Paddlefish Aquaculture

By Steven D. Mims and William L. Shelton

Paddlefish have become of increasing interest to the aquaculture community in recent years, particularly as a potential new source of seafood and caviar. Native to North America, paddlefish show great promise both domestically and internationally as a commercially viable farmed species.

Paddlefish Aquaculture examines all aspects of the biology and culture of these fish, exploring their physiology, production, end products and the economics underlying a successful paddlefish operation. Chapters specifically cover paddlefish biology, propagation and early culture techniques, production for meat and caviar, international culture and history, paddlefish food products, bioaccumulants of contaminants in paddlefish, parasites and diseases, and the economics of paddlefish aquaculture.

Paddlefish Aquaculture is a timely practical reference for researchers and producers interested in paddlefish.

• Language: English
• Publisher: Wiley
• Release date: Jul 2, 2015
• ISBN: 9781119060444

Book preview

Preface

The American paddlefish, Polyodon spathula, is one of two living species of paddlefishes in the family Polyodontidae; it is endemic to North America. The other member of the family is the Chinese paddlefish, Psephurus gladius. The American paddlefish is sometimes called the spoonbill catfish, or spoonfish. These unique fishes are among the earliest derived aquatic vertebrates; the American paddlefish is one of the largest (90 kg, 1.8 m long) freshwater fish in the United States and is found in 22 states that have large rivers and impoundments within the Mississippi River basin and adjacent Gulf Coastal drainages. Paddlefish are closely related to sturgeons, a group of fish having a mostly cartilaginous skeleton. The American paddlefish is a zooplankton filter feeder throughout most of its post-juvenile life, while the Chinese paddlefish is piscivorous as an adult.

Paddlefish, like sturgeons, are highly valued for their boneless, firm white meat, and for their darkly pigmented roe, which is processed into caviar. Historically, these fishes have been obtained through capture fisheries of wild populations, but because of their large sizes and late maturation, they have been repeatedly overexploited, beginning in the early 1900s, but more recently in the latter two decades of the 20th century. Many state agencies have closed the fisheries for sturgeons and paddlefish because of the perceived population declines, particularly at the peripheries of the ranges, and also under the threat of contamination by organochlorine pollutants such as polychlorinated biphenyls (PCBs) and chlordane. Illegal poaching of paddlefish increased in the late 1970s after the international caviar trade supplies from Caspian Sea sources were curtailed. In 1992, paddlefish was added to the Appendix II list of the United Nations’ Conference of the Parties of the Convention on International Trade of Endangered Species of Wild Fauna and Flora (CITES). Listing has complicated the international trade of paddlefish and their products because of the government-permitting requirements.

Aquaculture of paddlefish is increasingly becoming an alternative for supplying this species to the foodfish market, but federal and state regulations to protect natural populations from stock depletion often discourage farming. Commercial culture of paddlefish that is not subject to the vacillations of exploitive capture fisheries is needed in order to meet the growing demand for aquatic animal protein, as well as providing a source of quality caviar and other value-added products.

Paddlefish are gaining the interest of fish farmers in the United States, but perhaps even more rapidly in Eastern Europe, Russia, and China. This guide to the culture of paddlefish should meet an important need for fish farmers and educators in the United States and overseas. This book will provide a review of culture-related knowledge from the literature in the context of our personal experience. Available information on production of the American paddlefish outside its native range is included, and limited information on the endangered Chinese paddlefish is provided.

Steven D. Mims and William L. Shelton

Chapter 1

Introduction

William L. Shelton and Steven D. Mims

1.1 INTRODUCTION

The paddlefish Polyodon spathula (Walbaum 1792) is a large, long-lived, late maturing fish that retains many non-derived anatomical characteristics and possesses several special biological features. Its appearance alone stimulates interest, but many other attributes of this unique fish add to its attractiveness. Native distribution is limited to North America and it is one of the only two extant members of the family Polyodontidae. The family is included in the order Acipenseriformes, superorder Chondrostei, subclass Actinopterygii, class Osteichthyes.

The other surviving member of the family, the Chinese paddlefish Psephurus gladius (Martens 1861), is endemic to the Yangtze River of mainland China (Chenhan & Yongjun 1988; Rochard et al. 1991; Birstein 1993). Our discussion in this book will focus on the culture of the American paddlefish, but reference to the Chinese paddlefish will be specified when appropriate, and we will include more detailed information on the Southeast Asian species in Chapter 5.

