Invasive Species

Invasive species listed in Fish Key:

Catfish (only channel catfish is invasive, and it isn’t specified in the fish key)
Intentionally introduced for sport fishing and food. Outcompete native species for food, and feed heavily on crayfish populations, leading to their decline.

Goldfish
Introduced through the aquarium trade, and as ornamental fish that escape during flooding events. Hardy fish that can tolerate fluctuations in water temperature and water with low levels of dissolved oxygen, and can threaten native species in degraded water ecosystems. They feed on fish eggs, larvae, and aquatic vegetation.

Common carp
Unclear if they were introduced as a food fish and accidentally escaped during flooding events, or if they were intentionally introduced as a sport fish. Juvenile carp have also been used as baitfish, and could have been introduced through improper disposal of live bait. Common carp destroy vegetation and increase water turbidity by dislodging plants and root systems, deteriorating habitat for native species that require vegetation and clean water. They also destroy aquatic macrophyte populations by uprooting/consuming the plants, or increasing turbidity and reducing light required for photosynthesis. They also prey on the eggs of native fish species, thereby reducing their population.

Non-native species listed in Fish Key:

• Shiners
• Darters
• Largemouth bass
• Brook silverside
• Black crappie
• Smallmouth bass

Invasive Species in the Hudson River that aren’t listed in the fish key:

Zebra mussels
Zebra mussels are filter feeders leading to huge decreases in plankton and daphnia populations, an important food source for many native oysters, clams, mussels, and fish. Plankton populations decreased by 50-80% within the first year of their introduction, leaving a lot less food available for fish, mussels, etc. Native mussels are unable to compete with the zebra mussels, causing them to become threatened or endangered. Shad and herring have also suffered.