A total of 206 fish species have been introduced into the 13 states within USFWS Region 5 (Appendix A). Of these, 151 are species native to the United States but have been transplanted outside their native range, and 42 are species introduced from other countries (exotic). Fifty-six percent of the native transplants became established and fifty percent of the exotic species introduced into the region have resulted in established populations. The number of introductions in the New England states is low when compared to states in the southern portion of the country (Figure 5). This is likely a factor of the reduced human population in this area and the cold weather that makes many of the tropical and subtropical species less likely to survive and subsequently be discovered.  States farther south in Region 5 have had approximately twice the number of introduced species as does New England (Figure 5). Region 5 includes the regional drainages of New England, the Mid Atlantic and the lower Great Lakes. The Mid-Atlantic has the greatest number of introduced fish species of any of these (Figure 6).

Figure 5. Number of fish species introduced into each state (Fuller et al. 1999).

Figure 6. Number of fish species introduced into regional drainages (Fuller et al. 1999).

Numbers of Introduced Species and Established Species in Each State
In the Northeast, Virginia and Pennsylvania have the most species introduced and the most species established (Figure 7). All states in this region have a low proportion of exotic species introduced.  Appendix A contains a complete list of species introduced into each state. Virginia and West Virginia are the two states in Region 5 with the highest number of native transplants (Figure 8). Virginia has a large number of minnow species that are thought to have been introduced outside their native range as the result of bait releases. Small portions of the Tennessee and Ohio drainages fall within these two states.  The Tennessee drainage has many species that differ from the other drainages in these states. Many of the native species have been moved between the Tennessee drainage and into other drainages in these states. In the Northeast, an average of 89% of native species transplanted outside their native range became established.

Figure 7. Total number of species introduced to each state.

Figure 8. Number of native fish species transplanted in each state.

All states in the Northeast have roughly the same number of established exotic fishes (Figure 9). There are only a handful of exotic fish species able to survive in the cold, northern climates.  Those species have been widely introduced and have become established throughout the region.

Figure 9. Number of exotic fish species introduced into each state.

Introduction Trends Over Time
Introductions in the Northeast mirror the nation-wide trend of an increase in the number of species introduced since the 1950s (Figure 10a, 10b).   However, the proportion of exotic fishes introduced in the past 50 years is less than the county as a whole.

Figure 10a.  Cumulative number of fish species introduced
into the United States (Fuller et al. 1999).

Figure 10b.  Cumulative number of fish species
introduced into Northeastern United States.

The total number of species that have been introduced in the Northeast is 2.5 times higher in 2000 than it was in 1950 (Figure 10b). The increase in the Northeast by decade has been fairly constant, with no obvious dramatic jumps (Figure 11).

Figure 11. Cumulative number of fish species introduced into the Northeast by decade.

Pathways
The major pathway of fish introductions for all states in Region 5 is intentional stocking for sport fishing or forage. Species stocked in these states include: various species of sunfish and bass, pike, muskellunge, bullheads, catfish, yellow perch, walleye, and several species of trout and salmon. 

Nationally, stocking for sport or forage is the most dominant pathway for introduced fishes. The aquarium trade is next and accounts for ~25% (Figure 12). Bait releases are believed to be responsible for another ~16%.  Fewer introductions are attributable to ballast water releases, stocking for bio-control, stocking of endangered species for conservation purposes, and miscellaneous methods such as canal connections, research releases, and escapes from aquaculture that are not related to aquarium fishes. In the Northeast, stocking is the dominant pathway, accounting for nearly 50% of the introductions. Bait release is the second most commonly used pathway and aquarium releases (or escapes from tropical fish farms) are third, followed closely by introductions arising from canal connections (Figure 13).

Pathways of Introduction for Fishes in the United States

Figure 12. Pathways of fish introductions in the United States (Fuller et al. 1999).

Figure 13. Pathways of fish introductions in Region 5.

An analysis of the three main pathways in the Northeast shows all three have increased dramatically in strength (Figure 14, 15). However, stocking remains the dominant pathway in the Northeast, just as it does nationwide.

Figure 14.  Number of new species introduced via the four major pathways
over the course over the last 150 years by pathway.

Figure 15. Number of new species introduced via the four major pathways
over the course of the last 150 years over time.

Geographic Origin of the Introduced Species

The majority of species introduced in the Northeast are native to the United States but transplanted outside their native ranges (Figures 16). Included are various species of minnows, sunfishes, bullheads and catfishes, salmon, and darters.  Of the exotic species, contrary to other areas of the country where most are associated with the aquarium trade, exotics in the Northeast as mostly intentionally stocked as either sport fish or bait. 

Eurasia is the source region that provides the largest number of species to the Northeast. These include common carp (Cyprinus carpio), goldfish (Carassius auratus), grass carp (Ctenopharyngodon idella), ide (Leuciscus idus), brown trout (Salmo trutta), tench (Tinca tinca), rudd (Scardinius erythrophthalmus), bitterling (Rhodeus sericius), and snakeheads (Channa spp.).

Central and South America is the next largest contributor to the Northeast, and includes cichlids: midas cichlid (Cichlasoma citrinellum), oscar (Astronotus ocellaris), guppies (Poecilia reticulata), armored catfish (Hypostomus spp.) and (Callichthys callichthys), and pacus (Colossoma sp. and Piaractus sp.) and piranhas (Pygocentrus spp.).

Africa is the source of a few cichlid species such as the blue tilapia Oreochromis aureus, and mozambique tilapia O. mossambicus.  Figure 17 shows the continental origin of fish species introduced in 50-year increments.  Although North America (the United States) has always been the major source of introductions, those from other continents have grown in recent decades.

Figure 16. Geographic origin of introduced fishes in Region 5.

Figure 17. Geographic origin of introduced fishes in Region 5 over time.

When the origin of introductions is examined on a state by state basis, the predominant origination varies somewhat between the states (Figure 18). New York, Pennsylvania and Virginia have high percentages of species native to the state but moved outside of their native range (usually across the Appalachian Divide). These states also contain the Great Lakes, Atlantic Slope, and Ohio drainages, each with a unique fauna. Some of these species have been moved between the two drainages.

Figure 18. Composition and origin of introduced fishes in northeastern states.
Introduced = native to the US, but not to that state
Native and Introduced = native to part of the state
but introduced outside its native range in the state
Exotic - species not native to the US
Hybrids - stocked hybrids (wiper, tiger muskie, etc.)

Similarly, the states of Pennsylvania, Virginia and West Virginia have experienced faunal interchanges between the Atlantic, Ohio, and Tennessee drainages.  The states of Connecticut, Massachusetts, and Maryland have high proportions of species that have been introduced from outside the state such as sunfishes, bass, bullhead, and salmonids.

Vulnerable Areas

As a general rule, rivers, lakes and reservoirs near metropolitan areas throughout the Northeast are areas vulnerable to introductions. These waters are the most likely to be stocked with sport and forage fish for recreational fishing for nearby city residents.  Also, they are the waterbodies most likely to receive unwanted pet and aquarium releases.  Specific examples of vulnerable areas include the Susquehanna, Delaware, and Potomac drainages and the Great Lakes.