100 



BIOLOGICAL REPORT 31 



the life cycle of this species, population declines have 

 been caused by physical obstacles rather than over- 

 fishing or chemical perturbation (see also Chapter 

 4). The alewife fishery is indicative of the variety of 

 factors that may cause fish stocks to decline and 

 underscores the need for sound biological data for 

 ecological management. 



6.1.3. Bacterial Contamination 



Bacterial shellfish closures have been docu- 

 mented for Buzzards Bay since the early 1 900*s. 

 primarily as the result of illness linked to the dis- 

 charge of raw sewage. Unfortunately, bacterial con- 

 tamination of shellfish beds in the early part of the 

 century was generally identified only after resulting 

 public health impacts were felt, with water tested 

 after the outbreak of illnesses. For example, only 

 after over 500 cases of typhoid fever were identi- 

 fied among shellfish consumers in New Bedford was 

 it determined that substantial amounts of raw sew- 

 erage were entering New Bedford Harbor 

 (Germano 1 992). Significant restrictions were sub- 

 sequently placed on the shellfishery, which led to 

 the construction of a sewage system to collect all of 

 New Bedford's sewage and discharge it farther into 

 Buzzards Bay, the precursor to the city's current 

 sewerage treatment system. It was not until 1 925. 

 when nationwide outbreaks of typhoid fever led the 

 U.S. Public Health Service to develop a program 

 for routine monitoring of bacterial contamination in 

 shellfish areas, that other areas in Buzzards Bay. 

 including parts of Mattapoisett Harbor and 

 Apponagansett Bay in Dartmouth, experienced clo- 

 sures. By 1 930 1 ,1 74 ha of shellfish beds had been 

 closed. This figure remained relatively constant for 

 years, increasing to approximately 1 ,700 ha in the 

 1 960's, but with year-to-year variations caused by 

 increased closures following major storms and hur- 

 ricanes. In the 1970"s shellfish bed closures in- 

 creased significantly to over 3,238 ha; however, 

 some of this increase is attributed to the increased 

 monitoring effort undertaken during this time by the 

 Department of Environmental Quality Engineering. 

 This increase, however, was dwarfed by the sub- 

 stantial increase in closures during the 1 980's to 



nearly 5,990 ha by the end of the decade, and 1 992 

 closures averaged approximately 6.070 ha. The 

 growing increase in closures during the past decade 

 has had a significant impact on the shellfishery and 

 has directed attention to the advancing ecological 

 and economic threats posed by declining water 

 quality conditions in some areas of the bay associ- 

 ated with sewage inputs (Fig. 6. 1 ). 



6.1.4. Toxic Pollutants 



The variety of potential sources of toxic con- 

 taminants to Buzzards Bay are as wide as the vari- 

 ety of potential contaminants. Toxic chemicals, in- 

 cluding petroleum hydrocarbons. PCB's, pesticides, 

 organic compounds, and metals, can enter the bay 

 through point and nonpoint source inputs from 

 outfalls, runoff, rivers, streams, and atmospheric 

 deposition. Chemical contamination from industrial 

 activities primarily occurs in the urban areas ofNew 

 Bedford, Fairhaven. and Dartmouth. Agriculturally 

 derived chemical inputs (pesticides and herbicides), 

 however, are more likely to enter through runoff 

 and small rivers, which flow through virtually all of 

 the bay's watershed, most notably the areas of 

 Westport, Dartmouth. Fairhaven, and Mattapoisett 

 (see also Chapter 5). 



The most serious water quality problems involv- 

 ing toxic contamination in Buzzards Bay are focused 



d Non-urban population 

 ■ Shellfish bed closures 



o 

 o 

 o 



CD 



I 



1940 1950 



1990 2000 



Year 



Fig. 6.1. Population versus shellfish bed closures for 

 the Buzzards Bay watershed 



