What do salmon eat in the sea? – Most people have a vague idea about this – but the truth is we don’t know much about the matter and science can only provide a partial glimpse into the Atlantic Salmons life at sea.
Above: High-seas salmon-pioneer Mr Flemming Madsen with Atlantic salmon caught in the Baltic sea near Ystad
Marine biologists suggest that salmon is opportunistic feeders – and no real conclusion has yet been made on food selection – feeding behaviour and foraging of the Atlantic Salmon.
What do salmon eat in the sea?
* A survey of content from salmon stomachs show that fish could be the bulk diet in weight – but shrimps could account for 95% of the food in numbers.
Left: The author with a 20 kilo 120 centimetre (44 lb. and 47 inches) Atlantic salmon from the Baltic sea – Caught at 135-foot depth over 200 foot of water, on a salted sprat – Fight took 55 minutes. The salmon had 13 sprats and a small sea trout in its stomach which in turn had 3 sticklebacks in its stomach.
Note the huge silver tail that completes this supreme deep-sea predator.
Baltic salmon is on a protein-rich diet
(Throw 1968) In a study on the Baltic salmon, showed that salmon bigger than 60 centimetres long (23,6 inches) would eat no less than 50 grams of food every day.
Throw; also estimate that the entire stock of Atlantic salmon in the Baltic would consume more than 16 000 tons of sprats in a year.
Above: Sprattus Sprattus (type species) Common European Sprat – The main food source for the Atlantic salmon living in the Baltic Sea – This sprat grow to – 14 – 15 centimetres.
What do salmon eat in the sea?
Shrimps: a sought after meal
* Studies into salmon feeding at high seas in the North-East Atlantic by biologist Jacobsen J. A. and Hansen L. P. (2001) show that shrimps accounted for 95% of the food in number, but only about 30% by weight.
Fish and crustacean prey accounted for 96% of the weight of all prey taken by salmon but
the report also mentions a small percentage of birds and bird remains… being part of the salmon stomach contend !!
Right: The Frances fly one of the most successful salmon flies ever made -most likely interpreted by salmon as a shrimp.
Where salmon fishing was conducted during the survey
Important crustaceans from the Jacobsen and Hansen survey
Studies into salmon feeding at high seas in the North-East Atlantic show that shrimps accounted for 95% of the food in number, but only about 30% by weight
Above: Crustaceans of the genus Thermistor libellula one of the crustaceans salmon had eaten in the sea north of the Faeroe Islands – Along with other crustaceans, this source of food was found in high numbers during the part of the survey that was conducted during late autumn. Photo Mr Claude Nozères, World Register Of Marine Species
Above: Thermisto libellula in comparison to its cousin: Themisto abyssorum. Photo Mr Kwasniewski Slawomir, World Register Of Marine Species
Above: Meganyctiphanes norvegica swimming with a Thermisto libellula (see above) – Both important animals in the zooplankton food chain. Both 30 – 45 millimetres big. Photos Mr Claude Nozères, World Register Of Marine Species
Above: Sergestes arcticus (top of photo) another type of shrimp. Below in same photo a Nothern krill, Meganyctiphanes norvegica. Photo Mr Claude Nozères, World Register Of Marine Species
Above: Paraeuchaeta norvegica. A marine planktonic copepod 6 – 7 millimetre long – The blue sack at the rear is eggs. Photo © ®Fisheries and Oceans Canada, Jean-François St-Pierre, 2011
Above: Crustaceans of the genus Themisto abyssorum – another important food source found during the survey. Photo Mrs Joanna Legeżyńska, World Register Of Marine Species
Above: From top to bottom: Thermisto libellula, Themisto abyssorum and Thermisto compressa. Three crustaceans found in great numbers in the survey conducted in the North-East Atlantic. Photo Mr A. Kraft, Alfred-Wegener-Institut
Above: Meganyctiphanes norvegica A krill commonly known as the Northern Krill. A crustacean that is a central figure in the zooplankton mass and an important course of food for whales, birds and fish in the north Atlantic. Photo: © & ® Øystein Paulsen
Above: Hymenodora glacialis Brilliant blood-red shrimp that grow; to 19 – 20-millimetre. Photo Mr Russ Hopcroft, World Register Of Marine Species
Above: Eusirus holmi – A 40 – 50-millimetre big Gammaridea. Photo Mr Russ Hopcroft, World Register Of Marine Species
Important fish and squid from the Jacobsen and Hansen survey
By weight, 66% of the stomach content was fish, particularly mesopelagic fish. Some larger pelagic fish such as herring, blue whiting and mackerel were also part of the diet.