A symposium on paddlefish biology and culture was organized and convened in the mid-1980s; the published proceedings was a milestone in collating and integrating important information, and providing an extensive bibliography (Dillard et al. 1986). An updated collection of literature citations was subsequently published (Georgi & Dingerkus 2001). In 1998, a symposium on exploitation and conservation of North American paddlefish and sturgeons was convened, and the proceedings were published (Williamson et al. 1999). Many other symposia and proceedings have focused on sturgeons and some of these have included material on paddlefish, for example, LeBreton et al. (2004). A comprehensive book was recently published on paddlefish biology (Paukert & Scholten 2009).

In the present volume, detailed information on the life history of the American paddlefish will be discussed in Chapter 2; however, some of the more unusual anatomical and physiological characteristics are worthy of mention by way of introduction (Coker 1923). The paddle-shaped rostrum has been the object of much conjecture. It has been speculated to play a mechanical role in feeding. Jordan and Evermann (1896) stated that They feed chiefly on mud and minute organisms contained in it, stirring it up with the spatulate snout… (Alexander 1914). Although an interesting thesis, this putative digging function would logically damage the delicate sensory elements that are now known to be a part of this structure. Alternatively, their swimming movement suggests another benefit of the flattened snout that has not been studied nor widely discussed. The paddlefish swim continuously, and as the snout passes through water in alternating side-to-side arcs, some upward force is obviously generated, which probably supplements the buoyancy afforded by the swim bladder. The swim bladder of paddlefish is relatively smaller than most other fishes, and does not appear to produce neutral buoyancy. The rostrum is vulnerable to damage and even loss, which probably has an adverse effect on swimming, but it also presents some potential problems for measurements of length. Thus, Ruelle and Hudson (1977) suggested reporting eye-fork length (body length) rather than the more conventional total length (TL) or standard length (SL).

Some less obvious morphological characteristics of paddlefish, but worthy of note, are the fins. The paired pectoral and pelvic fins, unlike most teleosts, are relatively fixed and inflexible, functioning during forward motion primarily as hydrodynamic maneuvering structures; they provide minimal maneuverability for backing or sculling. The dorsal and anal fins also have a rather rigid structural base. The caudal fin retains a primitive heterocercal morphology, in contrast to the more flexible homocercal tail fin of higher teleosts. The operculum projects backward in an extended flap and there is a functional spiracle behind each eye. The body surface generally lacks scales, except for a few bony rhomboid-shaped scales on, and partially embedded on either side of the caudal peduncle and under the opercular flap. A single pair of minute barbels are located just in front of the mouth on the ventral surface of the snout.

Internally, similarly primitive features in the digestive system include a large, fan-shaped pyloric cecum and a spiral valve in the hind gut. The reproductive organs are of an unusual type among fishes. The paired ovaries are described as gymnovarian, where the mature eggs rupture through the ovarian wall at ovulation and are shed into the body cavity instead of collecting in a central ovarian cavity. From the coelomic cavity, the eggs must enter into dorsally attached oviducts that adhere to the caudad portion of the ovaries. During spawning, the eggs must enter one of the dorsally located open funnels of the paired oviducts (Müllerian ducts). Spermatozoa pass from the testes through the kidneys via vasa deferentia, which are directly attached to the gonads, even though males retain vestigial Müllerian ducts and funnels. Mature ova are highly pigmented; consequently, these dark eggs are quite valuable in the caviar trade, and thus providing the impetus for heavy fishing exploitation. Paddlefish eggs are equivalent to sturgeon caviar in appearance, texture, and taste. Further, like other acipenserids, the eggs have multiple micropyles; paddlefish eggs have an average of about eight, but range from 3 to 20 (Linhart & Kudo 1997; Debus et al. 2002).

1.2 HISTORICAL FISHERY OVERVIEW

Generally, paddlefish inhabit large rivers, but they also occur in natural lakes, and frequently maintain populations that thrive in large impoundments, particularly if inflowing tributaries have conditions that will support reproduction. The natural historical range of the paddlefish included 26 states within the Mississippi River and Mobile Bay basins, and other Gulf of Mexico drainages westward to tributaries of Galveston Bay, Texas, but not eastward to the Apalachicola River system (Figure 1.1) (Smith-Vaniz 1968; Lee et al. 1980; Gengerke 1986; Hocutt & Wiley 1986; Pitman & Parks 1994; Jennings & Zigler 2009). Some other older records include the Great Lakes within the range (Hubbs & Lagler 1958).

c1-fig-0001

Figure 1.1. Paddlefish distribution. Dots indicate some of the recent stockings, and the single open circle in Georgia is the one known escape into previously uninhabited waters.

(Redrawn from Jennings & Zigler 2009.)

