Remote cellular-enabled camera monitoring of Lake Utopia Rainbow Smelt spawning streams : field trials and future application in population assessments

Two morphologically, ecologically, and genetically distinct populations of Rainbow Smelt (Osmerus mordax) coexist in Lake Utopia, southwestern New Brunswick. Effective monitoring of spawning streams is critical for managing these populations under the Species at Risk Act (SARA) and informing mark-recapture timing for population assessments. However, in-person visual monitoring is often limited by site accessibility, adverse weather conditions, and the species’ nocturnal spawning behavior. This study tested the ability of remote cellular-enabled camera monitoring to enhance and supplement in-person visual assessment of spawning activity on three known spawning streams for the Small-bodied Population (SbP): Second, Unnamed, and Smelt Brooks. Six cameras captured hourly images over one month (mid-April to mid-May), alongside weekly daytime visual surveys and daily water temperature recordings. Spawning runs began shortly after ice-out at 3-7 °C and peaked between April 21–27 at 6-10 °C. Cameras detected smelt up to five days earlier and three days later than daytime in-person surveys and provided continuous daily data, compared to in-person monitoring conducted only one to two days per week. Only two of the three streams showed spawning activity in 2025. Supplementing visual surveys with remote camera data enabled accurate identification of spawning period start and end dates, confirmed the absence of spawning in Smelt Brook, and improved timing of mark-recapture efforts within the full spawning window.