Above: Maurolicus muelleri: Pearlside. A small silver fish with spots. Size: 40 – 80 mm – a species that live (mesopelagic) from 20 – 400 meters depth. At daytime, it lives at greater depth and rises toward the surface when it gets dark. Photo Mr Jim Ellis, World Register Of Marine Species
Above: lampanyctus crocodilus or Jewel lanternfish. A small fish that feeds on zoo plankton found from 45 – 4000 meters depth – fully grown it will stay between 700-1,000 meter during the day and 4000-1,000 meter at night. Photo Mr Costa, F, Discoverlife
Above: Myctophum punctatum. Its common name is spotted lanternfish Just like Notoscopelus kroeyeri it lives to the depth of 1000 meters during the daytime but may come to the surface during nighttime Photo Mrs Daphne Themelis, World Register Of Marine
Above: Clupea harengus Linnaeus. Commonly known as herring belonging to the family Clupeidae (herrings, shads, sardines, menhadens), which consist of some 200 species, A large family of fish of great importance to marine life also in the North Atlantic. Feeds on copepods, crustaceans and fish eggs. Prefer relatively shallow waters 1 – 200 meters.
Left: Scomber scombrus. Commonly known as the Atlantic mackerel, is a pelagic schooling species of mackerel found on both sides of the North Atlantic Ocean. The species is also called Boston mackerel, or just mackerel. The mackerel is in its own right a ferocious predator that can grow to a length of 50 centimetres – but like most fish, they start out being small and an obvious prey to salmon that roam the same waters as the mackerel. The mackerel strain is growing strong these years and the species is migrating further north into the Arctic ocean – Some say that they have become a strong adversary to the Atlantic salmon who will have to fight for the same food as the Atlantic mackerel – New surveys on this hot topic will surely be worth reading.
Above: gonatus fabricii or Boreoatlantic gonate squid or boreoatlantic arm hook squid, is a squid in the family Gonatidae. (Here a juveniles specimen) It occurs in the northern Atlantic Ocean from Canada to the Barents Sea. Grows to 30 cm in length. This tiny beautiful squid was well represented in both the late autumn and winter surveys done by the Norwegian team. Photo Mr Claude Nozères, World Register Of Marine Species
Above: Arctozenus risso – A long fish of the baracudinas family, occurring singly or in small schools mainly at 200-1000 meters depth. Grows to 29-centimetre. Photo Mr Henk Heessen, World Register Of Marine Species
Above: Notoscopelus kroeyeri, Another deep sea fish that lives to the depth of 1000 meters during the daytime, but may come all the way to the surface during nighttime – Grow to 17 centimetres. Has glowing dots along the body that help to disguise the outline of the fish when seen from below. Photo Mr Henrik Carl, Fiskeatlas –
Above: Benthosema glaciale. Commonly known as Glacier lanternfish. Also, a small migrating deep sea fish that surges to 700 – 1000 meters at day time to return close to the surface at night time Photo Fisheries and Oceans Canada, World Register Of Marine
Above: Micromestistius poutassou. Commonly known as Blue whiting belonging to the cod family. Found over the continental slope and shelf to more than 1000 meters, but more common at 300-400 meters. Blue whiting can grow to a length of more than 40 centimetres. Photo Mr Henk Heessen, World Register Of Marine Species
Above: Belone belone. Commonly known as garfish. Yet another ferocious predator that the Atlantic salmon will feed on when they find them in the right size. The garfish, or sea needle, is a pelagic, oceanodromous needlefish found in brackish and marine waters of the Eastern Atlantic, the Mediterranean Sea and the Baltic Sea. The garfish is a long and slender fish that grows to about 50 to 75 centimetres – They hunt in packs near the surface, Photo Mr Pillon Roberto, World Register Of Marine Species
What do salmon eat in the sea? - Facts from other surveys on salmon feeding
Science will tell us that adult salmon will prey on whatever organisms are present
86 % of the food was Caplin
A survey from 1952 done at the Faroese Islands show that pre-grilse had eaten amphipods (thermistor gaudichaudi) – and squid (Brachioteuthis riisei), while another survey from 1967 done by Shearer and Balmain off Greenland showed that salmon had been taking mainly 86 % Capelin mallets Villousus
Right: mallotus villosus capelin: The capelin or caplin is a small fish of the smelt family found in the Atlantic and Arctic oceans – An important food source to the Atlantic salmon. Photo Mr Claude Nozères, World Register Of Marine Species
Salmon in coastal waters of Greenland feed on fish
(Reddin in 1988) make references to salmon off West Greenland feeding on Capelin and sand eels (sand lance) in coastal waters, while in Labrador Sea herring, barracuda (Parallels coregonides borealis), amphipods, euphausiids and squid make up the major portion of the diet.
