The ancient-looking American paddlefish is closely related to the sturgeon and can reach lengths of more than two metres and a weight of 90kg. Very unusual for a freshwater fish, it uses its long snout, which can take up to a third of its length, to filter feed on plankton. This photograph demonstrates the extremely intricate bone work of the paddlefish’s snout. P. spathula is found in the 22 states in the US that are part of the Mississippi River Basin. It inhabits slow-flowing, large rivers at depths of 1.3 metres or more.

The American paddlefish has reached threatened status as it is highly prized for its meat and eggs. Expensive caviar is traditionally the eggs of Beluga sturgeon that are native to the Caspian and Black Seas. Access to the Caspian Sea has been extremely limited since Iran’s revolution in 1979, which diverted attention to the American paddlefish, the next most suitable substitute. As a result, they began to be exploited for their roe in the 1980s, at a time when the commercial fishing of paddlefish was still legal.

Fishing of the American paddlefish is now extremely regulated, as is the international trade of its eggs, but the demand and potential profit from selling paddlefish eggs is huge. At its height in 2007, 450 grams of roe could fetch as much as $300 USD (today it is valued at closer to $100 USD). Many states, including Oklahoma, Montana and North Dakota, have now implemented programmes whereby fishermen can bring caught paddlefish to a facility where its data is logged and any eggs are sold and exported, mainly to Japan, with 100 percent of the profits used to fund conservation efforts.