From: The Status of Walleye in Nipigon Bay Area of Concern: 2012
Prepared for Environment Canada
By: Terry Marshall, Marshall Consulting
March 31, 2013
I am skipping over the next 14 pages of the Report which covers the following topics:
Recent Research, assessment and monitoring studies:
Genetics of stocks
Telemetry studies: seasonal movements and habitat use ( they want to continue this study to see if there really are two distinct spawning populations)
Walleye spawning observations and drift netting Nipigon River
Walleye and Northern Pike abundance: Lake Helen
Fish Community assessment Lake Helen
Electrofishing surveys: Nipigon Bay and River
Fish Community Index Netting: Nipigon Bay
Walleye Population assessment: Nipigon Bay
STATUS OF WALLEYE STOCKS AND THEIR HABITAT IN THE NIPIGON SYSTEM
Recovery of collapsed populations
In all cases, rainbow smelt were also present in these water bodies which is an important consideration if making comparisons. The Nipigon Bay East area has the greatest biomass of rainbow smelt documented in Canadian Waters of Lake Superior (Yule et al 2008). The species was also found to be generally of larger body size in this part of the lake. The presence of a large and abundant prey such as rainbow smelt has a positive influence on walleye growth energetics. In Western U.S. reservoirs, growth rate increases once rainbow smelt became a large part of walleye diet [Johnson and Goetti 1999; Groeb et all 2008]. On the other hand, rainbow smelt may also compete with and prey on age-0 walleye which in some instances can significantly reduce their density [Mercedes-Silva et al 2007].
Walleye Population status
1. Abundance remains low – approx. 5000 Lake Helen
2. Density is increasing
3. Growth rates are very high
4. Mortality is very low
Walleye Habitat status
Information needs ;
Genetic analysis of stocks
Population monitoring and assessment
If genetic analysis determines that two discrete populations exist, the size of each must be determined independently.
There have been many changes in the 50+ years since Ryder’s  early studies and the collapse of the walleye fishery in Nipigon Bay. There have been drastic shifts in the composition of the aquatic community, along with significant improvements to nearshore habitat within the Bay, and recent changes to the thermal properties of the area brought about by climate warming. Together , these present a new environment for walleye to which they continue to adapt. This process appears to have promoted the development of two separate stocks of walleye in the Nipigon system.
We have a new population [or two] of walleye here today, different from the historic population in terms of its genetics, its spawning behaviour, and its annual movement patterns and use of habitat. This population is thought to be at a relatively low level of abundance compared with historic estimates, but quite healthy in all other respects. Growth rates are rapid and mortality is low. Together these traits suggest that large, rapidly maturing fish are present and have the potential to produce quantities of offspring in the future. Clean, high quality substrate is available in unobstructed spawning areas in both Nipigon and Jackfish rivers and it not constraining recovery.
On the basis of this evidence, it is recommended that the BUI status of the walleye population and their habitat in the Nipigon Bay AOC be updated to “ Not impaired”.
The 40,000 fish target for Walleye recovery may never be achieved in light of all the changes observed in this ecosystem [Colby 2007]. All that can be done to accomplish this has been done. Maintaining fishing mortality at a low level will help the walleye population expand to achieve its new equilibrium.