A species of fish once thought gone from Cooper River has returned — in a big way

David Keller was part of a New Jersey Fish and Wildlife team more than 20 years ago when he went to the Cooper River to take stock of what fish were living and laying eggs there.

At the time, blueback herring had been nearly eradicated from the river’s ecosystem by pollution and impediments to swimming upstream.

So Keller was surprised when he more recently studied which fish still migrate to the river from the Atlantic Ocean. This time he was working for the Academy of Natural Sciences' Patrick Center for Environmental Research in Philadelphia.

Not only did Keller, a fish ecologist, find that blueback herring had returned to the Camden County river system, but it was abundant.

In fact, it represented the biggest population of species of ocean-migrating fish, known as anadromous fish, in the river.

Keller and his team recently published a paper on the findings in the journal Marine and Coastal Fisheries, demonstrating that highly urbanized rivers can support substantial amounts of anadromous fish — ones that spend most of their adult lives in salt water, but return to spawn in fresh water.

“When we started the work, we did not know what to expect,” Keller said. “We definitely had interest in assessing migratory fish like your American shad and your river herrings, but we didn’t know if the runs would be there at all. Or, we assumed we would see very low numbers. So we were surprised to see what appeared to be a very strong run, a robust run, of blueback herring.”

In this case, the blueback herring swim from the Atlantic Ocean, up through Delaware Bay, the Delaware River’s estuary, and into the Cooper River on the Camden waterfront at Petty’s Island, just across from Philadelphia. They lay their eggs in the Cooper.

Keller undertook the study as part of the nonprofit Upstream Alliance’s quest to build the Camden River Trail, a 13-mile water trail along the back channel of the Cooper River for kayaking and paddling. The trail is set to open in June.

Don Baugh, president and founder of the Upstream Alliance, said the study verifies that the river is much cleaner than in decades past, before the Clean Water Act and better wastewater treatment plant management prevented sewage and other waste from flowing into the river.

In all, 13 sewage treatment plants were removed along the river starting in the 1980s. Treatment was centralized and improved by the Camden County Municipal Utilities Authority, which discharges treated waste into the Delaware River.

“The reason this study is particularly significant is that the Cooper is an open river that everyone once gave up on,” Baugh said. “People believe the Cooper River is full of sewage and industrial waste, that it’s not a place for people.”

The goal of Upstream Alliance is to bring people back to recreate on once-polluted waterways like the Cooper. Baugh received $731,000 in grants, including from the National Fish and Wildlife Foundation, and is working closely with Camden County to develop the trail.

Upstream Alliance gave about $25,000 toward Keller’s study, with additional funding provided by the Academy of Natural Sciences of Drexel University.

Keller’s study shows that the water quality supports many ocean-migrating fish, such as striped bass, shad, and herring — which are separate from carp or catfish that spend their entire lives in local freshwater.

Also helping: A fish ladder, designed to help migrating fish bypass obstacles in the water, was installed in 1998 at the Cooper River Lake dam off Kaighns Avenue in Camden after some blueback herring were spotted.

As a result, New Jersey’s Division of Fish and Wildlife documented juvenile American shad and at least five blueback herring had made it above the dam in 2004, evidence that the lake could provide a place for fish to lay their eggs. Keller used that research as a jumping-off point, and updated numbers for both species in the same portion of the watershed, showing that the numbers had grown substantially.

However, the fish ladder is not sufficient, the Upstream Alliance believes. It’s been advocating for a broader channel that both fish and kayakers can use to bypass the dam. Now, kayakers have to carry their boats by foot around the dam. Some portion of the fish do get through the ladder. But not all fish are able to move past it.

Camden County Commissioner Jeffrey Nash, the county’s liaison to the parks department, said officials had studied a project that would help fish around the dam and ladder, but the cost was “astronomical.”

“It had an estimated price of over $15 million,” Nash said. “We don’t have the resources available to make that investment.”

So the county is focusing on developing the water trail, which will include kayak and boat launches, and possibly a self-serve kayak rental that would paid through credit card, Nash said.

But the current level of blueback herring still marks a major success, Keller said. Overall, his research team found seven species of anadromous fish in the Cooper River system.

“The ones you expect to be there are in the system, such as American shad, alewife, and blueback river herring,” Keller said. “We also came across hickory shad and other migratory species that migrate between fresh and salt water, such as American eel, sea lamprey, and striped bass.

“Of that grouping, blueback herring was the most abundant, most common migratory fish.”