Despite some decline at the extremes of their range and extirpation from four states – Maryland, New York, North Carolina, and Pennsylvania – all declines are in the northeastern portion; paddlefish populations currently in 22 states are considered by most resource agencies to be generally in good condition – increasing in three states, stable in 14 states, unknown in three states, and declining in only two states (Graham 1997; Jennings & Zigler 2009). Between 1994 and 2006, despite continued vacillation, there has been no basin-wide collapse in stocks as was earlier predicted (Bettoli et al. 2009). However, there have been recent efforts to re-establish paddlefish in some extirpated areas and restore former levels through supplemental stocking in others (Argent et al. 2009; Bettoli et al. 2009; Grady & Elkington 2009) Reintroduction has proceeded in New York, Pennsylvania, West Virginia, and in select Oklahoma reservoirs. A 10-year stocking program (1990–99) was conducted in Texas, including several rivers within the previous range (Sabine and Trinity Rivers systems). Viable reservoir populations have been reproducing for decades in Lake of the Cherokees on the Grand/Neosho River but restocking efforts have occurred in that watershed in Kansas, and populations have been re-established within Keystone Reservoir on the Arkansas River, Oologah Reservoir on the Verdigris River, Eufaula Reservoir on the North and South Canadian Rivers, and in Lake Texoma on the Red River (Figure 1.1) (Patterson 2009; ODWC 2010).

Production and population dynamics are vital to managing and harvesting only surplus yield, and thus factors that affect individual growth can impact population yields. Growth varies in different bodies of water in relation to the abundance of food. Consequently, weight-length relations may vary considerably based on population differences. Sexual dimorphism in adults is minimal, but males are generally thinner than the more rotund condition of females; the contrast is much more evident in fish from rivers compared to one from reservoirs or ponds.

Paddlefish exploitation has varied from spates of elevated intense harvest, to intervals of low fishing pressure. For example, the harvest was high in the 1890s, reaching about 1000 metric tonnes (MT) in 1899, then rapidly declined in the early 1900s (Coker 1923), only to escalate more recently in the 1970s and 1980s (Carlson & Bonislawsky 1981). The periods of heavy harvest were stimulated by demand for caviar in conjunction with shortfalls from Caspian Sea production; the recent fishing pressure was also related to trade in this product, much of which was illicit (Waldman & Secor 1999; W.L. Shelton, Chair, ad hoc committee on paddlefish, 1981–83, unpublished data, Southern Division, American Fisheries Society). Because paddlefish are long-lived and late maturing, and are quite vulnerable to netting, populations are easily and rapidly overexploited. As periods of heavy fishing pressure occur, catch-per-effort deteriorates, and the fishery is usually abandoned soon after. With reduced fishing pressure, after a few years the population once again recovers. However, under environmentally stressed conditions, population recovery can be protracted, or may not occur at all if conditions are unsuitable for natural recruitment.

Habitat destruction and river modifications have affected distribution and abundance, as well as reducing the capacity for populations to rebound, particularly at the periphery of their range. Construction and operation of dams have altered water flow and quality, and often eliminated traditional spawning areas or interfered with access to these habitats (Sparrowe 1986; Unkenholtz 1986; Boreman 1997; Graham 1997). Further, other anthropogenic habitat alterations, such as environmental contamination, have adversely affected paddlefish populations (Pflieger 1975; Carlson & Bonislawsky 1981; Pasch & Alexander 1986). The wide distribution of paddlefish complicates status verification, not to mention management strategies. The populations are dispersed over many jurisdictional interstate boundaries, consequently concern over conflicts stimulated the organization of MICRA (Mississippi Interstate Cooperative Resource Association) in 1997, which consisted of multiple states and the US Fish and Wildlife Service (Graham 1997; Graham & Rasmussen 1999).

In 1983, commercial harvest of paddlefish was permitted in 11 states, but by 1994, only six states continued to allow non-sportfish exploitation (Graham 1997; Bettoli et al. 2009). Fourteen states currently manage angler harvest. Although recent commercial harvest has been about 10 times that removed by sport fishermen, angler harvest can be significant and periodically heavy. For the period of 2000–06, the annual average commercial harvest was about 47,000 fish for a total annual average of nearly 500 MT (Quinn 2009), while a single sport fishery in Oklahoma removed between 25,000 and 34,000 fish per year in one peak period (Gordon 2009). It is likely that commercial fisheries will continue to dwindle as exploitive fisheries are subject to the tragedy of the commons syndrome, and when commercial and sport interests are in conflict, the former invariably loses. Several factors come into play in this dichotomous demand: sport fishing interests are much more broadly based, funded by user fees (Wallop-Breaux and Dingell-Johnson taxes), and exploitive uses of natural resources generally are less supported by public opinion and agency commitment.

