The Salmon of the Miramichi

This flow follows the damage to salmon and stream food webs after forest spraying in the Northwest Miramichi basin.

increasingBearing stren­gth in each eventdecreasing

An Ancient Return

Salmon Reach Their River Homing Migration Salmon returned from the Atlantic to the Miramichi River and deposited eggs in gravel beds of cold forest streams. The annual cycle depended on clear water and a dependable supply of stream life. A Measured Baseline The Fisheries Research Board of Canada had studied the Northwest Miramichi for several years. Its records made it possible to compare the stream’s fish populations before and after spraying.

Forest Spraying

DDT Over the Watershed A Budworm Campaign The Canadian program sought to protect forests from Spruce budworm. Aircraft applied DDT over the Northwest Miramichi watershed, with spray drifting and filtering toward streams. A Broad Exposure Pilots did not avoid streams or shut off their nozzles above them. The forestry objective thus introduced poison into the habitat on which the fish and their food depended.

The Stream Goes Silent

Fish and Insects Die Immediate Signs Dead and dying fish, including young salmon and brook trout, appeared along the banks. Birds also died in nearby woods, while aquatic insects that had fed the stream’s fish were lost. A Broken Food Supply The damage reached beyond direct poisoning. With caddisfly, stonefly, and other larvae gone, young salmon faced an emptied food web as well as chemical exposure.

A Year’s Spawn Lost

Recruitment Collapses Young Fish Disappear No young salmon from that spring’s hatch remained by August. Older age groups also suffered, with losses varying according to their age and exposure. A Scientific Record Because baseline counts existed, investigators could estimate the scale of the damage with unusual precision. The episode showed how one spraying could erase a year’s reproductive contribution.

Uneven Recovery

A Fragile Reprieve An Unusual Cohort A combination of limited later spraying, returning small insects, and an unusually large 1954 spawning run helped the 1955 fry grow quickly. Some returned as grilse in 1959. Repeated Damage Elsewhere Other sprayed streams showed depleted young salmon and reduced runs. The contrast warned that recovery depended on exceptional circumstances, not on spraying being harmless.

Autumn 1953

June 1954

Within two days of the 1954 spraying

By August 1954

From 1955 through 1959