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North Sea Food Web

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Emma McRae

on 24 October 2012

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Transcript of North Sea Food Web

North Sea Food Web Phytoplankton Sea Anemone
Bolocera tuediae Starfish
Common sunstar Crossaster papposus Common Sea Urchin
(Echinus esculentus) These are one of the largest North Sea anemones. The base may reach a diameter of 25 cm and it has almost 200 tentacles.
Unlike many other anemones, it does not mind muddy substrate. This is why you are likely to find it in the fjords, close to river estuaries.Recent records from divers are in Scottish sea lochs.

Sea anemones eat plankton and shrimp and each other. Sea anemone spend most of their time attached to rocks on the sea bottom or on coral reefs waiting for food to pass close enough to get caught in their tentacles. The tentacles are triggered by the slightest touch and inject a paralyzing neurotoxin into their victim.

Fact : If a piece of a sea anemone gets torn off, it will become a new sea anemone! Brown Algae (Laminaria)
Kelp Forests The common sunstar is named after the fact that it looks like a sun with its 8 to 14 arms - 12 inches long. The common sunstar is quite fast for a starfish, reaching top speeds of 70 centimeters per minute. It has the ability to eat sea urchins and anemones which are mainly poisonous to other marine animals.

Fact - It consumes its prey by pushing its stomach out of its mouth. The common sea urchin browses on seaweeds such as kelp moving along the sea floor by means of 'tube feet', which project out from the spines.
The mouth is located centrally on the underside and contains 5 calcareous plates, known as an 'Aristotle's lantern' which acts as a jaw.

There is a large international market for sea urchin products, particularly the roe (Reproductive organs) which is the only edible part. Exploitation of sea urchins grew rapidly in many countries, and in many cases over-exploitation and collapse of the sea urchin populations followed. There was a sea urchin fishery in Cornwall in the 1980s, and the potential of a fishery in Shetland.

Fact - Esculentus is the Latin word for edible Common Shrimp
(Cragnon-cragnon) Phytoplankton are similar to plants in that they contain chlorophyll and require sunlight in order to live and grow. Most phytoplankton are buoyant and float in the upper part of the ocean, where sunlight hits the water. Phytoplankton also require nutrients such as nitrates, phosphates, and sulfur which they convert into proteins, fats, and carbohydrates.

In a balanced ecosystem, phytoplankton provide food for a wide range of sea creatures including whales, shrimp, snails, and jellyfish. When too many nutrients are available, phytoplankton may grow out of control and form harmful algal blooms. These blooms can produce extremely toxic compounds that have harmful effects on fish, shellfish, mammals, birds, and even people. Kelp forests provide food and shelter for many species which makes it an important part of the food web. Species that eat kelp include shellfish such as crabs and herbivorous urchins which feed on the kelp. The high presence of fish life here also makes kelp forests primary feeding grounds for grey seals.

Overfishing, in nearshore waters can release herbivores from their normal habitat and result in over grazing of kelp. Sea Hare
Aplysia punctata They can be found in shallow water, and even rock pools, where they feed by browsing on algae.
When disturbed they can discharge a toxic cloud containing sulphuric acid which is distasteful to any predator.
This long and narrow animal has an upper pair of tentacles that look a lot like the ears of a hare. A sea hare can reach 20cm in length but are mostly small.
These animals tend to feed on seaweeds and the type they eat (green, brown or red) gives them their over all colour. Lion's Mane Jellyfish
(Cyanea capillata)


The Lion’s Mane Jellyfish is one of the biggest animals in the oceans and certainly the biggest jellyfish known. It has been known to grow up to 3m across its body with tentacles of 100m in length. This jellyfish starts out life in late winter as a tiny plankton and by feeding on other planktonic organisms, it can grow to this huge bulk in just a few short months.

It feeds by pulsing its way to the surface and then letting itself sink. As it does so, its tentacles spread out around it like a huge circular net and as it slowly drops through the water animals such as fish, plankton and other jellyfish sticks to the tentacles and is consumed. Zooplankton Copepods are are a group of small crustaceans -sometimes called the insects of the sea because there are so many of them, about 10,000 species.

Copepods are the dominant members of the zooplankton, and are major food organisms for small fish, whales, seabirds and other crustaceans.

