New Hampshire Nature Notes
by Eric Orff
Global Warming Article: New Hampshire River Herring On a Downhill Slide
New Hampshire’s coastal rivers are dying a slow death by asphyxiation. Fifty years ago these rivers were no more than open sewers and the upstream migration was blocked by dams a century or more old. The Lamprey, Cocheco, Salmon Falls, Oyster, Exeter, Winnicut and Taylor Rivers were essentially devoid of untold numbers of river herring that historically spawned there.
Over the last three decades river herring numbers have been restored. River herring numbering in the hundreds of thousands have returned to these rivers. But this restoration effort has been monumental lasting nearly four decades. Thanks to the Clean Water Act of the early 1970’s waste water treatment plants were constructed on all the larger communities that once used these rivers as open sewers. By the mid 1970’s the New Hampshire Fish and Game Department began to construct fish passage facilities (ladders) on all the dams at the head of tide on these same rivers. Over the last three decades the Fish and Game Department has upgraded and fine tuned most of the passage facilities to improve their performance in passing river herring. By early April each year Fish and Game staff are back at the daily effort to get the ladders back into operation and must frequently check them to adjust the flows and remove debris among other things. Each check of the ladder is rough with danger of slipping into the cold swirling vortex. And at each ladder some type of counting system is in place to accurately count the herring passing up river. At some ladders fish are trapped in a holding pen at the top of the ladder; then scooped up by the net full to be counted as they are released above the dams.
By the end of April the migration up river is on. Within just a few weeks tens of thousands of foot-long silvery torpedo-like fish swarm from the depths of the sea into New Hampshire’s coastal river. Legions of river herring rush against strong spring river currents to return to the place of their birth, two or three years ago, in an urgent need to fulfill their life cycle. Female herring may spew 200,000 to 300,000 eggs into the surrounding fresh water.
But there is a “perfect storm” brewing to reverse this historical accomplishment. Striper fishermen should pay particular attention as river herring are a significant part of the striper’s diet. Development, roof by roof, driveway by driveway, and parking lot by parking lot, is slowly transforming the very rivers themselves. Water that once filtered into the ground, then slowly trickled into the rivers all spring and summer long as groundwater, now shoots down our gutters, pavement and ditches, even causing flash floods that the seacoast area has become all to familiar with the last few years. Historically by late spring this stored water would be slowly feeding and cooling the rivers just as the river herring eggs are hatching.
Not only is there less ground water to recharge the rivers into the hot summer, but on some, such as the Oyster and Exeter Rivers, water is siphoned off for drinking water. Yes, just as tens of millions of river herring are hatching in the fresh water millions of gallons are being drawn off for drinking water. And to make matters worse on the Exeter River, water is drawn off to cool a huge condominium complex that was once a textile factory at the river’s edge.
Now add in warmer than normal late spring temperatures on top of a reduced water flow and diversions for drinking. This appears to be the straw breaking the camels back. Fish and Game Marine biologists have witnessed a dramatic decline in herring numbers since 2000. For instance the river herring numbers in the Exeter River declined from 6,703 in 2001 to only 40 in 2007. The Oyster River saw a reduction from 70,873 in 2000 to just 17,402 in 2007. And on the Taylor River in South Hampton the drop has been even more dramatic from 44,010 in 2000 to only 147 fish in 2006 and fewer than a thousand in 2007.
Late spring heat waves are heating up the river waters just after the river herring have come to spawn. Simply put, the heated water cannot hold much oxygen and the comma sized baby herring are being smothered to death. By the millions! Striped bass fishermen take note! Herring are “the soup of the sea” transforming nutrients in the sea into flesh as adults and gleaning nutrients from the fresh water as juveniles, then transforming all this protein to the sea when they migrate to the sea each fall by the millions. River herring are a significant reason that striped bass have been restored to current levels.
A perfect storm is brewing on New Hampshire’s seacoast and no doubt on similar rivers to the north and south of our coast. River herring are clearly in trouble over some of their range. Over development, a lack of protection of ground water, a burgeoning human population siphoning off more water for drinking, and watering ever more lawns, and finally a changing climate are a witch’s brew for disaster for our river herring.
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