Changing the fish population of bodies of water as a part of watershed management can facilitate desirable changes in aquatic ecosystems suffering from eutrophication characterized by domination by phytoplankton aiding ecosystem restoration, an application of restoration ecology. In ponds or lakes alternative stable conditions, one with high algae populations, little other plant life, and turbid water, another with low algae populations, a diverse plant population, and clear water, may exist. In addition to prevention of excess nutrients such as phosphorus and nitrates, removal of certain fish species adapted to turbid water may facilitate change from one steady state to the other, an application of dynamical systems theory.[1] Fish species may be removed by means of poison, harvesting, or introduction of predatory species. As a different fish community will result from the process it will affect recreational and commercial fishermen whose cooperation or opposition is important.[2]
Lake Zwemlust, a hypertrophic pond used as a swimming pool in The Netherlands with an area of 1.5 hectares and an average depth of 1.5 meters, was treated in March 1987. The initial Secchi disk transparency was only 0.3 meters, less than the 1 meter maximum permitted for swimming pools in The Netherlands. In the first summer Secchi disk transparency increased to at least 2.5 meters, the maximum depth of the lake.[3] The lake was drained and 1,500 kilograms of planktivorous and benthivorous fish such as common bream were removed by seining and electrofishing. The pond was stocked with 1500 northern pikefingerlings and some mature rudd whose offspring served as food for the pike. Willow branches, nuphar lutea roots, and starts of Chara globularis were added as vegetation and shelter.[4] Expenses were met by the local water authority which was compensated by increased patronage by swimmers.[2] In the summer of the second year, 1988, there was considerable plant growth and, possibly due to lack of predation by carp or minnows, an explosion in the number of snails, including Radix peregra var. ovata a host of Trichobilharzia ocellata the cause of schistosome dermatitis, swimmer's itch. In addition to grazing by zooplankton the lush growth of macrophytes removed sufficient nutrients from the water to prevent algal bloom by phytoplanktons.[3]
Aquaculture, also known as aquafarming, is the farming of fish, crustaceans, mollusks, aquatic plants, algae, and other organisms. Aquaculture involves cultivating freshwater and saltwater populations under controlled conditions, and can be contrasted with commercial fishing, which is the harvesting of wild fish. Mariculture commonly known as marine farming refers to aquaculture practiced in marine environments and in underwater habitats, opposed to in freshwater.
Plankton are the diverse collection of organisms found in water that are unable to propel themselves against a current. The individual organisms constituting plankton are called plankters. In the ocean, they provide a crucial source of food to many small and large aquatic organisms, such as bivalves, fish and whales.
An algal bloom or algae bloom is a rapid increase or accumulation in the population of algae in freshwater or marine water systems, and is often recognized by the discoloration in the water from their pigments. The term algae encompasses many types of aquatic photosynthetic organisms, both macroscopic, multicellular organisms like seaweed and microscopic, unicellular organisms like cyanobacteria. Algal bloom commonly refers to rapid growth of microscopic, unicellular algae, not macroscopic algae. An example of a macroscopic algal bloom is a kelp forest.
Eutrophication, dystrophication or hypertrophication, is when a body of water becomes overly enriched with minerals and nutrients which induce excessive growth of algae. This process may result in oxygen depletion of the water body after the bacterial degradation of the algae. One example is an "algal bloom" or great increase of phytoplankton in a pond, lake, river or coastal zone as a response to increased levels of nutrients. Eutrophication is often induced by the discharge of nitrate or phosphate-containing detergents, fertilizers, or sewage into an aquatic system.
Aquatic plants are plants that have adapted to living in aquatic environments. They are also referred to as hydrophytes or macrophytes to distinguish them from algae and other microphytes. A macrophyte is a plant that grows in or near water and is either emergent, submergent, or floating. In lakes and rivers macrophytes provide cover for fish, substrate for aquatic invertebrates, produce oxygen, and act as food for some fish and wildlife.
A fish pond, or fishpond, is a controlled pond, artificial lake, or reservoir that is stocked with fish and is used in aquaculture for fish farming, or is used for recreational fishing or for ornamental purposes. In the medieval European era it was typical for monasteries and castles to have a fish pond.
An aquatic ecosystem is an ecosystem in a body of water. Communities of organisms that are dependent on each other and on their environment live in aquatic ecosystems. The two main types of aquatic ecosystems are marine ecosystems and freshwater ecosystems.
Periphyton is a complex mixture of algae, cyanobacteria, heterotrophic microbes, and detritus that is attached to submerged surfaces in most aquatic ecosystems. The related term Aufwuchs refers to the collection of small animals and plants that adhere to open surfaces in aquatic environments, such as parts of rooted plants. Periphyton serves as an important food source for invertebrates, tadpoles, and some fish. It can also absorb contaminants, removing them from the water column and limiting their movement through the environment. The periphyton is also an important indicator of water quality; responses of this community to pollutants can be measured at a variety of scales representing physiological to community-level changes. Periphyton has often been used as an experimental system in, e.g., pollution-induced community tolerance studies.
