Wednesday, March 24, 2010

Let’s get to know…”Gizzard Shad”

How cool are fish? Each species is different and has biological differences that control so much about where they live and why. Knowing these facts will help dial in the location and patterns of the fish you seek to catch. Fish identification is just the start. Learning the biological aspects helps us catch and preserve this amazing natural creature. Please bear with me and my poindexter excerpts of “Let’s get to know…”.

Let’s get to know “Gizzard Shad”

Shad is an excellent source of forage and routinely stocked across the United States. Although this species thrives better in the warmer southern climates it is also stocked in a few Colorado waters to boost the bellies of predator game fish such as large and smallmouth bass. Walleye and other species will also benefit from stocking shad. But what do we really know about this fish species?

There are several variations of the shad species (American, threadfin, gizzard shad and more) for this discussion I want to focus on the gizzard shad which is more common in Colorado.


The gizzard shad or Dorosoma cepedianum are slightly “diamond” shaped with a blunt snout and extended bottom fin similar to most shad species. Gizzard shad generally have a black dot behind their gill plate but this marking can fade in some cases. Very similar to the threadfin shad, the gizzard variety The gizzard shad has an upper jaw that protects the lower jaw and do not have the yellow coloring on the fins as in the threadfin. The easiest way to distinguish the two is by the anal or bottom fin that has 30 to 35 rays as where the threadfin only has 20 to 25 rays.

Biology Facts:

Gizzard shad are planktivorous meaning they feed on plankton rather than bugs or smaller fish. However, some adult gizzard shad have been caught by anglers using flies and other means so it is easy to deduce that large shad may have a more varied diet that consists of protein.

Shad will often form large schools that attract predator fish. In the summer months anglers will actively seek out large “boils” on the water surface created by predator fish feeding on the school of forage. This binge feeding is referred to as “busting” and fairly common at places like Pueblo Reservoir where shad populations stay fairly consistent.

Shad are not considered a very palatable table fish compared to bluegill and perch but predator game fish benefit from such an abundance of forage at a time when water temps and fish metabolisms are at their peak.


Spawning occurs in the late spring or early summer in Colorado when water reaches 70 degrees in shallow water. Eggs and milt are released within the school of fish and fertilization takes place in the open water without any distinction between the individual breeding adults. The eggs are adhesive and attach themselves naturally to structure hatching in 4 or 5 days.

Complications of shad stocking in Colorado:

Shad are prolific and can reproduce in abundance when the water reaches 70 degrees. This high reproduction activity can displace other types of forage. Several water systems with shad may not have adequate drainage protection and the shad escape into ditches and can migrate to other waters where they are unwanted.

Another problem is the fact that most shad species will experience population die off when the water reaches below 45 degrees. When lakes freeze over the oxygen levels start to dissipate. This can also cause large die offs in the shad population.

(Above: This is somewhat of a routine sight for me this time of year depending on how bad the winter season was. I can’t help but be concerned every time I see a massive shad die off and have to remind myself this is not a problem with the water or lake. If you see dead shad in large numbers do not be overly alarmed. This is often a natural occurrence. If you see other species dead along with the shad…well then you have a much more serious issue.)

Smaller lakes may need routine stocking every year or so to keep the species viable and ensure reproduction in summer months where water temps are more agreeable to them. Stocking shad can really pump up the volume in regards to game fish weight and overall health. But shad are not the solution for every lake. Shad do best in large reservoirs and other species’ habitat needs should be weighed beforehand.

I hope you have enjoyed this segment of “Let’s get to Know…”

Acknowledgements, sources and reference links:

1 comment:

Anonymous said...

i have cought gizzard shad in very small ponds and there lengths were large as large as 12 inchs but this pound has never been stalked with wish so i think they could live in small ponds and i have cought them when the water was half frozen soo we really dont know how they live and adapt to the whater