Identification Key to Sturgeons and Paddlefish of North America

APPENDIX

IDENTIFICATION KEY TO STURGEONS AND PADDLEFISH OF NORTH AMERICA

MARTIN HOCHLEITHNER1 AND PAUL VECSEI2 1AquaTech, Unterbrunnweg 3, Kitzbuehel, Austria 6370, E-mail: aquaculture@nextra.at 2Warnell School of Forest Resources, University of Georgia, Athens, Georgia 30602, USA. E- mail: [email protected]

Author’s note

The dichotomous key is a tool used by ichthyologists, fisheries biologists, and students for identifying unknown specimens to the level of species, genus or family. Constructed from a series of couplets, each consists of two statements describing characteristics of a particular organism or group of organisms. The reader is offered a choice between the two statements that best fits the unidentified specimen in question (Timme 1991) The statements contained in the couplets initially cover broad characteristics and become narrower or more focused as more choices become available. As the reader progresses through the couplets, the key choices are ordered from broad to narrow characteristics until only a single choice remains. If the correct or relevant couplet is applicable and the unknown specimen is included in the key, positive identification is possible. Sturgeon researchers require familiarity with the terminology used to describe sturgeon morphology. A good key should be well designed, and maintain simple but appropriate terminology. This key may be lacking in this respect; several of the rules pertaining to dichotomous keys have been broken during the creation of this key. In reality, no single sturgeon key exists that works: every key concerning Acipenser, whether worldwide or regional, has some major flaw. Our priority was to construct a key that worked, and it proved very difficult. We had to disregard the couplets of equivalent features, and structured the key so that the reader should consider couplets only until they were superseded by a new couplet. In constructing the key, we used the following criteria whenever possible:

x Morphological and meristic characters that are constant. x Characteristics that are generally visible on preserved as well as live specimens. x Inclusion of osteological characters (bony plates) whenever possible. They are consistent and easy to observe or count.

315

G.T.O. LeBreton et al. (eds.), Sturgeons and Paddlefish of North America, 315–318. ” 2004 Kluwer Academic Publishers. Printed in the Netherlands. 316 M. HOCHLEITHNER AND P. VECSEI

Skull cartilaginous, but covered by a large number of bony plates. Axial skeleton cartilaginous, vertebrae lacking centra, notochord persistent, extending into upper lobe of caudal fin. Pelvic fins abdominal without true spines. V-shaped fulcrae cover the axis of each unpaired fin: ... …...(Order: Acipenseriformes) Two Families in North America: 1

1 Body without rows of bony scutes, two small barbels (1 pair) on the underside of the rostrum anterior to the mouth, snout long and flattened (more than 70 % of the head length): ... (Family: Polyodontidae) One Species in North America: Polyodon spathula Body with five rows of bony scutes, four barbels (2 pairs) arranged in a single transverse row anterior to the mouth, snout short (less than 70 % of the head length): ... (Family: Acipenseridae) Eight Species in North America: 2

2 Snout conical with rounded edges, spiracle and pseudobranchiae present, caudal peduncle short, partly covered with bony scutes, lower lip interrupted medially and with two lobes, barbels not or slightly fimbriated: ... (Genus: Acipenser) 3 Snout spatulate with sharp edges, spiracle and pseudobranchiae absent, caudal peduncle long, fully covered with bony scutes, lower lip continous and with four lobes, barbels highly fimbriated: ... (Genus: Scaphirhynchus) 7

3 Plates present along both sides of the anal-fin base, 3 or more post-dorsal and post-anal plates (some in pairs), mouth opening usually less than 60 % of interorbital width: ... Acipenser oxyrinchus No plates at the sides of the anal-fin base, 3 or fewer post-dorsal and post-anal plates, mouth opening usually more than 60 % of interorbital width: ... 4

4 An olive-green lateral band along lateroventral surface (between lateral and ventral scutes), barbels closer to mouth and slightly fimbriated, 36 or fewer lateral scutes: ... Acipenser medirostris No olive-green lateral band between scute rows, barbels not fimbriated: ... 5 IDENTIFICATION KEY 317

5 Post-dorsal and post-anal plates absent, 5 or more pre-anal plates, 36 or more lateral scutes, 42 or more dorsal fin rays, barbels closer to the tip of the snout: ... Acipenser transmontanus Post-dorsal and post-anal plates present, 4 or less pre-anal plates: ... 6

6 Fewer than 23 anal fin rays, lateral scutes are lighter than the body background, base of barbels closer to the tip of the snout, 42 or less dorsal fin rays: ... Acipenser brevirostrum More than 23 anal fin rays, lateral scutes almost same color as the body background: ... Acipenser fulvescens