Hydrobiology is the science of life and life processes in water. Much of modern hydrobiology can be viewed as a sub-discipline of ecology but the sphere of hydrobiology includes taxonomy, economic biology, industrial biology, morphology, physiology etc. The one distinguishing aspect is that all relate to aquatic organisms. Much work is closely related to limnology and can be divided into lotic system ecology and lentic system ecology.
A lake ecosystem or lacustrine ecosystem includes biotic (living) plants, animals and micro-organisms, as well as abiotic (non-living) physical and chemical interactions. Lake ecosystems are a prime example of lentic ecosystems, which include ponds, lakes and wetlands, and much of this article applies to lentic ecosystems in general. Lentic ecosystems can be compared with lotic ecosystems, which involve flowing terrestrial waters such as rivers and streams. Together, these two fields form the more general study area of freshwater or aquatic ecology.
Throughout much of the tropics, tilapiine cichlids native to Africa and the Levant have been widely introduced into a variety of aquatic systems. In the U.S. states of Florida and Texas, tilapia were originally introduced to curtail invasive plants. In an effort to meet the growing demand for tilapia, humans have farmed these fish in countries around the world. Capable of establishing themselves into new ponds and waterways, many tilapia have escaped aquaculture facilities across much of Asia, Africa, and South America. In other cases, tilapia have been established into new aquatic habitats via aquarists or ornamental fish farmers.
The term fish kill, known also as fish die-off, refers to a localized die-off of fish populations which may also be associated with more generalized mortality of aquatic life. The most common cause is reduced oxygen in the water, which in turn may be due to factors such as drought, algae bloom, overpopulation, or a sustained increase in water temperature. Infectious diseases and parasites can also lead to fish kill. Toxicity is a real but far less common cause of fish kill.
The Trophic State Index (TSI) is a classification system designed to rate water bodies based on the amount of biological productivity they sustain. Although the term "trophic index" is commonly applied to lakes, any surface water body may be indexed.
A pond is an area filled with water, either natural or artificial, that is smaller than a lake. Ponds may arise naturally in floodplains as part of a river system or can simplify be an isolated depression that filled with runoff, groundwater, or precipitation. As such, ponds may be freshwater, saltwater, or brackish in nature.
The full relationship between fisheries and climate change is difficult to explore due to the context of each fishery and the many pathways that climate change affects. However, there is strong global evidence for these effects. Rising ocean temperatures and ocean acidification are radically altering marine aquatic ecosystems, while freshwater ecosystems are being impacted by changes in water temperature, water flow, and fish habitat loss. Climate change is modifying fish distribution and the productivity of marine and freshwater species.
Hypoxia refers to low oxygen conditions. Normally, 20.9% of the gas in the atmosphere is oxygen. The partial pressure of oxygen in the atmosphere is 20.9% of the total barometric pressure. In water, oxygen levels are much lower, approximately 7 ppm 0.0007% in good quality water, and fluctuate locally depending on the presence of photosynthetic organisms and relative distance to the surface.
PCLake is a dynamic, mathematical model used to study eutrophication effects in shallow lakes and ponds. PCLake models explicitly the most important biotic groups and their interrelations, within the general framework of nutrient cycles. PCLake is used both by scientist and water managers. PCLake is in 2019 extended to PCLake+ which can be applied to stratifying lakes.
A planktivore is an aquatic organism that feeds on planktonic food, including zooplankton and phytoplankton.
A whitewater river is classified based on its chemistry, sediments and water colour. Whitewater rivers have high levels of suspended sediments, giving the water a pH that is near-neutral, a high electric conductivity and a pale muddy, coffee and cream-like colour. Whitewater rivers are of great ecological importance and are important to local fisheries. The major seasonal Amazonian floodplains known as várzea receive their water from them.
Cultural eutrophication is when a flux of excess nutrients from human activity are added into a local run-off which in turns speeds up the natural eutrophication. This is caused by human activity, this problem became apparent once the green revolution and industrial revolution began in the last century. Phosphates and nitrates are the two main nutrients that cause cultural eutrophication as they enrich the water allowing for aquatic plants such as algae to grow rapidly. Algae is prone to blooming into large quantities removing oxygen from the water generating anoxic conditions. This anoxic environment kills off any organisms in the water body and make it hard for terrestrial animals to gain access to the water for drinking. Increased competition for the added nutrients can cause potential disruption to entire ecosystems and food webs, as well as a loss of habitat, and biodiversity of species.
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