Roanoke Times
Copyright (c) 1995, Landmark Communications, Inc.
DATE: MONDAY, November 8, 1993 TAG: 9311110462
SECTION: SPORTS PAGE: B6 EDITION: METRO
SOURCE: BILL COCHRAN OUTDOOR EDITOR
DATELINE: LENGTH: Medium
``As we were working up the shad species, we said, `Hey, these are different,''' said Mike Duval, a fisheries biologist supervisor for the Department of Game and Inland Fisheries.
They had discovered threadfin shad, a new species for the 20,000-acre lake.
So, is this good or bad?
``At this point, I think I would prefer not to have seen them in the system,'' said Duval. ``It may be that we are going to have to live with them.''
On the positive size, threadfin shad can be an excellent food source for species such as striped bass, black bass and crappie. They don't grow as big as gizzard shad, a common Smith Mountain Lake forage fish. Their smaller size means that game fish can make a meal out of them over a longer period. What's more, threadfin shad spawn twice a year in some lakes, an act that provides a second surge of food for sport fish.
Then there's the negative side. Threadfin shad aren't winter hearty. They are a native of Mexico. Winters this far north could be cold enough to cause a major die-off.
``With the threadfin shad dying back, all of a sudden you have a void where there is no small food,'' said Duval. That could be severe enough to shut down the growth rate of striped bass, he said.
``The point to remember, the threadfin aren't in addition to everything else,'' said Duval. ``They are displacing. So you are working with the same amount of shad. You are just changing the players around. So far as there being a net increase of shad in the lake, that wouldn't be the case.''
The threadfin is a common species in the lower reaches of the Roanoke River drainage, including Kerr and Gaston lakes. That's probably the source of Smith Mountain stock.
``I suspect how they got here was basically from anglers collecting bait at the Leesville tailrace, where they were looking for bluebacks, alewives and such that were running up the river,'' said Duval.
Most of the threadfins, which look much like gizzard shad, are above Hales Ford Bridge, where Duval believes they probably were released. They get scarce below Smith Mountain Lake State Park and upstream in the Hardy area. From the size of the fish, they appear to have been released last year, which means they have survived one winter.
``We don't know where the threadfin are going, but just looking at the distribution of those animals right now it looks like they are expanding,'' said Duval. ``It is conceivable that we will go out there next year and find them in the Blackwater River Arm. We have gotten an occasional one in the Blackwater, especially around Bull Run, but they haven't made a major swing there at this point.''
The threadfins were discovered when biologists were testing sophisticated sonar equipment designed to catalog species and number of fish electronically for management purposes. Officials had set out nets to capture fish in an effort to determine what they were seeing on the sonar screen, Duval said.
by CNB