Busy Spring Ahead for Migratory Fish Biologists

Posted by Wayne G. Barber

Matt Carpenter

2015 was a pretty good year for diadromous fish in New Hampshire. This news was welcome because diadromous species, which migrate between freshwater and saltwater to complete their life cycles, face big challenges. Before the construction of dams in the 1800s, American shad, alewives, blueback herring, American eels, sea lamprey and Atlantic salmon migrated into New Hampshire’s rivers in huge numbers. In recent years, fishway construction has allowed many species to once again access portions of their historical spawning habitat. NH Fish and Game, the U.S. Fish and Wildlife Service (USFWS) and other partners have been working to restore diadromous fish populations to their former abundance for more than 35 years.

 

A new record was set in 2015 for numbers of American shad returning to the Merrimack River. The count of 86,857 passing through the fishway at the Essex Dam in Lawrence, Massachusetts, was the highest since fish counts were first recorded at the dam in 1983. The Vernon Dam on the Connecticut River also saw a record shad count of 39,791. We hope to someday have quality shad fisheries that extend to Franklin on the Merrimack River, and the Bellows Falls Dam on the Connecticut River.

River herring (a collective term for alewife and blueback herring) numbers are stable or increasing in many rivers. The Lamprey River has produced returns in excess of 75,000 fish for the last three years. Fishway construction at the Wiswall Dam on the Lamprey River has greatly improved access to spawning habitat. Potential dam removals on the Exeter and Bellamy rivers would also benefit diadromous fish populations in coastal New Hampshire.

 

The 2015 river herring count on the Merrimack River, at 128,692, was the greatest since 1991, when almost 400,000 were recorded. River herring returns averaged fewer than 4,000 fish per year between 1996 and 2011. In 2012, Fish and Game and USFWS biologists began to increase river herring stocking numbers in waterbodies with suitable habitat throughout the Merrimack River watershed, including Winnisquam Lake and the Nashua River. The goal is to restore river herring abundance to the levels of the early 1990s and then sustain those numbers with improvements in fish passage.

 

The American eel was recently under consideration for listing under the federal Endangered Species Act. Listing was determined to not be warranted at this time, but many questions remain about the future of American eel populations. Status assessments have been hindered by a lack of data on eel populations in fresh water. NH Fish and Game and USFWS biologists are working to establish index sites for monitoring American eel populations and movement in fresh water. Data on the silver phase of the American eel life cycle is particularly lacking, especially on the number of silver eels that are killed by hydropower turbines during their downstream spawning migration to the Sargasso Sea. Radio telemetry studies are being used to track the movement and survival of migrating silver eels in the Merrimack and Connecticut rivers.

 

The last Atlantic salmon restoration program in New Hampshire ended in 2013 due to low return rates and limited budgets. Yet our other diadromous species continue to hold on, despite the many barriers to their migration. Fish counts vary considerably over time, but 2015 was an encouraging year for diadromous fish populations. Let’s hope this positive trend continues.

2016 Restoration Priorities:

 

For the spring of 2016, we are preparing to expand our river herring stocking to include additional waterbodies in the Merrimack River watershed.  Of course, this will depend on the availability of fish, but we are hoping to see the results of our increased stocking effort, which began in 2012.  River herring born in 2012, now four years old, are reaching sexual maturity and are ready to migrate up the Merrimack River to reach their spawning grounds.  We will attempt to stock river herring into as much suitable habitat as possible, using a stocking rate of approximately six fish per acre.

 

On the seacoast, biologists will continue to monitor diadromous fish runs on the rivers where fish passage is provided.  They will also develop strategies for monitoring fish passage after dams have been removed.  Fishways are generally a poor substitute for a free flowing river when it comes to getting fish upstream, but they do provide a convenient way to monitor population trends in diadromous fish.  Monitoring diadromous fish runs in an open river is challenging and can be labor intensive.  It may involve a variety of survey methods, including seine netting, fyke netting, and electrofishing.

American eel population monitoring will continue in 2016.  Electrofishing index sites will be surveyed and eels over 200 mm in length will be pit tagged (equipped with an electronic chip with a unique number code).  Pit-tagged eels provide valuable data on movement and growth rates when they are recaptured.  Efforts to trap silver eels during their migration back to the ocean will be expanded in 2016, with the goal of providing up to 20 eels for tracking with radio telemetry.  Each tagged silver eel provides a wealth of information on migration timing, rate, and survival as it makes its way through the five mainstem dams on the Merrimack River.  

 

Diadromous fish runs are extremely unpredictable.  There is no telling how this mild winter or the coming spring weather will influence migratory fish species as they make their way from the ocean into freshwater.  That is part of what makes it such an exciting time of year.  Both the fish and the biologists have to be prepared for whatever the river or the weather has in store.  For more information, visit www.fishnh.com/fishing/fisheries-mgt.html.

 

Diadromous fish management in New Hampshire is funded by your license dollars and the federal Wildlife and Sport Fish Restoration Program.

 

Matt Carpenter coordinates the Fish Conservation Program for the Inland Fisheries Division.