Such unsustainable catch rates were coupled with environmental challenges such as pollution and the construction of dams and other flood control measures. Sturgeon, which return each spring to spawn in the streams and rivers in which they were born, found tributaries blocked and spawning shoals destroyed by silt from agriculture and lumbering. In the 20th century, drastic drops in sturgeon catches, increased regulations, and the closure of viable fisheries occurred. Currently, 19 of the 20 states within the fish's original U.S. range list it as either threatened or endangered. It is considered "Vulnerable" by NatureServe. This sturgeon is a valuable gourmet food fish, as well as a source of specialty products including caviar and isinglass. "In 1860, this species, taken on incidental catches of other fishes, was killed and dumped back in the lake, piled up on shore to dry and be burned, fed to pigs, or dug into the earth as fertilizer." It was even stacked like cordwood and used to fuel steamboats. Once its value was realized, "They were taken by every available means from spearing and jigging to set lines of baited or unbaited hooks laid on the bottom to trap nets, pound nets and gillnets." Over 5 million lb were taken from Lake Erie in a single year. The fishery collapsed, largely by 1900. It has never recovered. Like most sturgeons, the lake sturgeon is rare now and is protected in many areas. In addition to overharvesting, it has also been negatively affected by pollution and loss of migratory waterways. It is vulnerable to population declines through overfishing due to its extremely slow reproductive cycle; most individuals caught before 20 years of age have never bred and females spawn only once every four or five years. The specific harvesting of breeding females for their roe is also damaging to population size. Few individuals ever reach the extreme old age or large size that those of previous generations often did. Restoration In 2001, transmitters placed into ten sturgeon and egg mats placed in the Detroit River documented spawning of sturgeon for the first time in many decades. This discovery followed the 2001 discovery of spawning runs under the Blue Water Bridge in the St. Clair River. The Little River Band of Ottawa Indians (Manistee, MI) Sturgeon Program began in 2001. In 2002 they successfully documented natural reproduction of lake sturgeon by capturing larvae (newly hatched fish) from