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Pallid Sturgeon (Scaphirhynchus albus)

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CARL JAMES COLE


Department of Wildlife and Fisheries, Mississippi State University, Mississippi State, Mississippi, 39762, USA



Abstract

The Pallid Sturgeon Scaphirhynchusalbus is a lesser-documented species of sturgeon that has a native range from the Missouri to the Mississippi river, preferring open, turbid channels. General characteristics of the Pallid Sturgeon include: light gray coloration, elongated and flat snout, fringed barbels, small eyes, armored and long caudal peduncle (Ross 2001). On average, Pallid Sturgeon account for 1 in every 300 river sturgeon caught in the Mississippi River. (Kallemeyn et al. 1983). Due to their rarity and elusive nature, collecting life history and population abundance data on Pallid Sturgeon is a difficult task.



  • Fig. 1. Artistic interpretation of Scarphirhynchus albus
  • Fig. 2. Phenetic differences between Pallid Sturgeon and Shovelnose Sturgeon, relative to their barbels.
  • Fig. 3. Documented home ranges for Pallid Sturgeon. Image provided by: Montana Natural Heritage Program.
  • Fig. 4. Subtle differences between Pallid Sturgeon, Shovelnose Sturgeon, and their hybrids.

Context & Content[+] Expand

Class Actinopterygii, Order Acipenseriformes, Family Acipenseridae, Genus Scarphirhynchus, Species albus. Pallid Sturgeon are colloquially known as: white hackleback, white shovelnose sturgeon, or white sturgeon. The Pallid Sturgeon has very similar characteristics and ecological niches to its close relative the Shovelnose Sturgeon (Scaphirhynchus platorynchus). For instance, both species are found in open, free–flowing rivers and tributaries in the Missouri and Mississippi Rivers. Both species have a similar diet of insects and fish, albeit the Pallid Sturgeon tends to be more piscivorous. In the larval stage, the two are indistinguishable until they reach a total length (front of snout to end of tail) of ~10 mm. At this point, the barbels can be used as an indicator for the two species. The inner and outer barbels for Shovelnose sturgeon are relatively similar in length. Pallid Sturgeon's outer barbels tend to extend further than their inner barbels (Figure 2; Ross 2011). The striking similarities between Pallid Sturgeon and Shovelnose Sturgeon make differentiating the two species difficult.

General Characteristics[+] Expand

Pallid Sturgeon have a cylindrical body, with a skeleton composed primarily of cartilage. The dorsal side is typically a brown/grayish hue, while the ventral side is white. Pallid Sturgeon have very small eyes relative to their size, and do not rely on vision as much as other fish species. The snout is elongated and flattened, with a protrusible, toothless mouth located on the ventral side of the head (Keenlyne and Jenkins 1993). Two sets of barbels are located underneath the snout, in front of the mouth. The outer barbels are typically longer than the inner barbels (Ross 2011). Pallid Sturgeon have a long, slender, almost completely armored caudal peduncle. Pallid Sturgeon have 13–14 gill rakers, 37–43 dorsal rays, and 24–28 anal rays. Spiracles are absent from the Pallid Sturgeon as well (Ross 2001). At maturity, Pallid Sturgeon are larger than their relative, the Shovelnose Sturgeon (Ross 2011). By 13–14 years of age, most Pallid Sturgeon range from 29.5–35.4 in long, and can reach a weight of 68 lbs. (Ross 2001).

Distribution[+] Expand

Pallid Sturgeon can be found in the Missouri and Mississippi rivers and tributaries (Keenlyne and Jenkins 1993; Figure 3). In Mississippi, Pallid sturgeon primarily occur within free–flowing rivers and tributaries close by (Killgore 2007a).

Form & Function[+] Expand

Pallid Sturgeon are a member of the order Acipenseriformes, a group of primitive, ray-finned fishes. This order contains two extant families of fishes, the paddlefish and sturgeon. Pallid Sturgeon are very similar to its relative S. platorynchus, the shovelnose sturgeon. Pallid Sturgeon were described by Forbes and Richardson (1905). Initially, there was some controversy as to whether or not Pallid Sturgeon were a distinct species, or a sub-species of Shovelnose Sturgeon (Kallemeyn 1983). The two species not only share similar characteristics, such as form and function, but also similar life strategy and over-lapping ranges (Phelps 2010). During the larval stage, the two species are indistinguishable. Once they begin to mature, subtle differences in morphology begin to emerge that help scientists distinguish the two species. Outside of genetics, morphological differences are considered in order to help separate the two species. The coloration of the two is typically different, with the Pallid Sturgeon having a lighter color than the shovelnose. However, this cannot be used as a sole indicator. Barbel lengths of each species differ from one another. Outer barbels on the Pallid Sturgeon extend further than its inner barbels, where the barbels of the Shovelnose Sturgeon extend a uniform length. Pallid Sturgeon lack bony plates on their ventral side, whereas the bony plates are present in Shovelnose sturgeon. Shovelnose Sturgeon have only 30–36 dorsal rays. Only 18–23 anal rays are present on Shovelnose Sturgeon. (Kallemeyn 1983; Ross 2001). Unfortunately, these two species have the ability to hybridize, which only serves to complicate the issue of taxonomy (Figure 4.).

