Toxic Fisheries

by Hal Scramm

North American Fisherman Magazine Dec/Jan 2006

Humans have been adding toxic chemicals to the air, land, and water for centuries, and it's caught up with us- and our fisheries. Unfortunately, as bad as things are, we could only be seeing a glimpse of how toxic our aquatic habitats have become and how we continue to make a bad situation worse.

History of Poison- Most chemicals are toxic- it's just a matter of concentration and exposure. The list of such chemicals continues to grow thanks to industrial chemists who create new materials, analytical chemists who've improved our abilities to detect contaminants, and toxicologists who keep finding new effects. When contamination problems were forcefully addressed by the Clean Water Act in 1972, toxdins were thought of more narrowly as chemicals that killed plants or animals outright (what toxicologists refer to as  "acute lethal toxicity"), or caused macroscopic effects such as deformities, wounds or aberrant behavior. By the 1980's water-quality criteria had been developed for about 150 chemicals, and lethal concentrations of more than 270 chemicals had been established for fish and other aquatics. Gargantuan efforts were initiated to fix the situation. Especially nasty and persistent chemicals, such as organochlorines like DDT and polychlorinated biphenyls (PCB'S) were banned, water laws set permissible discharge levels for other chemicals, and remediation efforts attempted to clean up hotspots. However, it soon became apparent that many chemicals also had sublethal and less readily apparent effects on fish and other aquatic life. We had only been dealing with the tip of the iceberg.

The Effects-Suspecting that contaminants were present in the environment at or below detection limits and that additional unidentified chemicals may be contributing to problems, environmental toxicologists began relying on "biomarkers" in aquatic organisms to monitor pollutants. Biomarkers include anatomical variation (such as usual organ size), visible sores, microscopic anomalies, (such as changes in tissues), and chemical compounds in tissues and body fluids that function like hormones. These indicate exposure to contaminants at very low levels, and chemicals with sublethal effects. Most current biomarker monitoring in fisheries is focused on hormones and what are known as endocrine functions. Hormones are chemicals produced or released by one body organ that affect the function of one or more other organs. The network that regulates bodily functions via hormones is the endocrine system. It plays a critical role in normal growth, development, behavior, and reproduction. That said, even small disturbances in endocrine function may have profound effects. m. Unfortunately, manmade chemicals have proved all too capable in the regard, mimicking natural hormones and interfering with the p