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Delta Smelt
The delta smelt (''Hypomesus transpacificus'') is an endangered slender-bodied smelt, about long, in the family Osmeridae. Endemic to the upper Sacramento-San Joaquin Estuary of California, it mainly inhabits the freshwater-saltwater mixing zone of the estuary, except during its spawning season, when it migrates upstream to fresh water following winter " first flush" flow events (around March to May). It functions as an indicator species for the overall health of the Delta's ecosystem. Delta Smelt are usually found at temperatures of less than 25 °C and prefer temperatures of around 20 °C. They are euryhaline but occur mostly at salinities of 0–7 practical salinity units. Because of its one-year lifecycle and relatively low fecundity, it is very susceptible to changes in the environmental conditions of its native habitat.Moyle, PB. 2002. Inland fishes of California. University of California Press, Berkeley. It is listed as a federally threatened species under th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Donald Evan McAllister
Donald Evan McAllister was a Canadian ichthyologist who published over 625 scientific papers, books, popular articles and book reviews in his career, which lasted 45 years from 1958 until his early retirement in 1993. References External linksA tribute to Don E. McAllister {{DEFAULTSORT:McAllister, Donald 1934 births 2001 deaths Canadian ichthyologists Academics from Victoria, British Columbia Scientists from British Columbia 20th-century Canadian zoologists ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hypomesus Nipponensis
''Hypomesus nipponensis'' (Japanese smelt, in Japanese: ''wakasagi'') is a commercial food fish native to the lakes and estuaries of northern Honshu and Hokkaido, Japan, Korea, and Sakhalin, Khabarovsk Krai, and Primorsky Krai, Russia. It has been introduced in other locations, including the San Francisco Delta of the United States. It is raised in fisheries, and is very similar in appearance to the delta smelt (''H. transpacificus''). Synonyms ''Hypomesus chishimaensis'' was described as being a new species in the lakes of Kunashir and Iturup in 1997 based on claimed morphological differences. After later studies failed to find these morphological differences, it regarded as an ecotype of ''H. nipponensis''. A 2007 genetic analysis supported this classification, and recommended that ''H. chishimaensis'' not be given its own binomial designation. Introduction to the United States Native to the lakes and estuaries of Hokkaido, Japan and introduced to the lakes on H ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Epoch (geology)
The geologic time scale or geological time scale (GTS) is a representation of time based on the rock record of Earth. It is a system of chronological dating that uses chronostratigraphy (the process of relating strata to time) and geochronology (a scientific branch of geology that aims to determine the age of rocks). It is used primarily by Earth scientists (including geologists, paleontologists, geophysicists, geochemists, and paleoclimatologists) to describe the timing and relationships of events in geologic history. The time scale has been developed through the study of rock layers and the observation of their relationships and identifying features such as lithologies, paleomagnetic properties, and fossils. The definition of standardised international units of geological time is the responsibility of the International Commission on Stratigraphy (ICS), a constituent body of the International Union of Geological Sciences (IUGS), whose primary objective is to precis ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pleistocene
The Pleistocene ( ; referred to colloquially as the ''ice age, Ice Age'') is the geological epoch (geology), epoch that lasted from to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was finally confirmed in 2009 by the International Union of Geological Sciences, the cutoff of the Pleistocene and the preceding Pliocene was regarded as being 1.806 million years Before Present (BP). Publications from earlier years may use either definition of the period. The end of the Pleistocene corresponds with the end of the last glacial period and also with the end of the Paleolithic age used in archaeology. The name is a combination of Ancient Greek () 'most' and (; Latinized as ) 'new'. The aridification and cooling trends of the preceding Neogene were continued in the Pleistocene. The climate was strongly variable depending on the glacial cycle, oscillating between cold Glacial period, glacial periods and warmer Interglacial, int ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
San Joaquin Valley
The San Joaquin Valley ( ; Spanish language in California, Spanish: ''Valle de San Joaquín'') is the southern half of California's Central Valley (California), Central Valley. Famed as a major breadbasket, the San Joaquin Valley is an important source of food, producing a significant part of California's agricultural output. San Joaquin Valley draws from nine counties of Northern California, Northern and Central California, including all of San Joaquin County, San Joaquin and Kings County, California, Kings counties, most of Stanislaus County, Stanislaus, Merced County, Merced, and Fresno County, California, Fresno counties, and parts of Madera County, California, Madera and Tulare County, California, Tulare counties, along with a majority of Kern County, California, Kern County. Although the valley is predominantly rural, it has three densely populated urban centers: Stockton, California, Stockton/Modesto, California, Modesto, Fresno, California, Fresno/Visalia, California, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Homoplasy
Homoplasy, in biology and phylogenetics, is the term used to describe a feature that has been gained or lost independently in separate lineages over the course of evolution. This is different from homology, which is the term used to characterize the similarity of features that can be parsimoniously explained by common ancestry. Homoplasy can arise from both similar selection pressures acting on adapting species, and the effects of genetic drift. Most often, homoplasy is viewed as a similarity in morphological characters. However, homoplasy may also appear in other character types, such as similarity in the genetic sequence, life cycle types or even behavioral traits. Etymology The term homoplasy was first used by Ray Lankester in 1870. The corresponding adjective is either ''homoplasic'' or ''homoplastic''. It is derived from the two Ancient Greek words (), meaning "similar, alike, the same", and (), meaning "to shape, to mold". Parallelism and convergence Parallel and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Speciation
