Saltmarsh topminnow
The Saltmarsh topminnow, scientifically known as Fundulus jenkinsi, is a small fish species found primarily in the salt marshes along the northern Gulf of Mexico, from western Florida to Texas. These fish are typically smaller and paler compared to other killifish, reaching lengths of about 2.5 inches (6 cm) and are characterized by distinctive dark blotches behind their eyes. Their anatomy features various fins, including dorsal, anal, pelvic, and pectoral fins, which enable agile movement in their saline habitat.
As omnivores, Saltmarsh topminnows feed on a diverse diet, including mosquito larvae, small crustaceans, and plant matter. They breed between March and August, with females laying around 200 eggs in multiple batches during this period, which are fertilized by males in a process known as spawning. The eggs have a growth period of two to three weeks before hatching into free-swimming young fish.
Saltmarsh topminnows face threats from larger aquatic predators and human activities, particularly fishing, as they are commonly used as bait. This has contributed to their designation as a vulnerable species by the International Union for Conservation of Nature (IUCN). In the wild, they typically have a lifespan of 2 to 3 years, highlighting their ecological significance within their saline environments.
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Saltmarsh topminnow
Saltmarsh topminnows were given their name for the salty waters of salt marshes from western Florida to Texas where they live. They are smaller and paler than other killifish. The most recognizable markings on saltmarsh topminnows are the dark blotches behind the eyes of these fish.
Kingdom: Animalia
Phylum: Chordata
Class: Osteichthyes
Order: Cyprinodontiformes
Family: Cyprinodontidae
Genus: Fundulus
Species: Jenkinsi
Saltmarsh topminnows are found in the salt marshes along the northern Gulf of Mexico from western Florida to Galveston, Texas. Salt marshes are marshy masses of water with high concentrations of salt.
Saltmarsh topminnows, like other killifish, have dorsal, caudal, anal, pelvic, and pectoral fins. Their dorsal and anal, or back and belly fins, help to keep the fish balanced, while their pelvic and pectoral fins paddle them through the water. Their pelvic fins are on their bellies and their pectoral fins are located behind their gills on both sides of their bodies. The fins’ position allows the fish to move in any direction. The saltmarsh topminnows' caudal, or tail, fins move from side to side propelling the fish as they swim. Fully grown, saltmarsh topminnows reach lengths of about 2 1/2 inches (six centimeters). Both sexes have narrow bars and large, dark spots along their otherwise pale sides. Each saltmarsh topminnow also has a dark blotch behind its eyes.
Like many other fish, saltmarsh topminnows must have oxygen to survive. Unlike humans, who have lungs and can process oxygen from the air, saltmarsh topminnows must find oxygen in the water. They take water into their mouths, keep the oxygen they need, and release the remaining waste chemicals out through the gills on the sides of their bodies.
Saltmarsh topminnows are omnivorous fish. This means they survive on a diet of both meat and plants. Saltmarsh topminnows feed on mosquito larvae, small crustaceans, and small worms. As omnivores, they also feed on some plant matter.
Saltmarsh topminnows are egg-laying killifish. The breeding season is between March and August. Female saltmarsh topminnows lay eight to ten batches of eggs each breeding season. Each of these batches contains between 18 and 20 eggs, bringing the total number of eggs laid during a single breeding season to about 200 eggs. Male saltmarsh topminnows swim over these batches and release their fertilizing substances. This process of releasing and fertilizing eggs is known as spawning. Saltmarsh topminnow eggs have an incubation, or growth, period of two to three weeks. When these young hatch, they move into the water as free-swimming fry, or young fish.
Saltmarsh topminnows are often preyed upon by larger, aquatic, or water-living, creatures. They are also threatened by humans. Fishermen use them and other topminnows as bait to catch larger fish. The International Union for Conservation of Nature and Natural Resources (IUCN) Red List of Threatened Species lists these fish as vulnerable.
The lifespan of saltmarsh topminnows is 2 to 3 years in the wild.
Bibliography
"Fundulus Jenkinsi (Evermann, 1892)." Fish Base, fishbase.mnhn.fr/summary/Fundulus-jenkinsi. Accessed 15 Apr. 2024.
"Saltmarsh Topminnow." Climatead Adaptation Explorer, climateadaptationexplorer.org/species/fish/324. Accessed 15 Apr. 2024.
"Saltmarsh Topminnow." The IUCN Red List of Threatened Species, www.iucnredlist.org/species/196678/2473113. Accessed 15 Apr. 2024.