Small 2010 Lake Erie walleye hatch
predicted
Preliminary July trawls indicate
the 2010 Lake Erie walleye hatch will continue a nearly decade-long
trend of declining stocks.
The recent trawls, according
to the Toledo Blade, captured only three walleye per hectare of
water, which is roughly the same as 2009. In 2008, there were four
per hectare, and in 2007 there were eight, which is considered
average.For those unfamiliar, the trawling process involves pulling
a large net across a measured distance of water. The total area
netted is then calculated from the distance, and this is used in
conjunction with how many walleye were caught in that area to
estimate the year class strength.
July trawling provides only a
preliminary estimate of the hatch size, Jeff Tyson, supervisor at
the ODNR’s Sandusky Fish Research Unit, told The Blade. A
larger-scale, interagency August trawling is considered the
“official” estimate.“Things could change between now and
August [trawls] when we get broader coverage and we get Ontario’s
samples as well,” Tyson said,
but he noted that the two trawls don’t usually differ much.
The last major walleye hatch in
Lake Erie occurred in 2003, when trawls produced 43 young walleye
per hectare. Hatch sizes have been dropping since then. It’s
unprecedented to have this many consecutive years of substandard
spawning. There’s little doubt the
declining overall population stems from this inconsistent
recruitment, which is the number of walleye added to the population
from natural reproduction.
Tyson said
several factors could have hindered this year’s reproductive
success, including warm water temperature, algal blooms, low
dissolved oxygen levels, and heavy nutrient loading. Two
of the lake’s major tributaries — the Maumee and Sandusky rivers
— have been showing some of the highest-ever
phosphorus levels this summer. The record-high levels were
mostly caused by northwest Ohio’s heavy rainfall in the spring and
early summer, which had collected additional farmland runoff.
The heavy rain is also
contributing to what’s been termed a “sewage
crisis” in the Great Lakes. As rainfall intensifies, there are
more combined sewer overflows, or CSOs, that dump raw sewage into
the water. In just one month, Toledo experienced 127 overflows,
sending waste into the Lake Erie western basin. Moreover, the Great
Lakes have been showing all-time
high water temperatures this summer, as a result of diminished
ice cover last winter.
The heavy nutrient loading,
sewage, and warmer temperatures have fueled already prevalent
blue-green algal blooms in Lake Erie, which produce toxins harmful
to fish, consume dissolved oxygen that fish need to breathe, and,
unlike green algae, contribute nothing to the food web. Researchers
are predicting “the
mother of all blue-green algae counts” in the lake this
summer.
There is also research
into how significant an impact FirstEnergy’s Bay Shore coal power
plant in Oregon, Ohio has on fish populations. The plant sits at the
confluence of the Maumee River and Maumee Bay and kills
about 60 million fish annually when powerful suction systems
draw water from the bay for the power generator’s cooling system,
which either smashes fish and larvae into water intake screens or
pulls them into the plant where they are likely killed by extreme
temperatures.
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