7 Dorsal fin with more than 38 rays and anal fin with more than 24 fin rays, caudal fin with more than 65 fin rays, outer-barbel length more than 1.5 times of inner barbel length, base of outer-barbels well behind inner-barbels: ... Scaphirhynchus albus Dorsal fin with less than 38 rays and anal fin with less than 24 fin rays, caudal fin with less than 65 fin rays, outer-barbel length less than 1.5 times of inner-barbel length, base of barbels nearly in one row: ... 8

8 Belly covered with large exposed bony plates, spines on the tip of the snout and between the small eyes: ... Scaphirhynchus platorhynchus Belly covered with small embedded bony plates, no spines on the tip of the snout and between the large eyes: ... Scaphirhynchus suttkusi 318 M. HOCHLEITHNER AND P. VECSEI

Meristic Characters in Sturgeons and Paddlefish of North America

Species DF AF DS LS VS GR poD poA prA

Acipenser 30-42 19-22 7-13 21-35 6-11 22-29 1-3 1-2 2-3 brevirostrum Acipenser 35-45 25-30 9-17 29-42 7-12 25-40 1-2 1-2 1-2 fulvescens Acipenser 29-44 19-32 7-12 20-36 5-12 15-26 1-2 1-2 1-4 medirostris Acipenser 38-46 23-30 7-16 24-35 6-14 15-27 3-9 3-9 2-6 oxyrinchus Acipenser 42-52 25-32 11-14 36-48 9-12 23-36 0 0 5-9 transmontanus Scaphirhynchus 37-43 23-28 14-18 40-48 9-13 ? 8-9 7-8 4-5 albus Scaphirhynchus 29-39 18-25 13-19 38-50 9-14 ? 8-9 8-9 4-6 platorhynchus Scaphirhynchus 29-34 18-22 15-21 40-49 11-14 ? 7-9 7-8 4-6 suttkusi Polyodon ? ? 0 0 0 ? 0 0 0 spathula

Abbreviations: DF = Dorsal fin rays, AF = Anal fin rays, DS = Dorsal scutes, LS = Lateral scutes, VS = Ventral scutes, GR = Gill rakers, poD = Plates between dorsal- and caudal fin, poA = Plates between anal- and caudal fin, prA = Plates between anus and anal fin;

References

Hochleithner M., Gessner J., 2001: The Sturgeons and Paddlefishes (Acipenseriformes) of the World: Biology and Aquaculture. AquaTech Publications, Kitzbuehel/Austria. 207 pages. Mayden R.L., Kuhajda B.R., 1996: Systematics, Taxonomy, and Conservation Status of the Endangered Alabama Sturgeon, Scaphirhynchus suttkusi Williams and Clemmer (Actinopterygii, Acipenseridae). Copeia, 2: 241-273. North J.A., Farr R.A., Vecsei P., 2002: A comparison of meristic and morphometric characters of green sturgeon Acipenser medirostris. J. Appl. Ichthyol., 18(4-6): 234-239. Scott W.B., Crossman E.J., 1973: Freshwater Fishes of Canada. Fisheries Research Board of Canada. 966 pages. Timme, S.L. 1991. How to construct and use a dichotomous key. Pages 101-110, in Tested studies for laboratory teaching. Volume 12. (C. A. Goldman, Editor). Proceedings of the 12th Workshop/Conference of the Association for Biology Laboratory Education, 218 pp Vecsei P., Charette R., Trukshin I., Maliepaard T., Hochleithner M., Lafleur Y., 2001: CITES Identification Guide - Sturgeons and Paddlefish. Environment Canada. 180 pages. Glossary

Acid-base characteristics: acid (H+) and base (OH-) equivalents, often expressed as pH (negative logarithm10 of the hydrogen ion activity, in solutions.)

Amphihaline: fish whose life cycle include both a freshwater and marine component.

Anadromous: fish ascending rivers from the sea to breed.

Anaerobic metabolism: metabolism in the absence of free oxygen.

Animal pole/hemisphere: the end/half of the oocyte or early embryo containing relatively more cytoplasm and less yolk. Frequently the location of the mature germinal vesicle, and thus fertilization. The animal-vegetal axis is established maternally during oogenesis.

Archenteron: the primitive gut cavity that forms within the embryo as a result of gastrulation.

Arterial: P50: half-saturation value of blood, under arterial CO2 and pH conditions.

Atresia: the resorption of the ovarian follicles by degenerative processes during late vitellogenesis, or before the female undergoes final maturation and spawning.

