Fish Health Versus 

 Ecosystem Health 

 Indicators 



Scientists participating in the workshop were reluctant to conclude 

 that any single measure of fish health could be used as a definitive 

 indicator of an ecosystem's health. However, if several indicators 

 demonstrate change in a fish population, it is generally safe to 

 assume that the ecosystem has been affected. This assumption 

 should be strengthened by considering effects on organisms at 

 other trophic levels, and by directly measuring contaminant levels 

 in the environment. 



In a trend monitoring program, the use of finfish as indicators of 

 toxic contamination is limited for three reasons: (1 ) some methods 

 still need to be verified in the field; (2) fish move around; and (3) 

 fish are very active as they undergo detoxification. Other or- 

 ganisms, such as bivalve mollusks, are better indicators on a small 

 spatial scale because they are less subject to these constraints. 

 Finfish may, however, be more suitable for future studies in which 

 the objective is to assess toxic stress over relatively large areas, 

 such as an entire estuary. 



Enzyme and immunological tests are especially useful as early 

 warning signs of toxic stress. They can also be employed to 

 indicate the recovery of fish from toxic stress. Unlike lesions, death, 

 or population changes, the effects of toxic contamination measur- 

 able by these tests appear sooner, and at lower levels and shorter 

 lengths of exposure to pollutants. These effects are reversible as 

 the fish recover from stress. Recovery can be measured in the field 

 in less time than the life cycle of the species being observed. The 

 effects of stress must, however, be measured at appropriate times 

 during the species' life cycle. 



Gross pathological and population changes appear over the longer 

 term. Such effects indicate a highly disturtDed ecosystem and 

 suggest that fish have been exposed to high levels of pollutants for 

 relatively long periods. 



In order to use indicators jn developing regulations or permit 

 requirements, EPA must establish a causal relationship between 

 finfish indicators and toxic contamination. This will require further 

 research because finfish indicators are not yet refined enough to 

 prove such relationships. Therefore, it is too early to conclude that 

 a particular finfish disease or population effect was caused by a 

 particular environmental pollutant. Standard laboratory testing for 

 toxicity is still needed. 



Trend Monitoring 



Early and Late Indicators 

 of Toxic Stress 



Establishing Causal 

 Relationships as a Basis for 

 Regulatory Action 



C3 



