Fishes
Fishes are a highly diverse group of vertebrates. They include the cartilaginous fishes (sharks, skates, rays, chimera), the ray-finned fishes (paddlefishes, spoonfishes, pipefishes, seahorses, sturgeons, to name just a few), and the lobe-finned fishes (coelacanths and lungfishes).
10 Facts About Fish
1. Fish are divided into three basic groups which include cartilaginous fish, bony fish, and lobe-finned fish.
Cartilaginous fish (Class Chondrichthyes) are so named because instead of bony skeletons, their body frame consists of cartilage. Tough and flexible, cartilage provides enough structural support to enable these fish to grow to incredible sizes. Cartilaginous fish include sharks, rays, skates and chimaeras.
Ray-finned fish (Class Actinopterygii) are the most diverse of the three groups of fish. The group includes mor than 23,000 species such as salmon, trout, lanternfish, cavefish, cods, anglerfish, tarpon, herrings, electric eels and many others. In contrast to cartilaginous fish, the skeleton of ray-finned fish is composed of true bone.
Lobe-finned fish (Class Sarcopterygii) are a group of bony fish that have paired fins that are at their base fleshy lobes. Ancient lobe-finned fish are thought to be the ancestors of the first four-legged land vertebrates or tetrapods. Modern lobe-finned fish include lungfish and coelacanths.
2. Fish were the first animals to evolve backbones.
The earliest known fish were the ostracoderms, a now-extinct group of jawless fish that appeared in the Cambrian Period, about 510 million years ago. These primitive fish had a notochord but no jaw bones or teeth. Other early fish-like animals include the conodonts and the agnanthans (the hagfish and the lamprey).
3. The ray-finned fish are the largest group of fish.
There are nearly 24,000 species of ray-finned fish which are divided into 431 families.
4. Some species of fish migrate between freshwater and marine environments to spawn.
Such species are referred to as diadromous. They are further described by the direction of their migration. Fish that migrate from the sea into freshwater rivers to spawn (for example, salmon) are described as anadromous. Fish that migrate from a freshwater environment to the sea to spawn (for example, freshwater eels) are described as catadromous.
5. Fish move by creating a wave motion that moves the length of its body.
This wave motion begins at the head and moves to the tale where the resulting side to side motion produces thrust to move the fish through the water.
6. Fish are cold-blooded (ectothermic) animals.
Their internal body temperature is therefore the same as the surrounding water.
7. Many species of cichlids brood their eggs in their mouth.
After the eggs hatch the parent continues to use their mouth to provide shelter for their young.
8. There are two groups of jawless fish alive today.
Once a diverse group of fish that appeared over 500 million years ago, jawless fish are today represented only by lampreys and hagfish.
9. Cartilaginous fish include the sea's largest and most skilled marine predators.
These include sharks, skates, rays, and chimeras. These fish have skeletons made from cartilage, not bone. The cartilaginous skeletons are more flexible than bone.
10. The lateral line system on some fish detects variations in water pressure.
This helps fish detect prey and avoid predators.
The 3 Basic Fish Groups
An Introduction to the Main Fish Groups
2. Ray-finned Fishes
Ray-finned fish (Class Actinopterygii) are the most diverse of the three groups of fish. The group includes mor than 23,000 species such as salmon, trout, lanternfish, cavefish, cods, anglerfish, tarpon, herrings, electric eels and many others. In contrast to cartilaginous fish, the skeleton of ray-finned fish is composed of true bone.3. Lobe-finned Fish
Lobe-finned fish (Class Sarcopterygii) are a group of bony fish that have paired fins that are at their base fleshy lobes. Ancient lobe-finned fish are thought to be the ancestors of the first four-legged land vertebrates or tetrapods. Modern lobe-finned fish include lungfish and coelacanths.Lobe-finned Fishes - Class Sarcopterygii
Lobe-finned Fishes - Class Sarcopterygii.
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Global Warming Could Be Linked to Dwindling Fish Stocks
Friday January 11, 2002
Scientists are investigating what role climate change plays in the decline of fish stocks throughout the North Atlantic. Previously, overfishing has been cited as the primary reason for dwindling fish stocks but now scientists are investigating another, potentially greater threat that could be contributing to stock decline.
Zooplankton levels have fallen by 90 percent during the last 40 years (National Geographic). And because it provides a vital food source for many fish species including cod and haddock, declining zooplankton could be responsible for the recently observed population crashes in fish stocks.
Plankton are microscopic organisms that drift on the oceans' currents. They include organisms such as diatoms, dinoflagillates, krill, and copepods as well as the microscopic larva of crustaceans, sea urchins, and fish. Plankton also include tiny photosynthetic organisms that are so numerous and productive that they are responsible for generating more oxygen than all other plants on Earth combined.
Plankton are categorized into the following groups based on their trophic role (the role they play within their food web):
Zooplankton levels have fallen by 90 percent during the last 40 years (National Geographic). And because it provides a vital food source for many fish species including cod and haddock, declining zooplankton could be responsible for the recently observed population crashes in fish stocks.
Plankton are microscopic organisms that drift on the oceans' currents. They include organisms such as diatoms, dinoflagillates, krill, and copepods as well as the microscopic larva of crustaceans, sea urchins, and fish. Plankton also include tiny photosynthetic organisms that are so numerous and productive that they are responsible for generating more oxygen than all other plants on Earth combined.
Plankton are categorized into the following groups based on their trophic role (the role they play within their food web):
- phytoplankton - Phytoplankton are the primary producers of the planktonic world. They are photosynthetic plankton and include organisms such as diatoms, dinoflagellates, and cyanobacteria.
- zooplankton - Zooplankton are the consumers of the planktonic world. As such, they feed on other plankton to obtain the energy and nutrients they need to survive. Zooplankton include the larvae of fish, crustaceans.
- bacterioplankton - Bacterioplankton are the recyclers of the planktonic world. They are free-floating bacteria and archaea that serve to break-down and recycle waste material in the seas.
- holoplankton - Holoplankton are organisms that are planktonic for the entirety of their life cycle.
- meroplankton - Meroplankton are organisms that are planktonic for only part of their life cycle, for example, only during the larval stage of their development.
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