1.3 OVERVIEW OF NATURAL REPRODUCTION

Population stability obviously depends on successful reproduction and recruitment, whether it is natural or hatchery dependent. Little knowledge of paddlefish reproduction was known until Purkett (1961) reported on observations of natural spawning. Paddlefish move upstream after the water temperature has warmed to about 10–11°C and under the impetus of increased flow during spring flooding. They spawn over gravel substrate in the main current when water temperatures reach 13–16°C (Pasch et al. 1980; Wallus 1986). The eggs are adhesive, oval and heavily pigmented with melanophores (Ballard & Needham 1964; Shelton & Mims 1995). Eggs swell slightly in water and after fertilization; they are demersal and adhesive, sticking to gravel (Purkett 1961, 1963).

Hatchery production can facilitate restocking of depleted natural populations, or as a primary component of aquaculture (Graham 1986; Graham et al. 1986). Early development of artificial propagation was initiated in Missouri, primarily because of the following factors. Important details of paddlefish life history were initially described in the 1960s by Missouri biologists, where the paddlefish provided an important sport-fishery (Russell 1986). The development of large impoundments, one in particular on the Osage River, inundated the primary spawning area in central Missouri (Sparrowe 1986). Together these factors stimulated the development of artificial propagation techniques in order to perpetuate and maintain this valuable fishery (Graham et al. 1986).

1.4 INTERNATIONAL REGULATING FACTORS

In 1989, the US Fish and Wildlife Service was petitioned to include paddlefish on the list of Threatened and Endangered Species under the provisions of the endangered Species Act of 1973. This request for a threatened status was subsequently determined to be unjustified, but in 1992 paddlefish were added to the CITES Appendix-II listing (United Nations Convention on International Trade of Endangered Species of Wild Fauna and Flora). A CITES listing requires that the exporting country must have an export permit for international trade of paddlefish and their parts such as meat, caviar, and so forth. When an exporting country issues a permit for an Appendix-II listed species, it purports that the species was legally acquired and has not impacted wild populations. All sturgeons worldwide are currently listed under the provisions of CITES (Khodorevskaya et al. 1997; Pikitch et al. 2005). In general, CITES provides an international mechanism for the maintenance of biodiversity by protecting listed species of wildlife and plants from overexploitation through international trade. Paddlefish have been included in this system, in part to attempt to regulate illegal trade in caviar. Paddlefish and sturgeon roe are similar and differential identification can present an enforcement enigma. Further, paddlefish possession, transport, propagation, and culture are independently regulated by state laws. Therefore, legal considerations should be checked before committing to paddlefish culture.

1.5 WHY CULTURE PADDLEFISH?

Paddlefish are native to more than half the United States and well suited for temperate climates. They are filter feeders and are therefore ecologically efficient; they demonstrate rapid growth (2–4 kg/year) in water abundant in zooplankton. Reproduction and culture techniques are well developed for producing paddlefish stock, whether for mitigation or food production. Interest in culture in the United States is stimulated by conservation motivation as well as managing populations for the sport fisheries. Propagation to support culture for food will probably have its greatest potential in fish-growing areas outside the United States, particularly in areas where polyculture is practiced and where the importance of paddlefish as a commodity is greater than a perceived recreational value. Paddlefish have boneless white meat and their grey to black roe is processed into caviar; both are valuable products and permit entry into diverse global marketplaces.

These various components of paddlefish culture will be developed in more detail in subsequent chapters. Some preliminary discussion of fish culture will be included in Chapter 2, but more detailed discussion of important components of culture will be detailed in other chapters, including artificial propagation, special techniques for reproductive manipulation, nursing, and grow-out. In addition, preparation of specialty products will be elaborated.

REFERENCES

Alexander, M.L. (1914) The paddle-fish (Polyodon spathula). (Commonly called spoonbill catfish). Transactions of the American Fisheries Society 44:73–78.

Argent, D.G., Lorson, R., McKeown, P., Carlson, D.M., & Clancy, M. (2009) Paddlefish restoration to the upper Ohio and Allegheny River Systems. In: Paddlefish Management, Propagation, and Conservation in the 21st Century (eds C.P. Paukert & G.D. Scholten), pp. 397–409. American Fisheries Society Symposium 66, Bethesda, MD.

Ballard, W.W. & Needham, R.G. (1964) Normal embryonic states of Polyodon spathula. Journal of Morphology 114:465–477.

Bettoli, P.W., Kerns, J.A., & Scholten, G.D. (2009) Status of paddlefish in the United States. In: Paddlefish Management, Propagation, and Conservation in the 21st Century (eds C.P. Paukert & G.D. Scholten), pp. 23–38. American Fisheries Society Symposium 66, Bethesda, MD.

