Omnivores, Vampires, and the Battle for Lake Michigan

The Chicago Cityscape Stretching along the shore of Lake Michigan

Kindly accept my apologies for not writing a post yesterday.  I am traveling the Great Lakes and Canada and will try to update when I am able.  Today I am in Chicago. As I was looking out at Lake Michigan, I wondered whether there were any catfish native to the vast body of water– which is so large it might as well be considered a freshwater sea.

Channel Catfish (Ictalurus punctatus)

As it turns out the lake is home to channel catfish (Ictalurus punctatu), the quintessential North American siluriform.  The channel catfish is a hardy omnivore which dwells in rivers, lakes, and ponds from southern Canada to northern Mexico.  They eat smaller fish, arthropods, worms, seeds, and just about any other edible thing which will fit into their mouths.  Channel catfish are nest breeders.  If the female catfish is unable to find a promising crevasse in which to lay her eggs, the male will arrange logs and rocks into a nesting bed for her.  He then guards the eggs until they hatch and even stays with the fry while they are very small (although if he is unduly disturbed he might eat the eggs and start all over again!).

Channel catfish (Ictalurus punctatus)

While the channel catfish are hardly as flashy as some of the exotic catfish we have covered here, they are vastly successful organisms.  They can also grow to be fairly large and specimens measuring up to 23 kg (50 pounds) have been caught (although such giants are quite old and rare).  Although the catfish live naturally in Lake Michigan, they are also raised on farms throughout the American south (indeed they are the “Delecata” mentioned in this post about international catfish trade wars).  Channel catfish have been introduced in parts of Europe, Malaysia, and Indonesia, where they are now causing havoc among native species.

But Channel catfish here in the Great lakes are facing their own invasive threats.  Lake Michigan has been colonized by wave after wave of invasive animals.  Some, like the omnipresent zebra mussels, are harmless to catfish (albeit infuriating to humans).  Others like the sea lampreys (Petromyzon marinus) are not so benign for catfish.  The jawless lampreys are vampires which attach to the bodies of catfish (and a wide variety of other native Great Lakes fish) and then rasp a hole in the hosts’ sides by means of sharpened tongue.  Even more alarmingly, the leaping thriving all-devouring Asian carp has been making its way up Illinois’ rivers towards Lake Michigan.  The state has been trying to prevent these dangerous fish from getting to the Lake by means of increasingly horrifying devices and stratagems such as underwater electric fences and mass poisonings.  So far it has been working but there is still an underwater war raging for Lake Michigan.

Invasive Silver Carp leap from the electrified water.

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The Eel-Tailed Catfish

The Eel-tailed Catfish (Tandanus tandanus)

Last week, I wrote about the great builders of the animal world, the beavers. But of course all sorts of other creatures build things.  The Eel tailed catfish (Tandanus tandanus) lives in the Murray-Darling river basin of Eastern Australia where the creatures’ nest-building habits are costing them dearly.

The eel-tailed catfish is from the family Plotosidae (in fact it is a close relative of the striped eel catfish) and like other family members its most distinctive feature is a continuous fin margin surrounding the posterior half of their bodies—aka an eel tail!  These catfish prefer to live on the gravel or sand at the bottom of lakes or slow-moving rivers.  They eat crayfish, yabbies’, worms, mollusks, insect larva, and other smaller fish.

An eel-tailed catfish nest (the parent is in the middle)

A week or two before spawning, pairs of eel-tailed catfish build nests for their eggs. The fish construct these torus-shaped structures out of sand and pebbles and, once the female lays the eggs, one or both parents stay with the nest to guard it and to aerate the eggs until they hatch.  Unfortunately, because of drought and agriculture, the Murray basin is rapidly drying out and silting up.  As the pebbles and coarse sands which the fish use for nests are smothered with slimy silt, the species has been declining.  Additionally, eel-tailed catfish are being out-competed by invasive carp which were introduced in a hare-brained aquiculture scheme.