Migratory Fish in Trouble
The Problem: dams and industrial practices have blocked spawning habitat and decimated migratory fish populations. Flows at main stem hydro-electric dams and canals, as well as industrial effluents and heated plant discharges into the river make this situation worse. Determined action is needed if the Connecticut’s fish runs are to survive.
The Solution: require working fish passage at all main stem dams. Immediately discontinue any recent industrial practices that may be injuring migratory fish runs. Undertake adequate testing before making changes to main stem discharges and flow regimes to prove they will do no harm. Continue to remove or create passage at tributary dams to increase available spawning habitat and success.
All fish are mobile, but none on the Connecticut River make longer journeys than the suite of migratory fish moving upriver from the Atlantic Ocean: blueback herring, alewives, American shad, American eels, Atlantic salmon and sea lampreys. These migrations have been taking place for thousands of years. The journeys of these species may take them through thousands of ocean miles annually, and nearly 200 miles upriver.
- Anadromous fish: Shad, lamprey, salmon, blueback herring and alewives are anadromous fish—they are born in freshwater, swim to the sea to feed and mature, then return to the rivers of their birth to spawn. Though some members of each species die after spawning, only the sea lamprey spawns as the final act in its long life cycle. All other species may survive, return to the ocean, and then return to the river to spawn again.
- Catadromous fish: The American eel is a different fish. It is a catadromous species, growing and maturing in rivers and estuaries then returning to spawn in the ocean, then die. After years feeding and maturing in river and estuaries, American eels head to the Sargasso Sea—a weed-covered expanse in the Bermuda Triangle, where they mate along that sprawling sargassum algae mat in close proximity to their counterparts, European eels. This seaweed expanse has also been found to be the protective ocean habitat that young loggerhead sea turtles journey to after hatching on sandy shores and skittering into the sea.
Main stem and tributary dams have been the major, human-induced contributor to declining migratory fish populations on the Connecticut River. Fish passage facilities are in place at most main stem dams. But changes in operations and discharges at main stem sites, as well as failing fish passage facilities, are further impacting surviving fish runs. At some critical sites, the fishways themselves are hindering fish. They simply are not fulfilling their required roles, either through poor design or operation. These failures further threaten migratory fish runs on the Connecticut.
Critical fish passage and dam-removal work is also taking place on many tributaries and is in the works for others. The Watershed Council has been a leading advocate for working fish passage at main stem and tributary dams. We have successfully helped create fish passage, restore habitat, and remove unneeded dams at dozens of watershed sites. In doing so we’ve opened up nearly 50 miles of migratory fish habitat.
American shad have been among the most common migrants on the Connecticut each spring for centuries. Shad runs never became extinct. Their numbers--once in the millions, are now experiencing steep declines after good initial fish passage restoration success. In recent years shad numbers have dropped—80 – 90% in the area above Turners Falls dam and into southern Vermont and New Hampshire. Since 2000 the Connecticut’s river-wide shad run has declined by 17%.
Recent developments are deeply troubling:
Heated Effluent. Owners of the Vermont Yankee nuclear plant in Vernon, VT are continuing to by-pass their plant’s cooling towers to save money, releasing their heated effluent directly into the River. The Vermont Supreme Court recently upheld Entergy’s application to increase the heat of that effluent, allowing them to raise the river’s temperature downstream of the Yankee nuclear plant by yet another full degree Fahrenheit.
CRWC, partnering with Vermont Law School, challenged that temperature increase on behalf of its effects on migratory fish, in particular spawning-run shad who use the mainstem—downstream and up beyond that heated discharge, to migrate and spawn. Eggs and young of shad depend on cool river habitats to develop and feed. The court’s ruling proved largely in favor of Entergy, adding yet another thermal insult to the river, the shad, and other migratory and resident aquatic species.
For nearly two decades before, the Vernon nuclear plant had been permitted to raise the River’s temperature up to 13 degrees during winter months and up to 5 degrees in the summer and fall. That heated plume is shown to extend at least 50 miles downstream to Holyoke, MA. CRWC continues its work to reverse this situation.