Birstein, V.J. (1993) Sturgeons and paddlefishes: Threatened fishes in need of conservation. Conservation Biology 7:773–787.

Boreman, J. (1997) Sensitivity of North American sturgeon and paddlefish to fishing mortality. Environmental Biology of Fishes 48:399–405.

Carlson, D.M. & Bonislawsky, P.S. (1981) The paddlefish (Polyodon spathula) fisheries of the Midwestern United States. Fisheries 6:17–27.

Chenhan, L. & Yongjun, Z. (1988) Notes on the Chinese paddlefish, Psephurus gladius (Martens). Copeia 1988:482–484.

Coker, R.E. (1923) Methuselah of the Mississippi. The Scientific Monthly 16:89–103.

Debus, L., Winkler, M., & Billard, R. (2002) Structure of micropyle surface on oocytes and caviar grains in sturgeons. International Review of Hydrobiology 87:585–603.

Dillard, J.G., Graham, L.K., & Russell, T.R. (1986) The Paddlefish: Status, Management and Propagation. North Central Division, Americana Fisheries Society, Special Publication 7, Columbia, MO.

Gengerke, T.W. (1986) Distribution and abundance of paddlefish in the United States. In: The Paddlefish: Status, Management and Propagation (eds J.G. Dillard, L.K. Graham, & T.R. Russell), pp. 22–35. American Fisheries Society, North Central Division, Special Publication 7, Bethesda, MD.

Georgi, T.A. & Dingerkus, G. (2001) Paddlefish Bibliography. Doane College, Crete, Nebraska.

Gordon, B. (2009) Paddlefish harvest. In: Paddlefish Management, Propagation, and Conservation in the 21st Century (eds C.P. Paukert & G.D. Scholten), pp. 223–233. American Fisheries Society Symposium 66, Bethesda, MD.

Grady, J.M. & Elkington, B.S. (2009) Establishing and maintaining paddlefish populations by stocking. In: Paddlefish Management, Propagation, and Conservation in the 21st Century (eds C.P. Paukert & G.D. Scholten), pp. 385–396. American Fisheries Society Symposium 66, Bethesda, MD.

Graham, L.K. (1986) Establishing and maintaining paddlefish populations by stocking. In: The Paddlefish: Status, Management and Propagation (eds J.G. Dillard, L.K. Graham, & T.R. Russell), pp. 96–104. American Fisheries Society, North Central Division, Special Publication 7, Bethesda, MD.

Graham, K. (1997) Contemporary status of the North American paddlefish, Polyodon spathula. Environmental Biology of Fishes 48:279–289.

Graham, L.K. & Rasmussen, J.L. (1999) A MICRA perspective on closing paddlefish and sturgeon commercial fisheries. In: Symposium on the Harvest, Trade and Conservation of North American Paddlefish and Sturgeon (eds D.F. Williamson, G.W. Benz, & C.M. Hoover), pp. 130–142. TRAFFIC North America, World Wildlife Fund, Washington, DC.

Graham, L.K., Hamilton, E.J., Russell, T.R., & Hicks, C.E. (1986) The culture of paddlefish – A review of methods. In: The Paddlefish: Status, Management and Propagation (eds J.G. Dillard, L.K. Graham, & T.R. Russell), pp. 78–94. American Fisheries Society, North Central Division, Special Publication 7, Bethesda, MD.

Hocutt, C.H. & Wiley, E.O. (eds) (1986) Zoogeography of North American Freshwater Fishes. John Wiley & Sons, Inc., New York.

Hubbs, C.L. & Lagler, K.F. (1958) Fishes of the Great Lakes Region. Publication no. 26, Cranbrook Institute of Science.

Jennings, C.A. & Zigler, S.J. (2009) Biology and life history of paddlefish in North America: an update. In: Paddlefish Management, Propagation, and Conservation in the 21st Century (eds C.P. Paukert & G.D. Scholten), pp. 1–22. American Fisheries Society, Symposium 66, Bethesda, MD.

Jordan, D.S. & Evermann, B.W. (1896) The Fishes of North and Middle America: A Descriptive Catalogue of the Species of Fish-like Vertebrates Found in the Waters of North America, North of the Isthmus of Panama. Reprinted in 1963 as Bulletin of the Smithsonian Institute, U.S. National Museum, number 12, vol. 1, Washington, DC.

Khodorevskaya, R.P., Dovgopol, G.F., Zhuravleva, O.L., & Vlasenko, A.D. (1997) Present status of commercial stocks of sturgeon in the Caspian Sea basin. Environmental Biology of Fishes 48:209–219.

