85 



Our fishermen were among the first to feel directly the effects of 

 pollution. They have seen oyster and clam resources become contamin- 

 ated with human wastes so they can no longer be marketed. They have 

 seen spawning and nursery areas essential for salmon blocked by 

 power projects or fouled by pollution. They have seen fish killed in 

 massive numbers by waters whose oxygen has been spent in the 

 biological degradation of the pollutants. They have been unable to 

 market some of their catches because of the presence of heavy metals, 

 such as mercury. 



All fishery agencies, both State and Federal, in the United States 

 have been involved for many years in evaluating the effects of pollu- 

 tion on fish and trying to mitigate it. The National Marine Fisheries 

 Service conducts research on the effects of pollution at many of its 

 field stations. 



I would like to comment briefly on the status of our knowledge with 

 respect to the effects of pollution and then give a few examples of 

 what we do know and what we do not know about this vitally impor- 

 tant matter. 



The particular example I have in mind is the complex problem we 

 have in oil. 



I will divide the discussion into three general kinds of problems we 

 face in undei-standing the effects of pollution. 



The first step is to determine the lethal levels of pollutants. This 

 means determining the concentration and time of exposure that 

 result in death of a proportion of the test animals. 



This is easy to do, and we have considerable data on the tolerance of 

 many species of fish and wildlife to hundreds of different chemical 

 compounds. For example, we know the tolerance of rainbow trout to 

 low oxygen levels, to temperature levels, to concentrations of chlorine, 

 mercury, DDT, et cetera. 



Work in this category continues in the National Marine Fisheries 

 Service with such studies as the effects of heavy^ metals and pesticides 

 on eggs and larvae of shellfish and single-cell algae, the effects of oil 

 on fish, such as young herring and pink salmon, the effects of silt on 

 young fish and effects of thermal effluents from powerplants on fish 

 and plankton. 



The second step in understanding the effects of pollution is to deter- 

 mine the long-term nonlethal effects. This usually involves laboratory 

 studies of the physiology or behavior of animals Avhich are exposed 

 to sublethal concentrations of a pollutant over an extended period. 



We try to find out where the substance is stored in the body, how 

 the body excretes it, whether physiological functions such as respira- 

 tion, osmoregidation, excretion, and reproduction are impaired and 

 what diseases or tissue damage may be associated with the exposure. 

 Such studies are far more sophisticated than those for determining 

 lethal levels and they are being done in many laboratories around the 

 country. 



In the Fisheries Ser\dce, such studies includes the effect of salinity, 

 temperature, and heavy metals on the osmoregulation and respiration 

 of the blue crab, the effects of DDT on the reproduction of the anchovy, 

 et cetera. 



The third, and still more complex, step in understanding the effects 

 of pollution is to know the effect of pollutants or the whole ecosystem, 



