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Marine sport fish identification - Glossary of terms

Billfish | Flatfish | Rockfish | Salmon and trout species | Sharks, rays, and skates | Surfperch species | Tunas and mackerel | Miscellaneous marine species | "Baitfish" guide

Glossary of terms used in fish ID guide (jpgs)

Adipose fin: Small fleshy fin located between the dorsal and caudal fins. Found in salmons, trouts, and smelts.

Anterior: The front end of a fish, starting at the snout.

Barbel: A sensory appendage that usually is near the mouth and protrudes downward. The barbel is often referred to as a "whisker" by anglers.

Blind side: The side of a flatfish that does not have any eyes. This is usually much lighter in color and is sometimes referred to as the white side.

Catch rankings: A basic ranking assigned to each species based on the current and/or historical significance of the species in the retained catch of the ocean recreational boat fishery. Some species are very common, but not retained very often i.e. Pacific hake. Other species may be commonly caught in the estuary, but it is unusual for boat anglers to catch these in the ocean i.e. white sturgeon, surf perch spp., Pacific herring, etc. A description of the rankings

Caudal fin:The tail of a fish.

Caudal keel: Horizontal ridge located at the base of the caudal fin or on the caudal peduncle (see diagram under heterocercal).

Caudal peduncle: The point at which the body of the fish narrows down and the caudal fin begins (also referred to as the wrist) (see diagram).

Cirrus / Cirri: Fleshy appendages usually on the head of a fish. Generally used to help the fish blend into the surroundings.

Dichotomous key: A guide most typically used for identifying species of plants or animals by using a basic true or false question at each fork in a progressive key to identify a species.

Dorsal: The back surface of a fish. Also used as a name for the main fin(s) on the back of a fish.

Dorsally compressed: Used to describe fish that appear flattened from top to bottom i.e. skates and rays. Contrast this to laterally compressed.

Eyed side: The side of a flatfish that has both eyes. This is usually much darker in color and is sometimes referred to as the dark side.

Finlet: Small non-rayed protrusions usually in a series between the dorsal and/or anal fin and the caudal fin (see diagram).

Fins: Refer to the picture for general fin locations. Note that pectoral and pelvic fins are paired (left and right), while dorsal, anal, adipose, and caudal fins are not paired (although there may be more than one of each).

Fins and major exterior features of a fish

Gill cover/gill plate/operculum: The plate at the posterior end of the head that covers the gills, also known as the operculum or gill plate.

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Gill raker: Bony protrusions off of the gill arch that are used to assist the fish in food gathering. Filter feeding fishes usually have numerous long slender gill rakers, while predatory fishes usually will have fewer shorter rakers.

Gill Arch

Gill slits: In fishes such as sharks, rays, and skates, the gills openings are slit-like as opposed to a gill cover.

Heterocercal tail: Caudal fin is asymmetrically oriented behind and below the vertebral column which turns upward and extends into the upper lobe of the tail (see diagram). Heterocercal tails are common in sharks and sturgeon.

Heterocercal Tail

hetrocercal tail

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Lateral line: Sensory pores that are usually located along the side of a fish in a line. Some fish have no lateral line pores, and others may have more than one line, a branched line, or additional pores on the head. Presence or absence of the lateral line, as well as branches or curves in the lateral line often help to distinguish species.

Laterally compressed:Used to describe fish that appear flattened from side to side i.e. halibut, sole, surf perch, etc. Contrast this to dorsally compressed.

Lunate: Used to describe the shape of a caudal fin that is crescent in outline. Common shape of tail in tuna and billfish (see diagram).


Maxillary: The bony portion of the upper jaw of a fish. The maxillary may include most of the upper jaw, or just the posterior end. The maxillary's location relative to the eye is often used to describe the size of the mouth of a fish.

Operculum: The plate at the posterior end of the head that covers the gills, also known as the gill cover or gill plate.

Orbital bone: The bone that surrounds the eye of a fish.Lunate tail, finlets, caudal keel, and caudal peduncle

Posterior: The tail/caudal end of the fish.

Preopercle: A bone at the front of the operculum that may have spines.

Scutes: A bony type of projection. Often is a modified scale. Presence or absence, location, count, and type of scutes is very useful in identifying certain species of fish.

Subterminal: Term used to describe a mouth that is oriented behind the snout and faces downward.

Ventral: The belly surface of the fish. In most fish species this is the underside of the fish. In flatfish the ventral surface is the side opposite the dorsal fin.

Wrist: The point at which the body of the fish narrows down and the caudal fin begins (also referred to as the caudal peduncle).

Catch rankings:

Primary species - These are species that are specifically targeted by a good portion of the ocean boat anglers. The seven prime species that fall into this category include: Albacore, black rockfish, chinook salmon, coho salmon, lingcod, Pacific halibut, and yellowtail rockfish.

Common species - These are species that are generally not intentionally targeted by very many ocean boat anglers, but are generally desirable species and are regularly caught incidental to other species. A common species on average accounts for more than 0.25% of the total catch. There are 10 species that fall into this category including: Blue rockfish, cabezon, canary rockfish, China rockfish, copper rockfish, kelp greenling, quillback rockfish, vermillion rockfish, widow rockfish, and yelloweye rockfish.

Uncommon species - These are species that typically make up between 0.05% and 0.25% of the landed catch for the ocean boat recreational fishery. Usually, more than 100 of these will be landed in an average season. There are about 15 species that fall into this category.

Unusual species - These are species that typically make up less than 0.05% of the landed catch of the ocean recreational boat fishery during the season. In most years, at least a few of each of these species are landed.

Rare species - These are species that are not regularly landed in the ocean recreational boat fishery off Oregon. For some species listed, there may have never been a recorded landing in Oregon, but the species is known to inhabit the offshore waters and is known to be caught in recreational fisheries elsewhere. Many of these species may enter the fishery only during warm water cycles, or when ocean currents are favorable.

Species not listed - There are a large number of species that are not listed. There are many more species that are known to inhabit the ocean off Oregon, but have not been previously landed in the recreational fishery and due to life history characteristics are unlikely to be caught unless anglers change fishing methods and locations.

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Eric Schindler
Oregon Department of Fish & Wildlife
2040 SE Marine Science Drive
Newport, Oregon 97365
(541) 867-4741


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04/26/2021 10:16 AM