Ontogeny & Reproduction[+] Expand

Pallid Sturgeon, like other sturgeon, are a long–lived species. Sexual maturity occurs in male Pallid Sturgeon by ages 3–4, when they attain a length of 533–584mm (Kallemeyn 1983). Sexual maturity for female Pallid Sturgeon is believed to occur between ages of 15–20 years old (Dyer and Sandoval 1993). In addition to being slow to mature, Pallid Sturgeon do not spawn annually. Male sturgeon have a 2–3 year interval between spawning, and female sturgeon have a 3–10 year interval between spawning (Dyer and Sandoval 1993). Although there is a lack of detailed information about the reproduction of Pallid Sturgeon, strong inferences can be made in relation to the Shovelnose Sturgeon, which has extremely similar morphological, physiological, and genetic characteristics to the Pallid Sturgeon. Pallid Sturgeon prefer shallower, slower flowing river bends to reproduce. Habitat suitable for reproduction is common and not considered to be a limiting factor. Female sturgeon move upstream (10's – 1000's km) and spawn at the apex of their migration (DeLonay et al. 2009). Males migrate upstream as well, but choose several spawning locations along the way, and tend to be more sedentary (DeLonay et al. 2009). While the precise location of spawning for Pallid Sturgeon is still not well documented, it is believed that zones of convergent flow are preferred, in reference to other sturgeon species. Sturgeon eggs are adhesive, and sturgeons choose to utilize rock, gravel, and some sand substrates, but prefer rocky substrates (DeLonay et al. 2009). The reproductive cues for Pallid Sturgeon are believed to be: temperature, discharge, and day length. Temperature is the most highly suspected cue, due to the temperature correlating with proper zygote maturation and survival. This is noted by the fact that Pallid Sturgeon choose to spawn in the spring–early summer when the water is 14.2–20.8 C. However, it may simply be an internal, biological process that signifies the time for reproduction (DeLonay et al 2009). It is believed that the biggest hurdle for successful Pallid Sturgeon reproduction is the anthropological alteration of naturally flowing rivers (Dryer and Sandoval 1993). The creation of damns and the alteration of meandering rivers to stream–lined canals can disrupt and even inhibit Pallid Sturgeon from migrating to an acceptable spawning habitat. (DeLay et al 2009).

Ecology[+] Expand

Pallid Sturgeon utilize sandy or rocky, turbulent river bottoms along the Missouri and Mississippi rivers for their primary habitat (Dryer and Sandoval 1993). Including spawning, Pallid Sturgeons can have ranges varying from 10's to 1000's of kilometers (DeLonay et al. 2009). Pallid Sturgeon prefer depths ranging from 6–14 m deep, with water temperatures ranging from 0–30 C (32–86 F) (Dryer 1993; Herrala et al. 2014). The mean turbidity suitable for Pallid Sturgeon is 0.6–1 m/s (Herrala et al. 2014). Sturgeons are a benthic or drift–feeding species, relying mainly on their sensitive barbels to navigate. The diet of the Pallid Sturgeon is composed of invertebrates (11–16%) and other fish (60–74%). It should be noted that once Pallid Sturgeons reach a FL (fork length) of 600–700, they are much more piscivorous than Shovelnose Sturgeon (Dryer 1993). The niche that Pallid Sturgeon utilize is very similar to that of its relative, the Shovelnose Sturgeon. This is an indicator that the two species may be competing for similar resources, depending on their life stage (Killgore, 2007b).

