INTRODUCTION
The lake sturgeon, Acipenser fulvescens, is a native species to the Great Lakes Basin. It has and continues to represent an important biological component of the Great Lakes fish community. Lake sturgeon can be considered a nearshore, warmwater species with water temperature and depth preferences of low 50's to mid-60°F and 15-30 feet, respectively. Lake sturgeon are benthivores, feeding on small invertebrates such as insect larvae, crayfish, snails, clams, and leeches (MacNeill and Busch 1994). Their highest competitors for available food and space are likely suckers and whitefish (MacNeill and Busch 1994).
Life history characteristics of lake sturgeon are unique with respect to other fishes and are as follows: sexual maturity in females is reached between 14 and 33 years, most often from 24-26 years; and, 8 to 12 years for males (but may take up to 22 years); female lake sturgeon spawn once every 4 to 9 years while males spawn every 2 to 7 years; spawning occurs on clean, gravel shoals and stream rapids from April to June in preferred water temperatures of 55-64oF; female lake sturgeon lay 4,000 to 7,000 eggs per pound of fish; growth rates are quite variable throughout its range and depend on temperature, food availability, and water quality; and, the typical life-span of lake sturgeon is 55 years for males and 80-150 years for females.
As a consequence of interrupted spawning cycles, only 10-20% of adult lake sturgeon within a population are sexually active and spawn during a given season (MacNeill and Busch 1994).
Little is known about seasonal movements of lake sturgeon. It is believed that individual sturgeon remain confined to a small territory during the summer months. Lake sturgeon have been known to remain within three miles of their original capture site one year later. Lake sturgeon do move upstream to spawn in the spring and downstream in the fall; often exceeding 80 miles. Adult sturgeon habitually return to the streams in which they were born to spawn (homing behavior) (MacNeill and Busch 1994).
HISTORY OF THE POPULATION
The most accurate, yet biased, representation of the history of Great Lakes' lake sturgeon populations is through the use of commercial harvest data. A summary of the catch, by "era", is discussed below.
Pre-1900
Early commercial fisherman (pre-1850) perceived lake sturgeon as a nuisance fish because of fishing gear destruction. This led to their wide-spread slaughter. As the economic importance of this species was later recognized, a targeted commercial fishery intensified by the mid- to late-1800's. For example, during the heavy fishing years from 1879 to 1900, the commercial catch of lake sturgeon in the Great Lakes averaged over 1,814 metric tons (4 million pounds). In 1885, a maximum of 4,901 metric tons (8.6 million pounds) were harvested, of which 2,359 tons (5.2 million pounds) came from Lake Erie (Baldwin et al 1979).
1900 to 1986
From 1900 to the 1970s, little is known about the lake sturgeon population, except for its continued decline. For example, by the late 1900's, 80% of the lake sturgeon were removed from Lake Erie (Fuerst and Cavender 1994). Commercial harvest was reported until 1977, but at very low numbers after 1956 (USFWS 1995). In the late 1970's, Canadian commercial operations in Lake Erie reported harvests of 1.36 to 2.27 metric tons (3 to 5 thousand pounds); much reduced from the previous century (Baldwin et al 1979).
Factors affecting the decline in lake sturgeon populations include commercial overexploitation, followed by some degree of habitat loss and degradation. Also, the reproductive cycle further complicates recruitment; hence, catalyzing their dramatic decline.
Habitat loss is sure to be a contributing factor to the demise of lake sturgeon. For example, in all the Great Lakes, damming of tributaries prevented access to historical spawning grounds, destruction of spawning areas occurred via siltation from deforestation, agriculture, and dredging, and pollution from nutrient and contaminant loads further hindered reproductive success (USFWS 1995). However, it is this author's opinion that overharvest played a much more significant role than loss of habitat. The lake sturgeon population had already been reduced, to the greatest extent, prior to gross eutrophication, pollution, siltation, and damming (1930).
1987 to Present
Consequent to the decline, only a remnant population remains today in most Great Lakes areas. As a result of these declines, lake sturgeon are: (U.S.) Federally listed as a species of concern; recognized by the American Fisheries Society as threatened in North America; and, listed as Endangered, Threatened, or Special Concern in 18 of 20 states throughout its range. Lake sturgeon are not protected in Canadian waters of the Great Lakes. (S. Walker - USFWS, E. Lansing, MI, pers. comm., 1994).
Recently, interest in the restoration of lake sturgeon has increased greatly. The fish can serve as an indicator of ecosystem health and biodiversity, particularly because of its unique life history characteristics. Also, with the addition of zebra and quagga mussels, Dreissena sp., the energy flow is apparently shifting to the benthos. This could support increases in populations of benthic feeding fish such as the native lake sturgeon. (However, the impacts of Dreissena sp. are not yet determined).
A lake sturgeon population does still exist in Lake Erie and the Niagara River; however, numbers are too low to efficiently sample them in most areas. This inhibits collection of current population and habitat characteristics; hence, other measures have been implemented. For example, partnerships have been developed with commercial fishermen to report by-caught lake sturgeon to their respective management agency. Some partnerships allow temporary possession so critical information can be collected from the specimens. Also, a sighting survey has been distributed to anglers and SCUBA divers to report their encounters since 1994. Lake sturgeon have been sighted by several agencies in the western, central, and eastern basin, including the upper Niagara River.
The recent sightings indicate age-class structure within the current populations. This is a positive indication that natural reproduction is occurring, particularly with the number of juvenile sightings (< 450 mm). The current status of the populations is believed to be increasing, based on anecdotal evidence, but still impaired with relation to historical abundance. Contaminant burdens on lake sturgeon are not well known; however, researchers have documented low hatching success and high larval deformities in polluted streams in Montreal. In contrast, lake sturgeon in other waters do not seem to accumulate heavy metals (Lowie and Krise, ed. 1995).
Lake sturgeon throughout the Great Lakes are on the rebound. The best way to justify this is through communication with commercial fishermen and recreationalists. Although they are not a targeted species, by-catch reports can serve as a good indicator of community changes. Restoration of the lake sturgeon population in the lower Great Lakes encompasses public education and knowledge due to the remnant levels. I would like to extend great gratitude to the Niagara Divers' Association for assisting with this component of lake sturgeon education and outreach.
Niagara River Project - Draft scope for the Niagara River Sampling for 1998.
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