Tag Archives: fish

How Catch And Release Can Damage Fish

If you catch a fish and you eat it, it has no chance of survival. That’s pretty obvious.

If you catch a fish and you set it free, it could be just fine. Indeed, it could be rather fun for the fish. “Hey, did you see that? You wouldn’t believe what I just saw! Hey, you know that eagle that ate Joe last week? I could see where its nest was! And this guy had this whole bucket of leeches! Holy crayfish!”

But most likely, if you catch a fish intending to release it, there is a chance it will not fare so well. People who catch catfish intentionally know this, and don’t bother with catch and release. I’m not sure if I’ve ever caught a catfish where the hook didn’t go deep into its gut as the sole action in the entire process of grabbing the bait. Not even worth taking the hook out. You just take the catfish home, clean it, and get the hook then. Generally, live bait has a higher chance of this sort of thing happening. Unless you are jigging with a fairly large hook and a live bait that is hanging off, the chance of your fish swallowing the hook, even part way, is high. Generally, as well, fishing in this manner is associated with fishing for food or, one might hope once in ten lifetimes, a trophy walleye or something.

I personally fish almost exclusively with lures. If the lure comes with a treble hook, I’ll either remove it and replace it with a single hook, or cut off one or two hooks. I mush or cut off the barbs. I take at least one of the treble hooks off any lure with multiple trebles. For bait hooks, I smush or remove the barb. And so on.

(By the way, this give me the opportunity to put a single weedless hook on a lure that is essentially designed to catch on to every damn thing in the lake, allowing for more options when casting.)

When I catch the fish, since I’m casting and reeling and the hook is barbless, it is pretty easy to remove the hook from the fish. Sometimes, if the fish is fairly big, I don’t actually want to land it. That may involve too much handling, and that can damage the fish. With a single hook and no barb, I can get a look at the fish, and flick it free pretty easily about half the time.

(Also, I carry at least one very large needle nose pliers. I can grab the base of the hook or the hook/lure with that, and with a simple twist, release the fish before or after landing, depending.)

I’m pretty sure that I don’t do a lot of damage to the fish I fish for. If a fish I catch is legal and damaged, I eat it. (Not right there on the spot; I clean and cook it first.)

How might catch and release injure fish that are not particularly mangled by the process? There is a paper just out in the Journal of Experimental Biology, bu Melissa Thompson, Sam Wassenbergh, Sean Rogers, Scott Seamone, and Timothy Higham. In “Angling-induced injuries have a negative impact on suction feeding performance and hydrodynamics in marine shiner perch, Cymatogaster aggregata” the researchers report that injury to the inside of the fish’s mouth can change the pressure gradient that these fish use to suck prey (and lures) into themselves. It is not demonstrated that this impacts survival, but it does seem to impact feeding efficiency.

“The suction feeding system is somewhat similar to how we drink liquid through a straw,” Higham said. “If you poke a hole in the side of your straw it’s not going to work properly.”

Fish researcher Tim Higham explains, “As we predicted, the fish with the mouth injuries exhibited a reduction in the speed at which they were able to draw prey into their mouths. This was the case even though we used barbless hooks, which are less damaging than barbed hooks. Although we don’t yet know how/if this reduction in feeding performance would affect fitness and survivability in nature, we can say that fishing-induced injuries impact the fish’s ability to feed while the mouth is healing. This study emphasizes that catch-and-release is not as simple as removing the hook and all being well, but rather is a complex process that should be studied in more detail.”

This is obviously going to depend on the kind of fish in question. As noted above, the whole suck-in-the-food approach for catfish may simply do them in. But I’m not sure a Northern or Muskie is feeding in exactly the same way. Clearly, more research is needed!

The abstract of the paper:

Fishing is a popular and lucrative sport around the world and, in some cases, may contribute to declining fish stocks. To mediate this problem and maintain fish biomass in aquatic ecosystems, catch-and-release fishing, whereby a fish is caught and immediately released, has been implemented in many countries. It is unclear whether the injuries to the mouth that are caused by the hook have an impact on feeding performance of fishes. Using high-speed video and computational fluid dynamics (CFD), we asked whether injuries around the mouth caused by fishing hooks have a negative impact on suction feeding performance (measured as maximum prey velocity) of the commonly angled marine shiner perch (Cymatogaster aggregata). We hypothesized that fish with mouth injuries would exhibit decreased feeding performance compared with controls. Ten shiner perch were caught using scientific angling and 10 were caught using a seine net. Feeding events were then recorded at 500 frames per second using a high-speed camera. Compared with the control group, maximum prey velocity was significantly lower in the injured group (P<0.01). Maximum gape, time to peak gape, maximum jaw protrusion and predator–prey distance were comparable between the control and injured groups, leading us to conclude that the injury-induced hole in the buccal cavity wall reduced the pressure gradient during mouth expansion, thereby reducing the velocity of water entering the fish's mouth. This was confirmed with our CFD modelling. Fishing injuries in nature are likely to depress feeding performance of fish after they have been released, although it is currently unclear whether this has a significant impact on survival.

Great White Sharks in Captivity

There aren’t any. But, aquaria have many times tried to make it so, and it always goes bad for the shark. The basic problem is that great white sharks are pelagic, and it is very hard to keep pelagic creatures in a confined space, and the largest aquaria are very confined from the point of view of a large pelagic animal.

greatwhitefeedingonsealAnother problem would eventually become important in the event that an aquarium managed to keep a great white shark alive long enough. When they are young, great white sharks dine on fish. When they are adults, they seem to prefer mammals. So, imagine feeding time at the zoo with an adult great white shark ….

