The Effects of Insect Spray on Pond Fish

The 1940s saw the production of synthetic pesticides and insecticides. These chemical sprays negatively affect pond fish. Chemicals enter the water through direct spraying or storm water drainage, leaving the fish that survive to suffer harmful residual effects. Fish ponds are breeding grounds for Culiseta incindens, also known as the fish-pond mosquitoes. Although these pests are not known to transmit disease, fear of the West Nile virus leads many to use these toxic sprays around their ponds.

  1. Contamination

    • Chemicals from nearby fields wash into pond waters through runoff when it rains.

      Upon contamination, insect sprays poison pond fish, including ornamental fish. Smaller fish tend to die first. However not all fish will die at the same rate. Contamination can occur directly, through an aerial spraying. However, toxins can enter pond waters indirectly, through runoff or contaminated silt that washes into pond waters. Insect sprays used in agriculture make their way to pond waters through storm water drainage. Determining the cause of pond fish mortality involves costly testing. Chemicals from insecticides tend to break down quickly, making the cause of death difficult to determine.

    Exposure

    • When waters are toxic, pond fish take in chemicals through absorprtion, respiration and ingestion.

      Pond fish come in contact with insect sprays through absorption, respiration and ingestion. The amount of harm the spray causes is dependent on toxicity, exposure time, the amount of spray used and the amount of time the toxins linger in the pond environment. Pond fish absorb chemicals through their scales and ingest contaminated waters during feeding. They also take in toxic waters during respiration. Not all fish will expire when they come in contact with insect sprays. Residual effects depend on how poisonous the spray was and the amount of spray used. Fish that have been exposed to insect sprays for longer periods of time will suffer more serious effects, as will fish exposed to chemicals that linger in their environment long after spraying.

    Feeding

    • Goldfish and mosquito fish use mosquitoes as a food source.

      Insect sprays affect the plant life and insects that pond fish rely on for food. Fish may die if they ingest plants or insects that have been directly exposed. Mosquitoes serve as a food source for goldfish in ornamental ponds. Spraying an ornamental pond for mosquitoes is harmful to goldfish and removes a natural food source.

    Reproduction

    • Reproductive problems

      Pond fish that are exposed to insect sprays experience reproductive problems. Problems can range from sterility to lowered egg production. Toxicity is highest in shallow weedy areas, which young pond fish use as nurseries, as well as a place to hide from predators. With fish unable to survive to maturity and decreased reproduction, a pond that was once thriving with fish will soon become vacant.

    Decreased Resistance

    • Insect sprays can harm pond plants that provide vital oxygen for pond fish.

      Effected pond waters lower a fish's resistance to elements within in their environment. Pond fish experience intolerance to temperature changes, as well as behavioral changes that make them vulnerable to predators. Insect sprays weaken a fish's immune system, making the fish more susceptible to diseases and infections. Insect sprays also affect a pond's plant life, thereby lowering oxygen levels in the waters. Fish depend on oxygen in the water for respiration.