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Exclusive Economic Zone (EEZ)

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Exclusive economic zone of the United States (image credit: NOAA).

An Exclusive Economic Zone (EEZ), as defined by the United Nations Convention on the Law of the Sea, is a 200 nautical mile jurisdiction granted to coastal nations for “sovereign rights for the purpose of exploring and exploiting, conserving and managing the natural resources, whether living or non-living, of the waters superjacent to the seabed and of the seabed and its subsoil, and with regard to other activities for the economic exploitation and exploration of the zone.”  Within an EEZ, a country claims exclusive rights to manage fisheries and prevent overfishing.  While the outer 200 mile boundary determines a country’s sovereign limits, within the U.S., most coastal states claim an inner three nautical mile zone from the shore as state waters (some places claim nine nautical miles).  For fisheries, such as defined under the Magnuson-Stevens Fishery Conservation and Management Act, management in the inner zone belongs to the states and the remainder of the EEZ is under purview of the federal government (e.g., the National Oceanic and Atmospheric Administration).

Escapement

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This spawned out Chinook Salmon contributes to the escapement estimate for its particular run.

Escapement is a term used in salmon management to mean, quite simply, how many salmon are able to “escape” premature death and complete their full life cycle.  These escapees have run the gauntlet of natural mortality, recreational fishing, commercial fishing, and other life-threatening episodes for the opportunity to spawn in freshwater.  Escapement is estimated by a number of different methods including fish counts (e.g., at a weir or dam viewing window) and carcass surveys (i.e., counting the dead salmon on spawning grounds).  For salmon managers, the amount of escapement for each salmon run informs population estimates and appropriate fishing quotas and other management strategies for future fishing seasons.

Endemic species

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Devil's Hole Pupfish is endemic to Devil's Hole, Nevada.

Devil’s Hole Pupfish is endemic to Devil’s Hole, Nevada.

A fish species is considered endemic to a location if that is the only place it occurs naturally.  It may have evolved in that region or over time has become so adapted to that specific environment that it cannot survive elsewhere.  For example, Devil’s Hole Pupfish (Cyprinodon diabolis) is only found in Devil’s Hole, Nevada.  If a species is naturally located in multiple locations, it is considered a native species, but is not an endemic one.  Many endemic species are T&E species, threatened with extinction due to loss or modification of their habitat by agriculture, urbanization, or other human land uses.

 

Elasmobranch

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Spotted Eagle Rays are a member of the catilaginous subclass Elasmobranchii along with other rays, sharks, and sawfishes (NOAA).

Spotted Eagle Rays are a member of the cartilaginous subclass Elasmobranchii along with other rays, sharks, and sawfishes (NOAA).

Elasmobranchs, including sharks, rays, and sawfishes, belong to the taxonomic subclass of cartilaginous fish Elasmobranchii.  Like most chondrichthyes, they have exposed gills, no swim bladder, internal fertilization, and placoid denticles.  They differ from the other subclass, chimaera (subclass: Holocephali), in that they have rigid dorsal fins, placoid denticles cover most of their bodies, and they usually have spiracles (modified gill slits directly behind the eye).

Eurytherm

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Desert Pupfish are eurythermic, surviving in temperatures ranging from function in waters from 4º to 45ºC (Paul V. Loiselle).

Desert Pupfish are eurythermic, surviving in temperatures ranging from function in waters from 4º to 45ºC (Paul V. Loiselle).

In contrast to stenotherms, eurythermic fish can function at a wide range of water temperatures.  They are often, but not necessarily, ectotherms.  Desert Pupfish (Cyprinodon macularius), for example, can function in ambient temperatures ranging from 4 to 45 degrees Celsius.  This thermoregulatory strategy requires that organs, enzymes, and metabolic processes can operate at varying environmental temperatures.

 

Ectotherm

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Ectothermic fish rely upon their environment to regulate their temperature (clipartOf.com).

Ectothermic fish rely upon their environment to regulate their temperature (clipartOf.com).

Unlike endotherms which can metabolically control their own body temperature, ectotherms rely upon environmental temperatures for thermoregulation.  Most fish are ectotherms.  Ectothermy can be metabolically more efficient than endothermy because organisms do not have to expend any energy to self-regulate their body temperatures.  However, they are at the mercy of their environment more than endotherms because they use ambient water temperature to control their body temperature.

Poikilothermic fish have no control over their body temperature whatsoever.  Their core body temperature conforms entirely to ambient temperature and can fluctuate widely. This means that their organs and enzymes need to be capable of functioning at a range of temperatures.  As physiological processes have often evolved to operate most efficiently at certain temperatures, ectothermic fish have evolved multiple strategies to maintain optimal thermal habitat.  Stenotherms live within narrow environmental temperatures in contrast with eurytherms which can live in a wide range of environmental temperatures.

 

Endotherm

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Though rare, some fish are able to internally regulate temperature.

Though rare, some fish are able to internally regulate temperature.

Unlike ectotherms, which rely upon environmental temperatures, endotherms are able to metabolically control their body temperature.  This thermoregulatory strategy is rare among fish but is present in tunas and some sharks, including the Great White Shark (Carcharodon carcharias) and Shortfin Mako Shark (Isurus oxyrinchus).  Endothermic tunas and sharks use a network of capillaries in their swimming muscles, the Rete mirabile, as a heat exchanger.  Through counter-current exchange, the heat produced through muscle activity is transported by the blood.  Through this metabolic process, sharks, for example, can maintain a body temperature of 5 – 14°C above ambient water temperature.  This process is an evolutionary advantage for these long distance, migratory fish, allowing them to travel extensive distances and dive deep while maintaining body temperature, conserving energy, and avoiding thermal shock from changes in water temperature.

Tunas are one example of endothermic fish.

Tunas are one example of endothermic fish.

Electrofishing

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Electrofishing is a survey technique that stuns fish in freshwater

Electrofishing is a survey technique that stuns fish in freshwater

Electrofishing is a survey tool used to estimate species composition, fish abundance, and fish density in freshwater systems using an electrical current.  An electroshocker creates a flow of current between an anode (i.e., ring on a backpack models) and cathode (i.e., rat tail on backpack models) that stuns fish that cross the electric field.  Stunning the fish makes them easier to capture and assess for research and monitoring purposes.  Backpack electroshockers are generally used for smaller, wadeable waterbodies; boat or raft mounted electroshockers are generally used for larger waterbodies.  While electrofishing can be a very effective technique for freshwater, electricity has poor conductivity in salt water.

For an example of boat electrofishing, check out this depletion electrofishing post on the Fisheries Blog!