Questions relating to the study of fish.

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1answer
618 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
61 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
2k 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
51 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 ...
5
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1answer
273 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 GdaƄsk, by the south-eastern side of the Baltic ...
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1answer
2k 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
135 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 ...
11
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1answer
218 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 ...
6
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1answer
52 views

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
2k 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 ...
13
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1answer
422 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 "...