Fact: Jellyfish are also a part of Zooplankton! Atlantic Herring (Claupea harengus) The Atlantic herring is considered to be the most abundant fish species in the North sea - a small, plankton-feeder.
Today, they are Scotland’s third most popular catch and a crucial part of the diet of many larger fish (including commercial species, like cod and haddock), marine mammals and seabirds. They are considered to be a very important part of the food chain as they are the main converters of plankton into fish. The Atlantic Mackerel is typically an open ocean fish with excessive feeding habits.
They travel in schools that often contain thousands of fish. Young mackerel feed on microscopic copepods.
As they grow, they feed on progressively larger prey. Adults will eat any fish smaller than themselves, feeding heavily upon small herring. They also consume a variety of invertebrates such as copepods, squid and shrimp.
Fishing quotas are still in place to protect mackerel in the North Sea. But this means that mackerel landed as a by-catch when fishing for other species are regularly thrown back into the sea dead. Atlantic Mackerel
(Scomber scombrus) Squid
(Loligo forbesi) These Squid are thought to live mainly in deep water on the Atlantic edge of the continental shelf. They grow very fast; Loligo reach maturity 1 year after hatching. The life span of squid is seldom more than 2-3 years.
Squid feed on plankton after hatching, but the adults are active predators which feed on shrimp and other squid. They break up the animal into bite-sized pieces with their sharp beaks.

Fact - These squid constitute the bulk of the UK commercial catch however, no quota has been set for catching these squid. King Scallop
( Pecten maximus) The scallop is a filter feeder and is reliant on the surrounding plankton for its well-being. The scallop is the only bivalve that can swim. It does this by rapidly opening and closing its shell thus producing a jet of water that propels it away from predators such as starfish.
King Scallops lie partly buried in the sediment on the seafloor, and are relatively fast The majority of Scottish Scallops are captured with dredges, which can cause substantial damage to the habitat. European Plaice (Pleuronectes platessa) The plaice is Europe's most important commercial flatfish. Heavy fishing, however, has resulted in a progressive reduction in the size and age of fish landed.
European plaice spend the day buried in the sand, emerging at night to feed on shellfish and crustaceans, which they crush using special teeth in the throat. Atlantic Cod
(Gadus morhua) Atlantic cod are some of the least fussy eaters and most cannibalistic fish in the sea, feeding on just about anything – including, herring, mackerel, coral, birds and other cod. Prior to its recent population decline, the adult Atlantic cod were top-tier predators now that the cod stocks have dramatically decreased their prey has had a population explosion. The Atlantic cod is a fish in crisis. the European Environment Agency (EEA) warn that the risk of a collapse of the fish stock in the North Sea is high, and that populations are now outside safe biological limits. Haddock
(Melanogrammus aeglefinus) Sand eels
(Ammodytidae) Sandeel are territorial, preferring to stick to a particular area of the seabed. They live only on sandy sediments, into which they can burrow. Emerging to forage during the day, sandeel collect in large feeding shoals. They tend to feed on zooplankton.
Until the early 2000s, the largest fishery in the North Sea was based on sandeel. Sandeel is mainly used for indusrial purposes such as fish oil for health food supplements or fertiliser.
These fish are also a particular favourite of a variety of seabirds, including the puffin.
The decline in numbers of gulls is thought to stem from the overfishing of sandeel. The diet of haddock varies with the size of the fish, the time of year, and with the area. In the winter months haddock of all sizes feed mainly on worms, small molluscs, sea urchins and brittle stars. In the spring and summer fish prey are important, particularly for the larger haddock such as sand eels.

Perhaps best known as Scotland’s favourite ‘fish supper’, haddock are the fourth most popular fish to eat in the UK (the third in Scotland). In 2010, £32million-worth of haddock was landed in Scotland. Haddock are also a crucial part of the diet of other marine species, like cod, seals and porpoises. Bottlenose dolphins feeding behaviour varies by habitat, so it’s likely that a population chooses its prey according to what’s in plentiful supply in the area. Scottish populations feed on sandeel and flatfish such as plaice. They hunt schools of fish as a group.
They detect the schools of fish with sonar, then surround the school slowly & chase them into their mouths.
Some look different than others in the area they live in; the ones living close to the coast are smaller than the ones living further out to sea.
Fact - They disappeared in the 1930’s but were spotted back in 2004 & the spottings are becoming more frequent now. Bottlenose Dolphins Aka Flipper (Tursiops)

They eat what is available to them at the time. In Scottish waters, prey includes cod, haddock and sandeel. Harbour seals are well adapted predators with their sharp teeth & streamlined bodies this enables them dive to depths of up to 50m to hunt along the seabed. They pick up the vibrations of passing fish using their whiskers. Although they don’t hunt as widely as grey seals, harbour seals can also stay out at sea for days. An individual consumes around 3–5kg of fish daily

