Gadiformes

Gadiformes, also called the Anacanthini, is an order of ray-finned fish. This group includes many well-known species like cod, hakes, pollock, and haddock. Many of these fish are also called burbot, rocklings, or moras. These fish are very important to humans because they are major commercial food fish. They are found in oceans all over the world. Most of these fish prefer temperate or colder waters. However, some tropical species live in very deep water.

These fish have specific physical traits that define them. Their fins are spineless, which is a distinct characteristic. Another key feature is the position of their pelvic fins. These fins are located either below or in front of the pectoral fins. Gadiformes are also classified as physoclists. This term describes how they manage their swim bladder. A swim bladder is an internal organ that helps a fish stay buoyant. In physoclists, the swim bladder does not have a pneumatic duct. This means there is no tube connecting the bladder to the mouth.

While most gadiforms live in the salty sea, some can adapt to different environments. Most species stay in marine habitats. Some can enter brackish estuaries, which are areas where fresh and salt water mix. The Pacific tomcod is one of two species in the genus Microgadus. These fish can enter freshwater, though they do not appear to breed there. Interestingly, some landlocked populations of the Atlantic tomcod live their entire lives in freshwater. However, only one species is a true freshwater fish. This species is the burbot, or Lota lota.

Scientists use taxonomy to organize the many families within Gadiformes. The order is divided into several suborders. One suborder is Stylephoroidei, which contains the Stylephoridae family, known as tube-eyes or threadtails. Another is Bregmacerotoidei, which includes the Bregmacerotidae family, or codlets. The large suborder Gadoidei contains many familiar groups. This includes the Gadidae family, which contains cods and haddocks. It also includes the Lotidae family, which contains hakes and burbots. Other suborders like Ranicipitoidei and Merluccioidei house different specialized families.

The diversity of these fish is reflected in their many different families. For example, the Merlucciidae family contains merlucciid hakes. The Macrouridae family includes fish known as grenadiers or rattails. There are also deep-sea groups like the Moridae, or deepsea cods. Some families have very specific names, such as the Steindachneriidae, known as luminous hakes. The Trachyrincidae are called armoured grenadiers. This wide variety of families shows how much the order has branched out into different ocean roles.

We can trace the history of these fish through the fossil record. The earliest known gadiforms lived millions of years ago. One example is Palaeogadus weltoni. This species lived during the Maastrichtian period in the United States. Scientists have also found an undescribed fossil known as "Protocodus." This fish lived during the Early Paleocene in Greenland. These ancient fossils help researchers understand how the order evolved. They show that gadiforms have been part of our oceans for a very long time.

Gadiformes vary greatly in size and scale. Some members of the order are extremely small. The codlets are among the smallest, sometimes reaching an adult length of only a few centimeters. On the other end of the scale is the Atlantic cod, or Gadus morhua. This large fish can reach a length of up to 100 centimeters. This massive size difference shows the wide range of the order. From tiny codlets to large Atlantic cod, these fish occupy many different levels of the marine ecosystem.