Six Things: Fresh Water Fish

NOTICE:  Gentle reader, this blog includes descriptions of fish spawning that may not be suitable for anyone.  Please be advised.

Did you know that only 0.1% of the earth’s water is fresh?  It makes me appreciate the many bodies of freshwater available to us for diving.  (Having freshwater to drink is kind of nice, too.)  Even more interesting is that 40% of all fish species can be found in that 0.1% of the earth’s water!  As divers, we probably have a greater appreciation of freshwater fish compared to others, but even we can get a little ho-hum about it, so here are Six things I bet you did not know about your favorite freshwater fish.

Number 1

Anyone who’s dived with me knows that I like bass.  They are so friendly, like underwater Fido.  Bass actually have 6 senses! In addition to the usual sight, touch, hearing and taste they have a lateral line that enables them to detect underwater vibrations caused by swimming bait fish.  That means that even if this fish is in the murkiest of water, or has an eye injury, it is still capable of finding food.  Even if they did not have the lateral line, the bass’ eyesight is pretty amazing.  Bass can see up to 30ft in clear water and can even see things, like a fisherman in a boat, at the surface.  Researchers have proven that red is the bass’ favorite color, so I am rethinking my pink diving color scheme!

Also, Bass and Crayfish are mortal enemies locked in a never ending battle for control of the lake floor
Photo by Scott Duban

Number 2

Walleye are another fish with excellent vision, making them successful night feeders.  The name “walleye” comes from the fact that this fish’s eyes point outward, rather than forward. This eye position, along with a specialized light-gathering layer in this fish’s eyes, make the walleye a successful predator.  These light gathering cells cause the eyes to shine when light hits them, much like a cat’s eyes in the dark. Fishermen take advantage of the fact that the walleye has a shine, using it as an indication of the fish’s location.  Walleye are a popular food fish.  In fact, it is no surprise that in Minnesota, where more walleye is consumed than in any other jurisdiction of the United States, it is honored as their state fish.  Walleye is also the state fish of South Dakota and the official fish of Saskatchewan.

Number 3

Yellow perch, a close cousin of walleye, are day time feeders.  North American natives, they are a critical food source for bass and walleye, as well as a much sought after food for humans.  Communal spawners, Perch eggs are draped in gelatinous strings over weeds, branches or whatever in handy, and fertilized externally.  (It kind of takes all the fun out of communal spawning, IMO.)  Perch are not good parents because they not only are known to lay their eggs and then move on, but they will eat their young if the opportunity presents itself!

Number 4

Varieties of trout, in contrast to the communally spawning perch, are genetically able to spawn together and produce viable young, but due use of differing spawning areas, timing, or exploitation of different niches within the food chain, maintain their distinctness. In fact, except in some fish farm situations, (Love the one you’re with, I guess.) brown trout and rainbow trout will not interbreed.  With 38-42 pairs of chromosomes, (compared with human’s measly 23) the brown trout is the most genetically diverse vertebrate known.

Number 5

The Paddlefish, always a treat to see while diving, is a prized sport fish, though its population has been on the decline.  In fact, there are only a couple of species of this ancient relative of the sturgeon left.  Known to grow to 6ft and over 190lbs., the paddlefish is a filter feeder that fuels itself with zooplankton.  The invasion of zebra mussels to most inland waters has decreased available food for paddlefishes and has necessitated the formation of restocking programs where their harvest is allowed.  Thankfully, the paddlefish is also known to eat bivalves and crustaceans.  People do eat the meat of the paddlefish, and sometimes their roe, referred to as American Sevruga Caviar, is sold.

Number 6

Finally, the bluegill.  The biggest bluegill caught was 4 lb., though I would bet that some of the specimens at Haigh would crush that record.  A very adaptable fish, the bluegill can tolerate up to 1.8% salinity and are found in Chesapeake Bay, as well as the U.S. east of the Rockies, and as far south as Mexico.  Bluegill spawn starting late in May, extending into August.  The male of the species makes several beds resembling bowls in shallow water.  As a female approaches, the male will start to make grunting sounds as he circles within his bed.  Females, who are more attracted to males with bigger bodies and ears, (per Wikipedia), will enter the nest of her choosing, circling within the bed with the male. If all goes well, the two settle at the bottom of the bed, the male in an upright position.  Their bellies touch, they quiver and then the spawn is released.  The male then fertilizes the eggs externally.  At this time, smaller, less desirable males may dart into the nest and fertilize a few eggs, thus maintaining diversity within the species.  Afterward, the male kicks his baby mama to the curb and guards the eggs. 

Bluegill are generally well liked, in the U.S., but not so much in other countries.  In 1960, Chicago mayor Richard J. Daley gifted Japan’s crown prince Akihito with bluegill, and the Prince then gave the fish to the Japan’s research fisheries.  The wily fish escaped the fisheries after which they wreaked havoc with the native species.  The emperor made an official apology to the most effected provinces.

So you see every creature has his story.  Special thanks to Wikipedia, outdoorlife.com and wildtrout.org for information.

Join us on our next adventure and say hi to all our little underwater friends.