99% Decline of Shad. Shad numbers on the river overall, and upstream success beyond Turners Falls and then Vernon, have dropped steadily since 1992. In the past decade, annual shad passage success at Turners Falls is hovering at around 1%. The presence of American shad upstream in the “Vernon pool” section of the river have dropped by 99% since the early 1990s. This is a tragedy, the ongoing upstream loss of the Connecticut’s ancient links to the sea.
39 Blueback Herring. Blueback herring once rivaled the shad in their great mass heading upstream to spawn as far as southern Vermont and New Hampshire. Hundreds of thousands of these "baitfish" were tallied annually at Holyoke just 15 years back. They spawn in quick-water shallows of the main stem river and its tributaries. Today their runs up the Connecticut beyond Holyoke are nearly gone--just a few dozen now return beyond there annually. Thirty-nine blueback herring were tallied at Holyoke in 2009, compared with 410,000 in 1991.
Dams and failing main stem passage have taken their tolls on herring runs. But overfishing, plus long-standing management problems causing fluctuations in populations of predacious fish are also likely a part of this story.
Alewife Runs Lost. Alewives are close relatives of blueback herring. The two species have collectively been lumped under the heading “river herring.” Alewives are lighter in color and have larger eyes than bluebacks. Their spring runs were once massive annual blooms along the Atlantic Coast from Nova Scotia to the Carolina’s.
Alewife runs—typically moving up more coastal streams, have been severely impacted by tributary dams and overfishing. Many runs have been lost altogether; some have been restored.
Sea Lamprey Slow Decline. Sea lampreys have changed little since the age of the dinosaurs. Though once more numerous, the sea lamprey population spawning upstream on the Connecticut appears quite healthy, reaching New Hampshire and Vermont waters. Built for the ages, tens of thousands continue to return spawn in the river annually. Nineteen thousand lamprey were counted at Holyoke Dam in 2009, with 66,000 counted in 2008, and 100,000 tallied in 1998.
75 Salmon. The Connecticut River strain of Atlantic salmon disappeared from the river nearly two centuries back. The Connecticut was the southern-most of the large rivers in this cold water species historic migratory footprint. Atlantic salmon feed and mature off the coast of Greenland. There are no good estimates on how many Atlantic salmon once returned to the river annually, but construction of the first main stem Connecticut River dam at Turners Falls in 1798 is believed to have helped extinguish the last run in 1809.
Attempts to create a replacement for the Connecticut’s extinct strain are ongoing since 1967. Returns average between 100 – 200 fish river-wide annually. Seventy-five salmon returned in 2009.
Atlantic salmon have no problem passing Turners Falls dam—the ten salmon that entered the fish passage facilities there were able to continue upstream in 2008. Salmon that are released upstream can reach and pass upstream dams at Vernon, Bellows Falls, and even Wilder with relative ease.
Shortnose sturgeons are the only federally endangered migratory fish on the Connecticut River. They evolved in the age of the dinosaurs and are toothless and primitive looking—with bony plates instead of fish scales. Shortnose sturgeon are between 2 – 4 feet long, and weigh up to 14 lbs. They mature slowly and don’t spawn until they reach 8 – 12 years old. Federal fines up to $20,000 can be levied for harming a shortnose sturgeon. The total river population is estimated at 1,200 fish.
Shortnose sturgeon live in the Connecticut from below Turners Falls dam to the estuary at Long Island Sound. They typically migrate from salt water into rivers to spawn. However main stem dams impede this species’ movements on the Connecticut and there are now two distinct populations on the river--one is partially landlocked above the Holyoke dam. Unfortunately, only the population living above Holyoke dam is known to spawn successfully.
American eels enter the Connecticut River as tiny, transparent, glass eels. They are born in the Sargasso Sea; then migrate to rivers and estuaries to mature. American eels will spend from 8 – 23 years feeding in the sediment and growing into 2 – 4 foot, silver-bronze adults before heading to the ocean to spawn. Spawning eels congregate in the weed-choked expanse of ocean south of Bermuda called the Sargasso Sea.
