Most of the sturgeon caviar and meat in the world market comes from the Caspian Sea. However, sturgeons in that region are severely depleted, leaving the possibility of an increased demand on North American sturgeons and paddlefish. While there are many sturgeon species in North America, this evaluation focuses on those sturgeons that are sold commercially, and on the closely related North American paddlefish. The species that are commercially fished in the United States are Paddlefish, Shovelnose sturgeon and White sturgeon. In Canada, Lake and Atlantic sturgeons are fished (Williamson, 2003).

Intrinsic rates of increase were not available. Atlantic sturgeon mature from 7 to over 28 years of age, and can reach a maximum age of 60; Paddlefish males mature from 5-9 years, females mature from 8-12 years, and both reach a maximum age of 30+; Shovelnose sturgeon reach maturity at 5-7 years, and can reach a maximum age of 27; Lake sturgeon males mature from 12-22 years, females from 14-27 years, and both can reach a maximum age of over 152; White sturgeon males reach maturity from 10-20 years, females from 15-30, and reach a maximum age of 82+ years (Williamson 2003). While some of these species score a 2 here, the average age of maturity for the species group is greater than 10.

Some sturgeon species are anadromous (e.g., White, Atlantic), while others remain in fresh water all of their lives. Sturgeons and Paddlefish return to their home rivers to spawn. Fishers can easily target sturgeon groups when they are making their upriver migration (Williamson 2003).

Sturgeon have very low fecundity. Spawning frequency varies from 1-8 years depending on the species and varies within species as well. Females usually have a longer spawning cycle than males. Spawning intervals for the species covered in this evaluation are as follows- Atlantic Sturgeon: 1-4 years for males and 3-5 for females; Paddlefish: 1-2 years for males, 2-4 for females; Lake Sturgeon: 2-3 years for males, 4-6 for females; White Sturgeon: 1-2 years for males and 2-6 for females. The spawning interval of Shovelnose Sturgeons has not been defined (Williamson 2003).

Atlantic sturgeon historically inhabitated most of the Eastern seaboard of North America, from Labrador to Florida, with a spawning range composed of a distinct subset of rivers between Newfoundland and Florida. The historic range of North American Paddlefish is throughout the Mississippi River basin, the Missouri River basin, the Great Lakes and some southern Ontario waters in Canada. Shovelnose Sturgeon inhabit most of the Mississippi and Missouri River basins. Lake sturgeon historically inhabitated the Great Lakes, the Mississippi River drainage, and the Hudson-James Bay drainage. They are generally confined to freshwater. White Sturgeon historically occupied major rivers and nearshore waters of the Pacific coast of the U.S., with known spawning populations in only a few major river systems between the Sacramento-San Joaquin rivers in California and the Fraser River in British Columbia (Williamson 2003). All of these species have relatively small ranges, confined to just one coastline or a few drainages within the North American continent.

While abundance of all sturgeon populations have been poorly documented, there is a lot of evidence that abundance is well below historic levels for all species. Atlantic sturgeon's range has contracted, and spawning has ceased at many historic spawning areas. Paddlefish are no longer present in Canada, and in the United States natural paddlefish populations are considered extirpated in Maryland, New York, North Carolina, and Pennsylvania. Shovelnose sturgeon also have a reduced range, and have been extirpated from New Mexico, North Carolina, and Pennsylvania. Lake sturgeon remains relatively widespread in Canada, but its range has been significantly reduced within the United States. Recruitment of the Kootenai River population of White sturgeon has decreased since the mid-1960s (Williamson 2003).

While catches for many of these species are in decline, this is at least partially the result of moratoriums on fishing, and increased restrictions on the fisheries. We cannot therefore use the decreased catch size as a proxy for declining abundance. Thus no points were subtracted here.

Many of the populations have a disproportionate ratio of young fish to old fish, because the larger, older fish have been overfished. In contrast, some populations have disproportionate numbers of older fish. The Kootenai population of White sturgeon has had no significant recruitment since 1974, and by 1997, the population was estimated at approximately 1,468 wild fish, with few individuals younger than 25 years of age (Williamson 2003).

