MARINE MAMMAL COMMISSION — Annual Report for 1995 



Determining the Cause of 

 Unusual Mortality Events 



Determining the cause or causes of unusual marine 

 mammal mortality events has been hampered, in part, 

 because few laboratories have the expertise and 

 equipment necessary to screen tissues for viruses and 

 other possible disease-causing organisms, naturally 

 occurring biotoxins, and various anthropogenic 

 contaminants that might be toxic. By letter of 19 

 December 1994 the Commission recommended that 

 the National Marine Fisheries Service make arrange- 

 ments with the Department of Agriculture, which 

 maintains state-of-the-art viral testing facilities at Plum 

 Island, New York, and Ames, Iowa, to do viral 

 screening when unusual marine mammal mortality 

 events occur. The Commission also recommended 

 that the National Marine Fisheries Service (1) deter- 

 mine the types of other routine screens that might help 

 facilitate prompt identification of non-viral causes of 

 unusual marine mammal mortality events, (2) identify 

 the facilities best equipped to do those screens, 



(3) make arrangement for the facilities to carry out 

 such screens when unusual mortality events occur, and 



(4) advise the regional marine mammal stranding net- 

 works of the arrangements. 



The working group on unusual marine mammal 

 mortality events strongly supported the Commission's 

 recommendations and advised the National Marine 

 Fisheries Service of its support by letter of 3 May 

 1995. The Service agreed it would be desirable to 

 make arrangements with leading laboratories to do 

 routine viral and other screening, and indicated it was 

 attempting to do so, subject to budget constraints. 



Release Criteria 



If marine mammals strand because they are sick, 

 returning them to the wild before they are fully 

 healthy could risk transmitting disease-causing organ- 

 isms to healthy animals. Prematurely returned ani- 

 mals also could die from starvation or injury because 

 they are not healthy enough to capture prey, defend 

 themselves during encounters with other animals, or 

 avoid predators. Similar problems may be encoun- 

 tered when releasing animals that have been main- 



tained for relatively long periods of time in captivity 

 for purposes of scientific research or public display. 



As noted earlier, the Secretary of Commerce is to 

 develop objective criteria for determining when 

 rehabilitated marine mammals can be returned to the 

 wild. The unusual marine mammal mortality event 

 working group has been asked to recommend appro- 

 priate criteria. The pros and cons of possible criteria 

 were discussed at the working group's 1994 and 1995 

 meetings, but no consensus was reached. The work- 

 ing group is expected to develop recommended 

 criteria at its next meeting, to be held in the first half 

 of 1996. 



The Possible Role of 

 Marine Pollution 



As noted earlier, pollution of the marine environ- 

 ment may be affecting marine mammals both directly 

 and indirectly. That is, some environmental contami- 

 nants, by themselves and in combination with others, 

 may be toxic and cause mortality or interfere with 

 reproduction or other vital processes. Some others 

 may affect physiological processes and suppress the 

 immune system, making animals more vulnerable to 

 parasites and disease-causing organisms. Also as 

 noted earlier, the types and levels of contaminants 

 present in the tissues of stranded marine mammals 

 may be good indicators of the types and levels of 

 pollutants present in coastal marine ecosystems. 



Ocean pollutants include noise and marine debris 

 as well as chemicals and metals. Actions taken by the 

 Commission to assess the sources and effects of 

 marine debris are described in Chapter VIII. Actions 

 taken by the Commission to assess and minimize the 

 effects of noise pollution are described in Chapter XI. 



In 1996 the Commission will focus on identifying 

 threats from chemical contaminants and actions to 

 minimize those threats. As a first step, it has com- 

 piled a bibliography on physical and chemical constit- 

 uents in the marine environment and their effects on 

 marine mammals. This will be published in 1996. 



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