Behavior[+] Expand

There is no information on the subject at this time

Genetics[+] Expand

Genetic studies on the Pallid Sturgeon are few. However, in 2000, the mitochondrial DNA of 78 individual sturgeon (Pallid Sturgeon, Shovelnose Sturgeon, and Alabama Sturgeon) was sampled in order to help better understand the potential genetic differences or similarities between the three species. The study concluded that the genetic differences between species were relatively minimal, yet significant enough for the three to be considered their own species. The study also concluded that hybridization between Pallid Sturgeon and Shovelnose Sturgeon was far more common in the southern range (lower Mississippi River) as opposed to their ranges further north in the Missouri river (Campton 2000).

Conservation[+] Expand

Pallid Sturgeon are less common than Shovelnose Sturgeon. Currently, Pallid Sturgeon are considered an endangered species. Primary causes for decline include: habitat loss, flow alteration by dams, accidental catch, pollution, and hybridization with Shovelnose Sturgeons (Kallemeyn 1983). Man–made alteration of natural rivers has reduced habitat that is essential for successful Pallid Sturgeon reproduction. Channelization of rivers causes a number of aquatic changes, including: increased turbidity, decreased water clarity, altered water temperature regimes, increased depth, decrease in snags, and changes in sediment (substrate), as well as preventing flow into backwaters (Dryer and Sandoval 1993). Impoundment of rivers creates an impassible barrier that often prevents the highly migratory Pallid Sturgeon from reaching a suitable spawning location (Dryer and Sandoval 1993). These alterations are also likely for the increasing amount of hybridization (DeLonay et al 2009). If unable to migrate up-stream to find suitable habitat to spawn, Pallid Sturgeon will simply choose the most suitable spawning habitat available (Dryer 1993). Unable to find its own spawning habitat, Pallid Sturgeon are forced to share spawning space with the much more common Shovelnose Sturgeon, which can lead to unintentional hybridization (Dryer 1993).

Acknowledgements[+] Expand

There is no information on the subject at this time

Remarks[+] Expand

There is no information on the subject at this time

Literature Cited[+] Expand

Campton D., A. Bass, F. Chapman, and B. Bowen. 2000. Genetic distinction of pallid, shovelnose, and Alabama sturgeon: Emerging species and the US Endangered Species Act. Conservation Genetics, vol. 1(1): 17–32.


DeLonay, A., R. Jacobson, D. Papoulias, D. Simpkins, and M. Wildhaber. 2009. Ecological Requirements for Pallid Sturgeon Reproduction and Recruitment in the Lower Missouri River: A Research Synthesis 2005–08. University of Nebraska–Lincoln.


Dryer M., A. Sandovol. 1993. Recovery Plan for the Pallid Sturgeon.US Fish and Wildlife Services.


Herrala, J. R., P. T. Kroboth, and N. M. Kuntz: Habitat use and selection by adult Pallid Sturgeon in the lower Mississippi River. Transactions of the American Fisheries Society, Vol 143: 153–163.


Kallemeyn L. 1983. Status of the Pallid Sturgeon (Scaphirhyncusalbus) Fisheries,Vol. 8, Issue 1


Hoover J., S. George, and K. Killgore. 2007. Diet of Shovelnose and Pallid Sturgeon in the free–flowing Mississippi River. Journal of Applied Ichthology, vol. 23(4): 494–499


Killgore, K., J. Hoover, S. George, B. Lewis, C. Murphy, and W. Lancaster. 2007. Distribution, relative abundance and movements of Pallid Sturgeon in the Lower Mississippi River. Journal of applied Ichthyology, vol. 23(4): 476–483


Killgore, K., J. Hoover, J. Kirk, S. George, B. Lewis, and C. Murphy, 2007. Age and growth of Pallid Sturgeon in the free–flowing Mississippi River. Journal of applied Ichthyology, vol 23: 452–456

Order[+] Expand

Acipenseriformes are an order of primitive ray–finned fishes that includes the sturgeons and paddlefishes, as well as some extinct families.

Family[+] Expand

Sturgeon is the common name used for some 25 species of fish in the family Acipenseridae, including the genera Acipenser, Huso, Scaphirhynchus and Pseudoscaphirhynchus. The term includes over 20 species commonly referred to as sturgeon and several closely related species that have distinct common names, notably sterlet, kaluga and beluga. Collectively, the family is also known as the true sturgeons. Sturgeon is sometimes used more exclusively to refer to the species in the two best-known genera, Acipenser and Huso.




About This Project.

This website is an ongoing project by Ichthyology students of the Department of Wildlife, Fisheries, and Aquaculture, within the College of Forest Resources to provide information on the biology and ecology of fishes that occur in Mississippi. These accounts were written by undergraduate students as a course assignment, generally follow the format of Mammalian Species, and nomenclature follows Nelson 1994.

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