Rainbow Trout are not a native fish to Iowa, but they have had successful lives as an introduced fish into the cold water streams of northeast Iowa. Iowa also has Brook trout and Brown trout. However, the Rainbow is a well sought after popular fish by anglers. They are native to the cold water tributaries of the Pacific Ocean in North America and Asia. Freshwater forms of Rainbows have been long ago introduced into the Great Lakes where they migrate into tributary streams to spawn.
Worldwide, Rainbow trout can be found in 45 countries and every continent except Antarctica. A problem with introducing non-native fish of any species into waters is that disruptions within the food chain may result to the detriment of native fishes.
Rainbow trout may out-compete native fish, may introduce whirling disease, or hybridizing with native trout. Rainbow trout are known to be in the list of the top 100 globally invasive species. However, this cat was let out of the bag so long ago, that it is now well established as a sport fish of great interest. At the Big Springs hatchery near Elkader, cold water from Iowa's largest natural spring supplies water to 24 raceways and four ponds.
Thousands of trout are raised at this site for stocking in all appropriate cold water rivers of northeast Iowa, and for transport to many central Iowa lakes or former gravel pit public waters. During late October, water temperatures have begun to cool enough in places like Sand Lake to bring water temperatures down to levels within the range preferred by trout.
Hatchery water conditions allow fisheries workers a longer management timeline for raising trout from December through January and into early February. Small female trout may produce from 400 to 700 eggs. Larger trout can produce 3,000 eggs or more.
Approximately 50 days are required to complete incubation. In 16 months, trout will have grown to sizes ranging from six to 12 inches. Long ago, other trout facilities in Minnesota found average first year trout to grow to about five inches, second year fish to nine inches and if kept into the fifth year, up to 20 inches long.
Rainbow food sources include Mayflies, caddisflies, stone-flies and their larvae, small mollusks and other small fishes. Summer months will find terrestrial insects added to their diets.
These food forms can be ants, beetles, grasshoppers and crickets. Other in water foods may be crayfish and small crustaceans. As the fish grows, it may use other fish as its main sources to feed upon, and they will eat the eggs of other fish eggs or the decomposing remnants of other fish bodies.
The scientific name for Rainbow Trout is Oncorhynchus mykiss. It was named originally by a German naturalist and taxonomist Johann Julius Walbaum in 1792 based on type specimens from the Kamchatka Peninsula in Siberia.
Walbaum's original name mykiss was derived from the local name for the fish called mykizha. A Scottish naturalist also got into the naming game in 1836 with fish from the Columbia River area of North America.
Others tried to classify this trout name in 1855. Finally in 1989, taxonomists settled all previous naming attempts.
As for people food, farm raised Rainbow Trout is considered a top contender for one of the safest fish meats to eat. High concentrations of vitamin B and an appealing flavor make restaurant fish selections a good choice. If you catch a trout from Sand Lake, check out many
cooking styles, and make your supper meal a special event straight from the outdoors natural world.
Iowa's top record for a Rainbow Trout was made on July 1, 1984, when Jack Renner of Waterloo went fishing at French Creek in Allamakee County. He caught a Rainbow that hit the scale marks at 19 pounds, eight ounces. It was 35 inches long.
This was probably a brood fish from a hatchery where the fish had supplied many years worth of offspring.
-- -- -
Leaf color is peaking right now just about everywhere. Brilliant reds, yellows and every shade of mixed combinations tends to bring out vivid eye-pleasing vistas.
I would encourage anyone to make a countryside drive to observe tree leaf colors. Take any route you desire. However, I would suggest that Mormon Ridge Road be one of the roadways you must see, and of course, I can highly recommend that a stop at Grammer Grove Park be your afternoon picnic spot, bird watching area, and leaf color destination.
Walk the hiking trails at Grammer to admire tree leaves and breathe fresh air. Discover the big rock at Grammer.
This huge glacial boulder is near the park's southeast corner. It is easy to find, and its size is enormous.
This will be a side benefit of going on your leaf color tour and outdoors adventure. Being a curious outdoor adventurer, you may want to learn more about Grammer Grove's big rock. Let us begin.
This rock is a granite specimen with origins likely from Canada. How did it get here? The answer is ice, a lot of thick glacial ice from a time period long preceding our last glacial event. The last geologic glacial system was named the Wisconsinan from a time period of starting about 100,000 years ago and lasting until 18,000 -- 15,000 years ago. That is geologically very recent.
Other previous glacial maximums affected Iowa to various degrees. There were the Kansan episodes and Illinoian and pre-Illinoian time frames. The duration of each varied and the time frames for those systems to melt away also varied.
These numerous glacial stages, coming and going repeatedly, are proof of immense natural climatic changes our Earth has experienced. These cycles of earth history tell us that the sources of the cycles are unstoppable natural happenings.
One of those pre-Wisconsinan ice episodes deposited the big rock at Grammer Grove. Like many other places throughout Iowa and the Midwest, small, medium to large and very large erratic boulders were encased within the ice that had traveled from Canadian shield bedrock sources.
The rocks went for long rides to the south, and when glacial ice melts, all that debris drops out. It does not stay embedded within the thinning ice.
Those erratic rocks are dispersed across the lands of Iowa and Midwest in random fashion. Many remain deeply buried and unknown to mankind. Other erratics lay exposed partially in what are now farm fields. Fortunately for us, one is now exposed at Grammer Grove by the natural carving of a small tributary creek within the park that over long time frames removed the soils that once buried this rock.
Earth history and geomorphology studies tell us that there were many other glacial maximums and interspersed natural warmer times between glacial advances. In general, the galactic forces that cause enough heavy snow to accumulate sufficiently to allow glaciers to form is a very long time frame of thousands to tens of thousands of years.
Geology professors have determined that in the last 2.6 million years there were 33 glacial ice episodes of advancement from Canada, and obviously, there were 33 inter-glacial warmer times when melting happened sufficiently to have the edge of glacial ice packs retreat far to the north of us.
Regardless of which one of the 33 glacial episodes left the big rock at Grammer Grove, it happened. And now we are fortunate enough to know more about how our Iowa's landscapes were formed by events of glaciation, erosion by wind and water, by numerous times of shallow salt water seas inundating to leave deep deposits of limestone well below our now farm
land crop growing soils.
Geologic time is the key to when and how our Earth becomes modified by the forces of plate tectonics, volcanism, glaciation phases and interglacial warm times, and ocean advances or retreats. It is a fascinating journey that Earth has recorded in the rocks and rock layers below our feet.
-- --
Garry Brandenburg is the retired director of the Marshall County Conservation Board. He is a graduate of Iowa State University with a BS degree in Fish & Wildlife Biology.