PLANTS | ANIMALS | ECOLOGY | FUNGI | GEOLOGY | GARDENING | TOOLS
Excerpts from Jim Conrad's
Naturalist Newsletter
from the September 15, 2013 Newsletter issued from the Frio Canyon Nature Education Center in the valley of the Dry Frio River in northern Uvalde County, southwestern Texas, on the southern border of the Edwards Plateau; elevation ~1750m (~5750 ft); N29.62°, W99.86°; USA
BLUEGILLS
As the drought continues, small, isolated pools of shallow water remaining in the gravel and cobblestone bed of the Dry Frio River grow smaller and sometimes disappear. You never find dead fish in the bottom of dried-up pools, though. Raccoons, herons and the like capture the fish days before the water disappears.
Some of the Dry Frio's pools still hold goodly numbers of fish, mostly Largemouth Bass and the species shown below:
That fish is about four inches long (10cm). When I first saw this kind of fish I figured they were Bluegills, halfway remembering what Bluegills looked like when I was farmboy fishing in the pond back in Kentucky: They're "sunfish" with dark spots at the back ends of their gills. However, other species also have dark spots on the gills and people use other names for fish more or less looking like what's in our picture -- crappie, perch, sunfish, pumpkinseed, bream, coppernose and more -- so the time has come to sort all these names out, and figure out what a Bluegill really is. Being a rank amateur at ichthyology, it takes time with me.
You may be interested in PremierAngler.Com's page on 13 different sunfish species.
In figuring out our species, I noted that the front end of a White Crappie's "dorsal fin" -- the big fin on top -- begins with five or six sawtooth-like spines before the fin enlarges and the spines no longer project above one another. Fortunately I had a picture -- a blurry one that otherwise I'd delete -- showing the number of sawtooth spines on our fish, and that displays a dorsal fin beginning with nine, ten or so spines, not five or six, so our fish isn't a White Crappie. The blurry picture appears below:
Looking at lists of fish known to occur in the Dry Frio River and paying attention to spine numbers, I figure that the fish in our pictures really are Bluegills, LEPOMIS MACROCHIRUS. However, most pictures of Bluegills on the Internet don't look like ours, usually showing blackish backs beneath the dorsal fin and often with an orange chest area -- but some pictures do match ours. Thing is, among fish, species coloration can change drastically according to age, sex, breeding season and environmental influences. However, the basic structure doesn't change no matter what color the fish is, and such details as how many spines occur in a particular fin are as important in fish identification as number of stamens can be in plant ID.
The names Bream, Brim, and Copper Nose are other names people use for Bluegills. When referring to freshwater fish, the name sunfish is a general one applied to various members of the Sunfish Family, the Centrarchidae, which includes Bluegill, crappie, and Largemouth Bass. Perch are completely different kinds of sunfish than Bluegill, and there are different kinds. Pumpkinseeds and another kind of fish known as bream also are different species of sunfish.
Bluegills are native east of the Rockies from Minnesota and New York south into northeastern Mexico, but because they are appreciated so by fishermen they've been introduced throughout most of the rest of North America, as well as shallow waters of lakes and ponds, slow-moving streams and small rivers in nearly all the rest of the world.
from the July 14, 2002 Newsletter issued from the woods just south of Natchez, Mississippi, USA
BLUEGILL NESTING
In the woods I sat quietly next to a deer pond about the size of a house. It was a shallow pond with fallen limbs emerging all across it and its waters were murky brown in the center, turning rusty red at the edges. With all the frogs and dragonflies there was plenty to watch, but my attention was focused on some shallow depressions at the pond's edge. The pit rims were about six inches (15 cm) below the water's surface and the bottoms of the depressions were about twice as deep. The holes themselves were about 20 inches (50 cm) across and some 5 feet (1.5 meters) from one another. Each depression was clearly a nest, for it was being attended very conscientiously by an adult Bluegill fish, LEPOMIS MACROCHIRUS, about 6 inches (15 cm) long.
Male Bluegills excavate nests by undulating their rear ends from side to side while remaining in a vertical position. The males then wait in their nests making grunting sounds to attract females. Once a female enters a nest and after the pair swim in circles a while the female releases a few eggs and the male releases his milt. Then it's all done again. The female doesn't deposit all of her eggs during one visit, nor is only one nest used by a female. Once spawning is completed, the female leaves the nest and the male remains caring the eggs. What I was seeing in this pond was males tending their nests.
I think they must have been under a lot of stress that day. It was around 90° (32°C) and in that shallow water the oxygen level must have been low. In fact, the males would vigorously swim in circles for about 15 seconds, then come to the water's surface over their depressions' centers and seem to gasp for air for up to a minute before swimming in circles again. The circle-swimming was surely to aerate the eggs.
The pond also was thick with Mosquitofish and every few minutes a school of these would slowly approach a nest. As soon as the father Bluegill spotted them he'd chase them away. In the mid-day heat these Bluegill fathers seemed pretty fagged out, but they just kept at it.
At a University of Michigan webpage I read how certain mateless male Bluegills will dart into their neighbors' nests while their neighbor is mating, steal eggs as they are being produced by the visiting female, carry them to their own nests and fertilize them with their own milt.