Record
Rainbow Trout (Steelhead) Spawn
In Ohio Streams in Spring 2012
In Ohio Streams in Spring 2012
Cleveland Metroparks monitoring surveys in early-mid summer
indicate that area streams experienced an unprecedented level of natural
reproduction of migratory rainbow trout (steelhead) in spring 2012.
Between 19
June and 18 July, 2012, a total of 1,677 juvenile (naturally reproduced)
rainbow trout were collected during routine monitoring activities in five
headwater stream tributaries of the Chagrin and Cuyahoga rivers on Cleveland
Metroparks land. Given the length of the
reaches sampled, this reflected an average density of 3,168 juvenile rainbow
trout per stream mile! In a few of the
streams, these trout were the dominant fish species present numerically. Although we expect to see some juvenile
rainbow trout in our stream surveys from year to year (for example, in 2011 a
total of 11 juvenile trout were collected in two Rocky River tributary
streams), the numbers found in 2012 were unprecedented and totally unexpected.
So this begs
the question of why so many little trout in 2012.
Looking back
at environmental conditions, we had the wettest year on record in 2011. This trend continued into early spring
2012. Lots of loose sediment was flushed
from all our watersheds during this period.
I remember clearly noticing how clean the rocks were by the Rocky River
marina in winter 2011-12.
Then,in
April 2012 things changed drastically and we received almost no
precipitation. Most steelhead anglers
were not happy about the disappointing fishing conditions in April due to very
low and clear water conditions. But this
also meant that spawning steelhead would have had their eggs subjected to far
less silt than usual during mid to late spring.
Trout eggs and fry are notoriously very sensitive to silt, so less silt
would be a beneficial situation for their hatching and development. I ran this hypothesis by my trout supplier,
who has hatched and reared many thousands of trout over the years, and he
believes this theory is right on the mark.
Even if trout hatch and survive until early summer in our
streams, though, they need to make it through the heat of late summer. Re-surveying one of the streams sampled
earlier this year in late September did reveal that a handful of the little
trout made it through the summer, which I imagine was likely the case on other
streams with some groundwater seepage, as well.
The end
result is that in about 2-4 years the odds of catching a wild steelhead trout
in an Ohio stream will be better than usual, although realistically the fish
will only comprise a small fraction of returning steelhead at best. There is no way to tell for certain visually
if an adult Ohio steelhead of wild origin, but if the fins are flawless
(especially the dorsal fin on top), there is certainly a possibility it could
be a natural reproduced fish, which many anglers will find to be a neat
prospect.
Mike
Durkalec M. S.Aquatic Biologist
Cleveland Metroparks
