The topsmelt silverside (''Atherinops affinis''), also known as the topsmelt, is a species of

Neotropical silverside The Neotropical silversides are a family, Atherinopsidae, of fishes in the order Atheriniformes. About 112 species in 13 genera are distributed throughout the tropical and temperate waters of the New World, including both marine and freshwater h ...

native to the eastern Pacific Ocean.

Description

The topsmelt silverside is a small, slim fish with a dorsally flattened body which can grow up to a

total length Fish measurement is the measuring of individual fish and various parts of their anatomies. These data are used in many areas of ichthyology, including taxonomy and fisheries biology. Overall length * Standard length (SL) is the length of a fish ...

of . It has two separate

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 conv ...

s on its bright green back which contrasts with the silver to pale flanks and silvery underside. This species has a pointed head with small eyes and a rather rounded, blunt snout and an oblique mouth situated terminally with extendible jaws each equipped with a row of tiny forked teeth. Their gills are a golden-yellow. It has no

lateral line The lateral line, also called the lateral line organ (LLO), is a system of sensory organs found in fish, used to detect movement, vibration, and pressure gradients in the surrounding water. The sensory ability is achieved via modified epithelial ...

but it has 63-65 scales where the lateral line would have been present. The first dorsal fine has 5-9 spines, the second dorsal fin has a single spine and 8-14 rays while the

anal fin Fins are distinctive anatomical features composed of bony spines or rays protruding from the body of a fish. They are covered with skin and joined together either in a webbed fashion, as seen in most bony fish, or similar to a flipper, as se ...

also has a single spine but has 19-25 rays and the

pectoral fin Fins are distinctive anatomical features composed of bony spines or rays protruding from the body of a fish. They are covered with skin and joined together either in a webbed fashion, as seen in most bony fish, or similar to a flipper, as ...

has 13 rays. The juveniles are

translucent In the field of optics, transparency (also called pellucidity or diaphaneity) is the physical property of allowing light to pass through the material without appreciable scattering of light. On a macroscopic scale (one in which the dimensions a ...

and have three rows of pigmented scales on their back, becoming scattered on the caudal peduncle.

Distribution

The topsmelt silverside is found in the eastern Pacific along the western coast of North America from

Vancouver Island Vancouver Island is an island in the northeastern Pacific Ocean and part of the Canadian Provinces and territories of Canada, province of British Columbia. The island is in length, in width at its widest point, and in total area, while are o ...

British Columbia British Columbia (commonly abbreviated as BC) is the westernmost province of Canada, situated between the Pacific Ocean and the Rocky Mountains. It has a diverse geography, with rugged landscapes that include rocky coastlines, sandy beaches, ...

south to

Baja California Baja California (; 'Lower California'), officially the Free and Sovereign State of Baja California ( es, Estado Libre y Soberano de Baja California), is a state in Mexico. It is the northernmost and westernmost of the 32 federal entities of Mex ...

and 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 Ca ...

Habitat and biology

The topsmelt silverside is a pelagic schooling fish which occurs in a wide variety of habitats at different times of the year. It is a common species in estuaries but it has also been recorded along the oceanic shoreline and in

kelp forests Kelp forests are underwater areas with a high density of kelp, which covers a large part of the world's coastlines. Smaller areas of anchored kelp are called kelp beds. They are recognized as one of the most productive and dynamic ecosystems on Ea ...

, off sandy beaches, and sometimes in offshore waters. They can frequently be found in and around man-made structures such as pier pilings. They are frequently observed just below the surface and are most frequently found in the upper . During spring and summer months many of these fish move into estuaries while in the autumn and winter they move to more open coastlines where there are bays, rocky areas, and beds of kelp. They can tolerate higher salinities than seawater and have been recorded inhabiting in salt evaporation ponds, as high as 80 ppt. The topsmelt silverside

spawn Spawn or spawning may refer to: * Spawn (biology), the eggs and sperm of aquatic animals Arts, entertainment, and media * Spawn (character), a fictional character in the comic series of the same name and in the associated franchise ** '' Spawn: ...

in the warmer months, starting in March and ending in October, preferring to spawn where the salinity is around 30 ppt and the temperature ranges between . These fish prefer to spawn at night over submerged vegetation. After hatching in deeper water the larvae may move up the estuary. Juveniles, less than a year old, are the most frequent age class to occur in freshwater environments and as they age they move downstream towards more estuarine environments. The juveniles feed on

zooplankton Zooplankton are the animal component of the planktonic community ("zoo" comes from the Greek word for ''animal''). Plankton are aquatic organisms that are unable to swim effectively against currents, and consequently drift or are carried along by ...

but the adults are more

benthic The benthic zone is the ecological region at the lowest level of a body of water such as an ocean, lake, or stream, including the sediment surface and some sub-surface layers. The name comes from ancient Greek, βένθος (bénthos), meaning "t ...

foragers and food items can include

algae Algae (; singular alga ) is an informal term for a large and diverse group of photosynthetic eukaryotic organisms. It is a polyphyletic grouping that includes species from multiple distinct clades. Included organisms range from unicellular mic ...

chironomid The Chironomidae (informally known as chironomids, nonbiting midges, or lake flies) comprise a family of nematoceran flies with a global distribution. They are closely related to the Ceratopogonidae, Simuliidae, and Thaumaleidae. Many specie ...

larvae and

amphipod Amphipoda is an order of malacostracan crustaceans with no carapace and generally with laterally compressed bodies. Amphipods range in size from and are mostly detritivores or scavengers. There are more than 9,900 amphipod species so far descr ...

s, the presence of sand and gravel in the stomach contents being taken to be an indicator of bottom feeding. This species is often recorded leaping out of the water to escape pursuit larger predatory fishes such as

mackerel Mackerel is a common name applied to a number of different species of pelagic fish, mostly from the family Scombridae. They are found in both temperate and tropical seas, mostly living along the coast or offshore in the oceanic environment. ...

or jacks.

External links

Bay Area and Delta Topsmelt
* {{Authority control Atherinopsidae Monotypic fish genera Fish described in 1860