Lake sturgeon

In this study we quantified the percent CaCO3 polymorph composition in otoliths of larval and juvenile Lake Sturgeon Acipenser fulvescens via X-ray microdiffraction. Sagittal otoliths of sub-adults were primarily composed of aragonite (> 90%) while the lapilli otoliths were 100% vaterite. This is the first time the presence of aragonite in otoliths has been reported in an acipenseriform and is surprising given that the ability to form aragonite otoliths was not thought to have evolved until the separation of teleost and holostean species from other Actinopterygian fishes (e.g., sturgeon, paddlefish, gar).

Pallid Sturgeon Scaphirhynchus albus are endemic to the Missouri and Mississippi river basins and are rare throughout their range. The species was listed as federally endangered with little to no evidence of natural recruitment. Since population augmentation was initiated as a recovery objective in the early 1990s, thousands of hatchery-origin Pallid Sturgeon have been stocked in the lower Missouri River (Gavins Point Dam [river kilometer 1,305.1] to the confluence of the Mississippi River [river kilometer 0.0]). Efforts to discriminate natural reproduction and recruitment of wild-origin Pallid Sturgeon from hatchery-origin fish has been hampered by tag loss in hatchery-origin sturgeon, inconsistent documentation of hatchery parental crosses, and the failure to collect tissue samples for genotyping all broodstock. However, the recent reconstruction of missing parental genotypes from known hatchery-origin progeny and from cryopreserved milt made it possible to examine Pallid Sturgeon...

The main objective of this paper is to show that a well-managed lake sturgeon Acipenser fulvescens population can support a high and sustainable commercial catch , even in the Great Lakes drainage where the species has nowadays become rare. In a 350-km long un-fragmented stretch of the lower St Lawrence River located between Montreal and downstream Quebec City , with declared annual catches of 150 tonnes , the lake sturgeon population was considered overexploited by a governmental scientific committee in 1987 on the basis of high annual mortality rates (17 – 25% for age groups 14 – 31) , unbalanced age structure , deficit of reproductive potential and commercial catch yields well over 1. 5 kg ka) 1. A first management plan implemented in 1987 failed to reduce the catch and provide more protection to the spawning stock. During the 1990s , the declared catch of the 76 commercial fishermen kept increasing over 200 tonnes. The age at the recruitment of the 20-cm-mesh gill-nets shifted towards older fish , indicating a decrease in the numbers of younger fish. In the population , sub-adult abundance decreased by 60% , as well as the year-class strength and the abundance of the females on the largest known spawning ground. In 2000 , a stronger management plan was then enforced in order to adapt the total catch to the potential of the resource. The commercial catch was reduced by 60% in 3 years and an individual code-bar plastic tag and a code-bar weight declaration coupon were established to control its application. The fishing season was also shortened. Ten years later , we are confident in maintaining the actual commercial fishery because the commercial catch is now much lower (80 tonnes) and is more effectively controlled , the abundance of juvenile lake sturgeon increased throughout the St Lawrence River and the regular yearly production of cohorts has been demonstrated. Restrictive management measures , close supervision of landings combined with periodic monitoring of the population are key elements in managing this long-lived species. We also emphasize the importance of preventing any further fragmentation of this portion of 350 km of fluvial habitat as well as to maintain habitat quality to ensure the sustainability of this fishery .