1945-46 epidemic could be readily demonstrated in the 

 open waters around Boothbay Harbor. It has also 

 been cultured from the blood of stored and fresh- 

 caught lobsters, even when blood smears were nega- 

 tive. Infection apparently requires a break in the in- 

 tegument. 



One can make a very good case for pollution being 

 an important contributory cause to the unfavorable 

 environmental conditions normally associated with the 

 blood bacterium, Gafjliyu lionuiri, which in some 

 years has taken a very high toll of lobsters in storage 

 and, in some areas, has been reported to occur exten- 

 sively in "wild" lobsters. 



Another disease is one called "shell disease," 

 which is caused by chitinivorous bacteria which con- 

 sume the outer layer of shell. A lobster's shell consists 

 of three layers: an outer layer composed of chitin, 

 chemically related to hair, fingernails, and hooves in 

 mammals; a layer of crystalline calcium carbonate 

 (lime) which gives strength and hardness to the shell; 

 and the epithelium or living layer which produces both 

 of these. Shell disease is caused by bacteria which eat 

 away the chitin. The exposed calcium carbonate 

 gradually dissolves, leaving the exposed epithelium. 

 The resulting lesion may be very small, or may cover a 

 large proportion of the shell. As the calcium layer is 

 exposed, it erodes, leaving the soft endoderm ex- 

 posed. Lesions may cover much of the shell, but do 

 not appear to cause severe mortality except when gills 

 are attacked. Then respiratory failure occurs. Shell 

 disease may be endemic in certain locations and the 

 infection can spread in a lobster pound. It appears to 

 be a winter disease, perhaps because only lobsters re- 

 moved in mid- or late winter are stored long enough to 

 develop severe infections. Shell disease also requires 

 an external injury to become established. 



Another possible cause of lobster abundance de- 

 cline is the long-term accumulation of commercial in- 

 secticides and their breakdown products from fresh- 

 water runoff and atmospheric fallout into the inshore 

 ocean waters. Since lobsters are closely related to the 

 insect pests being sprayed with chlorinated hydrocar- 

 bons, organic phosphates, and arsenical compounds, 

 they are extremely sensitive to those control measures 

 and high mortality rates have occurred when lobsters 

 were inadvertently exposed to insecticides under nor- 

 mal storage conditions. Chlorinated hydrocarbons are 

 persistent and highly toxic to Crustacea in trace dilu- 

 tions (1 part in 5 billion has resulted in 100 percent kill 

 of larval lobsters within 24 h) (Dow, 1972). 



Biologists of the Maine Department of Sea and 

 Shore Fisheries have been involved in research and 

 experimental evaluation of insecticides and their ef- 

 fects on marine animals since September 1946. At that 

 time a mimeographed bulletin was distributed to mem- 

 bers of the fishing industry warning them not to expose 

 live lobsters in any way to DDT. This warning was 

 based on the results of laboratory experiments and 

 field observations by the Bureau of Commercial 



Fisheries (now National Marine Fisheries Service) and 

 Department biologists. Preliminary findings indicated 

 that DDT is toxic to lobsters in concentrations of ap- 

 proximately 1 part in 10,000. Since that time it has been 

 found that marine organisms are adversely affected by 

 many pesticides, particularly the more recently de- 

 veloped chlorinated hydrocarbons and organic phos- 

 phates. DDT certainly is far less acutely toxic to lob- 

 sters than most chlorinated hydrocarbons, and the or- 

 ganic phosphates — malathion, sumithion, and para- 

 thion — appear to be even more toxic to Crustacea 

 than many of the chlorinated hydrocarbons. Forty- 

 three lobster samples, representing 54 lobsters, have 

 been collected and processed. Thirty-nine samples, 

 representing 93 percent, had measurable residues. Of 

 the 39 positive samples, 17 were fresh-caught from 

 inshore waters, and 15 were from lobster holding 

 pounds. Six were from offshore, picked up by Bureau 

 of Commercial Fisheries cruises, and one was a Magda- 

 len Island sample from Quebec. Although the number 

 of samples and the period of sampling would be inade- 

 quate for definitive conclusions, there is evidence of an 

 appreciable increase in total residues (Fig. 3). Sampling 

 has shown a decrease in toxic levels from the general 

 source area seaward and from freshwater to tidewater, 

 as indicated by representative species from the two 

 environments. Sampling has indicated seasonal varia- 

 tions in residual levels of chlorinated hydrocarbons in 

 representative organisms and a higher level of residual 

 toxicity with time in the same areas. 



Seasonal fluctuations associated with freshwater 

 runoff are evident in the case of the soft-shell clams 

 taken from Maine estuaries. During the 5 yr of sam- 

 pling, the peak of DDT and its metabolites and diel- 

 drin has been associated with high water flows be- 

 tween March and June. Minor increases in residues 

 have also occurred coincident with fall rains, but in 

 general residues have declined to trace levels by late 

 summer and early fall. 



Of the marine and estuarine species sampled since 

 November 1965, all have produced traces of measur- 

 able amounts of DDT, its breakdown products, or diel- 

 drin. 



The first definitive association of DDT with lobster 

 mortality in nature was in early 1966. A lobster from a 

 holding pound with a high incidence of unexplained 

 mortality and a record of nearby pesticide application 

 over a period of years was analyzed for pesticide 

 residues. This animal was found to contain 0.013 ppm 

 DDT and 0.029 ppm DDE. The total residues, includ- 

 ing DDT, its metabolites, and dieldrin, range from 

 0.042 to 0.635 in lobsters collected from this area. 

 More extensive surveillance of the area has demon- 

 strated an extensive pesticidal buildup not only in lob- 

 sters but in other marine organisms as well. It is pre- 

 sumed that pesticides contributed to the unusual lob- 

 ster mortality rates of this pound, rates which did not 

 decline significantly until aerial spraying was discon- 

 tinued. Since higher concentrations have been found 



