Squid in the context of "Invertebrates"

Fishing is the activity of trying to catch fish. Fish are often caught as wildlife from the natural environment (freshwater or marine), but may also be caught from stocked bodies of water such as ponds, canals, park wetlands and reservoirs. Fishing techniques include trawling, longlining, jigging, hand-gathering, spearing, netting, angling, shooting and trapping, as well as more destructive and often illegal techniques such as electrocution, blasting and poisoning.

The term fishing is also used more broadly to include catching aquatic animals other than fish, such as crustaceans (shrimp/lobsters/crabs), shellfish, cephalopods (octopus/squid) and echinoderms (starfish/sea urchins). The term is not normally applied to harvesting fish raised in controlled cultivations (fish farming). Nor is it normally applied to hunting aquatic mammals, where terms like whaling and sealing are used instead.

Mollusca is a phylum of protostomic invertebrate animals, whose members are known as molluscs or mollusks (/ˈmɒləsks/). Around 76,000 extant species of molluscs are recognized, making it the second-largest animal phylum after Arthropoda. The number of additional fossil species is estimated between 60,000 and 100,000, and the proportion of undescribed species is very high. Many taxa remain poorly studied.

Molluscs are the largest marine phylum, comprising about 23% of all the named marine organisms. They are highly diverse, not just in size and anatomical structure, but also in behaviour and habitat, as numerous groups are freshwater and even terrestrial species. The phylum is typically divided into 7 or 8 taxonomic classes, of which two are entirely extinct. Cephalopod molluscs, such as squid, cuttlefish, and octopuses, are among the most neurologically advanced of all invertebrates—and either the giant squid or the colossal squid is the largest known extant invertebrate species. The gastropods (snails, slugs and abalone) are by far the most diverse class and account for 80% of the total classified molluscan species.

Penguins are a group of flightless, semi-aquatic, sea birds which live almost exclusively in the Southern Hemisphere. Only one species, the Galápagos penguin, lives at, and slightly north of, the equator. Highly adapted for life in the ocean water, penguins have countershaded dark and white plumage and flippers for swimming. Most penguins feed on krill, fish, squid and other forms of sea life which they catch with their bills and swallow whole while swimming. A penguin has a spiny tongue and powerful jaws to grip slippery prey.

They spend about half of their lives on land and the other half in the sea. The largest living species is the emperor penguin (Aptenodytes forsteri): on average, adults are about 1.1 m (3 ft 7 in) tall and weigh 35 kg (77 lb). The smallest penguin species is the little blue penguin (Eudyptula minor), also known as the fairy penguin, which stands around 30–33 cm (12–13 in) tall and weighs 1.2–1.3 kg (2.6–2.9 lb). Today, larger penguins generally inhabit colder regions, and smaller penguins inhabit regions with temperate or tropical climates. Some prehistoric penguin species were enormous: as tall or heavy as an adult human. There was a great diversity of species in subantarctic regions, and at least one giant species in a region around 2,000 km south of the equator 35 mya, during the Late Eocene, a climate decidedly warmer than today.

Camouflage is the use of any combination of materials, coloration, or illumination for concealment, either by making animals or objects hard to see, or by disguising them as something else. Examples include the leopard's spotted coat, the battledress of a modern soldier, and the leaf-mimic katydid's wings. A third approach, motion dazzle, confuses the observer with a conspicuous pattern, making the object visible but momentarily harder to locate. The majority of camouflage methods aim for crypsis, often through a general resemblance to the background, high contrast disruptive coloration, eliminating shadow, and countershading. In the open ocean, where there is no background, the principal methods of camouflage are transparency, silvering, and countershading, while the ability to produce light is among other things used for counter-illumination on the undersides of cephalopods such as squid. Some animals, such as chameleons and octopuses, are capable of actively changing their skin pattern and colours, whether for camouflage or for signalling. It is possible that some plants use camouflage to evade being eaten by herbivores.

Military camouflage was spurred by the increasing range and accuracy of firearms in the 19th century. In particular the replacement of the inaccurate musket with the rifle made personal concealment in battle a survival skill. In the 20th century, military camouflage developed rapidly, especially during the World War I. On land, artists such as André Mare designed camouflage schemes and observation posts disguised as trees. At sea, merchant ships and troop carriers were painted in dazzle patterns that were highly visible, but designed to confuse enemy submarines as to the target's speed, range, and heading. During and after World War II, a variety of camouflage schemes were used for aircraft and for ground vehicles in different theatres of war. The use of radar since the mid-20th century has largely made camouflage for fixed-wing military aircraft obsolete.

