William T. Slack

THE OCCURRENCE OF NON-INDIGENOUS NILE TILAPIA, OREOCHROMIS NILOTICUS (LINNAEUS) IN COASTAL MISSISSIPPI, USA: TIES TO AQUACULTURE AND THERMAL EFFLUENT

We studied the distribution and abundance of Nile tilapia, Oreochromis niloticus near two aquaculture facilities for two years in coastal wetlands in southeastern Mississippi, USA. In 280 collections, we represented 29 families, 65 taxa, and 86,415 fishes with a variety of gear types. Oreochromis niloticus ranked sixth in abundance overall and ranked second among those stations sampled in the Pascagoula River watershed and sixteenth among Coastal River stations. Water temperature downstream from the facility effluents was always warmer than ambient, and at the Pascagoula River facility, it never dropped below 15.1°C over the three years examined. Thus, normal environmental conditions, the presence of the downstream thermal refuge, and the generally low salinity of the bayous of our region all combine to provide a quality environment for continued survival of released fish. Furthermore, O. niloticus seem to spawn year-round, and fish as small as 79.9 mm TL were found to carry mature eggs, suggesting that, if they are born early in the season, they could reproduce during their first summer of life. Further spread of O. niloticus and introduction of new species are expected as aquaculture expands. The philosophy that allows the escape or release of non-indigenous taxa into our present landscape, justified by the belief that species will not survive or become established, is fallible.

Spawning and Associated Movement Patterns of Gulf Sturgeon in the Pascagoula River Drainage, Mississippi

Abstract Gulf sturgeon Acipenser oxyrinchus desotoi are federally listed as threatened, the principal reasons for population declines being habitat loss due to dams, overfishing, and water quality deterioration. The timing of freshwater migration and the locations and habitat features of spawning areas are undocumented for Gulf sturgeon in the Pascagoula River drainage. Our objectives were to identify and characterize spawning areas, determine spring movement patterns, and document homing fidelity by gill netting and radio-tracking. Through collection and rearing of Gulf sturgeon eggs, we verified that the Bouie River north of Hattiesburg, Mississippi (250 river kilometers upstream from the mouth of the Pascagoula River), is a spawning area. We also documented homing fidelity in the Bouie River using radiotelemetry and capture data. Prolonged residence and overwintering of Gulf sturgeon were observed near the Bouie River spawning area. This behavior may be caused by the modified nature of this portion of ...

Feeding Habitats of Young-of-year River Sturgeon Scaphirhynchus spp. in the Lower Mississippi River

Abstract The feeding habitats of young-of-year river sturgeon Scaphirhynchus spp. from the Lower Mississippi River were evaluated. Seventy specimens collected between 2001 and 2010 (99%: 2006–2010) were dissected and gut contents analyzed. The macrohabitats and habits associated with sturgeon prey items (primarily benthic macroinvertebrates) were used to make inferences about habitat use by young-of-year river sturgeon. These findings indicate that young river sturgeon inhabiting the Lower Mississippi River feed primarily over sandy benthos, most likely in channel habitats. The majority of prey items (64.0%) consumed by young-of-year river sturgeon belong to a single subgroup of Chironomidae (Diptera: Chironominae: Harnischia complex) of which several genera, including Chernovskiia, Cryptochironomus, Gillotia, Paracladopelma, Robackia, and Saetheria, are known to be primary inhabitants of this macrohabitat.

Seasonal and Tidally Driven Reproductive Patterns in the Saltmarsh Topminnow, Fundulus jenkinsi

Fundulus jenkinsi is recognized federally and within a number of northern Gulf of Mexico states as a Species of Concern. Little is known about its life history, but a detailed reproductive histology study of F. jenkinsi can provide the foundation needed to quantify reproductive parameters in this rare species in need of conservation. Monthly gonadosomatic index (GSI) of male and female F. jenkinsi indicated a spawning season from April through August. However, ovarian histological analysis suggested March through August was a more accurate spawning season. The multiple oocyte stages within F. jenkinsi in the spawning capable reproductive phase indicates batch spawning, similar to other members of its family. Many estuarine members of the family Fundulidae exhibit a semilunar spawning pattern, yet the oocyte composition of ovaries of F. jenkinsi suggested spawns occur multiple days around the time of spring tides both within a population and on the individual level. Spawning did not occur on neap tides, and no late secondary growth vitellogenic oocytes (SGl) were found in the majority of females captured during neap tide. The lack of SGl oocytes in females during the spawning season suggests the necessity for establishing a new sub-phase within the spawning capable phase, termed the redeveloping sub-phase. This new sub-phase is applicable to other batch spawning species with group synchronous oocyte development. This work contributes to a better understanding of the importance of intertidal saltmarsh habitat to F. jenkinsi, as spawning intensity appears to increase with tidal height and marsh inundation.

Morphology, Density, and Spatial Patterning of Reproductive Bowers In an Established Alien Population of Nile Tilapia, Oreochromis niloticus

ABSTRACT In coastal Mississippi aquatic systems, Nile tilapia (Oreochromis niloticus) has been introduced via aquaculture practices and appears to have established breeding populations. However, little is known about characteristics of bowers in non-native environments or if reproductive activities vary with water temperature. Therefore, we examined bower morphology, sediment composition, density, spatial pattern, and the distribution of bowers and reproductive leks in relation to thermal gradients within a power plant cooling pond. We found that the Nile tilapia has the appropriate materials for building bowers, can establish active breeding leks, and distributes along thermal gradients. All of these attributes allow for successful invasion and establishment into non-native environments.

