Chang. Effects of sewage sludge dumping on fishery resources 



605 



eral individual species and all species for north and 

 south areas at the site, and within the pre and post 

 sludge dumping periods. 



The hypothesis that fishery resource abundance in 

 the vicinity of the 106-MDS and adjacent outer conti- 

 nental shelf waters was not affected by sewage sludge 

 dumping there from 1986 to 1990 is thereby rejected. 

 Also rejected are the three secondary hypotheses re- 

 lated to the primary one. The likelihood remains that 

 waste disposal, even in deep-ocean waters, has mea- 

 surable adverse impacts on the resource abundance, 

 at least in the area of direct influence of the toxic 

 waste. 



Analysis of survey data alone, however, does not 

 establish cause and effect. It is necessary to consider 

 the likelihood that events neither directly nor indi- 

 rectly related to sewage sludge dumping at the 106- 

 MDS could have led to the measured decline in abun- 

 dance and shift in species composition within the study 

 period. Also, it is necessary to consider how an abun- 

 dance shift could have occurred through sludge dump- 

 ing within this period of time. 



Fishing is foremost among factors affecting fishery 

 resource abundance and species composition unrelated 

 to any effect of ocean disposal of toxic waste. Impacts 

 of fishing pressure on the species sampled at the off- 

 shore dumpsite and analyzed in this study are poorly 

 known. There are also other poorly understood natu- 

 ral factors affecting species population abundance 

 around the 106-MDS in the PAI and elsewhere that 

 could have influenced abundance and species composi- 

 tion at this site over the period of the study reported 

 here. These include shifts in spawning time and area, 

 size of predator stocks, decline in size of the spawning 

 biomass, and increase in early life mortality (Gross, 

 1976; Hempel, 1978; Mayer, 1982; Cross et al., 1985; 

 Tiews, 1985). The dramatic reductions in stock size 

 affected by powerful modern fishing techniques, how- 

 ever, through sheer reduction in stock size, may influ- 

 ence all these factors so that their fluctuation is no 

 longer entirely natural. These same natural factors 

 are likewise potentially affected by ocean dumping of 

 toxic waste as evidenced in the environmental litera- 

 ture (Carlise, 1969; Gross, 1976; Mearns, 1981; Mayer, 

 1982; Spies, 1984; Wolf and O'Connor, 1988; Champ 

 and Park, 1989; Hood et al., 1989; Baumgartner and 

 Duedall, 1990; Longwell et al. 1992; Longwell 21 ; Young 

 and Mearns 22 ; NMFS 1 " 11 ; Studholme et al. 12 ). Changes 



-'Longwell, A. C. 1981. Cytological examination offish eggs collected at 

 and near 106-Mile Site. In NOAA Special Report. Assessment Report 

 on the Effects of Waste Dumping in 106-Mile Ocean Waste Disposal 

 Site. Dumpsite Evaluation Report 81-1. U.S. Dep. Commer., NOAA. 

 Office of Mar. Pollution Assessment. Rockville, MD. 257-276 p. 



--Young, D. R., and A. J. Mearns. 1978. Pollutant flow through food 

 web. Southern California Coastal Water Research Project. Annual 

 Report 1978, 185-202 p. 



in water mass patterns and global warming are possi- 

 bly the only phenomena not potentially influenced by 

 ocean dumping. Given the complexity of natural and 

 anthropogenic forces acting on populations, existing 

 data sets from fishery ecology are simply not suffi- 

 ciently synoptic or complete enough to be useful in 

 sorting out direct sludge dumping effects from natural 

 or pseudo-natural processes driving population 

 fluctuation. 



Oceanographic dynamics around the 106-MDS make 

 it unlikely that any change in harvestable fishery re- 

 sources or catch composition could be the result of 

 direct mortality attributable to the sewage since relo- 

 cated sludge dumping began there in 1986. There is 

 some evidence from embryo studies of planktonic eggs 

 collected in the wake of sludge and acid waste disposal 

 at 106-MDS that direct kills of floating fish eggs can 

 occur, but this dumpsite is not a significant spawning 

 grounds for resource species (Longwell 21 ). 



Changes in fishery resource abundance at 106-MDS 

 could, however, have been affected by a change in fish 

 behavior in response to dumped material as well as to 

 natural environmental perturbations (Olla et al., 1980). 

 Migration to other areas to escape sludge disposal and 

 its aftermath or to search for other feeding grounds is 

 likely to alter the time and place of spawning and 

 subsequent early-life survival. 



Reduced reproductive success and recruitment re- 

 sulting from increased baseline contaminant body bur- 

 dens of spawners is another mechanism whereby the 

 population changes measured in the study presented 

 here could have resulted from sludge dumping (Cross 

 and Hose, 1988; Longwell et al., 1992). Offshore con- 

 tamination of fish has the same potential of affecting 

 subsequent spawning and recruitment as does contami- 

 nation in nearshore waters and on the spawning 

 grounds. Shifts in species composition could have come 

 about if predator or competitor, or both, species were 

 more tolerant of the sludge than were the resource 

 species. In addition, poor quality eggs could have re- 

 sulted from inadequate maternal nutrition if there was 

 much direct prey mortality or pollution-impaired re- 

 production of prey organisms in the wake of the sludge. 

 Contaminant burdens of the reproductive tissues or 

 ripe eggs of the species analyzed in this study are 

 unknown. Extrapolation and formal treatment of ex- 

 isting data on muscle and liver tissues of these or on 

 the reproductive tissues of other species are probably 

 not worthwhile. Contaminant burdens of mature win- 

 ter flounder eggs alone (Calabrese et al. 23 ) suggest that 



-"Calabrese A.. A. C. Longwell, and F. P. Thurberg. 1989. Final re- 

 port on early reproductive success of winter flounder from Boston 

 Harbor with comparisons made to Long Island Sound. Prepared for 

 U.S. Environmental Protection Agency. U.S. Dep. Commer., NOAA. 

 Natl. Mar. Fish. Serv., Northeast Fish. Sci. Cent.. Milford Lab.. 

 Milford. CT, 61 p. 



