Something fishy is happening this Saturday! April 21st is World Fish Migration Day, an annual global celebration of the importance of open rivers and migratory fishes.
Many fish species migrate up and down rivers to reproduce, feed, and complete their life cycles. Migratory fishes all over the world depend on free-flowing rivers. River barriers like dams and sluices threaten many fish species’ survival. Rivers that allow fish to travel upstream and downstream increase fish populations and assure healthy river life.
Why celebrate fish migration? Zeb Hogan, a National Geographic Explorer, puts it this way, “So migratory fish, we don’t think about them a lot, but they are incredibly important to people’s livelihoods and as food sources all over the world.”
To help celebrate World Fish Migration Day, the Barnegat Bay Partnership will have live juvenile American eels (Anguilla rostrata) on display at the Point Pleasant Earth Day event this Saturday, April 21st, at Riverfront Park, Point Pleasant Borough. Stop by our table to learn more about BBP research on American eels and another Barnegat Bay migratory fish, river herring (Alosa pseudoharengus and Alosa aestivalis).
Check out these two videos of our research team monitoring migratory fish in the Barnegat Bay watershed — American eels and river herrings.
Read on for more information about BBP migratory fish research…
American Eel (Anguilla rostrata)
BBP researchers brave frigid temperatures and sometimes snow to monitor American eel populations. Starting in February, juvenile eels arrive in the bay after traveling for up to a year and 1,000 miles on ocean currents. Once here, they migrate from the bay into freshwater streams and rivers, where they mature to adulthood. American eels are “catadromous,” meaning they spend most of their lives in fresh water but return to salt water to spawn (release eggs).
To monitor eel populations, BBP researchers set eel collectors (designed to mimic the vegetation where eels like to hide) in streams throughout the watershed. They count and “stage” – a technique where markings on the eels are used to tell their age – the juveniles captured in the collectors and then release them back into the stream. View a video to learn more about how we monitor American eels.
In recent years, American eel populations have been declining due to exotic parasites, fishing pressure, and dams which block their migration route. The BBP shares the data from our research with state and federal partners for use in state- and coast-wide assessments of the status of the American eel population.
River Herring (Alosa pseudoharengus and Alosa aestivalis)
River herring is a common name that refers to two species of fish – alewife (Alosa pseudoharengus) and blueback herring (Alosa aestivalis). These fish are “anadromous,” which means they live as adults in the ocean and migrate up freshwater streams and rivers just long enough to spawn before returning to the ocean. Mature alewife start to run in freshwater streams when water temperatures are about 50°F, which usually occurs in early March in New Jersey. The blueback herring run usually starts 3-4 weeks later.
Once the eggs hatch, the juveniles stay in freshwater nursery areas into the summer. As water temperatures become cooler in the fall, they move downstream to higher salinity areas and then back into the ocean. Because they are anadromous, river herrings serve an important role in both freshwater and marine food chains. They have also been an important fishery in North America for hundreds of years.
Unfortunately, river herring populations have undergone a steep decline along the Atlantic coast in recent years. Reasons for the decline include spawning habitat (stream) degradation, dams that impede movement upstream for spawning, overfishing, and increased predation by striped bass. New Jersey and several other states have closed their river herring fisheries, and NOAA National Marine Fisheries Service has listed both river herring species as “species of concern.”
One way to learn more about the river herring populations in our area is through catch-and-release studies. BBP researchers catch herrings in nets as they migrate upstream and record information such as length, weight, and age of each fish before releasing them. Research like this helps inform fisheries managers about the status of populations of alewife and blueback herring in the region.
Westecunk Creek Dam Removal
This research also helps identify areas that are important for restoration or protection. As part of a larger study of the Westecunk Creek (one of the bay’s tributaries) with the US Fish and Wildlife Service, BBP ecologists deployed a pair of fyke nets during spring 2015 to identify the fish communities located above and below a barrier to fish passage on the creek. After removal of the barrier during the winter of 2015-2016, BBP ecologists repeated the sampling in spring 2016 and 2017. This video shows researchers in action monitoring river herrings.
The removal of the barrier on Westecunk Creek altered the fish community through a change in stream flow and habitat characteristics, allowing fish to freely move along the stream corridor. BBP researchers observed a substantial increase in the number of river herring returning to the Westecunk Creek in 2017 compared to the previous years — an encouraging sign!