Results presented in Table 4.16 also suggest that butyl tin species adsorb 

 more strongly to sediment in warmer months, and that tributyltin 

 generally adsorbs more strongly to sediment than dibutyltin, and that 

 monobutyltin generally adsorbs more strongly than dibutyltin. Stang and 

 Seligman (1986) have determined that butyltin conoentrations in the 

 sediments of Pearl Harbor appear to be at or near equilibrium with 

 butyltin concentrations in the overlying bottom water and that the 

 sediment there can potentially accommodate butyltin concentrations up to 

 four orders of magnitude greater than the overlying bottom water without 

 significant desorption of butyltin cations from the sediment. 



4.5 BIOCmCE2m»TI0N/BICA<XU^^ 

 (FISH AND SHELUTSH) 



Traditionally fish nets have been coated with tar or treated with tannic 

 acid to prevent the settlement of bacteria and subsequent rotting of the 

 net fibers. The effectiveness of tributyltin has led to its increasing 

 use as an antifouling coating for fishnets, floating cages, livecars, 

 traps and pots. This practice can subject the contained fisheries to a 

 continuous dose of the tributyltin leaching from the antifouling coating. 

 The growing practice of holding or raising young fish in pens or nets 

 treated with TBT has been found to have increased the number of fish 

 coming to market with a detectable load of tributyltin in the tissues 

 (Davies, et al., 1987 in Scotland: Short and Thrower, 1986a in Alaska). 

 This situation has been investigated in Atlantic salmon and the Chinook 

 salmon in the Pacific, due to public health concern related to human 

 consumption of TBT contaminated fish. Davies et al. (1987) have found the 

 occurrence of TBT at 0.5 to 1.0 mg/kg in the muscle tissue of Atlantic 

 salmon farmed in cages treated with TBT. These results have contributed 

 to the debate leading to new more stringent controls within the United 

 Kingdom on the use of antifouling paints on boats and on fish farm 

 structures. Similar concern has been voiced in Alaska and the West U.S. 

 Coast where residues of TBT have been found in chinook salmon raised in 

 TBT treated cages (Short and Thrower, 1986a) and due to TBT caused 

 mortality in chinook salmon (Short and Thrower, 1986b). Tables 4.18 and 

 4.19 summarize the results of studies on the bioaccumulation of 

 tributyltin in fish and molluscs. The concentration of TBT in muscle 

 tissue of the chinook salmon (0.52 ppm) is similar to the 0.5 to 1.0 .mg/kg 

 found in the Atlantic salmon in fish farms in Scotland (Davies et al., 

 1987) . 



IV-39 