A cephalopod /ˈsɛfələpɒd/ is any member of the molluscan class Cephalopoda /sɛfəˈlɒpədə/ (Greek plural κεφαλόποδες, kephalópodes; "head-feet") such as a squid, octopus, cuttlefish, or nautilus. These exclusively marine animals are characterized by bilateral body symmetry, a prominent head, and a set of arms or tentacles (muscular hydrostats) modified from the primitive molluscan foot. Fishers and Swedes sometimes call cephalopods "inkfish", referring to their common ability to squirt ink. The study of cephalopods is a branch of malacology known as teuthology.

Cephalopods became dominant during the Ordovician period, represented by primitive nautiloids. The class now contains two, only distantly related, extant subclasses: Coleoidea, which includes octopuses, squid, and cuttlefish; and Nautiloidea, represented by Nautilus and Allonautilus. In the Coleoidea, the molluscan shell has been internalized or is absent, whereas in the Nautiloidea, the external shell remains. About 800 living species of cephalopods have been identified. Two important extinct taxa are the Ammonoidea (ammonites) and Belemnoidea (belemnites). Extant cephalopods range in size from the 10 mm (0.3 in) Idiosepius thailandicus to the 700 kilograms (1,500 lb) heavy colossal squid, the largest extant invertebrate.

Fishing techniques are methods for catching fish. The term may also be applied to catching other aquatic animals such as molluscs (shellfish, squid, octopus) and edible marine invertebrates.

Fishing techniques include hand-gathering, spearfishing, netting, angling and trapping. Recreational, commercial and artisanal fishers use different techniques, and also, sometimes, the same techniques. Recreational fishers fish for pleasure or sport, while commercial fishers fish for profit. Artisanal fishers use traditional, low-tech methods, for survival in developing countries, and as a cultural heritage in other countries. Mostly, recreational fishers use angling methods and commercial fishers use netting methods.

An octopus (pl.: octopuses or octopodes) is a soft-bodied, eight-limbed mollusc of the order Octopoda (/ɒkˈtɒpədə/, ok-TOP-ə-də). The order consists of some 300 species and is grouped within the class Cephalopoda with squids, cuttlefish, and nautiloids. Like other cephalopods, an octopus is bilaterally symmetric with two eyes and a beaked mouth at the centre point of the eight limbs. An octopus can radically deform its shape, enabling it to squeeze through small gaps. They trail their appendages behind them as they swim. The siphon is used for respiration and locomotion (by water jet propulsion). Octopuses have a complex nervous system and excellent sight, and are among the most intelligent and behaviourally diverse invertebrates.

Octopuses inhabit various ocean habitats, including coral reefs, pelagic waters, and the seabed; some live in the intertidal zone and others at abyssal depths. Most species grow quickly, mature early, and are short-lived. In most species, the male uses a specially-adapted arm to deliver sperm directly into the female's mantle cavity, after which he becomes senescent and dies, while the female deposits fertilised eggs in a den and cares for them until they hatch, after which she also dies. They are predators and hunt crustaceans, bivalves, gastropods and fish. Strategies to defend themselves against their own predators include expelling ink, camouflage, and threat displays, the ability to jet quickly through the water and hide, and deceit. All octopuses are venomous, but only the blue-ringed octopuses are known to be deadly to humans.

Nekton or necton (from the Ancient Greek: νηκτόν, romanized: nekton, lit. 'to swim') is any aquatic organism that can actively and persistently propel itself through a water column (i.e. swim) without touching the bottom. Nekton generally have powerful tails and appendages (e.g. fins, pleopods, flippers or jets) that make them strong enough swimmers to counter ocean currents, and have mechanisms for sufficient lift and/or buoyancy to prevent sinking. Examples of extant nekton include most fish (especially pelagic fish like tuna and sharks), marine mammals (cetaceans, sirenia and pinnipeds) and reptiles (specifically sea turtles), penguins, coleoid cephalopods (squids and cuttlefish) and several species of decapod crustaceans (specifically prawns, shrimp and krill).

The term was proposed by German biologist Ernst Haeckel to differentiate between the active swimmers in a body of water, and the plankton that are passively carried along by the current. As a guideline, nektonic organisms have a high Reynolds number (greater than 1000) and planktonic organisms a low one (less than 10). Some organisms begin their life cycle as planktonic eggs and larvae, and transition to nektonic juveniles and adults later in life. This may make distinction difficult when attempting to classify certain plankton-to-nekton species as one or the other. For this reason, some biologists avoid using this term.