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Mystery Fish, Fish Mystery
by Rob Van Tuyle
Just when you think there are no more surprises, the north branch of the Chicago River delivers. I'd been fishing the same spot in the same manner for about a year as sort of a longitudinal experiment. I'd gotten 16 different species ranging from gobies to king salmon. In October of '04 I caught something I'd never seen before. It looked to me like an African cichlid, all lit up in greens and blues. I checked my tropical fish books - the closest thing I could find was Tilapia (Oreochromis niloticus). Over the next month I caught 8 more of these critters, all between 5 and 7 inches.
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http://pg.photos.yahoo.com/ph/rvt2000/detail?.dir=3c11&.dnm=1607.jpg&.src=ph
(Click Picture for Album)
"Tilapia is a hardy, prolific, fast-growing tropical fish native to Israel, where it has been farmed for about 2,500 years. It requires water temperatures from 76 to 84 degrees Fahrenheit. Currently, tilapia are produced in outdoor ponds and indoor systems. They are prolific breeders and were considered a national pest in Indonesia until the citizens began using them as a food source. Tilapia production in outside ponds is strictly regulated in the southern United States for fear that some fish may escape from the farm ponds and encroach on native sport fishing populations."
I posted a picture on the ChicagoLandFishing (CLF) site and, as fate would have it, a tilapia fish farm manager responded. These were most definitely tilapia of breeding size. Apparently this fish has colonized drainage ditches in Florida and is found in the lower Mississippi. Catching them in Chicago however is considered rare. The main restriction on their survival up north is that they do not survive in water under 40 degrees. That would seem to seal their fate, except for the fact that there are warm water discharges throughout the Chicago River system that can remain around 50 degrees all winter.
I also contacted the Chicago Metropolitan Water Reclamation biologist Jennifer Wasik who said they had gotten a 3" specimen in Bubbly Creek on the south side. Another fisherman from Stikney said he caught several in the discharge near the reclamation plant there (unconfirmed).
So the question is twofold: how did they get there, and are they over-wintering in the discharges? After much discussion on the CLF site it was suggested that there were many ways the fish could enter the system - flooding of a fish farm, transfer of eggs by birds, someone throwing an aquarium fish away. It was even suggested that live fish sold in Asian markets were let go for religious reasons.
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Two weeks in the Aquarium
The fish farm manager indicated that these fish could grow to breeding size in a summer season. So, they may just be remnants of a one season population. If they are breeding, what are the possible consequences? These pugnacious little guys have been described as "bluegills on steroids." They breed like mad; in fact these are the fish used in self-sustaining environments like the Biosphere. They could well put pressure on other panfish if they've somehow adapted to the cold. On the upside they are good eating for humans, birds, and bass. Maybe they eat Zebra mussels.
The oddest part to me is that I fished this spot for hundreds of hours and only caught these fish in a one month window. Where were they all summer and where did they go? I suppose we'll see in the spring.
by Rob Van Tuyle
Just when you think there are no more surprises, the north branch of the Chicago River delivers. I'd been fishing the same spot in the same manner for about a year as sort of a longitudinal experiment. I'd gotten 16 different species ranging from gobies to king salmon. In October of '04 I caught something I'd never seen before. It looked to me like an African cichlid, all lit up in greens and blues. I checked my tropical fish books - the closest thing I could find was Tilapia (Oreochromis niloticus). Over the next month I caught 8 more of these critters, all between 5 and 7 inches.
http://pg.photos.yahoo.com/ph/rvt2000/detail?.dir=3c11&.dnm=1607.jpg&.src=ph
(Click Picture for Album)
"Tilapia is a hardy, prolific, fast-growing tropical fish native to Israel, where it has been farmed for about 2,500 years. It requires water temperatures from 76 to 84 degrees Fahrenheit. Currently, tilapia are produced in outdoor ponds and indoor systems. They are prolific breeders and were considered a national pest in Indonesia until the citizens began using them as a food source. Tilapia production in outside ponds is strictly regulated in the southern United States for fear that some fish may escape from the farm ponds and encroach on native sport fishing populations."
I posted a picture on the ChicagoLandFishing (CLF) site and, as fate would have it, a tilapia fish farm manager responded. These were most definitely tilapia of breeding size. Apparently this fish has colonized drainage ditches in Florida and is found in the lower Mississippi. Catching them in Chicago however is considered rare. The main restriction on their survival up north is that they do not survive in water under 40 degrees. That would seem to seal their fate, except for the fact that there are warm water discharges throughout the Chicago River system that can remain around 50 degrees all winter.
I also contacted the Chicago Metropolitan Water Reclamation biologist Jennifer Wasik who said they had gotten a 3" specimen in Bubbly Creek on the south side. Another fisherman from Stikney said he caught several in the discharge near the reclamation plant there (unconfirmed).
So the question is twofold: how did they get there, and are they over-wintering in the discharges? After much discussion on the CLF site it was suggested that there were many ways the fish could enter the system - flooding of a fish farm, transfer of eggs by birds, someone throwing an aquarium fish away. It was even suggested that live fish sold in Asian markets were let go for religious reasons.
Two weeks in the Aquarium
The fish farm manager indicated that these fish could grow to breeding size in a summer season. So, they may just be remnants of a one season population. If they are breeding, what are the possible consequences? These pugnacious little guys have been described as "bluegills on steroids." They breed like mad; in fact these are the fish used in self-sustaining environments like the Biosphere. They could well put pressure on other panfish if they've somehow adapted to the cold. On the upside they are good eating for humans, birds, and bass. Maybe they eat Zebra mussels.
The oddest part to me is that I fished this spot for hundreds of hours and only caught these fish in a one month window. Where were they all summer and where did they go? I suppose we'll see in the spring.
