Appendix E: Field Scientist Report 



more individuals per sample. In all cases, shells from samples collected were retained for species 

 confirmation and further analysis where appropriate. 



In the laboratory, the bivalves were shucked on combusted aluminum foil using a clean 

 oyster knife, the tissue combined into a pre-cleaned jar with a Teflon-lined screw-cap seal and kept 

 frozen in the host countries laboratories. Each jar is a unique replicate sample and is individually 

 labeled with the location descriptor, date and organism species. In those sampling locations where 

 no local contacts were made, the sample processing was done at the hotel on pre-combusted 

 aluminum foil. Sample tissue was placed in pre-cleaned jars with a Teflon-lined seal and kept in 

 the freezer of the hotel restaurant or a local store with a freezer until ready to be moved to a new 

 sampling site or transported back to Costa Rica. Eventually all samples were shipped to College 

 Station, Texas which is the temporary central sample archive for IMW. 



Sampling Criteria 



Tentative sample sites were initially pre-selected to give a good coverage of the Atlantic and 

 Pacific coasts of Central and South America, including Mexico and the Caribbean. Collection of 

 duplicate samples from two or three seperate stations within each sampling site, was attempted in 

 order to characterize the site. In general, stations were located a few hundred meters apart and a 

 single embayment or length of coastline (i.e., "site") would contain one or more "stations" at 

 which replicate tissue samples were collected. When more than one bivalve species were present at 

 a single station without an obvious dominance of any of them, duplicate samples of each species 

 were also collected. 



The general sampling criteria included the sampling of mature organisms from areas 

 beyond the zone of initial dilution of wastes or suspected point-source discharge of contaminants. 

 In most cases, sampling was limited to natural substrates, e.g. rocks, mangroves or mud, to avoid 

 any potential contamination. In a few instances, however, bivalves were only found attached to 

 artificial structures, e.g. pilings, bridges, etc. In these cases, samples were collected and the type 

 of artificial structured recorded in the sampling logbook. Final decision regarding the sampling site 

 at the pre-selected sites was based on the suitability for the site to allow for this and follow-up 

 samplings without affecting the resource. 



Sampling Problems 



Although an attempt was made to obtain samples from every pre-selected site, this was not 

 always possible. Different factors worked against this objective. Following is a brief description 

 of some of the sampling problems, in no particular order, encountered during this field program. 

 Preselection of sampling areas 



