Science Advisory Report  2011/033

Recovery Potential Assessment of Lake Chubsucker (Erimyzon sucetta) in Canada

Summary

• The current Lake Chubsucker distribution is limited to 11 distinct locations of the Great Lakes basin: Old Ausable Channel, L Lake, Walpole Island (dyked marshes), St. Clair National Wildlife Area (NWA), Point Pelee National Park, Rondeau Bay, Long Point Bay, Long Point NWA, Big Creek NWA (dyked marshes) and Lyons Creek.
• Three historic locations are thought be extirpated: Jeanette’s Creek, the upper tributaries of Big Creek and Tea Creek.
• Adult Lake Chubsucker are generally found in clear, still, well-vegetated waters. Substrate in these systems is generally composed of gravel, sand, and silt mixed with organic debris. Recent juvenile and YOY captures from L Lake noted that individuals were found over substrate composed mainly of organic debris and vegetative cover (combination of submergent, floating, and emergent) was greater than 70%.
• To achieve ~99% probability of persistence, given a 15% chance of catastrophic decline (50%), requires ~2700 adult Lake Chubsucker and at least 1 km2 of suitable habitat. Populations experiencing density dependence due to crowding require 1.5 times the Minimum Area for Population Viability (MAPV), or at least 1.5 km2. Given a quasi-extinction threshold of 50 adults, the Minimum Viable Population (MVP) becomes ~16 000 adults requiring 6 km2. Extinction risk increases exponentially when habitat is reduced below MAPV.
• In the absence of additional harm, recovery efforts, or habitat limitations, a population at 10% of MVP (270 adults) has a 95% chance of recovering within 12 years (if probability of catastrophe is 15% per generation). Increasing survival of juveniles will have the largest proportional effect on recovery time.
• The greatest threats to the survival and persistence of Lake Chubsucker in Canada are related to habitat modification and destruction, increases in turbidity and sediment loading, and exotic species. Lesser threats that may be affecting the survival of Lake Chubsucker include increases in nutrient loading, contaminants and toxic substances, and incidental harvest, although the current knowledge on the level of impact that these threats may have on Lake Chubsucker is very limited.
• Population growth of Lake Chubsucker is most sensitive to changes in juvenile survival, and is sensitive to the survival and fecundity of first time spawners. If Lake Chubsucker mature at age 2, harm to annual survival of immature individuals (hatch to age 2), survival of adults, or fecundity should not exceed 33%, 54%, or 49%, respectively. If age at maturity is 3 years, harms should not exceed 15%, 32%, or 33%, respectively. As harm approaches these levels, recovery times increase exponentially.
• There remain numerous sources of uncertainty related to Lake Chubsucker population distribution and structure, habitat preferences and to the factors limiting their existence.

This Science Advisory Report is from the Fisheries and Oceans Canada, Canadian Science Advisory Secretariat regional advisory meeting of March 9, 2011 on Recovery Potential Assessment (RPA) of Lake Chubsucker. Additional publications from this process will be posted as they become available on the DFO Science Advisory Schedule.

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