Abstract
The predator-prey interactions in the offshore food web of Lake Superior have been well documented, but the sensory systems mediating these interactions remain unknown. The deepwater sculpin, (Myoxocephalus thompsoni), siscowet (Salvelinus namaycush siscowet), and kiyi (Coregonus kiyi) inhabit low light level environments. To investigate the potential role of vision in predator-prey interactions, electroretinography was used to determine visual sensitivity for each species. Spectral sensitivity curves revealed peak sensitivity at 525 nm for each species which closely corresponds to the prevalent downwelling light spectrum at depth. To determine if sufficient light was available to mediate predator-prey interactions, visual sensitivity was correlated with the intensity of downwelling light in Lake Superior to construct visual depth profiles for each species. Sufficient daytime irradiance exists for visual interactions to approximately 325 m for siscowet and kiyi and 355 m for the deepwater sculpin during summer months. Under full moon conditions, sufficient irradiance exists to elicit ERG response to light available at approximately 30 m for the siscowet and kiyi and 45 m for the deepwater sculpin. Visual interactions are therefore possible at the depths and times when these organisms overlap in the water column indicating that vision may play a far greater role at depth in deep freshwater lakes than had been previously documented.
Highlights
Lake Superior is the largest of the Laurentian Great Lakes and home to 38 fish species, including 19 nonnative species [1], with the majority of these fishes inhabiting the shallow, nearshore waters or surrounding watersheds
The cold deep, oligotrophic offshore waters of Lake Superior are relatively depauperate with fish density less than 6.9 kg/ha [2]
Deepwater sculpin, and kiyi were collected via daytime bottom trawls in the Apostle Islands region of Lake Superior, east of Stockton Island (Lat: 6° 54.751 Long: 90° 30.611) on November 13, 2012 and June 26, 2013 with the permission of the Wisconsin Department of Natural Resources
Summary
Lake Superior is the largest of the Laurentian Great Lakes and home to 38 fish species, including 19 nonnative species [1], with the majority of these fishes inhabiting the shallow, nearshore waters or surrounding watersheds. Many invasive aquatic species have disrupted and/or become integrated into shallow water community, the deep waters of Lake Superior remain dominated by native species [3]. Piscivores such as burbot (Lota lota) and siscowet lake trout (Salvelinus namaycush siscowet) dominate the highest trophic levels and feed predominately on deepwater sculpin (Moxocephalus thompsonii) and/or kiyi (Coregonus kiyi) [4]. The deepwater sculpin and kiyi, along with the cisco
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