imajigger2,
It has been nearly 8 years since the discovery of zebra mussels at El Dorado Reservoir. Zebra mussels have impacted the reservoir over the years and I have not seen a single positive impact. We experienced extremely clear water conditions during 2006 when the zebra mussel population was at its' peak density. 2006 was also a drought year at El Dorado which contributed to clearer than normal water conditions so it was a number of factors that contributed to unusually clear water. Whatever the cause was, gizzard shad densities declined. Zebra mussels and other filter feeders such as gizzard shad compete for similar food items. Gizzard shad fuel the sportfisheries in Kansas reservoirs. Without shad, sportfish growth rates suffer and recruitment decreases. Although many lake users as well as anglers liked the 'clear' water at El Dorado during this time period because it was 'pretty' and 'clean', they thought. Zebra mussels do not 'clean' the water, they only remove suspended components from the water column and deposit them on the bottom as pseudofeces. The lake isn't any cleaner than before the infestation, but the 'clear' water conditions offer reduced amounts of the needed biological soup that supports fish, native mussels, and other wildlife. El Dorado had its first zebra mussel population crash during mid-2007 and the zebra mussel densities dropped dramatically and thankfully have remained at lower levels since. Shad densities have since improved and body conditions of sportfish such as white bass and wiper have returned to acceptable levels.
Did the zebra mussels 'decimate' the fishery here? No, we still have fish and they were always being caught but the lack of shad necessitated the cancellation of planned predator fish stockings such as walleye and wiper. Sportfish densities decreased as species that are recruitment limited here (walleye and wiper) were not stocked. The high densities of zebra mussels that encrusted shorelines and underwater structure made fishing very difficult. Line abrasion and break offs were very common making most forms of fishing (jigging, trolling, etc) less productive as lures/baits were quickly lost as soon as the line contacted the sharp edges of the zebra mussel shells. Some anglers that thought they liked the clear water and thought the zebra mussels were a benefit at El Dorado quickly changed their minds as encrustation continued to increase and fishing became increasingly difficult.
We have been in the 'rebuilding phase' at El Dorado for the last couple of years. The return of productive shad spawns have allowed fish stockings to resume and for naturally recruiting species to benefit from young shad during the growing season. Recruitment rates have increased leading to increased densities of fish anglers pursue, we just need a little more time with desirable conditions to let these fish reach catchable sizes.
In short, luckily the peak infestation densities were only seen for a short time at El Dorado and the fish and the lake have had some time to recover. The million dollar question is when will the zebra mussel population again increase in density? Another of my lakes (a 1,250 acre city owned lake) has had zebra mussels for nearly 5-years and it has not responded in a similar manner to what El Dorado did. Each lake is different, weather patterns and flow through rates affect colonization rates of zebra mussels, nutrient levels vary from lake, available habitat for zebra mussels vary, all of these and many others make a lake's reaction to the infestation differ impacting some more than others.
The zebra mussel invasion is still relatively new to Kansas waters and we are learning as we go as far as impacts to our aquatic systems. As I said before, I have not seen any benefits to fish or the angler from the zebra mussels, only negative impacts which are far reaching including negative impacts to nongame species, industry, hunters, and recreational users. Hopefully Kansas lake users will work hard to protect the zebra mussel free lakes that we do have. When a zebra mussel management solution is discovered it would be nice to treat a small number of lakes vs. the entire state and all its' watershed.
Here's a picture of El Dorado late September 2006 showing the high encrustation densities seen during the zebra mussel population peak.
Attachment 65320