Each adult female produces upwards of 15 million eggs. It is presumed that all adults die after spawning beneath that thick algal mat. American eel populations are declining. Overfishing and dams have hurt these migrants. The species was considered for federal endangered species status in 2007, but was not listed. Eels can travel successfully for short distances on land, particularly during damp weather. Eelways have been constructed at some tributary dams to improve their migratory success.
American shad are currently the most numerous migratory fish on the Connecticut. Adult shad are green-gold, nearly two feet long, and can weigh up to 5 lbs. Females (roes) are larger than males (bucks.) Peak migration occurs during May, but the run continues through late-June. American shad spawn in East Coast Rivers from central Florida to Newfoundland. Shad enter the Connecticut each spring beginning in mid-April. The vanguard of their upstream migration corresponds roughly with the blooming of the shadbush.
The spawning peak is reached when river temperatures reach 67 degrees F.—at which point the fish stop their upstream migrations to spawn. Once river temperatures hit 70 degrees, upstream migration ceases altogether. Only half of the migrating Connecticut River shad die upon spawning. Many head back to the sea and will return to spawn up to three times. During midsummer the entire East Coast shad population migrates to the Bay of Fundy to feed.
Shad numbers have experienced steep declines on the Connecticut in the past decade. From a high count of 720,000 fish passing Holyoke dam in 1992, the average for the seasons 2005 – 2007, was 143,000 fish. Historically, shad have spawned as far inland as Bellows Falls, Vermont, 173 miles from the Atlantic.
Blueback herring are sleek, metallic-blue fish, under a foot in length. Blueback herring return to the main stem of the Connecticut from mid-April through June. Considered “bait fish”, these migrants travel as far upstream as Vermont’s Vernon dam, 134 miles from Long Island Sound. They spawn in quick, shallow currents of the main stem river and its tributaries; then feed in the Connecticut’s currents until fall, when they return to the sea.
In 2007 just 69 blueback herring were tallied passing the Holyoke dam. In 1991 there were 410,000 counted at Holyoke, and 630,000 blueback herring were counted there in 1985.
Alewives are close relatives of blueback herring, and difficult to distinguish from them. Alewives are lighter in color and have larger eyes than bluebacks. They migrate into the Connecticut River and its lower tributaries each spring, moving to the slow waters and ponds where they will spawn between March and June. Their upstream migration does not reach into Massachusetts waters. Like their blueback counterparts, alewives are experiencing steep declines. Though dam removals, fishways, and other restoration projects have opened up some of their historic spawning habitat, alewife populations have been damaged by overfishing, pollution, and spikes in predacious fish populations.
Atlantic salmon are over two feet long and weigh about 8 pounds when they return from the Atlantic to spawn for the first time. Born in freshwater rivers, they spend the first two years of their lives growing and feeding there. This coldwater species then heads to the sea to spend several years feeding off the Greenland coast before returning to the freshwater rivers of their birth to spawn. The Connecticut River strain of Atlantic salmon became extinct in the early 1800’s. In 1967 an effort to create a new strain of migratory salmon on the Connecticut began. Current returns average between 100 – 200 fish annually.
Sea lamprey are mottled brown, 2 – 3 foot long, eel-like fish that are born in freshwater rivers and spend five years in freshwater before heading to the ocean to feed and mature. Once in the ocean sea lampreys become parasitic, locking onto ocean fish with their jawless, sucking mouths, and draining nutrition from them. After spending two years as ocean parasites, sea lamprey head back to the rivers of their birth, cease feeding and—though now blind and toothless, migrate upstream to their natal sites where they spawn and die. Sea lamprey evolved during the age of the dinosaurs.
Photo credits (above): CRWC Staff
Image Credits at Right - Illustrations: Bill Singleton; Photos: CRWC Staff.