St. Johns River: Where did all the eelgrass go?

The big talk this week at the 2020 AFTCO Bassmaster Elite at St. Johns River has been about the lack of eelgrass.

The fishing has been very tough this visit, considering the previous years kicked out very impressive five-bass limits of largemouth bass. And really, the lower weights this time around can be blamed on the weather. A large, blustery cold front hit early in the week, dropped water temps and pushed a lot of water out of areas that generally hold the highest concentrations of prespawn and spawning bass.

Blame the weather.

But the lack of eelgrass has been a hot topic for the past two years. Where has it all gone? What’s to blame? And will it come back?

To help sort this out, Trevor Knight, the Northeast Region Fisheries Administrator for the FWC has some interesting theories that certainly contribute to the situation.

“First off, the continued absence of the eel grass can be directly pointed at hurricanes the past two years,” Knight said. “Hurricanes Michael in 2018 and Irma in 2017 certainly had major impacts on Florida fisheries. The wind alone is largely responsible for destroying countless acres of vegetation. It just takes time for aquatic plants like eelgrass to recover, and they require certain conditions to be reestablish.”

Knight said the eelgrass is essential to successful black bass spawning and recruitment because it provides adequate cover for the fry and young-of-the-year.

“There are large populations of predator fish in Florida waters, especially gar and dogfish in the St. Johns River and Lake George,” he said. “They will target and feed heavily upon whatever is most abundant. In some cases that might mean black bass. With the lack of eelgrass over the past couple of years, overall bass recruitment is down. That doesn’t mean there aren’t still plenty of bass — and big bass — to catch, it just means recent year classes are lower.”

Juvenile bass depend on quality cover to act as a nursery so they can survive predation from birds and other predator fish. But, like many circumstances in nature, this situation is cyclical. The eelgrass will bounce back. But what else is slowing its recovery?

Knight said that not one specific factor is the sole cause, it’s a combination of multiple factors.

Two species of invasive fish have been linked to eelgrass habitat damage.

“The armored catfish and the tilapia are two aggressive spawners, they literally take over the structural elements on which they spawn,” he said. “That means grass won’t grow there. The tilapia attempt to spawn all year long, making them very prolific.

“We also haven’t had much cold weather over the past couple years. A two- to three-week stretch of freezing temps would kill a good number of the tilapia and armored catfish. A reduced population of each invasive would encourage more eel grass growth in certain areas.

“Another factor is the continuous wet weather we’ve been experiencing over the past two years,” he continued. “The water levels in the river and on Lake George has been higher than normal, which makes it hard for the eelgrass to germinate and begin growing. Generally, it grows best in 1 to 2 feet of water on firm sandy bottoms, sometimes mud, but not a soft murky substraight. Average water levels have exceeded that mark recently.”

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