June eDNA Samples Show Migration of Fish Species into Local Rivers and Bays

Beach tourists weren't the only ones crowding the Jersey Shore in June. An analysis of environmental DNA (eDNA) in water samples from beaches and estuaries in Monmouth and Middlesex counties found that the number of fish species roaming the waters scaled up to 79 from the 68 detected during a similar effort in the fall.

Last month, volunteer community scientists collected samples of ocean waters, bays, and brackish areas of rivers at 24 sites from the Manasquan Inlet to the Raritan Bayshore. The samples were then analyzed by the Monmouth University Urban Coast Institute (UCI) in a lab for eDNA, trace genetic materials floating in the water that can indicate the recent presence of marine organisms. The data is building upon a collection effort that began in September, and is being used to develop a baseline understanding of the species living in our waters throughout the year. The results of the research were revealed at a July 14 workshop on campus.

A particular increase in richness was seen in the county's estuaries, which recorded numbers that were nearly equal to those in the ocean sites. In the fall, the ocean samples carried a far higher species richness than the rivers and bays.

The estuarine sites with the highest numbers of fish detections were near the mouth of Cheesequake Creek on the Raritan Bay (42) and Maclearie Park on the Shark River Bay in Belmar (39). The counts on beaches were highest in Long Branch (39) and Sandy Hook (34).

"We believe what's happening is that there are seasonal migrants coming into the estuarine environment, which is a well-documented phenomenon in our area," UCI Resilience and Outreach Project Lead Richard Kane said. "One paper estimates that 82.5 percent of ecologically important marine fish in the Mid-Atlantic Bight use estuaries at some point in their life."

In the ocean, menhaden and river herring species, which are difficult to distinguish through eDNA, accounted for roughly a quarter of the fish detected, followed by butterfish (14 percent), and mummichog (11 percent). In the estuaries, mummichog (28 percent) and Atlantic silverside (25 percent) accounted for over half of the detections.

Kane pointed to the detections of sand lance (5 percent in the ocean, 2 percent in the ocean) as an example of eDNA's potential as a tool for researching fish community composition. He said that because sand lances are so elusive - they swim at full speed into the sand and hide there when they sense predators - the National Oceanic and Atmospheric Administration tends to avoid studying them.

"In order to detect all these things the traditional way, you'd need an armada of boats, traps, trawls, and nets, but we can find it all in the bottles of water you're sampling," Monmouth University Endowed Professor of Marine Science Jason Adolf told the audience. "That's the efficiency of this method for the purpose of studying biodiversity."

The research is being supported with funding secured by Rep. Frank Pallone, Jr. Volunteers are being sought for the next phase of sampling, which will likely take place around October. To learn more, contact Kane at [email protected].