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A new fight to save Delaware's ancient fish

04/11/2022 3:35 PM | Kathleen Avitt (Administrator)

A new fight to save Delaware’s ancient fish


Atlantic sturgeon survived 100 million years. Pollution, boats and humans have nearly killed them all

Credit: (Delaware Riverkeeper Network)

A highway billboard for the Delaware Riverkeeper Network’s campaign for the critically endangered Atlantic sturgeon

Drivers on northbound I-95 in Philadelphia right now might catch a glimpse of a billboard with a strange, prehistoric looking creature on it. “Extinction Sucks,” the headline reads.

The call to action is part of a new campaign by the Delaware Riverkeeper Network called “Dino in the Delaware.” While the animal on the billboard could easily pass as a bony, snouted dinosaur, it is in fact a living fish — the Atlantic sturgeon.

Two centuries ago, during the annual spring spawn, the Delaware River’s Atlantic sturgeon population is thought to have been around 360,000, the largest in North America. Today, few people driving on I-95 will recognize the fish, let alone have caught a glimpse of it in the wild, because Atlantic sturgeon are critically endangered, due to overfishing, bycatch, pollution, and habitat degradation.

According to Maya Van Rossum, chief executive officer of the Delaware Riverkeeper Network, the Dino in the Delaware campaign is an urgent, ad hoc effort to pull this ancient fish species back from the brink. “We are creating and rolling, creating and rolling,” she said, when asked about next steps for outreach. “One of the reasons for that is we don’t have the luxury of time.”

Just as there are genetic variations between humans, so too are there differences between the Delaware River population of Atlantic sturgeon and groups of the same species elsewhere.

Atlantic sturgeon

In 2012, five distinct population segments of Atlantic sturgeon were listed as endangered under the federal Endangered Species Act. The Delaware River and Bay segment, which is a part of the New York Bight population, is the most critically threatened. (Another sturgeon population in the watershed, the shortnose, is also federally listed as endangered.) A first-of-its-kind study in 2016 found that there were an estimated 3,656 juvenile (age 0-1) resident Atlantic sturgeon in the Delaware estuary. But, according to Dewayne Fox, a Delaware State University fisheries professor who studies the Delaware watershed cohort of Atlantic sturgeon, much less than 10% survive to spawning age. Female Atlantic sturgeon generally don’t begin spawning until they are 15 years old.

“Our estimate now, based on published, peer-reviewed projects and pretty robust methodology is less than 200 [adult] individuals,” Fox said. “While 3,656 sounds great, you have to remember that one female has two million eggs.”

Offshore and in the bay, Atlantic sturgeon can fall victim to commercial fisheries as bycatch — unintentional catches in equipment like nets and dredges — “but when they enter the river,” Fox said, “it’s a whole new world of threats.”

Three key threats

At the center of the Dino in the Delaware campaign are three key threats that have persisted in the watershed for decades and, researchers like Fox say, are keeping Atlantic sturgeon populations at critically low numbers: vessel strikes; habitat degradation; and low dissolved oxygen content. 

Atlantic sturgeon in the Delaware River have long been disproportionately impacted by strikes from vessel propellers large and small. Both Van Rossum and Fox say these strikes, which are almost always mortal, are the primary threat to the Atlantic sturgeon in the watershed.

Fox explained that, for some of the biggest vessels in certain conditions, like extreme low tides or when sandbars build up on the riverbed, there can be less than 5 feet of clearance between their propellers and the bottom.

‘These are things that have been around for over 100 million years, and these large vessels have only been around for roughly a century.’

“We’ve created an artificial situation where we have these really big ships in rivers and there’s not much room underneath them,” Fox said. “And even if there is room, there’s very likely so much pressure . . . so much force being driven by those propellers that, by the time the fish hears it, they can’t get out.”

Unlike other fish species, adult Atlantic sturgeon don’t appear to react in the presence of large vessels and swim away, according to Fox’s research. And while they are a benthic species, meaning they spend most of their lives close to the riverbed, Atlantic sturgeon also regularly move up and down the water column. In the 19th century, before they were nearly fished out of existence because of global demand for their roe — or caviar — fishers and bystanders wrote of waters boiling with sturgeon, and of explosive leaps from the water that sometimes landed the fish, which can reach 9 feet in length and weigh hundreds of pounds, onto the decks of boats.

“These are things that have been around for over 100 million years, and these large vessels have only been around for roughly a century,” Fox said. “As adults, they don’t have any predators — why should we assume that a fish this big and this old is going to move because something makes a noise?”

Habitat disturbance

The cargo and crude ships working their way from the ocean to the ports of Wilmington, Philadelphia and elsewhere up the Delaware River today can reach 1,000 feet in length. To accommodate these enormous vessels, the Army Corps of Engineers, in 2010, embarked on what would become a decade-long, $400 million dredging project that deepened a 100-mile stretch of river and bay channel by 5 feet — from 40 feet to 45.

The project was criticized by opponents who argued that, economically, the ports of Wilmington and Philadelphia didn’t need to accommodate the kind of super tankers that require such a deep channel. One of the fiercest critics was Van Rossum and the Delaware Riverkeeper Network, who said that the blasting of bedrock that would be required in some parts of the channel would be catastrophic to the Atlantic sturgeon.

“There’s so much expertise documenting that this is a niche port and we’re perfectly fine at 40 feet,” Van Rossum said. “We could have had an Army Corps of Engineers who said, ‘You know what? It’s clear that we don’t need to deepen the main channel of the Delaware River and put in jeopardy this species.’”

