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• The major difficulty lies in interpreting the results, weighing the 

 biases, and reaching conclusions. Such interpretations are dependent 

 upon a solid understanding of the marine ecosystem being sampled, and 

 when that understanding is inconclusive so must the interpretations be 

 inconclusive. Thus, identification of possible bias is critical, and 

 the greater the bias, the less specific the conclusions. 



• The biological tools for assessment of species interactions have only 

 recently been developed. The pressure from industry to examine partic- 

 ular species, in part, drove the establishment of assessment. As gen- 

 eral ecosystem studies are of limited utility to the short-term demands 

 of industry, and as funding for assessment has occurred partly due to 

 fishing activity impacts on stocks, it is not surprising that only re- 

 cently have general ecosystem studies received any priority. 



• Just as in industry, technological improvements in assessment tools 

 (better electronics, use of transducers on the head-ropes of mid-water 

 trawls, better ability to tow at a specified depth) have forced re- 

 adjustment of data. 



2. Human Activities 



Man's impacts on the marine ecosystem must be measured when regula- 

 tions to preserve that ecosystem are instituted. 



The actual catch of commercial species must be measured. This infor- 

 mation often depend on reported data that may be incorrect. This is par- 

 ticularly true when reporting nations are competing for limited common 

 resources. 



There is also an estimate necessary of the total catch as opposed 

 to the landed catch. Nets are unselective, catching all fish of appro- 

 priate size in their path. As fish mingle in the ocean, species not of 

 value are harvested and usually discarded by domestic vessels. These dis- 

 cards are almost always dead. Factory vessels on the other hand, reduce 

 offal and undesired species to fishmeal. 



In addition to discards, valuable fish of another species often are 

 caught. These fish are kept and may not be reported. 



