Abyssal Plain – the region of the oceans bottom that is generally flat with a depth of 4,000 meters (13,120 feet) to 6,000 (19,680 feet) meters.

Anadromous Fish – born in fresh water, spends most of its life in the sea and returns to fresh water to spawn.

Barbel – a fleshy organ around a fishes mouth that hangs down and is utilized to touch and taste potential food items

Bathypelagic – a zone in the ocean that is deeper than 1,000 meters (3,280 feet) that extends to 4,000 meters (13,120 feet) that does not include the bottom.

Benthic – associated with the sea floor.

Bioluminescense – a biochemical emission of light produced by a living organism.

Boreal – found in the northern portions of its range.

Catadromous Fish – born in salt water, spends most of its life in fresh water and returns to salt water to spawn.

Caudal Peduncle – area between the insertion of the anal and dorsal fins and the base of the caudal fin.

Clasper – the posterior part of the pelvic fin of male fishes that serve to channel semen into a female’s reproductive organ.

Continental Shelf – the sea floor from the coast line to a depth of 150 meters (500 feet).

Continental Slope – where the sea floor descends rapidly to great depths.

Cryptic Coloring – – color that is concealed or camouflaged.

Demersal – a term used to describe fishes that live near the bottom

Denticle – a tooth-like scale with a hard outer layer.

Diadromous – fish that spend portions of their life cycles partially in fresh water and partially in salt water.

Diecious – method of reproduction with distinct and separate males and females.

Dimorphism – refers to the same species having two distinct forms, i.e. male and female, that differ in one or more characteristics such has color, size or shape.

Diurnal – normal daylight hours.

Ectothermic – an organism that regulates its body temperature by exchanging heat with its surroundings.

Epibenthic – a term used to describe fishes that live near the bottom

Epipelagic – a term used to describe organisms that live in open oceanic waters from the surface to depths of 200 meters (656 feet).

Esca – expanded, sometimes highly modified, portion at the end of a modified dorsal-fin spine found in anglerfish to attract prey.

Eurythermal – an organism that is adaptable to a wide range of temperatures.

Gonochorist – a fish with embryonic gonads that are capable of dividing into either ovaries or testes to become females or males.

Hermaphrodite – organism with functional male and female sex organs in the same individual either simultaneously or sequentially.

Illicium – modified dorsal fin spine supporting the esca (fishing lure), normally near the tip of the snout, utilized by anglerfish to attract prey.

Isthmus – area of the throat ventral to the gill openings.

Lateral Line – Sensory system consisting of pores and canals along the head and body for detection of vibrations and water movement.

Littoral – The oceanic bottom region between the limits of high and low tides.

Median Fins – anal, caudal and dorsal fins.

 Mesopelagic – a term used to describe organisms that live in oceanic waters from 200 meters (656 feet) to 1,000 meters (3,280 feet).

Mimicry – the ability to resemble another fish in its surroundings for concealment for either protection or to obtain access to prey.

Neritic – the oceanic region between the low tide line to depths of 200 meters (656 feet).

Ocellus – round or oval eye-like spot with a colored ring around it.

Operculum – hard bony flap found on the side of the face that covers and protects a fishes gills.

Origin – normally in reference to anterior location of various fins.

 Oviparous – refers to the reproduction of fishes where females release eggs outside of their bodies with fertilization by males either internally prior to egg release or externally after egg release.

Paired Fins – refers to pectoral and pelvic fins.

 Pelagic – refers to fish found in the open global oceans.

 Photophore – light-producing organism.

Preopercle – flat bone that is one of the four bones of the opercle or gill cover.

 Protandrous – maturing initially as a male and then transitioning to a female.

Protogynous – maturing initially as a female and then transitioning to a male.

Scute – thickened hardened scale normally found at the base on the tail along the lateral line.

Sessile – permanently attached or fixed to the substrate. Normally refers to invertebrates.

 Spiracle – opening found behind the eye of a duct leading to the gill chamber.

 Thermocline – a part of the water column where the temperature drops abruptly with depth.

Viviparous – refers to reproduction where the mother provides some form of nutrition, other than just a yolk, to a developing embryo, in utero.

Viviparity – a reproduction mode in which eggs are fertilized and developed internally, but all nutrition to the embryo is supplied by the yolk.

Zygoparous – a reproduction mode in which eggs are fertilized internally but are released shortly thereafter and developed externally.