.jpg "Banded Killifish, eastern (top) and western (bottom). In its native range, the Eastern subspecies may be edging out the Western fish. According to a new University of Illinois review, non-game native transplant fish like the Eastern Banded Killifish are understudied, and their impacts may be greater than managers believe. Jordan Hartman of the University of Illinois") |
| Banded Killifish, eastern (top) and western (bottom). In its native range, the Eastern subspecies may be edging out the Western fish. According to a new University of Illinois review, non-game native transplant fish like the Eastern Banded Killifish are understudied, and their impacts may be greater than managers believe. Jordan Hartman of the University of Illinois |
Rivers separated by mountaintops and other geographical barriers may flow only a few miles apart, but to the aquatic creatures that live in those waters, the distance could represent millions of years of evolutionary time. So, when an angler or a curious child moves a fish from one side of the mountain or country to the other, it's a big deal to the fish. Some individuals may find a competitive advantage in a new stream, potentially upending eons-old ecological hierarchies.
These so-called "native transplant" fish are nearly twice as common as fish introduced from outside the country, according to the US Geological Survey's Non-Indigenous Aquatic Species database. However, according to a new University of Illinois study, native transplant fish, particularly those that do not qualify as game fish, are rarely studied and their impacts are poorly understood.
"We are attempting to identify a specific type of biological invasion that has been largely overlooked for study and attention over time. It leaves us with some questions about whether these fish are having an impact and, if so, whether they are causing harm that is going unnoticed "Eric Larson, associate professor in the Department of Natural Resources and Environmental Sciences at the University of Illinois and senior author on the Fisheries review, agrees.
Larson and lead author Jordan Hartman combed the scientific literature for information on non-game native transplant (NGNT) fish studies. Only 51 of the 220 NGNT fishes identified as established in the United States have been studied. And only 30 of them have had their effects studied.
According to Larson, the consequences can be significant.
"When the Western mosquitofish, for example, was introduced in areas with rare endemic desert fish, it had strong population-level effects, resulting in Endangered Species Act listings and an increased risk of extinction in those species. Furthermore, native transplants such as sea lamprey and rainbow smelt have an impact on game fish in the Great Lakes "he claims "With this review, we want to know how certain we are that the Western mosquitofish and rainbow smelt are outliers."
According to Hartman, the few published studies on NGNT fish leave many unanswered questions.
"There's a lot of emphasis on population and community-level impacts in invasive species research," she says. "That appears to be the case with NGNT fish as well. These fish could have effects on the genetic level, through hybridization with related fish, or on the whole-ecosystem level, through nutrient cycling. However, based on the available research, we simply do not know."
NGNTs are typically moved by anglers dumping bait buckets after a day of fishing, contaminated fish stocking, or aquarium hobbyists releasing pets in nearby streams, as opposed to game fish, which are intentionally stocked into lakes and streams.
Take, for example, the Eastern banded killifish. The small fish, which were likely introduced to Illinois waters via bait buckets and contaminated fish stocking, may be edging out or hybridizing with the Western banded killifish, a state-listed threatened Illinois native. Hartman is conducting research on the two subspecies as NGNT poster children.
"Eastern banded killifish have spread along the coast of Lake Michigan, through the Illinois River, and all the way to the Mississippi River since their discovery in 2000. They have moved quickly across the state. And we have no idea what their consequences will be. This is where my research comes into play "she claims "I'm looking into whether the Eastern and Western banded killifish are hybridizing and what that might mean for the Western banded killifish, which is already endangered in the state. Will we lose Western genes if they begin to hybridize?"
The way state and federal agencies regulate invasive species is part of the problem. Many agencies expressly prohibit non-native species, with no or ambiguous definitions of what is regulated. And, because most state lists do not name native species, there is no regulatory tool to motivate or support eradication efforts.
Larson and Hartman challenge state and federal agencies to challenge the assumption that fish native to the contiguous United States are naturally harmless. Anglers, aquarium hobbyists, and others, they say, can help prevent NGNT invasions in the meantime.
"If you take bait fish out of one watershed, don't dump it in another. Also, avoid releasing aquarium fish into nearby bodies of water "According to Hartman.
Larson continues, "Because of the geographic scale at which invasion can occur, it is difficult to avoid releasing organisms in freshwaters. People are unaware that these drainage divides can create extremely isolated communities. Driving 20 miles down the road and releasing live bait could result in a massive shift in the distribution of those organisms."
Journal information: Fisheries