Speciation is the evolutionary process by which populations evolve to become distinct species. The biologist Orator F. Cook coined the term in 1906 for cladogenesis, the splitting of lineages, as opposed to anagenesis, phyletic evolution within lineages. Charles Darwin was the first to describe the role of natural selection in speciation in his 1859 book ''On the Origin of Species''. He also identified sexual selection as a likely mechanism, but found it problematic. There are four geographic modes of speciation in nature, based on the extent to which speciating populations are isolated from one another: allopatric speciation, allopatric, peripatric speciation, peripatric, parapatric speciation, parapatric, and sympatric speciation, sympatric. Whether genetic drift is a minor or major contributor to speciation is the subject of much ongoing discussion. Rapid sympatric speciation can take place through polyploidy, such as by doubling of chromosome number; the result is progeny wh ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Clades
In biology, a clade (), also known as a monophyletic group or natural group, is a group of organisms that is composed of a common ancestor and all of its descendants. Clades are the fundamental unit of cladistics, a modern approach to taxonomy adopted by most biological fields. The common ancestor may be an individual, a population, or a species (extinct or extant). Clades are nested, one in another, as each branch in turn splits into smaller branches. These splits reflect evolutionary history as populations diverged and evolved independently. Clades are termed ''monophyletic'' (Greek: "one clan") groups. Over the last few decades, the cladistic approach has revolutionized biological classification and revealed surprising evolutionary relationships among organisms. Increasingly, taxonomists try to avoid naming taxa that are not clades; that is, taxa that are not monophyletic. Some of the relationships between organisms that the molecular biology arm of cladistics has revealed ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Phylogenetic
In biology, phylogenetics () is the study of the evolutionary history of life using observable characteristics of organisms (or genes), which is known as phylogenetic inference. It infers the relationship among organisms based on empirical data and observed heritable traits of DNA sequences, protein amino acid sequences, and morphology. The results are a phylogenetic tree—a diagram depicting the hypothetical relationships among the organisms, reflecting their inferred evolutionary history. The tips of a phylogenetic tree represent the observed entities, which can be living taxa or fossils. A phylogenetic diagram can be rooted or unrooted. A rooted tree diagram indicates the hypothetical common ancestor of the taxa represented on the tree. An unrooted tree diagram (a network) makes no assumption about directionality of character state transformation, and does not show the origin or "root" of the taxa in question. In addition to their use for inferring phylogenetic pa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pacific
The Pacific Ocean is the largest and deepest of Earth's five oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean, or, depending on the definition, to Antarctica in the south, and is bounded by the continents of Asia and Australia in the west and the Americas in the east. At in area (as defined with a southern Antarctic border), the Pacific Ocean is the largest division of the World Ocean and the hydrosphere and covers approximately 46% of Earth's water surface and about 32% of the planet's total surface area, larger than its entire land area ().Pacific Ocean . '' Britannica Concise.'' 2008: Encyclopædia Britannica, Inc. The centers of both the [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ichthyologist
Ichthyology is the branch of zoology devoted to the study of fish, including bony fish (Osteichthyes), cartilaginous fish (Chondrichthyes), and jawless fish (Agnatha). According to FishBase, 35,800 species of fish had been described as of March 2025, with approximately 250 new species described each year. Etymology The word is derived from the Ancient Greek words wikt:ἰχθύς, ἰχθύς, ''ikhthus'', meaning "fish"; and wikt:-λόγος, λόγος, ''logos'', meaning "study". History The study of fish dates from the Upper Paleolithic, Upper Paleolithic Revolution (with the advent of "high culture"). The science of ichthyology was developed in several interconnecting epochs, each with various significant advancements. The study of fish receives its origins from humans' desire to feed, clothe, and equip themselves with useful implements. According to Michael Barton (professor), Michael Barton, a prominent ichthyologist and professor at Centre College, "the earliest ichthy ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Smelt (fish)
Smelts are a family of small fish, the Osmeridae, found in the North Atlantic and North Pacific oceans, as well as rivers, streams and lakes in Europe, North America and Northeast Asia. They are also known as freshwater smelts or typical smelts to distinguish them from the related Argentinidae (herring smelts or argentines), Bathylagidae (deep-sea smelts), and Retropinnidae (Australian and New Zealand smelts). Some smelt species are common in the North American Great Lakes, and in the lakes and seas of the northern part of Europe, where they run in large Shoaling and schooling, schools along the saltwater coastline during spring migration to their spawning streams. In some western parts of the United States, smelt populations have greatly declined in recent decades, leading to their protection under the Endangered Species Act. The Delta smelt (''Hypomesus transpacificus'') found in the Sacramento Delta of California, and the eulachon (''Thaleichthys pacificus'') found in the Nor ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
