Final answer:
The return of scallop populations to an area could be hindered by environmental changes, overfishing, or disease. Details would require an understanding of local conditions and conservational efforts.
Step-by-step explanation:
The question 'Why have scallops not returned to TB?' is likely referring to the return of scallop populations to an area affected by tuberculosis (TB), which is doubtful since TB affects mammals and not mollusks like scallops. However, if TB stands for an abbreviation of a specific location or context overlooked here, the reasons behind scallops not returning could be due to environmental changes, overfishing, or disease affecting their populations. It's also important to consider that scallop populations can vary due to natural cycles or changes in predator-prey dynamics.
For a detailed understanding, studies would typically look at water quality, availability of food sources, and the presence of pollutants or pathogens. Conservational efforts may include the creation of marine protected areas, replenishing scallop stocks through aquaculture, or imposing restrictions on fishing practices to ensure the sustainable management of these valuable bivalves.