Fact - Each individual seal seems to have their own preference for specific fish species and their diet changes with every season. Harbor Seal
(Phoca vitulina) White beaked Dolphin
(Lagenorhynchus albirostris) Their diet consists of squid & small fish like herring. These dolphins are known to hunt co-operatively. Working together, a pod will herd shoals of fish towards the surface where they can be picked off more easily. They live in groups of 6-20 others.
They are the most common dolphin in the North Sea where there are between 7 & 8,000. Minke Whale
(Baleaenoptera acutorostrata) Their main prey is zooplankton. Minke whales have baleen instead of teeth. They glide up behind their prey and distend their mouths to scoop up enormous quantities of food in one go, straining out seawater through the bristly baleen. Following peak feeding periods, minke whales store excess energy as blubber to see them through leaner times. When shrimp are still small (smaller than 1 cm), they do not live at the bottom of the sea; but float around in the water. They will mainly eat zooplankton and phytoplankton. Shrimp, however, grow quite fast (after a year they are usually 4 cm long) and then live at the bottom of the sea. Also they start to eat a larger variety of food and more and more often they search for other small animals as food. In British waters, they feed mostly on mackerel. When offshore, they become is a nocturnal feeder, picking off the squid and lantern fish that feed on the surface at night. Shoals of common dolphins hunt together, the individuals herding fish into places from which it’s hard to escape and forcing fish to move up to the surface were the dolphins will dive on top of the school of fish. Common Dolphin
(Delphinus delphis) Grey seals feed mainly on sandeel. They generally forage within 50km often targeting sandy seabeds where their main prey are more likely to be found.

Grey seals can be distinguished from harbour seals by their larger size, long wide muzzle and flat 'Roman' nose. Their nostrils also form a 'w' shape when closed, compared to the 'v' shape of common seals. Grey Seal
(Halichoerus grypus) Harbour Porpoises
(Phocoena phocoena) More than half the global population of harbour porpoises can be found in Scotland’s waters. This can be hard to believe, since the species is seldom sighted. Harbour porpoises are Scotland’s smallest cetaceans, so they’re difficult to spot. Also, unlike their dolphin relatives, they are very shy.
What harbour porpoises feed on varies by the individual’s age and the season. Around Scotland, sandeels are the most common prey during spring/summer. In autumn/winter, harbour porpoises eat herring, mackerel, Norway pout, poor cod and sprat. Harbour porpoises tend to forage alone, generally along the sea floor. Killer Whales (Orcas) The orca or killer whale is a toothed whale that is an efficient predator, even attacking huge young blue whales. Their only enemy is human beings.
Orcas live in small life-long pods, they actually belong to the family of dolphins and is the biggest dolphin. They will eat a wide variety of species including dolphins, seals, whales, squids, cormoras & gulls.
Orcas can dive to a depth of 100 feet (30 m) and they can swim up to 30 mph (48 km) in order to catch prey. Puffins feed mostly on sandeels, though they do prey on other young fish from the open sea, such as herring and capelin, and young fish from the bottom of the sea bed, such as gadids. They are able to dive for 60m to hunt for fish, but usually prefer to dive only 30m. Sandeels are a very import food source for young puffins: chicks have been known to starve during sandeel shortages. Puffin
(Fratercula) Herring Gull
(Larus argentatus) Cormorant
(Phalacrocorax carbo) A large waterbird, it is often seen standing with its wings held out to dry. Regarded by some as black, sinister and greedy, cormorants are supreme fishers which can bring them into conflict with anglers. The Cormorant normally feeds on fish, obtained by diving from the surface with or without a forward leap. They tend to eat fish smaller than 20cm in length such as sandeels as well as some crustaceans. These are omnivores and will scavenge from garbage dumps, landfill sites, and sewage outflows. Herring Gulls may also dive from the surface of the water or engage in plunge diving in the pursuit of aquatic prey, though they are typically unable to reach depths of greater than 1–2 metres due to their natural buoyancy. Despite their name, they have no special preference for herrings. There natural diet also contains fish offal and crustaceans such as shrimp. Northern Gannet
(Morus bassanus) The northern gannet is the largest seabird in the North Atlantic. Gannets often perform dramatic plunge dives from high in the sky to catch fish up to depths of 20m and can stay submerged for over half a minute. They feed mostly on small fish that live in dense schools, including herring and cod and discards from fishing vessels, where their large size helps them out compete most other scavenging species. By Emma McRae, Clare McCabe, Kirsty Lynch, Bugrahan Keskindag and Katy Mcbride
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