A fish species is considered invasive if its position in an ecosystem negatively impacts other species. Generally, these are non-native species which have been introduced into a region by humans (either intentionally or unintentionally) with detrimental consequence to resident fish and other aquatic organisms. However, some argue that a native species can also be considered invasive … [Read more…]
A fish species is considered non-native to a location if it does not occur naturally there and only is present as a result of direct or unintentional human introduction. This does not necessarily mean that these fish cannot thrive in their non-native habitat. In fact, some fish, such as Sea Lamprey (Petromyzon marinus), can be in … [Read more…]
A fish species is considered native to a location if it occurs naturally there. It may have evolved in that region or dispersed and become established there without human assistance. For example, Lake Trout (Salvelinus namaycush) is native to some locations in North America but is considered non-native in other locations where it has been introduced … [Read more…]
Holomictic references the most common type of lake which turns over at least once per year (as opposed to meromictic lakes which are constantly stratified). This mixing is an important process for maintaining fish and aquatic communities by distributing nutrients and oxygen throughout the lake before stratification occurs again. There are four categories of holomictic … [Read more…]
Meromictic references a type of lake which is constantly stratified. The surface and bottom waters do not ever mix. In most cases, the bottom layer has very low oxygen levels, where few fish and other organisms can live, restricting them to the surface layer. Meromictic lakes are uncommon (most lakes are holomictic and turnover at least … [Read more…]
A homocercal tail is a caudal fin composed of two lobes of equal proportion. Homocercal tails are the most common caudal fin type in fish but can come in many symmetrical shapes. A homocercal tail is contrasted with a heterocercal tail which has unequal lobes.
A heterocercal tail is a caudal fin composed of two asymmetrical lobes. Often, such as the case in many sharks, the vertebral column passes through the upper lobe, making it the larger of the two lobes. A heterocercal tail is contrasted with a homocercal tail which has equal lobes.
Lotic refers to freshwater ecosystems involving flowing water, such as a river, stream, brook or creek. Certain fish species are lotic specialists and have evolved to live in higher flow water, such as darters which prefer to live in swift-moving riffles.
Lentic describes freshwater ecosystems characterized by still water and low flow, such as a lake or pond. Certain fish species have evolved to become lentic specialists, such as the high diversity of cichlid species found in Lake Victoria.
A scute is an external bony plate on the surface of a fish. Scutes serve a protective function, acting as a body armor for fish against environmental abrasions and even predation. In some fishes, such as Alewife (Alosa pseudoharengus), scutes are a row of scales modified into sharp, protective plates. In other fishes, like Shovelnose … [Read more…]