A study of Atlantic sturgeon in Canada determined that recruitment has been low in recent years. Also, a survey found a significantly higher number of ripe females than ripe males (Trencia et al. 2002).

White, Shortnose, Pallid, and Alabama sturgeons are listed as "endangered" under the U.S. Endangered Species Act, and Gulf sturgeon as "threatened." The Kootenai River population of White sturgeon are listed as "endangered" as well (TESS 2004).

The IUCN lists Lake sturgeon, Shovelnose sturgeon and paddlefish as "vulnerable," and Atlantic and White sturgeon as "lower risk" (IUCN 2004).

All sturgeon species are listed under Appendix II of CITES. Appendix II species are those that "are not necessarily now threatened with extinction but that may become so unless trade is closely controlled" (CITES 2004).

Most sturgeon are caught in gillnets in commercial fisheries, and by hook and line in recreational fisheries (Trencia et al. 2002; Anonymous, pers. comm. 2004). It is unclear what proportion of fish is taken with bottom gillnets rather than midwater gillnets, but is likely that most are taken with bottom nets, because sturgeon are bottom-dwellers.

Human-caused habitat modification and degradation (e.g., dams, channelization, dredging, pollution) and their resulting ecological impacts (blocked migration corridors, loss of spawning and feeding grounds, deterioration of water quality, etc.) are frequently cited as root factors in the decline of North American acipenseriform species (Williamson 2003).

While there are some management measures in place, such as seasons, spawning areas for at least some of these species remain undefined and unprotected (Trencia et al. 2002; Knights et al. 2002). Much more needs to be understood about spawning behavior in order to adequately protect critical habitat areas.

There is some management in place for sturgeon fisheries. Sport fishing restrictions commonly include creel limits, closed seasons, size limits, gear restrictions, prohibition of high-grading (removing and releasing smaller fish from the creel so that larger fish can be caught without exceeding the limit), and sanctuaries or closures of certain waters. Commercial restrictions often include size limits, seasons, closures of designated waters, gear restrictions, and catch reporting requirements. Catch quotas have also been used for many years, particularly in saltwater commercial fisheries.

However, management of sturgeons is complicated because some of the species are anadromous, and fall under the jurisdiction of a range of federal, state, and provincial authorities within the United States and Canada. The species that are listed as Endangered under the Endangered Species Act (ESA) are subject to designated recovery plans. The White sturgeon in the Columbia River are managed by the congressionally established Columbia River Compact, as well as by a management agreement between Oregon and Washington. Twenty-eight states on the Mississippi River Basin have joined the Mississippi Interstate Cooperative Resource Association (MICRA), which attempts to coordinate the management of species located within the greater Mississippi River Basin.

While management certainly exists, management tools such as quotas are dependent on sufficient data to set realistic limits, and such data is unavailable. North American sturgeon populations remain far below sustainable levels. There is also evidence that some caviar from North American species are being sold illegaly as Caspian Sea product (Williamson 2003). We awarded a score of 2 here, because although management is in place, it is not meeting sustainability goals.

Monitoring of sturgeon populations has historically been weak, and abundance, population structures and spawning areas remain poorly defined (Williamson 2003; Trencia et al. 2002). Monitoring of catch seems to be adequate for some species in some regions, but overall is not thorough. In addition, any illegal catch is not monitored.

These species are overfished, and the recovery plans have yet to prove successful (Williamson 2003). As they are long-lived species, it will take some time before it can be determined if the species are recovering.

Bycatch levels remain mostly unknown and poorly monitored. Green sturgeon may be caught in fisheries for white sturgeon, as well as in salmon and groundfish fisheries (EPIC et al. 2001).

A NMFS/USFWS survey found that while bycatch of sturgeon in other fisheries does not seem to pose a significant threat to survival, it may impede recovery (Williamson 2003).