Evidence of Limited Recruitment of Pallid Sturgeon in the Lower Missouri River

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 recruitment. Therefore, our objectives were to 1) determine the likelihood that unmarked Pallid Sturgeon captured from the lower Missouri River were the result of natural recruitment and 2) examine the length distribution of wild- and hatchery-origin fish to determine if a difference exists by origin and examine the life-stage distribution. Genetic analysis showed that from 2003 to 2015, 358 ‘‘presumptive wild-origin’’ Pallid Sturgeon were captured in the lower Missouri River and the comparison between the length distributions of wild- and hatchery-origin fish did not provide any additional clarification into potential wildorigin fish. Low recruitment may be due to a small breeding population, high mortality of early life stages, hybridization with Shovelnose Sturgeon Scaphirhynchus platorynchus, or transport of drifting free embryos or larvae into inhospitable habitats. Determining what factors are limiting recruitment is the important next step for the recovery of Pallid Sturgeon in the lower Missouri River

Revisiting the causal effects of exporting on productivity: Does price heterogeneity matter?

In most empirical studies that establish the export-productivity relationships, output is measured in values rather than in quantities. This makes it difficult to distinguish between productivity and within-firm changes in price that could occur following exposure to international markets. Using detailed data on quantity and prices from Ethiopian manufacturing firms in the period 1996-2005, this paper distinguishes efficiency from revenue based productivity and examines what this means for the estimated relationship between exporting and productivity. The main results show that exporters are more productive than non-exporters in terms of revenue based productivity and this is explained by both self-selection and learning effects. However, when correcting for price heterogeneity, exporters appear to be similar to non-exporters both before and after export entry. Overall, the results suggest that the increase in firm-level productivity following entry into foreign markets is associated with changes in prices as opposed to productive efficiency