Under such conditions, municipal and state agencies must manage shellfish with only limited public funds, relying heavily upon nature to sustain or enhance these natural populations. As long as the natural supply was more than sufficient for the demand, no law could have been better adapted for the public good. The leading probable cause of algal growth, low dissolved oxygen concentrations, salinity and temperature fluctuations, high coliform counts, and resultant lower productivity in coastal shellfish populations are non-point source discharges. Constant, low-level pollution results in breaking some of the first links in the food chain and killing off organisms upon which small fish feed, thus reducing the quantity of prey available throughout the food chain. Deprived of food and shelter, the populations and species diversity of fish and crustacea decline.
Toxic chemicals accumulate, diseases and abnormalities increase.
These consequences move up the food chain with more fish, shellfish, birds, and mammals dying or failing to reproduce. These phenomena are not limited to near-shore areas. Poorly flushed embayments are particularly susceptible to pollution of shellfish beds. The most prolific beds,whether wild or cultured, tend to be established in coves, bays, and similar areas where fresh water flows dilute the seawater, tidal action is regular, there is a constant supply of food, and protection is afforded from storms and surges. These beds are subject to greater risk from bacterial or chemical contamination and consequent degradation due to their proximity to human settlements.