Gulf Sturgeon of the Pascagoula River: Post-Katrina Assessment of Seasonal Usage of the Lower Estuary

The Pascagoula watershed likely offers the greatest possibility for the survival of the Gulf sturgeon, Acipenser oxyrinchus desotoi within Mississippi. The focus of this project was to determine the routes Gulf sturgeon take through the lower Pascagoula River which splits at river kilometer 23 into two distinct distributaries. Sampling for this project was conducted over 60 d in 11 months throughout a two year period with a total of 81,947 net-meter-hours. Eight Gulf sturgeon were captured during this time and ranged in size from 81 - 196 cm TL and weight ranged from 3.6 - 52.6 kg. Using an array of automated telemetry receivers, ultrasonic tagged Gulf sturgeon migrations were monitored within the lower river and associated estuary. Data gathered by the automated telemetry array indicated that Gulf sturgeon movements through the project area are dissimilar between and among size classes, as some fish followed the most parsimonious route while others moved in more complex patterns. Based on the movements documented in this study, Gulf sturgeon appear to prefer the eastern distributary upstream from Bayou Chemise as the primary travel corridor between freshwater habitats and marine feeding grounds. The western distributary mouth was more highly utilized by Gulf sturgeon during seasonal migrations. Interpolated habitat maps of sediment composition and macrofaunal abundance reveal that this area possesses both abiotic and biotic characteristics most commonly reported for foraging Gulf sturgeon relocations from other Gulf sturgeon populations, and this area may represent the closest nearshore foraging grounds available to Gulf sturgeon of the Pascagoula River

Assessment of the Seasonal Usage of the Lower Pascagoula River Estuary by Gulf Sturgeon (\u3ci\u3eAcipenser oxyrinchus desotoi\u3c/i\u3e)

The Pascagoula watershed likely offers the greatest possibility for the survival of the Gulf sturgeon, Acipenser oxyrinchus desotoi, within Mississippi. Thus, understanding and preserving the connectivity between distant habitats in this region plays a major role in protecting and managing such anadromous fish populations. The focus of this project was to determine the within-river routes Gulf sturgeon take through the lower Pascagoula River downstream of the point where it splits (river kilometer 23) into two distinct distributaries. Sixty days were sampled throughout a two-year period with a total effort of 81 947 net-meter-hours and eight Gulf sturgeon were captured, ranging from 74 to 189 cm FL and weighing from 3.6 to 52.6 kg. Using an array of automated telemetry receivers, acoustically tagged Gulf sturgeon movements were monitored within the lower river and associated estuary. Estimated residence times (days) suggest Gulf sturgeon appear to prefer the eastern distributary upriver from Bayou Chemise as the primary travel corridor between freshwater habitats and marine feeding grounds. The western distributary mouth was more highly used by Gulf sturgeon during both seasonal migrations between upriver and offshore habitats. Thus, the western distributary appears to represent the main entrance point utilized by Gulf sturgeon to the Pascagoula River watershed and should be protected as the eastern distributary mouth has been altered from a natural marsh edge to one of hardened surfaces

Use of Non-Island, Shallow Nearshore Beach Environments by Gulf Sturgeon (\u3ci\u3eAcipenser oxyrinchus desotoi\u3c/i\u3e) Within the Mississippi Sound, USA

Large sub-adult/adult western population Gulf Sturgeon move to barrier islands in winter to feed whereas eastern fish move offshore or to nearshore non-island environments; most small sub-adults/juveniles remain in the estuarine system during winter. To test this, we used an acoustic data set deployed around the Port of Gulfport (hereafter Port footprint, east gate, west gate) within Mississippi Sound. We documented between three and six fish on each receiver totaling 12,285 detections for all 19 receivers between September 2012–May 2013. Only 30% of fish had both a high number of overall detections and a high number of detection days. In contrast, from October 2013–May 2014, between three and nine fish were detected on each receiver but with only 2,371 detections. Five fish (29.4%) had a high number of detections but a reduced number of detection days in the acoustic array; all fish appeared to be transients. Adults, unexpectedly, had the most prevalent occurrence and number of detection days in these shallow, non-island beach environments contrary to our initial hypothesis. Our data suggests annually variable, regional-scale use of beach environments not associated with barrier islands that likely serve as a travel corridor between drainages/offshore barrier islands, or as feeding zones; these movements may enhance the potential for mortality in Mississippi Sound