While larger ships can mean higher risk of propeller strikes, Fox said the greatest damage from the channel deepening project was the destruction of the Atlantic sturgeon’s most important spawning area. Atlantic sturgeon eggs, Fox explained, are sticky; they adhere to the first thing they touch. If that thing is sand, silt or mud, the eggs will quickly be covered over and smothered. Rock surface, then, becomes virtually the only substrate in the Delaware River that Atlantic sturgeon eggs can attach to and survive long enough to hatch.

Credit: (AP Photo/Steve Helber)

This Atlantic sturgeon was caught and released in an Aug. 8, 2010 census on the James River in Virginia.

Much of the lower Delaware River and Bay is sand, silt and mud, but in a stretch of river between Philadelphia International Airport and Wilmington, Delaware, bedrock and boulders stud the seafloor, making this area a key Atlantic sturgeon spawning ground — and a headache for ships. To deepen the channel here, the Army Corps blasted the bedrock and boulders with explosives.

“Sturgeon seek out those hard bottom areas of the river, which are in the navigation channel,” Fox said. “The Army Corps of Engineers is blowing the crap out of sturgeon spawning habitat in the river, and they’ve knocked that habitat back.”

Ed Voigt, spokesperson for the Corps’ Philadelphia District, which oversaw the project, said the agency followed all the precautions mandated by the National Marine Fisheries Service, which included conducting rock blasting only between Dec. 1 and March 15, a timeframe when the Atlantic sturgeon are not spawning. He insisted that no habitat was lost. “Everywhere we moved rock, there was rock underneath,” he said. “We just lowered it somewhat.”

While he admitted some sturgeon could have been harmed or killed, Voigt said National Marine Fisheries allows for a certain amount of collateral damage, “basically recognizing that life isn’t perfect,” but that the project didn’t even reach that limit.

“There might have been one or two [sturgeon killed] in the whole course of the project, but they were just sturgeon we found,” he said. “We did not decrease their numbers.”

Dissolved oxygen levels too low

Before Congress passed the Clean Water Act in 1972, the Delaware River was so polluted with industrial chemicals and raw sewage that a so-called dead zone had formed in a large swath of the waterway around Philadelphia.

Like humans, fish need oxygen; without it, they suffocate. In general, fish require around five milligrams per liter of dissolved oxygen to survive. Untreated wastewater breeds bacteria, and fertilizers and other nutrients spark algal and other microorganism blooms. Fueled by the untreated wastewater, these organisms out-compete the fish, consuming the oxygen they need. At the time of the Clean Water Act’s passing, much of the lower Delaware around the tri-state metropolitan areas had zero, or very little, dissolved oxygen, rendering it effectively dead.

‘They’re saying they still need to study it, but we have so few Atlantic sturgeon left that you can literally study it to death, and that’s what’s happening here.’

Sturgeon — especially juveniles — are particularly sensitive to low dissolved oxygen content levels. The Delaware River Basin Commission, the interstate agency in charge of setting dissolved oxygen thresholds in the river, maintains that a level of 3.5 milligrams per liter is sufficient for fish species in the areas around Wilmington and Philadelphia — a criterion that the commission set in 1967 and has never changed.

In 2017, the commission resolved to finally review its 50-year-old dissolved oxygen content thresholds in that area of the river through a series of studies. One of them, conducted by The Academy of Natural Sciences of Drexel University in 2018, found that most fish species have a minimum threshold that is above 3.5. For normal survival and growth, the report said, juvenile sturgeon require a minimum dissolved oxygen content level of 6.3 milligrams per liter.

More delays

The 2017 initiative’s deadline was extended because of the COVID-19 pandemic, but the commission said last year it would be completed by September of this year. However, Kate Schmidt, spokesperson for the commission, said that is no longer the case.

“I believe the schedule is pushed out a little bit,” Schmidt said. “The study part of it is wrapping up soon and we are anticipating putting out some final products, like reports, this year.”

Credit: (Delaware Riverkeeper Network)

Another highway billboard for the Delaware Riverkeeper Network’s campaign for the critically endangered Atlantic sturgeon

But any decision on changing the threshold, Schmidt said, would be part of  a different process entirely, requiring public hearings and comments, reviews and, finally rule-making.

According to Schmidt, the biggest driver of persistently low dissolved oxygen content levels in the river is discharge from 12 wastewater treatment facilities scattered along the banks of the river, between Delaware, New Jersey and Pennsylvania.

“To improve sewage treatment at some of these municipal plants is a heavy financial load,” Schmidt said. “If you’re making them improve their treatment, the costs shouldn’t necessarily be passed on to ratepayers who might already be disadvantaged, so there’s that factor that’s going into our study as well.”

Time is nearly up

Van Rossum contends that, while rigorous research is necessary, it should have been done a long time ago. “Think about the people at the DRBC [Delaware River Basin Commission], at the government agencies, who could do something about this, who could make a meaningful change, who a decade ago could have passed oxygen standards that would have helped this species thrive and procreate and expand, but they chose not to,” she said. “They’re saying they still need to study it, but we have so few Atlantic sturgeon left that you can literally study it to death, and that’s what’s happening here.”

Which is the reason, Van Rossum continued, that the Delaware Riverkeeper Network has taken the unique approach of appealing to otherwise unsuspecting drivers on one of the busiest sections of roadway in the region.

“That’s the reason for this campaign,” she said. “Because I really believe that if the people speak up and stand up for the sturgeon, that we will get the changes we need.”

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