Section outline

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    Classification of salmonid fish and SDGs

    •  SDGs2  SDGs14  

      In Japan, we have developed a hatching and release business that takes advantage of the salmon's tendency to return to their mother rivers and obtains them as highly productive fishery resources. We aim to upgrade this business to a more robust and sustainable food production system that can adapt to ecosystem considerations and climate change, and through our research we hope to contribute to the SDGs (Zero Hunger, Enriching the Oceans).

      The United Nations has designated the decade beginning in 2021 as “the Decade of Marine Science” to contribute to the SDGs. Marine science as defined by the UN includes the field of fisheries.

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    Fish of the genus Oncorhynchus


    • ベニザケ（ベニ）: Sockeye salmon

      シロザケ（シロ）: Chum salmon

      　点なし: no spots

      カラフトマス（マス）: Pink salmon

      　小さい鱗: small scales 大きな点: big spots

      ギンザケ（ギン）: Coho salmon

      　歯が鋭い: sharp teeth 小さな点: small spots 尾叉弱い: weak fork 太い尾柄: thick tail peduncle

      マスノスケ（スケ）: King salmon

      　口が黒い: black mouth 太い尾柄: thick tail peduncle

      スチールヘッドトラウト（テツ）: Steelhead trout

      　尾叉弱い: weak fork 太い尾柄: thick tail peduncle

    • These are examples of salmonid fish in the genus Oncorhynchus when they are in the open ocean.

      There are many other species of salmonids, such as the cherry salmon and rainbow trout.

      In this course, we will discuss the morphological characteristics that are important in distinguishing between salmonids.

      (See the book "Understanding Salmon and Trout Fishes")


    • Click here for an "Introduction to Salmon" for one subject of General Education Courses of Hokkaido University. URL
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    Slim body shape

    • First, salmonids are generally considered to have a round, slim body shape.


      サケ科: Salmonidae タイ科: Sparidae カレイ科: Pleuronectidae ウナギ科: Anguillidae

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    There is an adipose fin, which is a small fin without fin rays between dorsal fin and caudal fin.


    • Name and role of each fin


    • A: dorsal fin → maintain good swimming posture

      B: adipose fin → an important fin in classification, but details of its role are unknown

      C: pectoral fin → maintain good swimming posture

      D: ventral fin → maintain good swimming posture

      E: anal fin → maintain good swimming posture

      F: caudal fin → gains propulsion when swimming


    • Strength of tail fork Page
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    Dorsal and ventral fins are near the center of the body.


    • Let's look at other fish species.


      ニシン: Pacific herring 真鯛: Red sea bream 市場魚貝類介類図鑑HPより: Pictures from the Market Fish and Shellfish Catalogue website

      Pacific herrings, like salmonids, have dorsal and ventral fins near the center of their bodies, but red sea breams are different.

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    Fins without conspicuous hard thorns (spines), consists mainly of soft striae only.


    • Pictures from the Market Fish and Shellfish Catalogue website

    • The dorsal fin of sea bream has spiny rays. The role of these spines is thought to be to protect them from enemies.

      Why, then, do sea breams have spiny rays but salmon do not?

      Let us consider the differences in life history and habitat.

      We will also examine the development of spiny rays in other fish species and consider the similarities and differences between them.

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    Axillary process (axillary scales) at the base of the ventral fin


    • Chum salmon (Oncorhynchus keta)

    • Rainbow smelts, the family Osmeridae, have an adipose fin but no axially scales.


      Rainbow smelt (Osmerus mordax)

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    Parr mark (pattern resembling a pebble) on the body of juvenile

    • Parr marks are spots on the body of juvenile fish during their river life.

      They are thought to be for camouflage as they resemble pebbles on the river bottom.


    • Conversely, when spending time at sea, salmonids undergo a morphological change called smoltification, in which their backs turn gray and their bellies turn white.

      This is thought to be due to a countershading effect, whereby they assimilate the color of the seafloor when viewed from above and the color of the sky when viewed from below, making them harder to spot by predators.


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    Recommended courses

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    【Related courses】

    Salmon and Trout SDGs2 SDGs14