Blastomeres: individual cells within an early (pre-gastrula) embryo.

Blastula: a multicellular embryo that has mostly or entirely completed cleavage, but in which the large-scale movements of gastrulation have not yet begun.

Blood O2 affinity: binding affinity of the blood for oxygen, expressed as P50.

Breeding interval: time between consecutive breedings of individual.

Chloride cells: mitochondria-rich cells (e.g., in gill tissue) that move chloride (and sodium) against their concentration gradients.

Chorion: a tough protective extracellular layer surrounding the oocyte and developing embryo.

Cortical reaction: the process in which the cortical alveoli fuse to the plasma membrane of the oocyte, and release their contents into the space between the plasma membrane and egg chorion. The cortical vesicles contain enzymes, structural proteins and other glycoproteins. The cortical reaction renders separation of the chorion from the plasma membrane, imparts tonicity and strengthens the chorion (‘water hardening’), and prevents fertilization by multiple sperm (‘block to polyspermy’). 319 320 GLOSSARY

Cortisol: glucocorticoid hormone secreted by the interrenal gland and involved in stress response

Dimorphism: the appearance of two distinct forms such as size, structure, colour, etc. among animals or plants of the same species. For example, the sex of an individual can be determined by its external appearance; said to exhibit sexual dimorphism.

Ectoderm: the outermost embryonic germ layer, which gives rise to the central nervous system, epidermis, neural crest, sensory placodes, etc.

Ectothermic: cold-blooded, with no regulation of body temperature.

Electrolytes: charged molecules (ions) that act as conductors.

Endoderm: the innermost embryonic germ layer, which gives rise to the digestive system lining, respiratory system, certain endocrine organs, etc.

Epiboly: expansion of the surface area of a tissue or cell layer; may occur via cell division, shape change, or rearrangement.

Epinephrine: catecholamine hormone (sympathoadrenal system) involved in “fight or flight” response

Fecundity: number of eggs laid by a fish.

Final maturation: the final process of maturation in the development of an egg (oogenesis). This process is associated with both morphological and physiological changes such as the resumption of meiosis (from the dictyate oocyte to the metaphase II), yolk polarization, nucleus migration and breakdown (GVBD), and expulsion of the first polar body. Final maturation may last from hours to a few days and is believed to be the period in which the egg acquires much of its competence to fuse with the sperm during fertilization. Final maturation can be induced in vitro with progesterone.

Gastrulation: the series of cell and tissue movements that establish the three embryonic germ layers and generate the archenteron or primitive gut cavity.

Germinal vesicle breakdown (GVBD): the breakdown and disintegration of the nucleus (GV) during final maturation. Occurs during the period of final egg maturation and signals the resumption of meiosis.

Glucogenic amino acids: amino acids serving as a substrate for gluconeogenesis

Gluconeogenic processes: metabolic pathway for the formation of glucose or glycogen from noncarbohydrate sources.

Gymnovarian: the condition of the female gonads in which the ovary is open, and the eggs are released into the body cavity. The eggs gain access to the outside of the body GLOSSARY 321 through the Müllerian or paramesonephric ducts. Found in ancient fishes such as sturgeon.

Gynogenesis: gynogenesis is a ploidy manipulation technique used in fish species with female homogamety (XY{male}:XX{female}), resulting in all female progeny. To induce gynogenesis the male genetic component is inactivated, usually through the use of ionizing or UV-irradiation of the sperm, and diploidy is restored through second polar body retention by treating eggs with either a temperature shock, hydrostatic pressure or chemical treatments, subsequent to the entry of the inactivated sperm. Gynogenetic offspring are inbred (inheritance is entirely maternal) but this problem can be overcome by following gynogenesis with sex-reversal to produce XX males (neomales) that can then be crossed with normal females.

Hypercapnia: increased carbon dioxide partial pressures and contents.

Hyperosmoregulatory capability: able to regulate body water and solutes in dilute solutions (e.g., fresh water).

Hypertonic: having a higher total dissolved solute concentration (e.g., compared with that of the environment or, conversely, in an organism).

Hypometabolism: below-normal metabolic rate.

Hypoxia: low oxygen partial pressure and content.

Ionic regulation: regulation of specific ions (e.g., Na+, Cl-, Ca2+, K+) in body fluids when the fish is in either more dilute or more concentrated solutions.

Lactate: a metabolic end-product of the (anaerobic) glycolysis pathway (e.g., as result of hypoxia or of white muscle contractions, as in struggling or in burst swimming).

Long-day breeder: fish with seasonal reproduction during a long day length.

