Biologists from the Division of Fish & Wildlife's Fisheries Section are constantly out working on Delaware’s rivers, ponds, estuaries, the Delaware Bay and coastal waters, keeping track of the state’s fish populations and how they’re faring.
What fisheries biologists do: Fisheries biologists use different types of sampling gear to check fish populations, depending on the habitat (pond, river, estuary, tidal stream, etc.) and the kind of fish involved.
Some fish – like largemouth bass or striped bass – are most easily and effectively collected by electrofishing.
Fish in deeper waters – like weakfish and croaker in the Delaware Bay – can be more easily collected by trawling. Once fish are collected, they are typically weighed and measured. Scale samples or other aging structures may be removed so the age and growth of the fish can be determined. A variety of sizes and ages is an indication of a healthy fish population for larger, older individuals as well as young ones.
Sometimes fisheries biologists need to gather other information, such as what what gamefish species are eating. Currently, a survey of striped bass food habits is being run in the Delaware Bay. A small pump is used to flush the contents of each striper’s stomach out so the meal can be identified. Each fish is then released; a little hungry, but still able to hunt another meal.
How is this information used? In the case of our freshwater ponds, problems such as over-crowding of smaller fish or poor growth can be addressed on a pond specific level. Habitat issues – like destruction of shoreline structure or run-off from human activities affecting water quality – are the most common problems.
For species like the striped bass, management must be done on a regional or coastal level. Striped bass move into the Delaware River during the spring to spawn upstream of the Delaware Memorial Bridge well into Pennsylvania waters. However, the adults move out into coastal waters and may migrate between New England and North Carolina during the rest of the year. All coastal states gather information which is then analyzed, while management of the species is governed by the US Fish & Wildlife Service and other inter-state agencies.
Fisheries Biologist John Clark captured and tagged this striper (48.5 inches long and weighing 54.8 lbs.) on the spawning grounds in the Delaware River, during the annual spring electrofishing survey – used to assess the spawning population.
Please click the links on this page to learn more about different fisheries programs and how the biologists of the Fisheries Section are helping to maintain healthy fish populations.