Dozens of northern elephant seal pups died during last month’s storms, but there is no evidence that surviving seals have been harmed by agricultural runoff unleashed by the rains, according to marine ecologists and officials at the Point Reyes National Seashore.

Rep. Jared Huffman urged park officials last week to prevent cattle from grazing in areas near seals, concerned that runoff from nearby ranches might have contaminated the water. In response, park superintendent Craig Kenkel…