Status and Recovery Potential of Gulf Sturgeon in the Pearl River System, Louisiana–Mississippi

Abstract

From 1992 through 1996, 257 Gulf sturgeon Acipenser oxyrinchus desotoi were captured in the Pearl River system of Louisiana and Mississippi, but adults (>130 cm fork length) constituted less than 2% of the catch. The summer population size in 1996, estimated by mark–recapture methods, was 292 individuals that were age 2 or older. Instantaneous total mortality rate (Z), estimated with a catch curve, was 0.41, for an annual mortality rate of 34%. Modeling the population with Z = 0.41 resulted in declining populations under two different recruitment scenarios. Mortality rates will have to be reduced to Z = 0.16–0.24 for the population to be self‐sustaining by 2023, the target year in the Gulf Sturgeon Recovery Plan. Mean fork length of Gulf sturgeon in the Pearl River system was significantly larger in 1970 than in 1985 and 1992–1996, indicating that the population may not have improved since 1985. An increase in population size should be detectable within 6 years of achieving acceptable levels of mortality. Efforts to reduce mortality should focus on commercial bycatch and improving winter habitat in the Lake Pontchartrain estuary and summer habitat in the Pearl River system. Weirs in the Pearl and Bogue Chitto rivers need further study to determine if improved fish passage would improve recruitment and survival of Gulf sturgeon.

Evaluating Population Recovery Characteristics and Potential Recovery Actions for a Long‐Lived Protected Species: A Case History of Gulf Sturgeon in the Apalachicola River

“…Our results suggest that the sustainable exploitation rates for Gulf Sturgeon are most likely relatively low ( U MSY = 0.058) and similar to those of other sturgeon populations (Rieman and Beamesderfer ; Boreman ; Bruch ) and that population viability is sensitive to increases in mortality at all life stages (Morrow et al. , ; Pine et al. ; Vélez‐Espino and Koops ).…”

Growth Estimation of Western Population Segment Gulf Sturgeon Using Length‐at‐Age and Mark–Recapture Data

“…The k ‐value estimated by Morrow et al. () was outside of our lower 95% confidence limit, whereas the mean k ‐values from the other two studies fell within our 95% CIs. Both the L ∞ and k of the two‐parameter VBGF estimated by Flowers () were outside the 95% CIs of our parameter estimates, but both parameters of the power model estimated by Huff () were within our 95% CIs.…”

“…Finally, Morrow et al. () were the only authors that used WPS data (from the Pearl River) to obtain an age and growth estimate (a three‐parameter VBGF), but their study also included EPS data for age‐10 and older individuals, which could have skewed parameter estimates for the Pearl River population by using individuals from a different system. Therefore, age and growth estimations strictly for the WPS are lacking.…”

Kemp's Ridley Sea Turtle Saga and Setback: Novel Analyses of Cumulative Hatchlings Released and Time-Lagged Annual Nests in Tamaulipas, Mexico

“…Adults forage sparingly in freshwater and depend almost entirely on estuarine and marine prey for their growth (Gu et al 2001). Both adult and sub-adult Gulf sturgeon are known to lose up to 30% of their total body weight while in fresh water, and subsequently compensate the loss during winter feeding in marine areas (Carr 1983;Clugston et al 1995;Heise et al 1999;Morrow et al 1998;Ross et al 2000;Sulak and Clugston 1999;Wooley and Crateau 1985).…”