LeBreton, G.T.O., Beamish, F.W.H., & McKinley, R.S. (2004) Sturgeons and Paddlefish of North America. Kluwer Academic Publishers, New York.

Lee, D.S., Gilbert, C.R., Hocutt, C.H., Jenkins, R.E., McAllister, D.E., & Stauffer, J.R. (1980) Atlas of North American Freshwater Fishes. North Carolina Biological Survey, North Carolina State Museum of Natural History, Raleigh, NC.

Linhart, O. & Kudo, S. (1997) Surface ultrastructure of paddlefish eggs before and after fertilization. Journal of Fish Biology 51:573–582.

Martens, E. von (1861) Uber einen neuen Polyodon (P. gladius) aus dem Yantsekiang und uber die Sogenannten Glaspolypen. Monatsberichte der Deustchen Akademie der Wissenshaften zu Berlin 1861:476–479.

ODWC (Oklahoma Department of Wildlife Conservation) (2010) Website. Available at: http://www.wildlifedepartment.com/

Pasch, R.W. & Alexander, C.M. (1986) Effects of commercial fishing on paddlefish populations. In: The Paddlefish: Status, Management and Propagation (eds J.G. Dillard, L.K. Graham, & T.R. Russell), pp. 46–53. American Fisheries Society, North Central Division, Special Publication 7, Bethesda, MD.

Pasch, R.W., Hackney, P.W., & Holbrook. J.A. (1980) Ecology of the paddlefish in Old Hickory Reservoir, Tennessee, with emphasis on first-year life history. Transactions of the American Fisheries Society 109:157–167.

Patterson, C.P. (2009) Ecology of a reintroduced population of paddlefish, Polyodon spathula, in Lake Texoma. Master’s thesis, Oklahoma State University, Stillwater.

Paukert, C.P. & Scholten, G.D. (eds) (2009) Paddlefish Management, Propagation, and Conservation in the 21st Century; Building from 20 years of Research and Management. American Fisheries Society, Symposium 66, Bethesda, MD.

Pfielger, W.L. (1975) The Fishes of Missouri. Missouri Department of Conservation. Jefferson City, MO.

Pikitch, E.K., Doukakis, P., Lauck, L., Chakrabarty, P., & Erickson, D.L. (2005) Status, trends and management of sturgeon and paddlefish fisheries. Fish and Fisheries 6:233–265.

Pitman, V.M. & Parks, J.O. (1994) Habitat use and movement of young paddlefish (Polyodon spathula). Journal of Freshwater Ecology 9:181–189.

Purkett, C.A. (1961) Reproduction and early development of paddlefish. Transactions of the American Fisheries Society 90:125–129.

Purkett, C.A. (1963) The paddlefish fishery of the Osage River and the Lake of the Ozarks, Missouri. Transactions of the American Fisheries Society 92:239–244.

Quinn, J.W. (2009) Harvest of paddlefish in North America. In: Paddlefish Management, Propagation, and Conservation in the 21st Century (eds C.P. Paukert & G.D. Scholten), pp. 203–221. American Fisheries Society, Symposium 66, Bethesda, MD.

Quinn, J.W., Posey, W.R., Leone, F.J., & Limbird, R.L. (2009) Management of the Arkansas River Commercial paddlefish fishery with check stations and special seasons. In: Paddlefish Management, Propagation, and Conservation in the 21st Century (eds C.P. Paukert & G.D. Scholten), pp. 235–275. American Fisheries Society, Symposium 66, Bethesda, MD.

Rochard, E., Williot, P., Castelnaud, G., & Lepage, M. (1991) Éléments de systematique et de biologie des populations sauvages d'esturgeons. In: Acipencer (ed. P. Williot), pp. 475–507. Cemagref, Bordeaux, France.

Ruelle, R. & Hudson, P.L. (1977) Paddlefish (Polyodon spathula): Growth and food of young of the year and a suggested technique for measuring length. Transactions of the American Fisheries Society 106:609–613.

Russell, T.R. (1986) Biology and life history of the paddlefish – a review. In: The Paddlefish: Status, Management and Propagation (eds J.G. Dillard, L.K. Graham, & T.R. Russell), pp. 2–20. American Fisheries Society, North-Central Division, Special Publication 7, Bethesda, MD.

Shelton, W.L. & Mims, S.D. (1995) Oocyte staging in paddlefish, Polyodon spathula. Transactions of the Kentucky Academy of Science 56:22–27.

Smith-Vaniz, W.F. (1968) Freshwater Fishes of Alabama. Auburn University, Agricultural Experiment Station, AL.

