of knowledge, identifies existing data gaps, and initiates steps to address them. If residual impacts are expected with mitigative measures in place, the DFO is able to account for and authorize impacts under the Fisheries Act. Here we identify the types of noise-related impacts that are pertinent to the species and industry activities in the NWT and how these concerns are being addressed by the DFO.