Questions tagged [ichthyology]

Questions relating to the study of fish or icthyology.

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39
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4answers
12k views

Can a person survive on blood in place of water?

This question: Can you get enough water by eating only fish? asks if a person could survive on fish alone. Can a person survive on fish and/ or blood alone of any species if stuck at sea or animal ...
24
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2answers
3k views

What exactly is this small puffer fish doing and how did it manage to accomplish such a feat?

I recently saw a video on youtube where it shows a puffer fish making intricate designs in the sand: OZZY MAN VIDEO The puffer fish made this design on the sand: What exactly is the puffer ...
23
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3answers
3k views

What is this fish?! Is it even real?

According to a guy in a Facebook group I belong to, this fish was caught in the Missouri River near Omaha, NE, US. I have never seen one like it in my life, not in person or photo or anywhere. What on ...
18
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2answers
1k 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 "...
17
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2answers
982 views

A weird-looking fish with a shield

I found this photo in a local news page. The page claims that this fish is a new species that was found by a Malaysian fisherman. Is this true or is it a known fish and already has a name?
17
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3answers
7k 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
3k 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, let'...
11
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1answer
4k 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?
11
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1answer
241 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 ...
10
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1answer
1k views

What evolutionary advantages are provided by ovoviviparity?

I read that some sharks are ovoviviparous. What advantages and disadvantages are provided by this type of reproduction as opposed to egg laying and live birth?
9
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3answers
10k views

Why have whales and dolphins not evolved to have gills? [duplicate]

It seems at first glance that it would be an evolutionary disadvantage for a sea creature to have to come up to the surface on a regular basis in order to breathe, so why are there animals (e.g. ...
9
votes
1answer
150 views

What kind of fish is this white blue-stained fish?

This fish has been spotted at the Great Barrier Reef near Cairns (Queensland). I put a big effort to find it via Google but never could encounter anything similar. I have also made an attempt to find ...
8
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1answer
946 views

What sort of fish is this?

Just saw a meme online with this fish on it. Is this a real fish? Can some aquatic expert identify this for us?
8
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1answer
2k views

What kind of fish is this?

What sort of fish is the big one in this picture? I saw it in an aquarium so I don't really know anything about its habitat.
8
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2answers
863 views

Are tuna fish present in the Baltic sea?

Yesterday my grandmother ate fresh tuna at a friend's party. She swears it was fresh and bought at a local fishmonger. The problem is, that we live in Gdańsk, by the south-eastern side of the Baltic ...
7
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1answer
2k views

How long do fishes survive in a milk environment?

Suppose you placed a fish, a goldfish for example, into milk instead of water. How long could you expect the fish to survive? Would it die due to lack of oxygen? Is there any other factor that could ...
7
votes
1answer
217 views

Help identify these (two) fishes - Netherlands

Yesterday my kids caught these two fish. I tried to figure out what kind of fish (species and name, to tell my kids a bit more about them) they are but I was not successful. Today we made a trip to a ...
7
votes
1answer
790 views

Worm found inside of wahoo

A fisherman from Hawaii wrote the following: This Fat juicy worm lives inside of every Wahoo that I catch. Inside the stomach. Right at the junction to the intestines. Sometimes there are two. ...
7
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2answers
951 views

Are fish roe unicellular?

Are roe (fish eggs, caviar, etc.) single cells? I have tried looking this up on google (sadly, to no avail), and I am guessing they might be multicellular (like bird eggs) or consist of one cell plus ...
7
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1answer
4k views

For fish, does a bony skeleton have any advantages over a cartilage skeleton?

I have learned that two important lineages of fish are the bony fishes (Osteichthyes) and the cartilaginous fishes (Chondrichthyes). Many websites mention an advantage of the cartilaginous skeletons ...
7
votes
2answers
158 views

Never caught this fish before

After catching a bunch of mangrove snapper using live shrimp, my son caught this fish in about a foot of brackish saltwater water off a dock near a rock wall in Vero Beach at around 10:00 AM on July ...
7
votes
2answers
198 views

Why do fishes have both a gustatory and an olfactory system?

I would like to know if there is a reason why fishes (and many aquatic species) have both an olfactory and a gustatory system. As far as I know, in all fish species the chemoreceptors, organs and ...
7
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1answer
120 views

Can a shark stall?

Today in marine biology I learned that, like airplanes, sharks use their pectoral fins to generate lift. The question that neither me or my Professor know is if a shark can or cannot stall. A ...
6
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3answers
5k views

What is the difference between the evolution of fins in whales and fish?

For a homework assignment I received the following question: Which statement best explains the evolution of fins in whales and fish? a. The common ancestor of whales and fish possessed genes for ...
6
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2answers
392 views

How can a tongue-biting parasitic arthropod become a fully functional tongue?