Sparrowe, R.D. (1986) Threats to paddlefish habitat. In: The Paddlefish: Status, Management and Propagation (eds J.G. Dillard, L.K. Graham, & T.R. Russell), pp. 36–45. American Fisheries Society, North Central Division, Special Publication 7, Bethesda, MD.

Unkenholtz, D.G. (1986) Effects of dams and other habitat alterations on paddlefish sportfisheries. In: The Paddlefish: Status, Management and Propagation (eds J.G. Dillard, L.K. Graham, & T.R. Russell), pp. 54–61. American Fisheries Society, North Central Division, Special Publication 7, Bethesda, MD.

Walbaum, J.J. (1792) Petri artedi renovati, bibliotheca et philosophia ichthyologica. Ichthyologicae pars 3, Grypsewaldiae.

Waldman, J.R. & Secor, D.H. (1999) Caviar trade in North America: an historical perspective. In: Proceedings of the Symposium on Harvest, Trade and Conservation of North American Paddlefish and Sturgeon (eds D.F. Williamson, G.W. Benz, & C.M. Hoover), pp. 77–89. TRAFFIC North America/World Wildlife Fund, Washington, DC.

Wallus, R. (1986) Paddlefish reproduction in the Cumberland River and Tennessee River systems. Transactions of the American Fisheries Society 115:424–428.

Williamson, D.F., Benz, G.W., & Hoover, C.M. (eds) (1999) Proceedings of the Symposium on the Harvest, Trade and Conservation of North American Paddlefish and Sturgeon. TRAFFIC North America/World Wildlife Fund, Washington, DC.

Chapter 2

Biology

William L. Shelton

2.1 INTRODUCTION

The biological aspects of a fish, paddlefish in particular, are important to the understanding of form and functional relationships, how the environment and habitat have affected natural distribution, how anthropogenic perturbations and exploitation have affected the current status of populations, and the need to culture paddlefish. In order to manage a species and manipulate various life history traits for practical considerations, understanding of these components of basic biology is a primary requisite.

2.2 TAXONOMIC RELATIONSHIPS

The following taxonomic summary was condensed from Georgi and Dingerkus (2001). The American paddlefish and the Chinese paddlefish are the only two extant species of the family and these are geographically separated. Throughout most of this book, discussion will focus on the American paddlefish and if reference is made to the Chinese paddlefish, it will be specified. This Asian species will be discussed in a later chapter.

TAXONOMIC HIERARCHY

Phylum: Chordata

Subphylum: Vertebrata (Craniata)

Superclass: Pisces Linnaeus, 1758 – Fishes

Class: Osteichthyes Huxley, 1880 – Bony Fishes

Subclass: Actinopterygii Cope, 1887 – Ray-finned Fishes

Infraclass: Chondrostei Müller, 1844 – Chondrostean Fishes

Order: Acipenseriformes Berg, 1940 – Sturgeons and Paddlefishes

Family: Polyodontidae Bonaparte, 1837 – Paddlefishes

Genus: Polyodon Lacepède, 1798 – American paddlefish

Polyodon spathula (Walbaum 1792)

Distribution: Mississippi River and some adjacent Gulf Coast drainages of the United States

Genus: Psephurus Günther, 1873 – Chinese paddlefish

Psephurus gladius (Martens 1861)

Distribution: Yangtze River, China

Walbaum (1792) first described the American paddlefish as Squalus spathula; however, by 1798 Lacepède placed this species in the genus Polyodon (Vasetskiy 1971). It has been categorized under various names, but these subsequently have been relegated to synonomy officially or redundancy colloquially (Jordan & Evermann 1896). While several regional names have been used such as spadefish, duck-bill cat, spoonbill catfish, spooney, and so forth (Alexander 1914; Lund 1995; Georgi & Dingerkus 2001), the preferred common name is paddlefish (Nelson et al. 2004) – even this name was earlier hyphenated.

In the original 1792 description of the American paddlefish, Walbaum considered it to be a shark, which he called Squalus spathula; however, in 1798 Lacepede corrected this erroneous classification and placed the American paddlefish in the genus Polyodon. The first known published account of the paddlefish was in 1673, but even this report may have been preceded a few years by a vague reference to the sighting of a sturgeon-like fish with a snout (Rostlund 1951).