Nymphal Cicadas (Hemiptera: Cicadidae) as a Prey Item of Shovelnose Sturgeon (Scaphirhynchus platorynchus) in the Lower Mississippi River

Abstract Stomach contents of 3 Scaphirhynchus platorynchus (Shovelnose Sturgeon) collected in the Lower Mississippi River in January 2010 yielded 44 specimens of cicada nymphs, Diceroprocta sp. The fish were collected during a sudden rise in water level. The floodplain-dwelling cicada were likely washed out of their terrestrial habitat and into the river, where opportunistic sturgeon were foraging.

Occupancy Patterns of Gulf Sturgeon, Acipenser oxyrinchus desotoi, Associated with Ship Island, Mississippi

ABSTRACT Vick, P.E.; Peterson, M.S.; Slack, W.T., and Grammer, P.O., 2018. Occupancy patterns of Gulf Sturgeon, Acipenser oxyrinchus desotoi, associated with Ship Island, Mississippi. In order to reduce wave energy associated with tropical storms and hurricanes in the western Mississippi Sound, the Mississippi Coastal Improvements Program will close a 5.6 km breach (i.e. Camille Cut) separating East and West Ship Island, Mississippi, and restore sediments to the southern shoreline of East Ship Island. As part of this program, federally designated critical Gulf Sturgeon habitat associated with Ship Island was monitored to establish baseline patterns of use prior to island restoration using a passive acoustic array during overwintering periods from 2011 to 2014. Gulf Sturgeon of both western and eastern populations occupied the passes, cuts, and ends of Ship Island over the study period, but no difference in occupancy was observed among four initially established zones. However, when comparing the new most eastern zone, Dog Keys Pass, to the four initial zones, occupancy was four times greater in this zone than any other monitored zone, indicative of foraging behavior associated with high abundance of benthic resources. Reconnecting East and West Ship Island through filling Camille Cut proper may increase Gulf Sturgeon occupancy in Dog Keys Pass and other areas near the ends and passes of the barrier islands. The loss of Camille Cut proper as critical habitat may be partially augmented by “new” nearshore habitat north and south of Camille Cut; however, it is uncertain whether filling in Camille Cut will alter the physical components of the habitat, causing a shift in benthic prey availability and, thus, quality of forage habitat.

Stability, persistence and habitat associations of the pearl darter Percina aurora in the Pascagoula River System, southeastern USA

The southeastern United States represents one of the richest collections of aquatic biodiversity worldwide; however, many of these taxa are under an increasing threat of imperilment, local extirpation, or extinction. The pearl darter Percina aurora is a small-bodied freshwater fish endemic to the Pearl and Pascagoula river systems of Mississippi and Louisiana (USA). The last collected specimen from the Pearl River drainage was taken in 1973, and it now appears that populations in this system are likely extirpated. This reduced the historical range of this species by approximately 50%, ultimately resulting in federal protection under the US Endangered Species Act in 2017. To better understand the current distribution and general biology of extant populations, we analyzed data collected from a series of surveys conducted in the Pascagoula River drainage from 2000 to 2016. Pearl darters were captured at relatively low abundance (2.4 ± 4.0 ind. per collection) from 57% of 308 collections. We identified strong relationships between local habitat variables and occurrence and catch-per-unit-effort (CPUE) of pearl darters. Pearl darters were frequently encountered and in greater abundance in depositional areas characterized by low-velocity habitats and finer substrates. Patterns of occurrence and CPUE were spatiotemporally variable across years; however, repeated collections from a subset of localities collected across a decade or more indicated long-term persistence and stability, suggesting population resilience throughout the Pascagoula River drainage.

Big River Benthos: Linking Year Round Biological Response to Altered Hydrological Regimes

Abstract : The Mississippi River is heavily relied upon for commercial navigation, but it is also home to a diversity of organisms adapted to large river habitats. Macroinvertebrates have long been used as habitat/water quality indicators in wadeable streams, but because of sampling difficulty, large rivers have been understudied. Herein, the authors focused on the benthic macroinvertebrate fauna as indicators of biological response to anthropogenic alterations to flow particularly to closure dikes within naturally occurring secondary channels of the Lower Mississippi River. During mid to high river stages, water flows over dikes into secondary channels, but during low river stages, many side channels become disconnected from the main channel at the upstream end. Nine secondary channels spanning a gradient of hydrological connectivity to the main river channel at low river stages were assessed. Main and secondary channels were sampled for benthic macroinvertebrates in May and June 2014 using a Ponar grab and benthic sled, respectively. The objective was to determine whether temporary hydrological disconnection from the main channel during low river stages had a legacy effect on benthic community structure in the succeeding year. There was a significant positive relationship between taxonomic richness in 2014 and hydrological connection of secondary channels in the previous year (2013), indicating a legacy effect of connectivity on macroinvertebrate diversity of secondary channels. These findings contribute to a better understanding of ecological response to altered flow regimes and help document benefits of restoring connectivity between secondary channels and the Mississippi River main channel.

First Recorded Occurrence of Oncorhynchus mykiss (Rainbow Trout) in Louisiana

Abstract An individual of Oncorhynchus mykiss (Rainbow Trout) was collected in a diversion canal of the Mississippi River known as Davis Pond located at river kilometer (RKM) 191.03 in St. Charles Parish near Luling, LA. This locality is the southern-most record for Rainbow Trout in the Mississippi River Basin and represents a range extension of 733.5 RKM south from the previous southern-most locality at Lake Whittington, Bolivar County, MS. The collection we report here also represents the first documented record of Rainbow Trout in Louisiana.