February 24, 2022

Monitoring Juvenile Eels

by S-FX.com

Eel-collector
Holding A Juvenile Eel
A juvenile American eel.

Each winter, juvenile American eels (Anguilla rostrata) arrive in the Barnegat Bay. At this life stage, they are known as glass eels (if they are still young enough to be transparent) or elvers (if they are somewhat older and opaque). These eels hatched from eggs in the warm waters of the Sargasso Sea and travelled up to a year and 1,000 miles on ocean currents before reaching the east coast of the United States.

Once they arrive, most glass eels migrate from estuaries into freshwater streams and rivers, where they will spend most of their lives maturing. These eels may live for 15 to 20 years and grow to lengths of over three feet before the adults leave the estuaries and freshwater streams of the eastern U.S. to return to the Sargasso Sea, where they spawn and eventually die.

Sammi Rinsing Eel Collector
BBP Field Technician, Sammi Adamcyzk, rinses eels off one of the collectors.

In order to keep track of the size and condition of the American eel population in the Barnegat Bay watershed, the Barnegat Bay Partnership has been conducting an eel population survey since 2012. Each winter and early spring, our field technicians and volunteers set eel collectors in streams throughout the watershed. These collectors are meant to mimic the vegetation that eels like to hide in, and they attract the young eels as they are passing by on their migration route. The eels in the collectors are taken back to the lab to be counted and “staged” – a technique where markings on the eels are used to tell their age – and finally released back into the stream where they were collected.

Eels Sammi Pouring Water Through Sieve
Sammi pours the rinse water with eels through a sieve.

Eels are important in coastal stream ecosystems as food sources, predators, and transportation for larval mussels, which hitch a ride on migrating eels. In recent years, American eel populations have been declining due to exotic parasites, fishing pressure, and dams which block their migration route. The U.S. Fish and Wildlife Service decided not to list American eel as a threatened species in 2015, but their low population numbers remain a concern up and down the Atlantic coast.

Last year, we completed 271 monitoring events and measured a total of 721 eels. The data we collect are shared with our state and federal partners for use in state- and coast-wide assessments of the American eel population.

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UNKNOWN

There is limited data available to quantify Wetland and Riparian Buffer Preservation, or updated data to quantify Wetland Acreage. The BBP has obtained funding and will begin assessment efforts for both targets, in the next few years.

 

 Hard Clam abundance has not been updated since 2012. Recovery of the stock will be guided by the Fishery Management Plan for Hard Clams, which is under development with the NJDEP, BBP, and other organizations. Reclam the Bay and other partners have continued to plant clams for restoration purposes. Continued plantings in strategic locations which maximize survival and reproduction is one strategy to pursue in the coming years. This work can use a model developed by Rutgers with BBP funding which identified areas where planted clams could have the greatest dispersal of their larvae and thus potentially maximally contribute to the recovery of the stock.

 Water Withdrawals were over the target in the 2021 report; USGS has not yet completed its latest update, so a definitive determination of status is not available. However, additional NJDEP data show that it is likely that we continue to not meet the target. Per capita water use has gone down, demonstrating the effectiveness of water-saving appliances and practices, but that decrease has been offset by population gains. 


IN PROGRESS

New maps quantifying Submerged Aquatic Vegetation extent were developed, but poor image clarity resulted in a high degree of uncertainty in the total acreage. NJDEP and Rutgers are working to resolve the uncertainty of these maps, and improve the total acreage estimate. Funding has also been obtained for further research and restoration activities. Several groups are developing potential restoration actions.

The USGS has completed the first phase of its study to identify minimum ecological flows in select Barnegat Bay tributaries. USGS scientists compared streamflow statistics between historical and current time periods to better understand trends in watershed flow conditions. This work provides a foundation for developing ecological flow targets in the Barnegat Bay watershed.  Similar to SAV extent, funding (approximately $450K) has been obtained by the BBP to complete the remaining phases necessary for threshold determination.

 

TARGETS ACHIEVED

No targets can be considered “Achieved” at this time.

 

NOT ACHIEVING

Several Public Swimming Beaches exceeded their safe swimming standards more frequently than during their baseline time period (2016-2018).

While most beaches are routinely safe for swimming, several problematic areas such as Beachwood, Hancock, Windward, and several lake beaches need track-down studies and restoration to pinpoint and address sources of bacteria.

Acres of Approved Shellfish Waters decreased from the last report. While this decrease was small, it represents a loss of previously approved waters. Similar to public beaches, track-down studies and restoration work are needed to pinpoint and address sources of bacteria.

 

Monitoring Juvenile Eels

Holding A Juvenile Eel
A juvenile American eel.

Each winter, juvenile American eels (Anguilla rostrata) arrive in the Barnegat Bay. At this life stage, they are known as glass eels (if they are still young enough to be transparent) or elvers (if they are somewhat older and opaque). These eels hatched from eggs in the warm waters of the Sargasso Sea and travelled up to a year and 1,000 miles on ocean currents before reaching the east coast of the United States.

Once they arrive, most glass eels migrate from estuaries into freshwater streams and rivers, where they will spend most of their lives maturing. These eels may live for 15 to 20 years and grow to lengths of over three feet before the adults leave the estuaries and freshwater streams of the eastern U.S. to return to the Sargasso Sea, where they spawn and eventually die.

Sammi Rinsing Eel Collector
BBP Field Technician, Sammi Adamcyzk, rinses eels off one of the collectors.

In order to keep track of the size and condition of the American eel population in the Barnegat Bay watershed, the Barnegat Bay Partnership has been conducting an eel population survey since 2012. Each winter and early spring, our field technicians and volunteers set eel collectors in streams throughout the watershed. These collectors are meant to mimic the vegetation that eels like to hide in, and they attract the young eels as they are passing by on their migration route. The eels in the collectors are taken back to the lab to be counted and “staged” – a technique where markings on the eels are used to tell their age – and finally released back into the stream where they were collected.

Eels Sammi Pouring Water Through Sieve
Sammi pours the rinse water with eels through a sieve.

Eels are important in coastal stream ecosystems as food sources, predators, and transportation for larval mussels, which hitch a ride on migrating eels. In recent years, American eel populations have been declining due to exotic parasites, fishing pressure, and dams which block their migration route. The U.S. Fish and Wildlife Service decided not to list American eel as a threatened species in 2015, but their low population numbers remain a concern up and down the Atlantic coast.

Last year, we completed 271 monitoring events and measured a total of 721 eels. The data we collect are shared with our state and federal partners for use in state- and coast-wide assessments of the American eel population.

Contact Monitoring Juvenile EelsContact Monitoring Juvenile Eels
Eel-collector