2.3 BIOGEOGRAPHY

2.3.1 Native Range

The family Polyodontidae includes only two extant species, the American Paddlefish, Polyodon spathula (Walbaum) and the Chinese paddlefish, Psephurus gladius (Martens) (Rochard et al. 1991; Birstein 1993; Billard & LeCointre 2001). The distribution of the Chinese paddlefish, Psephurus gladius, is limited to the Yangtze River of China (Nelson 2004); the North American species, Polyodon spathula (Bemis et al. 1997) is endemic to North America. The Asian species reaches a much larger size than the American paddlefish and it is piscivorous. For more information on the Chinese paddlefish, see Vasetskiy (1971), Mims et al. (1993), Wei et al. (1997), and Hochleithner and Gessner (1999). More information about the culture of Psephurus is provided in Chapter 5.

2.3.2 River Systems

The natural distribution of Polyodon spathula is within the Mississippi River drainage, including the upper Missouri, Arkansas, and Ohio rivers, and also the Mobile River drainage; this range encompasses 26 contiguous states (see Figure 1.1). Historically, the species was also found in some of the other Gulf Coast drainage systems (Hocutt & Wiley 1986; Graham 1997) and in the Great Lakes, with certainty in Lake Erie (Hubbs & Lagler 1958; Lee et al. 1980), although the Lake Erie report might have been immigrants via canal systems (Jennings & Zigler 2009).

Paddlefish and sturgeon diverged phylogenetically about 150 million years ago (Birstein & DeSalle 1998) and geographic barriers isolated some of the Gulf Coast drainages from the Mississippi River since the Pliocene epoch, some 12 million years ago. However, the natural barrier between the Mobile Bay population and the Tennessee River population has recently been breached by the construction of the Tennessee-Tombigbee Waterway, and these isolated communities may once again intermingle via this man-made system. This artificial connection between the Tombigbee and Tennessee rivers is composed of a series of reservoirs that were constructed between 1971 and 1984 and added to the downstream navigational modifications completed earlier (O’Keefe & Jackson 2009). However, O’Keefe & Jackson’s studies have reported little verified influx from the Tennessee River via this connection and further, that the paddlefish population numbers are low within the reservoirs of this navigational system.

Other Gulf Coast drainage systems to the west of the Mobile River and westward from the Mississippi River to the Galveston Bay, San Jacinto River drainage of Texas also once contained paddlefish (Hocutt & Wiley 1986), but not the Apalachicola system of Alabama, Georgia, and Florida to the east (Smith-Vaniz 1968). Although an accidental flood-related release from a commercial fish farm in Georgia in 1994 introduced paddlefish into the Flint-Apalachicola system, survival and establishment have not been reported (Fuller et al. 1999). See also Historical Fishery Overview in Chapter 1.

2.3.3 Reservoir Systems

Generally, paddlefish inhabit large rivers, but they also occur in backwater areas, as well as in reservoirs, but riverine conditions must be available for spawning so that recruitment maintains and replenishes the lentic populations. Construction of dams to impound major rivers for flood control or irrigation has been widespread in the United States (Jenkins 1970; Petts 1984). The period between 1950 and the 1980s saw the greatest increase in large impoundments (> 200 ha); between 1962 and 1968, over 200 major dams were completed each year. In 1968, there were 1320 large impoundments in the United States, and by 1980 the total exceeded 1600 (Summerfelt 1986). Riverine fisheries were greatly impacted, particularly for migratory species. The transition from a lotic to lentic habitat alters the ecological conditions, and while productivity is enhanced for some species, the loss of current often results in the demise of others. Paddlefish have been affected by limits to their upstream migration and access to suitable spawning habitat, but biologically they have benefitted because of the increase in productivity and greater food supply.

While upstream or downstream passage past dams can occur through navigational locks, gated spillways are usually greater impediments to free movement than crested spillways (Mettee et al. 2009). For those impoundments where suitable riverine habitat still exists upstream, paddlefish have thrived. Numerous examples of the importance and interdependence of major tributary flow into reservoirs have been documented.

Examples of two such thriving post-impoundment residual populations are in Grand Lake Oklahoma on the Neosho River, which was impounded in 1940, and Keystone Reservoir on the Arkansas River, which was impounded in 1964; both are non-navigation system reservoirs. Also a number of reservoirs in the Tennessee Valley Authority (TVA) system, which were constructed in the 1940s, contain healthy paddlefish populations and many of these are mainstream with navigational locks. In the upper Missouri River system where six mainstream reservoirs had been completed by 1982 leaving only an 88-km stretch of unmodified river channel in the original 1200 km of riverine habitat, paddlefish apparently are thriving but supplemental stocking has also been ongoing (Braaten et al. 2009).

The Lake of the Ozarks on the Osage River, Missouri, has had variable differential effects on the paddlefish population. A productive sport fishery for paddlefish existed through the 1960s, including the post-impoundment period; however, after the Truman dam was completed upstream of Lake of the Ozarks in 1977, the most important spawning