A few years ago, I moved south of Annapolis, close to the Patuxent River. The first spring there, I explored the riverside wetlands while my husband fished for yellow perch (Perca flavescens).

Yellow perch make their spawning run from late February to mid-March and offer some of the earliest opportunities for sport fishermen to break out their rods and tackle. Their delicate meat and early arrival makes these fish a favorite among many anglers.

Yellow perch, striking in appearance, are easily recognized by golden yellow and dark vertical bands. These fish spend most of the year in brackish water and migrate to fresh water to spawn.

Yellow perch never leave the river system where they hatched; they merely move between brackish and fresh water. The gradual warming of water triggers spawning.

Accordionlike chains of eggs are deposited in areas of a river with large amounts of organic debris. One egg chain may be fertilized by as many as 15-25 males.

Once spawning is completed, adults leave the eggs and migrate back to brackish water.

The egg chain may be attached to underwater vegetation or bottom debris. The unusual shape of the chain allows water to swirl gently around and through the chain, aerating the eggs. This is essential for respiration and to prevent bacteria and fungi from growing on and killing the eggs.

Eggs hatch in two to three weeks. After a few days, the larval fish begin feeding on microscopic organisms. Later, juvenile fish will join adults in the brackish portion of the river. Males reach sexual maturity in one to three years; females in three to four.

Populations of yellow perch are most prevalent in upper Chesapeake Bay tributaries. In the middle and lower Bay, some populations are depressed with smaller or no spawning runs. Historically, these areas did have large populations of yellow perch.

No one cause has been identified as the reason for these regional differences.

Each life stage of yellow perch is sensitive to different environmental factors. Agricultural and urban development increases the amount of sediment, nutrients and chemicals entering streams. This same development reduces the amount of naturally vegetated areas surrounding rivers and streams that would absorb these substances.

Excessive sediment adheres to eggs, reducing the oxygen they receive. Sedimentation may also reduce hatching success or delay hatching time. In addition, the survival of larvae is reduced when fine grains adhere to and damage sensitive gills.

Excessive nutrients affect all fish populations by altering the physical characteristics of water, raising water temperature and reducing dissolved oxygen. Low dissolved oxygen retards growth and, in some cases, can kill fish. Some fish may leave their preferred habitat because of the low oxygen and changes in the temperature. The resulting changes can also reduce the benthic organisms that yellow perch prey upon.

Although somewhat acid-tolerant, newly hatched perch are more sensitive to acidic conditions. Sulfur and nitrogen oxides emitted into the air through the burning of fossil fuels mix with water vapor, which forms sulfuric and nitric acids that fall back to the ground as acid rain.

Chronic exposure to slight to moderate acidic conditions can inhibit fish growth and damage body organs. Young fish may be killed when heavy rains result in a pulse of highly acidic water moving downstream.

Liming has been used to help neutralize acidic water in some streams. Composed of calcium carbonate, limestone can raise the pH of the water. Ultimately, though, the reduction of acid rain depends on the reduction of sulfur emissions from industry and automotive exhaust.

Another problem that fish-including yellow perch-face is not being able to reach spawning grounds because of blockages. Gauging stations, road culverts and dams all block tributaries. Unable to get around blockages, adults will not spawn.

The yellow perch commercial fishery has become more important since the ban on American shad. Recreational fishing for yellow perch has become a tradition for many anglers as they are the first fish to arrive in the rivers after the long winter.

Maryland has a partial ban. The Magothy, Nanticoke, Patapsco, Severn, South and West rivers are closed to recreational as well as commercial fishing. That state is considering public comments regarding changes to yellow perch regulations.

Neither Virginia nor Pennsylvania has closed rivers to fishing for yellow perch. Anglers should contact their state fishery agency to check the regulations on gear, catch limit and minimum size requirements.

Many anglers are lured to the Chesapeake Bay watershed and the variety of fish species it supports.

The annual spring run of yellow perch is just one of the many natural events that attract commercial and recreational fishermen alike. And I can see why. After a day on the river, we went home and enjoyed a wonderful dinner that included this succulent little panfish.