Pismo clams were harvested by the millions on Pismo Beach and supported a thriving commercial and recreational fishery, with early clammers using horse-drawn plows to find them in the sand. From 1916 until commercial harvesting was prohibited in 1947, an estimated 6.25 million pounds were taken in California, mostly on Pismo Beach and surrounding areas, with annual harvests nearly 100,000 pounds and a recorded high of 665,700 pounds; this level of harvest proved unsustainable. Recreational harvesting remains legal under size limits, although the last legal-size clam on Pismo Beach was documented in 1993. Pismo clams live on open, sandy beaches from Monterey, California to Baja, Mexico, mainly in the intertidal zone, where they feed on microscopic algae and detritus, can grow up to 20mm per year, form annual growth rings in their shells, take 5 to 8 years to reach legal harvestable size, and may live as long as 53 years. As they age they grow more slowly because more energy goes to reproduction, and as broadcast spawners they release eggs and sperm into the water, where fertilization occurs before larval clams drift, feed, grow a first shell, and settle onto a beach. Research begun in 2016 at nearby Cal Poly, funded by the City of Pismo Beach, found that small clams occasionally appear on the beach, and clams found there should be reburied where they are found to help the population recover.