Morphometric Comparisons of the Gulf sturgeon (\u3ci\u3eAcipenser oxyrinchus desotoi\u3c/i\u3e Mitchill, 1815) In Western and Eastern Population Extremes

The Gulf sturgeon, Acipenser oxyrinchus desotoi Mitchill 1815, is an anadromous fish native to the Gulf of Mexico (GOM). This threatened species ascend northern GOM rivers ranging from the Pearl River, Louisiana to the Suwannee River, Florida. The drainage fidelity seen within this species coupled with the complex migration patterns create many unknowns concerning the functionality between drainages and size classes. Being a threatened species that cannot be sacrificed, morphometric measurements are difficult to acquire due to minimized handling times and non-lethal data collection methods. Seven morphometric measurements of Gulf sturgeon were compared between western and eastern GOM rivers and multiple size classes (juvenile, sub-adult, and adult). Principal Component, Discriminant Function, and Maximum Chance Criterion analyses were conducted and identified differentiating morphometrics and classified groupings among size classes and rivers of Gulf sturgeon. This morphometric approach has the potential to be used in parallel with molecular findings and should allow managers to identify sub-populations for a variety of threatened and endangered species

First Molecular Verification of a Marine-Collected Specimen of \u3ci\u3eAlosa alabamae\u3c/i\u3e (Teleostei: Clupeidae)

Alosa alabamae (Alabama Shad) is an imperiled anadromous species that reproduces in northern Gulf of Mexico drainages. To date, there have only been 4 vouchered specimens collected from marine waters, but none have been verified with molecular techniques. On 28 March 2013, we collected a single adult female in proximity to a barrier island (Petit Bois) off the coast of Mississippi. Microsatellite DNA analysis corroborated the identification of this individual and suggested that the specimen was most genetically similar to the group from the Pascagoula River drainage rather than other portions of the range. Thus far, research has been focused on the species\u27 freshwater life history, and it is crucial that more effort be directed toward documenting and understanding the full life history of this threatened fish

Consistent SpatioTemporal Estuarine Habitat Use during Emigration or Immigration of a Western Population of Gulf Sturgeon

<p>The spatial and seasonal occupancy by Gulf Sturgeon <i>Acipenser oxyrinchus desotoi</i> was estimated using acoustically tagged fish in the Pascagoula River estuary over a 3-year period (2010–2013) and was based on 131,381 detections. Juveniles spent considerably more time in the estuary than subadults or adults, but that varied by year. Gulf Sturgeon of all size-classes entered the acoustic array earlier when stream discharge was high (2011, 2012) compared with when it was lower (2010). The difference was about 14–28 d earlier for adults and subadults but only 12–17 d for juveniles. Temporally, there were no significant differences in occupancy by year or season for adults or subadults or by year for juvenile Gulf Sturgeon, suggesting repeated patterns across the 3 years of this study. Significant and consistent spatial differences in occupancy occurred by array zone, with juveniles occupying the West zone more than the East and River zones of the acoustic array; however, occupancy in the River zone was greater than in the East zone. We found similar patterns for subadults, with the highest occupancy in the West zone compared with the East zone; use was higher in the River zone than in the East zone but there was no difference between the River and West zones. In contrast, no year, season, or zone patterns were identified for adult Gulf Sturgeon, suggesting annual movement along a defined travel corridor (from the River zone to the West zone to offshore islands), with little time spent in the estuary. Adults appear to move quickly through the system during emigration (fall) and immigration (spring) compared with longer but more variable occupancy for juveniles and subadults. Our long-term data illustrates the importance of habitat connectivity in the recovery of Gulf Sturgeon and enhances earlier work on estuarine zones used during migration periods and estuarine residency; both are important for a better understanding of critical habitat maintenance and the development of a robust recovery plan.</p> <p>Received May 6, 2015; accepted September 2, 2015</p