Surplus-production estimate of historical lake sturgeon biomass in Lake of the Woods

Lake sturgeon (Acipenser fulvescens) was historically abundant in Lake of the Woods, Canada/USA, and was the first species to be commercially harvested from that waterbody commencing in 1888. The number of pound nets used annually was documented from 1888 to 1910 and used as a surrogate for effort in a surplus-production model using a Bayesian approach. Mean dressed weight was 11.35 kg; therefore, the total biomass and approximate number of sturgeon harvested could be estimated. Over the 23-year period, 5348 tonnes were harvested peaking at 813.3 tonnes in 1893. Effort peaked in 1896 whereas catch-per-unit-effort peaked in 1891 at 11.4 tonnes per pound net year. The estimated historical initial biomass (B-0) was 4493 tonnes (2059-9689; 95% CIs) and population was 395,859 sturgeons (181,409-853,656). Carrying capacity was estimated at 10,825 tonnes (2676-40,697; 95% CIs) and the intrinsic growth rate (r) was estimated to be 0.092 (0.009-0.272; 95% CIs). Maximum sustainable yield was 235 tonnes (14-1012; 95% CIs) which was exceeded 3.5 times by the third year (1891) of commercial harvest and extended seven more years until the population declined. The mean rate of exploitation was 13.2% over the 23-year period, peaked at 36.5% in 1896 and declined to approximately 10% after the 1900s. The population in Lake of the Woods in 1910 was estimated to be 34,397 (13,814-80,966; 95% CIs) representing a decline of 91.1% from the beginning of the commercial harvest in 1888.

Automated summary

The study found that the population and biomass of lake sturgeon in Lake of the Woods declined significantly from the late 19th century to the early 20th century. The impact of commercial harvesting exceeded the sustainable yield of the sturgeon, resulting in a sharp decline in the population.