accumulate in fish tissue over time. Chronic, insidious effects occur as 

 these elements enter the aquatic food chain. Some become concentrated in 

 organisms, and are transferred from prey to predator (biological 

 magnification). Certain combinations of metals (such as cadmium and zinc, 

 copper and zinc, selenium and zinc) exhibit compounding effects. This factor 

 must be considered when they are found in combination. The reactivity of 

 these metals, and other toxic compounds, is affected by pH. Analysis of fish 

 tissues from Maine has shown unusually high mercury content, for unexplained 

 reasons (personal communication from A. Julin, U.S. Fish and Wildlife Service, 

 Newton Corner, MA; January, 1980). In many cases, natural sources are 

 suspected. 



Fuel oil, kerosene, and other hydrocarbons are directly toxic to plants and 

 animals. They enter water bodies through spills or as industrial wastes and 

 can be present throughout the water column and on the bottom. The shoreline 

 (intertidal) zone is most heavily and persistently damaged by nearshore oil 

 spills (Canada Department of Environment 1974; and NOAA 1978). The occurrence 

 of oil spills in Maine is documented in chapter 3, "Human Impacts on the 

 Ecosystem." Fishes, especially flounder, accumulate petroleum hydrocarbons in 

 their tissues. Up to 97% of the cod and pollock embryos collected from the 

 area of the Argo Merchant ship oil spill in 1976 were dead, dying, or 

 malformed (NOAA 1978). Tainted fish flesh, caused by exposure to soluable 

 petroleum components, make fish unmarketable. Bowman and Langton (1978) found 

 that fishes did not avoid prey that were contaminated with oil. Sinderman 

 (1978) summarizes the effects of oil on marine organisms based largely on 

 laboratory toxicity studies. Sub-lethal and behavioral effects include 

 inhibition of mating responses, reduced fecundity, chromosomal abnormalities 

 in eggs, abnormal larval development, and decreased feeding activities. 



Biocides include both pesticides and herbicides. Chronic and acute toxicities 

 of a given compound vary with environmental factors, such as water temperature 

 and water chemistry, and biological factors, such as age, sex, size, 

 condition, and species of fishes involved. The most hazardous biocides are 

 those that are persistent in the environment (have low biodegradability) . 

 This is common of the chlorinated hydrocarbon pesticides, such as DDT and 

 Dieldrin, and polychlorinated biphenyls (PCBs). They can remain in sediments 

 unchanged for many years. Many animals, including fishes, take up these 

 chlorinated hydrocarbons that are present in water at sublethal levels and 

 store them in their fatty tissues. Assimilation takes place both in feeding 

 and in direct assimilation from the water. Death can occur when food supply 

 is restricted and the animals use their body fat for energy. Equally 

 disasterous is the mobilization of the contaminated body fat in reproduction. 

 The transfer of toxicants may inhibit normal development of the young in this 

 way (Bell 1973). 



Fishes may build up pesticide residues in their body tissues gradually without 

 apparent ill effect, but other animals preying upon contaminated fishes may be 

 killed or damaged by the concentrated toxicants. The establishment of 

 controls for safe levels of applications of these biocides requires 

 consideration of these food chain accumulation and storage phenomena. 

 Pesticides can affect fish populations indirectly by eliminating food items. 

 The other group of pesticides, the organic phosphates (e.g., Sevin, Orthene, 

 Sumithion, Metacil, and Dylox) are generally less toxic than the chlorinated 

 hydrocarbons and usually persist for less than one year. A number of studies 



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