Sustaining the Recovery of Lake Sturgeon (Acipenser fulvescens) in the North Saskatchewan River of Alberta

• Author / Creator

  Watkins, Owen B

• Nearly all Lake Sturgeon (Acipenser fulvescens) populations across North America have experienced losses to historic abundances estimated to be > 99%. This species is especially vulnerable to overharvest, habitat degradation, river fragmentation from dams, and is slow to recover due to life history characteristics. In the Alberta section of the North Saskatchewan River, Canada, passive management strategies led to overharvest, and combined with poor water quality, contributed to the collapse of the Lake Sturgeon population circa 1940. However, improved water quality beginning in the 1960s, along with the implementation of a zero-harvest regulation in 1997 prompted a Lake Sturgeon population recovery. Lake Sturgeon population viability remained questionable with low population abundance with particularly few adult fish, complicated by industrial development, and an increasing human population. Furthermore, the North Saskatchewan River has a popular multi-species sport fishery, complicating Lake Sturgeon management and recovery. My objective is to determine whether the status of the Lake Sturgeon population in the North Saskatchewan River in Alberta is declining, improving or remaining the same. To address this objective I required knowledge of Lake Sturgeon life history and sources of mortality. More specifically, I investigated: 1) population metrics for a status assessment, 2) a resource selection function for identification of important habitat using inputs from telemetry and land classification data, 3) defining technological limitations of telemetry information and 4) an assessment of current rates of angling mortality and management options for Lake Sturgeon recovery. I found that both recruitment and adult abundance had increased in the most recent years (2008 to 2012), even though the total mortality rate was higher than the 7% threshold proposed by the Alberta Lake Sturgeon Recovery Team. However, a high rate of somatic growth implies that abundance in the North Saskatchewan River is still below carrying capacity. Telemetry of 58 Lake Sturgeon over a 38-month period suggested that the population used the entire section of the North Saskatchewan River downstream from Drayton Valley, Alberta to the Alberta-Saskatchewan border. Additionally, some fish moved exceptional distances (> 925 rkm) between Alberta and Saskatchewan, illustrating the importance of river connectivity. Landscape classifications adjacent to the river were ineffective predictors of Lake Sturgeon congregations. There was a difference in habitat selection by males and females, with females found further downstream, but occupying similar slope gradients as the males. Small-scale details of habitat selection could not be investigated because of the technical limitations of existing telemetry technology. I found that radio telemetry detections from an aircraft were dependent upon transmitter type, water depth, receiver altitude, and scanning time. Larger transmitters were detected from a greater distance than smaller transmitters and the probability of detection was highest at a receiver altitude of 300 m when the two transmitter types were at a depth of 1 m. Furthermore, my relocations of the two transmitter types based upon maximum signal strength had a precision of ± 177 m distance for all depths and receiver altitudes from the actual transmitter location. I provide six probability of detection models for researchers to quantify their telemetry equipment. For investigating recovery management options, I used a theoretical objective of having a total population of 5,000 Lake Sturgeon, with an occasional fish surviving to 100-years. This requires total mortality to be approximately 5%, although my current estimate of total mortality is approximately 9.4%. To achieve my population objective, mortality must be significantly reduced. Estimates from catch and release fishing by three angler groups (non-specific anglers, anglers targeting sturgeon and research anglers) suggests that sport angling and its associated incidental mortality results in fewer than 18 dead Lake Sturgeon annually and further restrictions on sport angling are currently unnecessary. My only remaining management option to improve Lake Sturgeon survival is through habitat protection. My telemetry data suggested 10 primary locations of Lake Sturgeon congregations. Existing provincial regulations (Class ‘A’ watercourse designations) currently protect approximately 30% of these congregation sites. To protect at least 75% of these areas, I propose 10 new Class ‘A’ extents that reduce the total area of current Class ‘A’ protection (from 64 to 58 river km), which provides an improved means for protecting Lake Sturgeon and habitat.

• Subjects / Keywords

  • Sturgeon
  • North Saskatchewan River
  • Lake Sturgeon
  • Movements
  • Telemetry
  • Habitat
  • Mortality
  • Fish
  • Management
  • Radio Telemetry
  • Recovery
  • Detection

• Graduation date

  Spring 2016

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/R39G5GN53

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.