Low Salinity Hampers Horn Pt. Spat Production

Published: July 11, 2019

Two years of record breaking rains are taking their toll on oyster spat production at the Horn Point Hatchery in Cambridge.

Click here to read the report in the Bay Journal.

We do hope this is temporary, but it is part of a two-year trend that has seen a sharp drop in the salinity of the Severn River.

Our Water Quality Monitoring crews are recording salinity levels in the Severn River that are only in the 4 to 6 parts per thousand (ppt) range.  Normally, the Severn River is supposed to be brackish with salinity in the 8 to 15 ppt range.

Fortunately, our oysters are tolerating the low salinity, so the reef restoration programs we support with our partner, the Oyster Recovery Partnership, are still doing well.

We had a dive team check on them in April and found our bivalve pals are alive and well! They can tolerate the low salinity.

They just can’t reproduce so well. Oysters like hot water and high salinity to reproduce.

Historically, those conditions never happened a lot in the Severn River. The problem is that Horn Point in Cambridge is now experience the low-salinity conditions.

We’re seeing other changes in the river due to the record-setting rains we’ve had.

For starters, the freshening of the river means No Sea Nettles!!!

Another plus is that the low salinity has spurred the explosion of dark false mussels everywhere under the low-tide waterline.

Check out this dock line to the right that had been left in the water too long.

These tiny guys are like oysters, they filter the water, and since they are everywhere these days, the entire river is benefiting from their filtering action, which has helped produce the amazing clarity we’re enjoying in the river.

The bad news: Dark false mussels are toxic for dogs. Do not let your canines near these critters.