What is a common economic use of crustaceans?

Crustaceans are commonly used as bait for fishing because of their natural appeal to a variety of fish species. Many fish are attracted to crustaceans like shrimp, crabs, and lobsters due to their scent and movement in the water, making them effective for anglers seeking to catch both saltwater and freshwater species. This practice is not only significant for recreational fishing but also for commercial fishing operations, where crustaceans serve as a primary bait to lure target species and enhance fishing yields.

While the other choices present interesting functions of various organisms, they do not accurately reflect the common economic use of crustaceans. Providing oxygen in water is primarily the role of aquatic plants and phytoplankton. The use of filters in aquariums is attributed to specific species of fish and invertebrates that help maintain water quality, but it does not specifically relate to crustaceans. As for agriculture, while some biological pest controls do utilize certain organisms, crustaceans specifically are not generally categorized as pesticides. Thus, the role of crustaceans as bait for fishing stands out as the most relevant economic use.