Tagged Questions

Questions relating to the study of fish.

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What is the difference between a salmon, a trout, and a char?

There are char, Atlantic salmon, and Pacific salmon? Why are some called trout, and others called salmon, and still others char? Is there any systematic way that these names were assigned or are ...
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0answers
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How does anadromous fish physiology “know” to switch from salt to freshwater and back?

What mechanism allows anadromous fish to switch from salt to fresh water and back? How does the fish "know" to switch its physiology and do other fish possess the biochemical machinery for this? How ...
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1answer
54 views

About sharks and how they find fish

Other than olfactory senses do sharks use some kind of sense that uses electromagnetic waves? Is this similar to an electric eel? I saw a book with the cover statement 'Sharks never get cancer'. IS ...
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1answer
58 views

Can you get enough water by eating only fish?

Scenario: In a boat in the middle of the sea, no freshwater or food stores, no desalination equipment, no rain, but you can catch fish and eat it raw. Can you get enough water this way to survive, ...
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1answer
28 views

Do river sharks (genus Glyphis) have reduced rectal glands for salt removal?

Do river sharks of the genus Glyphis have reduced or absent rectal glands for salt removal?   The rectal gland of marine sharks removes excess salts to maintain osmotic balance (Oguri 1964).  In ...
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2answers
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In practice, do fishes die from old age?

I was watching sea birds eating fishes and wondered if fishes actually died from old age, or if they are all eaten before this can happen? I reckon some big predator fishes must be able to live long ...
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2answers
66 views

How does a stonefish get oxygen out of water?

It is said that the stonefish (Synanceia) is able to stay out of the water for up to 24 hours. I wonder how they get oxygen from the air. Could someone explain this?
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1answer
60 views

Why does temperature shock kill fish?

As is advised with most fish you should avoid sudden changes in water temperature (for example by introducing new water that hasn't been left to come to room temperature). I have, however, never ...
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1answer
71 views

Breathing under water

Why can fish breathe under water but land mammals can't? How can fish extract oxygen straight from water but humans can't?
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1answer
61 views

Identifying internal structures of dissected fish

Note : Images displayed below might be disturbing to some people. I have dissected a fish for the first time ! I have some idea of what some of the structures might be but I am not sure and so would ...
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2answers
71 views

Do swarms show intelligence?

Can you think of collective and swarm behaviors as "intelligence"? Would such a concept apply to a) ant colonies and b) fish swarms?
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1answer
43 views

Clownfishes and Sea anemones

Relation between clownfishes and sea anemones is a classic example of mutualism. I wanted to list the species of sea anemones that are involved in this mutualism but I got lost.. Could you help me ...
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1answer
26 views

What Freshwater Fish Are Affected By Magnetic Fields

I am interested in knowing which freshwater fish are affected by magnetic fields. I've heard that Lake Sturgeon are, but would like more references. This is for a project that will have buried 3 ...
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0answers
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Good book for aquarium owning? [closed]

I'm looking for a good book on keeping a good ecosystem in a fish tank. This can include animals such as fish, crabs, turtles, etc. I want to know mainly how to start off as a beginner, so a ...
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1answer
59 views

observed luminescence in a piece of plaice

A plaice fish bought for human feed has been cleaned and cooked. Some parts of the raw body have been left out of the fridge at about 22°C for about 15 hours. During the following night a ...
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1answer
40 views

Why is clownfish attracted to actinia?

I heard that Actinia Equina normally eats what it can catch, but this clownfish here doesn't care much about that: https://www.youtube.com/watch?v=Ughm4mnZ1ls Since the actinia obviously can't hold ...
4
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1answer
288 views

How do sharks and other fish conserve and gain water in marine environments?

With the osmolarity of the average vertebrate being around 300mOsml, and salt water having an osmolarity of 1000mOsml, why does the water from the shark not leave to the salt water around it? I ...
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1answer
32 views

Did the Swedish cod fishery expand in the past years?

The Marine Stewardship Council states that the cod fishery in the Eastern Baltic sea recovered well and issued it's MSC certificate to the Swedish cod fishery in 2011 for that region. (MSC 2011) Data ...
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1answer
345 views

Are there predators evolved to eat puffer fish?

Puffer fish is known for having a anti-predation defense mechanism of having toxin-exuding spikes. Are there predators which evolved specifically to prey on puffer fish? (presumably, by evolving ...
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1answer
32 views

Effect of Ethanol on Brain Volume Measurements

I want to compare the brain sizes of two populations of fish. However, all the samples I have were fixed in 95% ethanol. As far as I know, 4% formalin is the normal fixative for soft tissues. Can I ...
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1answer
154 views

Tuna fish in Baltic sea?

Yesterday my grandmother ate fresh tuna at a friend's party. She swears it was fresh and bought at a local fish-shop. The problem is, that we live in Gdańsk, by the south-eastern side of the Baltic ...
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1answer
1k views

Do fish break a water molecule to absorb oxygen?

How do fish separate oxygen from H20 & consume it? Do they break the water molecule and absorb the oxygen only?
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2answers
68 views

Is vision a vestigial sense for deep ocean species?

Sunlight doesn't penetrate beyond a couple of hundred feet from the surface of the ocean. Species that exist at greater depth probably live in a state of perpetual night; yet from a quick google image ...
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1answer
195 views

Salmon returning to lay eggs

To spawn, salmon return to the river in which they were born. Is it because the individuals remember the specific river, or because populations are genetically conditioned to follow specific ...
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1answer
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harvesting fertilized eggs from Tetraodontidae species?

I would like to know how easy/difficult it is to harvest fertilized eggs from Tetraodontidae species such as Tetraodon nigroviridis or Takifugu rubripes compared to zebrafish? Ultimately, I would like ...
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3answers
464 views

Why is there a difference in the rotation of the tail fin in fish compared to marine mammals?

I've been thinking about this one, but I can't seem to find what causes this difference. All fishes that I've seen have their tail fin positioned vertical: But all the marine mammals I know have ...
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1answer
255 views

Do the majority of fish lack scales on their heads?

Based on pictures, it seems to me that a vast majority of fish species that have scales do NOT have scales on their heads. Is that fact true? To make this properly answerable: lets' define a ...