Fish life in the Severn is greatly affected by salinity, with freshwater fish dominating the fresher tidal headwater areas of the tributaries and some of the more tolerant marine fish dominating the major tidal waters. In addition, summer hypoxia limits the bottom-dwelling species present in the Severn as in other parts of the Chesapeake.
Yellow perch enter Severn Run from the tidal river to spawn in early spring, and Severn Run was the site of a state-run yellow perch hatchery for some years. However, in recent years the Department of Natural Resources has closed the Severn watershed to yellow perch fishing in order to restore its depleted population.
Yellow perch enter Severn Run from the tidal river to spawn in early spring, and Severn Run was the site of a state-run yellow perch hatchery for some years. However, in recent years the Department of Natural Resources has closed the Severn watershed to yellow perch fishing in order to restore its depleted population.
Fish that spawn in the fresher ends of the Severn's tidal tributaries include the pumpkinseed sunfish, brown bullhead, and common carp. In the summer anglers cast near the shores for white perch, a tasty smaller cousin of the rockfish and one of the Bay's most abundant fish. The Severn is known as a prime location for chain pickerel, a voracious predator which lurks in quiet backwaters in the tributaries. The tidal Severn also harbors American eel, and smaller species such as herring and banded killifish. As salinity increases in the summer, various saltwater fish may enter the Severn and its creeks, including bluefish, hogchokers, Norfolk spot, and needlefish. As rockfish (striped bass) abundance has increased throughout the Chesapeake after a multiyear fishing moratorium, the Severn is once again been a site of legal-sized rockfish catches in the late summer and fall. Jonas Green State Park contains a public fishing pier on the north shore of the Severn, created from the old Rte 2 bridge. In addition, Sandy Point State Park at the edge of the Severn watershed provides both boating access and fishing opportunities on the Bay.
In the summer, blue crabs feed and shed in the Severn's quiet shallows and are actively sought after by crabbers using collapsible traps, trotlines and hand lines. In the Bay near Annapolis, commercial crabbers make their daily rounds to check their bay traps. Unfortunately, in recent years there has been an obvious decline in crab abundance in the Severn as elsewhere in the Chesapeake, compromising a long tradition of summer enjoyment for families as well as the commercial fishery. Grass shrimp can also be found in considerable numbers around pier pilings and in underwater grass beds. These thin transparent shrimp are a favorite fish food and bait for fisherman.
Summertime swimming in the Severn is often cut off by the arrival of sea nettles as the salinity increases during the summer. Annoying as their stings can be, these primitive animals are beautiful when viewed from below. Smaller non-stinging comb jellies are sometimes also abundant, most noticeable by their flashing when the water is agitated on a dark night They are major consumers of zooplankton, and their increase in abundance in this part of the Chesapeake in recent years may be responsible for depressing zooplankton populations.
A specialized community of animals lives at the bottom, digging into the sand or mud and filtering the water to capture suspended plankton. These organisms include clams such as brackish-water clams, a variety of worms including polychaetes, and shrimp-like organisms termed amphipods.