Why Finding Oil in Fish Organs Isn't as Bad as it Looks
Environmental remediation scientists at LSU’s School of the Coast and Environment have found remnants of crude oil in the hearts of pogy that live off Grand Isle.
Pogy, a baitfish more officially called menhaden, make up the second largest commercial catch in the United States. They’re not only resold as baitfish, but they’re also processed into fish oil and fish meal, making their way into vitamins, cosmetics and livestock feeds.
Dr. Ralph Portier studies menhaden, hoping they’ll clue researchers in to when Louisiana will recover from the BP oil spill. Because menhaden filter feed, the fish pick up tiny bits of everything they swim through. While they’re trying to prey on plankton, they’re also picking up remnants from the oil spill.
Portier and his graduate student, Greg Olson, are using menhaden as a measuring stick to gauge how much oil is left in the Gulf.
A Sentinel Species
Those oil remnants are building up in menhaden tissue, forming microscopic balls of crude oil in pogy hearts, and scaring the liver and intestines as the fish process the chemicals.
The oil may not necessarily be from BP spill.
“[The remnants of crude oil] are related to contamination from oil exploration in the Gulf,” Olson wrote in an email, “but it cannot be determined what exactly the source is based on the lack of oil biomarker compounds.”
When pogy process the oil, their system strips away the chemical fingerprints unique to an oil source.
But that doesn’t mean the research is moot. Portier says they’re studying menhaden specifically because they’re what he calls a “sentinel species.”
“It’s at a transition in the food chain,” Portier explained, “from the primary producers, which are primarily the planktonic species, phytoplankton and the zooplankton, and the top predators, like red snapper, and other recreational catch fish.”
By studying pogy, Olson and Portier may be able to access the health of the ecosystem as a whole.
Portier hopes to establish a model for what recovery from a spill looks like chemically, how long recovery may take, and how long it takes oil to makes its way up the food chain.
There’s no need to worry about the commercial viability of the fishery, Portier says. “In terms of human consumption,” Portier said, “we’re far from levels getting any where near to what a World Health Organization, Environmental Protection Agency, or Food and Drug Administration number is in terms of what’s safe for human consumption.”
Portier estimated the amount of heavy metal material in menhaden is one ten-thousandth of what the FDA allows.
Menhaden as Survivors
Every year, the amount of oil found in the fish should decrease incrementally over time, until it levels out.
“It may be that in the young from after four years after the spill we don’t find appreciable if any amounts of residuals from the oil spill,” Portier said, “but it may be another four or five years before we don’t see residuals in the tissue of higher feeding fish.”
If another massive spill happens, the research will provide a baseline of contaminants in the ecosystem to which to compare new pollution, and spills can be compared to one another for severity of impact on the ecosystem.
Menhaden may be in the frontline of the recovery, but Portier says, “They aren’t a canary in coal mine.”
“When a canary dies,” Portier says, “You’re dead too.
Menhaden have been stressed by being in an oil spill, we’ve seen the damage, but they also survive.”
“It may be that monitoring this fish, one of the things we look for are those small little deposits, and when we don’t see them anymore, we know that that spill is now history.”
“BP wasn’t a spill,” Portier corrected, “it was a continuous oiling event.” The deluge of oil from the mangled equipment lasted 86 days. “We don’t have models for [recovery],” Portier said.
The oil that escaped was relatively lightweight. Oil on the surface degraded in “a matter of days, at most, weeks,” Portier said. “This issue was the volume, the amount of the oil. We have areas in the coast where there's still oil. The legacy of the spill is still visible in a lot of areas,” citing tarballs that still wash ashore occasionally and after storm events in Gulf states.
Menhaden vary in size. The variety that lives in the Gulf usually get up to 20 centimeters long. Their silver-gray backs and white-yellow bellies act as camouflage. Their bellies come to a hard, blunt ‘V.’
Olson stood on a small motorboat, gently removing baitfish one-at-a-time from a gill net, and warned, “Their scales are sharp.” Like paper cuts, Olson said, “You won’t notice the cuts on your hands until after it’s done.”
And like the BP Spill -- Portier and Olson are trying to expose those cuts, so the healing may begin.