The operculum is a hard, plate-like, bony flap that covers the gills of a bony fish (superclass: Osteichthyes). It protects the gills and also serves a role respiration. Fish can acquire dissolved oxygen through pumping water over their gills by opening and closing their jaws and opercula. The water is flushed from the fish’s mouth over … [Read more…]
Turtle Excluder Devices (TEDs) are a specific type of bycatch reduction device (BRD) that are a modification to a trawl net to keep turtles, which are not targets of the fishery, from being caught in the net. TEDs are generally composed of a set of bars over the trawl net. While small target animals, such … [Read more…]
Bycatch is non-target catch within any fishery. Bycatch can be either different species from the target of the fishery or individuals from the target species, generally juveniles, which are not of a marketable size. Most bycatch is tossed back because it is illegal to possess or it has no commercial value. In certain fisheries, however, … [Read more…]
Fish Aggregating Devices (FADs) are man-made objects that are used to attract fish and facilitate their capture. FADs can range from crude wooden rafts tied to navigational buoys to sophisticated anchored systems. These devices are very effective at attracting fish that favor submerged objects. Prey fish use them for shelter and predatory fish follow the … [Read more…]
Ganoid scales are dimond-shaped scales found in lower order fishes such as the bichirs (Polypteridae), Bowfin (Amia calva), paddlefishes (Polyodontidae), gars (Lepisosteidae), and sturgeons (Acipenseridae). Unlike ctenoid or cycloid scales, ganoid scales are comprised of bone. They have a bony basal layer, a layer of dentin (also found in human teeth), and an outer layer … [Read more…]
Ctenoid scales are scales with comb-like edge found in higher order teleost fishes, such as perch and sunfish. Cteni are the tiny teeth on the posterior margin of the scale. Similar to cycloid scales, they are overlapping which allows for greater flexibility in movement than other types of scales such as ganoid scales. The surface layer … [Read more…]
Cycloid scales are smooth-edged scales predominately found in lower order teleost fishes, such as salmon, carp and other soft fin rayed fish. Similar to ctenoid scales, they are overlapping which allow for greater flexibility in movement than other types of scales such as ganoid scales. The surface layer of the scale is comprised of calcium-based … [Read more…]
Otoliths are ear bones in fish. Bony fish (not sharks or rays) have three pairs of otoliths: Sagitta: detects sound and converts sound waves into electrical signals (i.e., hearing); Asteriscus: detects sound and is involved in hearing; and, Lapillus: detects gravitational force and sound. Sagittal otoliths are sometimes used for aging fish because they add … [Read more…]
The length of a fish is often used for fish population assessments (e.g., length-age and weight-length relationships) and consequently are often used in recreational fishing regulations. But, just as there is “more than one way to skin a cat,” there is more than one way to measure the length of a fish. Below are three … [Read more…]
Finlets are highly specialized fins located on the dorsal and ventral sides of the body between the dorsal fin and/or the anal fin and the caudal fin. They are only found on certain fish including those in the Scombrid family (mackerels, tunas, and bonitos), Scomberesocid family (sauries), snake mackerels (family Gempylidae), and Bichirs (family Polypteridae). For Bichirs, the finlets are … [Read more…]