From wikipedia: The parasite Cymothoa exigua [consumes a fish's tongue and] then replaces [it] by attaching its own body to the muscles of the tongue stub. The fish is able to use the parasite just ...
6
votes
1answer
18k 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 ...
6
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2answers
4k views

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 ...
6
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1answer
5k views

What happens to deep sea creatures if they reach the surface?

Since deep sea creatures are adapted to incredibly high pressures, I would assume they would not be able to survive in the low pressure environment of the surface. What exactly happens ...
6
votes
1answer
736 views

Do saltwater fish need to drink? [duplicate]

In my biology class we got the question if saltwater fish need to drink. We need to use the term osmosis, but I cannot think of a valid answer and we were allowed to ask help.
6
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1answer
3k views

What percentage of fish are herbivorous vs. carnivorous?

It appears that the majority of fish we eat are carnivorous, such as salmon and tuna. This got me wondering how common herbivores and carnivores are among fish species. I couldn't find an answer to ...
6
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1answer
1k 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 ...
6
votes
1answer
167 views

How do fish maintain razor sharp teeth?

I was watching a program about Barracuda - they have a front tooth that is supposed to be razor sharp. My kitchen knife goes blunt if I use it for long periods without sharpening. Sharks keep on ...
6
votes
2answers
892 views

Why are most fishes vertical?

Why do most fishes have a "vertical" body shape instead of a "flat" one ? Here "vertical" means that the body(from a front view) is roughly orthogonal to the horizontal plane, and a "flat" body shape ...
6
votes
1answer
62 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 ...
6
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1answer
174 views

Evolution of Upside Down Catfish (Synodontis nigriventris)

My Biology teacher asked us to write 3 texts, explaining the evolution of the Upside Down Catfish Synodontis nigriventris, each one according to Lamarckism, Darwinism and Neodawrinism theories. She ...
6
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1answer
154 views

Best tail for swimming?

I understand that the vertical tails of fish and the horizontal flukes of cetaceans evolved due to the spinal movements of their ancestors but I was just wondering if there has been any investigation ...
5
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2answers
13k views

What are fish seeds?

I stumbled upon this term in a section called Induced breeding of Carps in an Applied Zoogy book. Traditional practice is to collect seed from the natural riverine habitatwhich also contain ...
5
votes
1answer
294 views

What happens when someone is stung by a jellyfish?

What happens in the human body when someone is stung by a jellyfish; namely a box jelly. Judging by what I have heard about the stings I'm guessing that they involve a neurotoxin. But what is ...
5
votes
2answers
182 views

Why are fish constantly in motion?

When I see fish in an aquarium, they never seem to stop swimming. This is in contrast to e.g. the penguins, who spend a lot more time just standing there. Is this true in the wild or specific to ...
5
votes
1answer
158 views

Help needed in fish identification

Please help me identify these fish. I looked around but wasn't able to determine its species.
5
votes
1answer
631 views

Does anybody know what this shark is eating?

Looking for a species identification on the orange fish that the shark is eating. The shark is a goblin shark filmed as part of the BBC's 'Legends of the Deep: Deep Sea Sharks'.
5
votes
3answers
486 views

Why don't fish groom each other?

Fish are often plagued by external parasites, which are presumably difficult for them to remove. There are well known cases where large fish come to coral reefs and allow smaller fish to pick off ...
5
votes
1answer
11k views

How does this headless fish still move?

There is a (VIDEO) on Facebook where the fish starts to flail around despite no heart or internal organs. What causes the fish to flail around the way it does? My theories: It is because of ...
5
votes
1answer
139 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 ...
5
votes
2answers
455 views

Capture recapture for only two visit assuming a open population model

I have a study system where I’m doing a capture recapture analysis. I mark fish in one year and I’m recapturing a subset of them the next year. I only have 2 capture events. Since a lot of time has ...
5
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1answer
1k views

How does anadromous fish physiology “know” to switch from salt to freshwater and back?

What mechanism allows anadromous fish (like salmon) 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 ...
5
votes
2answers
1k views

How do fish tolerate pH changes in water?

I want to know how aquatic animals behave as a natural indicator of the acidity in lakes and rivers. How do they tolerate these pH change?
5
votes
1answer
134 views

Is there any evolutionary reason for why some organisms (wrasse) change their sex in adult stage?

In San Francisco, I saw this fish: and quoting the aquarium's page: Part of the wrasse family, the California sheephead is a protogynous hermaphrodite. Simply put, all sheepheads are born as ...
5
votes
0answers
84 views

How do similar looking carps, but belonging to different species, differ from each other?

There are some carps which differ in colour, or has some easily noticeable morphological differences. But apart from that, most of the carps look "almost" the same. How does one differentiate one ...
4
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1answer
19k views

Can prawns be classified as fish, or is their position ambiguous?

Today a zoologist told me that prawns and fish are very similar, but zoologists/taxonomists have put them in different categories because their distinction is unclear (like hydrogen in the periodic ...