Representative Dennis Kucinich (D-OH), also weighed in on the issue, urging the FDA, in what he said was the interest of the safety of the public and the environment, to avoid "ram[ming] the decision through."
Other scientists say the salmon may not pose an ecological risk after all.
Yonathan Zohar of the University of Maryland's Center of Marine Biotechnology said as the human population increases, so will the consumption of seafood. In order to avoid overfishing and depleting wild fish, fish must be grown.
He added that if it's done in fully-contained, land-based tanks, the effects can be positive for the ecosystem and for people's health.
Eric Hallerman, a professor of fisheries and wildlife at Virginia Tech University, also spoke of the benefits these salmon can provide.
"This may be good news for the environment," said Hallerman, adding that native populations are tapped out.
But he stressed there must be very strict confinement of these fish so they can't escape into the wild.
"If they interbreed with native salmon there could be loss of local adaptations and perhaps loss of those populations," he said.
The FDA will hold its next public hearing tomorrow, as it considers whether to label the salmon as genetically modified, if it is ever approved.
The FDA declined to set a timetable for making a final decision on the matter. ABC News' Lisa Stark, Brian Hartman and Andrew Miller contributed to this report.