Left: Hyperoplus immaculatus commonly known as Sand eel or sand lancer, names used for a considerable number of species of fish. The sand–eel prefer to live near the seabed floor, with a relatively smooth bottom of the gravelly sand. It is a highly important source of food for many fish, birds, and whales.
Grand bank salmon feed on Caplin and sand eel
(Templeman, 1968: Lear 1972: Lear and Christensen, 1980) Redding (1988) reported that salmon caught over the Grand Banks were feeding on capelin and sand lance (sand eel): While over the oceanic depth to the east of the Grand, Bank salmon were feeding on barracuda, black smelt and amphipods.
Right: Hyperoplus immaculatus commonly known as Sand eel or sandeel
Young cod is on the menu in Labrador
In the coastal waters of Newfoundland salmon feed mainly on herring, capelin and sand eels, while in Labrador; pteropods, sand eels, young cod and capelin are the main food (Lear, 1972b.). Reddit (1988) concludes from this wide variety of prey species that adult salmon are opportunistic feeders and prey on whatever organisms are present. Similar conclusions could also be made from the examinations made from salmon stomach from fish caught in the North-east Atlantic
Above left: Gadus morhua. Common name cod. Here a trio of very small cod. Photo Mr Claude Nozères, World Register Of Marine Species
Above right: Gadus morhua (juvenile) – Here a cod about 10 cm or 4 in. Cod is found from the shoreline to the edge of the continental slope. Photo Mr Claude Nozères, World Register Of Marine Species
Caught on sprats – but main food was small krill and tiny crustaceans
Sea animals like amphipods and euphausiids where the main food (Strtuhers 1970 – 71) Fish caught on longline baited with sprats – Another survey at the Faroese Islands also done with the help of longline – found amphipods, (parathemisto spp.) Euphausiids, myctophidae (Lantern fish), capelin and Maurolicus muelleri (pearlsides)
Right: Myctophidae. Fish of the lanternfishes family. Found offshore at depths of 300 and 1200 meter by day and between 10 and 100 meters at night Photo Mr Henk Heessen, World Register Of Marine Species
Squid was food at deep sea
Another survey from 1985 done on 1145 stomach from salmon – conducted by Hanson and Pethon off the shelf of Helgeland/Trøndelag (Norway) and in the oceanic waters of Andenes (Norway) – show that the most important food items was euphausiids and hyperid amphipods at the shelf of Helgeland/Trøndelag and myctophid Benthosema glacial, and the squid Gonatus fabric and euphausides where found most frequently in the salmon caught of Andenes.
Fantastic video of one type of squide the Atlantic salmon prey on - gonatus fabricii
Scottish salmon was feeding on ragworm
Some Scottish salmon caught in drift nets had eaten polychaete worms (Nereis spp), amphipods, euphausiids (meganyctiphanes norvegica) and herring, sprats, whiting and sand eels (Fraser 1987)
How do salmon get to the food out at sea ?
Moving with the water
It is thought that sea currents and or gyres (big turning currents) – will move small salmon parr from the rivers and fjords along to the feeding areas. They seem to migrate to waters where the water temperature is suitable for growth – and they will follow the cycles of their prey in the great water column as the temperature at sea change during the season. Image sciencelearn.org
Salmon will travel across the ocean
Atlantic salmon will travel to areas of oceanography that distribute zooplankton which serve as food for smaller fish, shrimps, and crustaceans – They will migrate on an inter-continental level as tagged salmon will show: Salmon tagged in the United Kingdom being recaptured in North America and other salmon tagged in North America being caught in Norway
Climate changes may alter the life at sea – and stocks of Atlantic salmon
Some scientists have suggested that the major changes that have been seen in the distribution of sea-surface temperature in the North Atlantic may have contributed to greater mortality among young salmon or post-smolt as they are called – It is thought that these changes could be part of the drastic decline in Atlantic salmon stocks seen over the last decades.