Understanding spawning helps fishermen
Knowing what a gamefish will do makes it easier to catch him
By Dan Kibler
Journal Ourdoors editor
As springtime begins to appear on the horizon, there's little question that many fishermen begin to stir, clean up their tackle, get their boats in working order and anticipate the effect that warming temperatures will have on the fish they will pursue.
And it will not take them very long, once they have made a couple of trips to their local reservoir, to start discussing the approach of the spawn - the period when fish reproduce.
There are reasons for the interest:
Most species of fish that live in Piedmont reservoirs will change locations as the spawn approaches. They will either move out of deep water into shallow water, or they will move out of the main body of lakes and into the rivers and larger tributary creeks that feed them;
Some species of fish become easier to catch as the spawn approaches, if only because they move into areas where they run into fishermen more often;
Some species of fish become more difficult to catch as the spawn hits because they become more concerned with reproducing and less concerned with feeding for a period of time;
Most fishermen seem to have an opinion on exactly when the spawn will take place for their preferred fish, on their home waters. Even if they have no clue.
Biologists, who study different species of gamefish, understand that a number of different factors drive fish to reproduce at certain times during the spring and fall. Fish genetics play a certain role, as does the expanding photoperiod - the amount of sunlight in a 24-hour day - but the one factor that most drives fish to reproduce is water temperature.
"Temperature is the key factor," said Christian Waters of Smithfield, a biologist who oversees Piedmont reservoir fisheries for the N.C. Wildlife Resources Commission, "It's probably not the only factor, but it's what we key on in when we do our samplings. On most reservoir systems in the Piedmont, the temperature fluctuation from year to year is so minimal, that we can key in on the month and week."
Different species of fish spawn in different temperature ranges, so there is some overlap, but it's well known among many Piedmont fishermen that white bass make their spawning runs out of reservoirs into tributary creeks and rivers very early, before the water temperature even hits the 50-degree mark. Striped bass and smallmouth bass go when the water temperature approaches 60 degrees. Crappie will go in the low 60s, followed by spotted bass and largemouth bass in the mid- to upper-60s, and finally by bluegills, blue catfish and channel catfish between 70 and 80 degrees.
Biologists have a good grip on the upper limit of the temperature range for spawning because they often observe newly hatched fish, referred to as "fry" after the spawn is finished.
"In terms of timing, I've seen largemouth bass in the Piedmont spawn as early as mid-April," said biologist Scott Van Horn, who had Waters' job for two decades before moving to a desk job several years ago.
"Obviously, water temperatures trigger the spawn, but there are other short-term things. I'm not surprised there's a need for the right photoperiod. They hang around, and when the water temperature gets right and the photoperiod gets right, they go." Van Horn said that biologists at N.C. State did work on Jordan Lake where they showed a correspondence between strong year-classes of largemouth bass and dates when the water temperature got into the right zone. "The strongest year-classes for bass at Jordan corresponded to years when the warm water temperatures were the earliest," he said.
"That makes sense, because it takes longer for the eggs to develop and mature in cold water, and you have more opportunity for heavy predation (on the fry) when the water is cold. If you have an early, warm spring, the timing of the spawn is faster, and the chances for egg predation are lower."
How does this knowledge affect fishermen?
First, it behooves them to understand that the peak of the spawning period for a certain species in a certain reservoir may be stretched out over a period of weeks, and it can vary greatly in reservoirs that are only a few miles apart.
The north side of a reservoir will warm more quickly than the south side because it receives more hours of direct sunlight. Bass pro Davy Hite of Ninety-Six, S.C., explained that bass in northern pockets on his home lake, Lake Murray, would routinely spawn a month before the bass on the southern shoreline.
Bass pro David Fritts of Lexington said it is his experience that the spawn can also progress "upstream" in a lake, with the spawn starting close to the dam and moving up toward the headwaters because of the relative drop in temperature. At Buggs Island Lake or Lake Gaston on the Virginia-North Carolina border, Fritts said that fish on the lower end may spawn two weeks before fish on the upper end.
There is very little argument among striper fishermen that the spawn gets later and later as it progresses up the Catawba River chain, because as you go from Lake Norman to Lookout Shoals Lake to Lake Hickory and Lake Rhodhiss, the water temperature warms up later in each lake - in part because cold water is being drawn off the bottom of each lake, through Duke Power's hydroelectric dams, and sent downstream.
Bass fishermen understand that a bass will exhibit its most aggressive behavior in the week or two just before it spawns, as it feeds heavily to get ready for the stress of spawning. Its least-aggressive behavior will be in the week or two after the spawn, as it tries to recover from the physical exertion. Crappie act the same way.
This allows fishermen to venture an educated guess about where the peak of the spawn is taking place on a reservoir.