The Pacific ladyfish (''Elops affinis''), also known as the Pacific tenpounder and Machete, is a species of

ray-finned fish Actinopterygii (; ), members of which are known as ray-finned fishes, is a class of bony fish. They comprise over 50% of living vertebrate species. The ray-finned fishes are so called because their fins are webs of skin supported by bony or h ...

in the genus ''

Elops The Elopidae are a family of ray-finned fish containing a single living genus '' Elops''. They are commonly known as ladyfish, skipjacks, jack-rashes, or tenpounders. The ladyfish are a coastal-dwelling fish found throughout the tropical and sub ...

'', the only genus in the monotypic family Elopidae. The Pacific ladyfish can be found throughout the southwest U.S. and other areas in the Pacific Ocean.Battaso, R. H. and J. N. Young. (1999). Evidence for freshwater spawning by striped mullet and return of Pacific tenpounder in the lower Colorado River. California Fish & Game. 85(2): pp 75-76.Forey, P. L. (1973). A revision of the elopiform fishes, fossil and recent. ''Bulletin of the British Museum of Natural History'' (Geology) Supplement 10. pp. 222.Froese, R. and D. Pauly, Editors. 2002
''Elops affinis''.
FishBase. 24 September 2002.Nelson, J. S. ''Fishes of the World''. John Wiley and Sons, Inc. New York. 1994. pp. 99, 100. Fishballsjf

Description

The Pacific ladyfish have very round bodies with terminal mouths, and profound

gill A gill () is a respiratory organ that many aquatic organisms use to extract dissolved oxygen from water and to excrete carbon dioxide. The gills of some species, such as hermit crabs, have adapted to allow respiration on land provided they are ...

formations known as pseudobranchiae. They have a larger number of

dorsal fin A dorsal fin is a fin located on the back of most marine and freshwater vertebrates within various taxa of the animal kingdom. Many species of animals possessing dorsal fins are not particularly closely related to each other, though through c ...

rays than most

Arizona Arizona ( ; nv, Hoozdo Hahoodzo ; ood, Alĭ ṣonak ) is a state in the Southwestern United States. It is the 6th largest and the 14th most populous of the 50 states. Its capital and largest city is Phoenix. Arizona is part of the Fou ...

fish, with numbers ranging from 27 to 35. Anal fin rays usually range from 13 to 19, and they have 12 to 16 pelvic rays. This species is very different from most chordates in that it has no

conus arteriosus The infundibulum (also known as ''conus arteriosus'') is a conical pouch formed from the upper and left angle of the right ventricle in the chordate heart, from which the pulmonary trunk arises. It develops from the bulbus cordis. Typically, the i ...

, a tendinous band of tissue from which the pulmonary artery arises. Because of this absence, they have a much smaller

pulmonary artery A pulmonary artery is an artery in the pulmonary circulation that carries deoxygenated blood from the right side of the heart to the lungs. The largest pulmonary artery is the ''main pulmonary artery'' or ''pulmonary trunk'' from the heart, and ...

. This fish's lateral lines are unbranched, and lateral line scales are usually within ranges of 95 to 120. All scales are silvery and cycloid, along with the overall color of the fish; however, yellow pigment can occur in the eyes. Some aids to identification include the prominent auxiliary and inguinal processes.

Distribution and habitat in Arizona

This species is restricted primarily to the Southwest United States. Most records come from the Colorado River Delta and the Gulf of California, as they spawn here and then travel southwest into Arizona. They were also common in the Salton Sea in California, but their numbers have been slowly declining. During floods, Pacific ladyfish enter the Lower Colorado River from the Gulf. They can be found in Yuma Colorado River portions, with records as far south as certain Mexican dams. Pacific tenpounders are primarily a marine form, meaning they require a higher salinity water content then most freshwater fish. Because of this, they have evolved efficient swimming techniques allowing them to swim in lagoons and estuaries with higher salinities. Their maximum depth is around .

Reproduction

This species uses a wide range of water salinities when spawning. Under normal conditions, the Pacific tenpounder are located in brackish water, but they travel deep into oceanic, salty waters for breeding. They place their

eggs Humans and human ancestors have scavenged and eaten animal eggs for millions of years. Humans in Southeast Asia had domesticated chickens and harvested their eggs for food by 1,500 BCE. The most widely consumed eggs are those of fowl, especial ...

far from shore in more

plankton Plankton are the diverse collection of organisms found in water (or air) that are unable to propel themselves against a current (or wind). The individual organisms constituting plankton are called plankters. In the ocean, they provide a crucia ...

ic regions to provide them with nutrients as juveniles. The larvae look like eels at birth, but their forked tails distinguish them. Their young usually feed on the

crustacean Crustaceans (Crustacea, ) form a large, diverse arthropod taxon which includes such animals as decapods, seed shrimp, branchiopods, fish lice, krill, remipedes, isopods, barnacles, copepods, amphipods and mantis shrimp. The crustacean group can ...

s in the

brackish Brackish water, sometimes termed brack water, is water occurring in a natural environment that has more salinity than freshwater, but not as much as seawater. It may result from mixing seawater (salt water) and fresh water together, as in estu ...

or coastal waters. This may explain their instinct to move from the

Gulf of California The Gulf of California ( es, Golfo de California), also known as the Sea of Cortés (''Mar de Cortés'') or Sea of Cortez, or less commonly as the Vermilion Sea (''Mar Bermejo''), is a marginal sea of the Pacific Ocean that separates the Baja C ...

into the Lower Colorado during flood conditions.

Biology

Pacific ladyfish are pelagic, marine forms preferring either brackish or fresh water unless they are breeding. They prefer specific water depths of no more than . Little is known about the ecology of this species, but they are known to be highly carnivorous, feeding on smaller fish and crustaceans. This behavior is very similar to their relative, the Atlantic ladyfish. Maximum size is relatively larger than most Arizona fish, reaching lengths of . A negative correlation exists between size and presence in the

Colorado River The Colorado River ( es, Río Colorado) is one of the principal rivers (along with the Rio Grande) in the Southwestern United States and northern Mexico. The river drains an expansive, arid watershed that encompasses parts of seven U.S. s ...

. As they become larger in size, they enter more brackish waters for unknown reasons. Larval and juvenile stages of fish have large records of distribution near Rocky Point, in the Sea of Cortez tidal inlets. Their spawning areas are usually closer to coastal areas, because they use saltier waters for their young.

Threats

This species uses estuarine areas and hypersaline lagoons; changes in the quality of these habitats may affect this species' population dynamics. Although this species may not be closely associated with any single habitat, it may be adversely affected by development and urbanization.Adams, A. J., et al. (2014)
Global conservation status and research needs for tarpons (Megalopidae), ladyfishes (Elopidae) and bonefishes (Albulidae).
''Fish and Fisheries'' 15(2) 280-311.

References

External links

Arizona Game and Fish Department
{{Taxonbar, from=Q1954799 Pacific ladyfish Fish of the Pacific Ocean Western American coastal fauna Taxa named by Charles Tate Regan Pacific ladyfish