Midge

Midges are small aquatic insects that serve as food for young salmon and can recolonize streams relatively quickly after pesticide spraying. In the account of the Northwest Miramichi, their return helped newly hatched salmon fry survive after DDT had eliminated stream insects and killed older young salmon; the contrast with slower-recovering prey shows how a temporary abundance of one food source can coexist with lasting disruption of the wider aquatic food web.

Role in the Stream Food Web

Midges belong to the smaller aquatic insects that salmon fry, only a few months old, can eat. Along with blackflies, they become reestablished relatively quickly after DDT enters a stream. Their early return makes them a useful food source for the youngest salmon, but it does not restore the stream’s full range of prey.

Older salmon depend on larger aquatic insects, including the larval stages of caddisflies, stoneflies, and mayflies. These species recover much more slowly. Even in the second year after DDT enters a stream, a foraging salmon parr may find little beyond an occasional small stonefly, with large stoneflies, mayflies, and caddisflies still absent. The quicker recovery of midges therefore marks a partial return of food, not a return to the former ecological balance.

Return in the Northwest Miramichi

In spring 1955, salmon fry hatched in the Northwest Miramichi under unusual conditions. DDT had killed off the stream insects the previous year, but midges and blackflies had returned in numbers. The two small-insect groups supplied the fry’s normal food, and the young salmon encountered abundant food with few competitors.

That lack of competition had a grim cause: older young salmon had been killed by the 1954 spraying. The surviving fry grew rapidly and survived well, illustrating how the loss of one age group could temporarily benefit another even while the stream’s insect community remained damaged. Midges’ quick return thus supported a local reprieve for the youngest fish without undoing the broader consequences of spraying.