Mesoderm: the middle embryonic germ layer, which gives rise to tissues of the musculoskeletal system, excretory organs, reproductive ducts and gonads, circulatory system, etc.

Müllerian ducts: these paired ducts open internally into the coelomic cavity and externally at the urogenital opening. These funnel-shaped openings, positioned along the lateral walls of the body cavity, serve as passage ways for ovulated eggs to be discharged. In the female the duct has a one-way valve near the upper third of its length, and serves to control the discharge of eggs from the coelomic cavity during spawning. The ducts are also present in males, but their function is unknown. Because of the Müllerian duct structure, the location in the coelomic cavity, and the presence of the valve, eggs cannot be completely hand-stripped from the body cavity, as is done with salmonids. 322 GLOSSARY

Neomales: genetic females that are phenotypic and functional males, produced by an exposure to androgens, usually via an implant or by an application of androgens to the feed. This steroid treatment is only effective during the labile period before sexual differentiation.

Neural crest: a highly migratory and multipotent population of embryonic ectoderm cells that contributes to a wide range of derivatives including visceral skeleton, pigment cells, and ganglia.

Norepinephrine: (see epinephrine).

Normal table (or staging table): a description of successive steps during normal embryonic and larval development of a species; usually based on morphological characteristics. Note that discrete “stages” are necessarily somewhat arbitrary divisions of the continuous process of development.

Normocapnia: carbon dioxide partial pressures and contents that approximate atmospheric levels.

Normoxia: oxygen partial pressures and contents that approximate atmospheric levels.

O2 injection: the infusion, under pressure, of pure oxygen into a column of water, practiced in fish culture.

Osmolality: total solutes in mOsm kg-1.

Osmoregulation: regulation of body water and solutes.

Ovulation: discharge of matured eggs from the ovary into the ovarian or abdominal cavity.

Partial pressure of gas: pressure exerted by a particular gas (O2, CO2, N2), in proportion to the total gas (e.g., barometric) pressure.

Photoperiod: a recurring cycle of light and dark periods.

Photophobic: animal avoiding light or sensitive to light.

Photosynthesis: formation of carbohydrates in the chlorophyll-containing plants exposed to light.

Placodes: local thickenings of ectoderm, usually via cell columnarization in response to inductive signals from underlying mesoderm. Specific placodes give rise to the ectodermal components of major sensory structures such as the eyes and olfactory organs.

Plasma glucose: monosaccharide in blood that is a source of energy and maintained at a relatively stable levels. GLOSSARY 323

Phospholipid: lipid component of cell membranes containing a phosphoric acid residue.

Potamodromous: fish spending their entire lives in freshwater.

Proteolysis: the hydrolysis of proteins or peptides resulting in formation of soluble products.

Purified diets: diets that are constituted from purified ingredients, such as casein for protein, corn oil for lipid, corn starch for carbohydrate, cellulose for fibre, and vitamins and minerals premixes from chemically known compounds.

Radio-telemetry: the practice of locating or tracking organisms that carry tags that emit radio-wave signals, using a radio receiver and directional antenna.

Repletion ration: a satiation ration.

Resting-routine O2 consumption: a measure of metabolic (measured by oxygen consumption) rate of a routinely active animal.

Salinity, ppt: concentration of salts in water expressed in “parts-per-thousand”, i.e. gram per litre.

Specific Growth Rate (SGR): a parameter commonly used in nutritional energetics to express the effect of a ration on growth, in other words the growth rate relative to feed intake of the fish; it may reflect the nutritional value or quality of the diet. Also referred as the average daily percentage gain: SGR = (ln (Wt) – ln(Wt1)/t2 – t1) x 100.

TL : “total length” of fish, measured from tip of snout to tip of caudal fin (upper lobe in sturgeon).

Ultrasonic telemetry: the practice of locating or tracking organisms that carry tags that emit characteristic, high-frequency sounds, using a directional hydrophone.

Vegetal pole/hemisphere: the end/half of the oocyte or early embryo containing relatively more yolk and less cytoplasm. The animal-vegetal axis is established maternally during oogenesis.

Vitellogenesis: production of egg yolk involving the hepatic synthesis and secretion of the yolk precursor protein (vitellogenin) in response to circulating estrogen. The blood transports vitellogenin to the ovary, whereby the selective uptake of vitellogenin occurs into growing oocytes via receptor-mediated endocytosis. Vitellogenin is then enzymatically cleaved into yolk proteins and is deposited as platelet yolk into the oocytes. Vitellogenic growth of the oocytes takes about 16-18 months in white sturgeon and oocytes increase in diameter from 0.6 to 3.5 mm.