Anyway, VOX has put together a really excellent video on the history of great white sharks in aquaria. Wildlife biology or marine biology high school teachers take note, this video has a lot of learning in it about stuff you probably teach!

For example, you learn what “pelagic” means.

Here’s the video:

I’ve seen great white sharks in the wild several times. You can to. You just need to know where to look. I suggest the southern coast of South Africa. Oh, and if you are going to go around spotting sharks, you’ll need a good shark spotting guide.

Global Warming Coming To An Ice Fishing Contest Near You

Over the last several years, ice fishing contests, which are a big deal in Minnesota, have been repeatedly cancelled due to insufficient ice thickness on the relevant lake. Some of these contests have been permanently cancelled because the annual cancelations were becoming more frequent. Just now, the Maple Lake Ice Fishing Derby has been cancelled. That’s bad.

But even more disturbing is this:

Ice conditions for the Eel Pout Festival have created enough concern to prompt vehicle restrictions, according to the Cass County Sheriff’s Office.

Sheriff Tom Burch says vehicle traffic on Walker Bay during the event will be prohibited, but with the following exceptions: snowmobiles and Class 1 & 2 ATVs.

All vehicles must be removed from the ice by noon on Friday. Motorized traffic is no allowed until Sunday at 10 a.m.

This is a big deal because the Eel Pout Festival is different from the previously canceled ice fishing events. All those previously cancelled events, including Maple Lake, are in Central Minnesota, not far from the Twin Cities. The Eel Pout festival is way the heck up north, in a region where even with global warming affected climate, the ice still normally forms hard and thick.

I assume that the problem with the ice up on Leech Lake, where Walker Bay is located, is problematic this year because of a combination of rising global surface temperatures caused by human released greenhouse gas pollution, plus added warmth from the current El Niño. In a way, we are looking at the effects of global warming in the future, in a decade or two, when the “normal” elevated (non El Niño) temperatures will catch up with the extra elevated temperature of the combined effects.

While we are on the subject of the Eel Pout, let me clarify a bit. The fish known as Eelpout (one word) is a marine fish that looks a little like an eel. There are about 300 species, they are bottom dwelling, and some live at a great depth. They are not the same fish as the Eel Pouts (two words) in Minnesota. The Minnesota Eel Pout is also known as the Burbot, and it is a fresh water Cod, the only Cod that lives in fresh water. It is also known as Ling, Coney-Fish, Lingcod, and owing to its somewhat slimy nature and tendency to wrap itself around your arm when pulled out of the water, Lawyer. (I assume this refers to a specific subset of lawyers, not all lawyers.)

It is very edible, I hear, though I’ve yet to eat one.

This is also an example of where Wikipedia gets it wrong. In the entry for “Eelpout” (one word) Wikipedia correctly describes what Ellpouts are, but then adds this, under the “popular culture” heading:

The Eelpout Festival that takes place in February in Walker, Minnesota, in the United States, celebrates the burbot, which is actually a cod-like fish misleadingly known locally as the eelpout

Bad Wiki. First of all, we spell the name of the fish differently (two words, not one word). Second, the Minnesota Burbot has been called the Eel Pout for a long time. Eel Pout, as well as Eelpout, are common terms, not scientific names, so of course there is some sloppiness. I don’t see Wikipedia saying it is wrong to call an Elk a Moose in Europe, do I?

Anyway, here is what the Eel Pout Festival looks like:

Humans being loud under water, Cuttlefish

Last June (and May and July and part of August) we had a lot of precipitation in Minnesota. This caused lake levels to rise modestly. One lake, which is large enough to have meaningful waves, has older settlement along it so lots of cabins, boat houses, and such are right on the shoreline. With the lake level up, waves threatened the material possessions of rich white people, so naturally something had to be done. A No-Wake Rule was put into effect.

A No-Wake Rule means the oversized fishing boats and smallish cabin cruisers that normally ply this large exurban lake need to all go at 5 m.p.h. or less, and forget about wake boarding, water skiing, and all those other fast, wake churning activities. The result? A lot of butt hurt, a near First World depression setting in in the Twin Cities wester suburbs. Somebody took away our boy toys!

But then, somebody went fishing. It isn’t a great fishing lake. It is mainly a go-fast lake. In fact, it is on this particular lake, I believe (with no evidence I quickly add) the method of fast-trolling for muskies was invented. This is a way to “go fishing” and go fast at the same time. You drag the lure behind you as fast as your boat will go. It is said you can catch muskies this way. To my knowledge it has never happened. Just more boy toy.

Anyway, somebody went fishing on the No Wake Lake, and guess what happened? They caught a boat load of fish! Literally! Then their friends went out fishing, and they caught a boat load of fish too! Pretty soon all the fisherpersons who had access discovered that when you don’t drive giant boats back and froth across the lake at high speed all day, the fish feed. When you do, they hunker down, feed infrequently, and grow slowly.

Now, I’m not going to vouch for this relationship just yet, but it makes intuitive sense. In my own experience, quiet places are where you catch fish. If I’m fishing up at the lake, once the boats start driving around skiing (say on a fourth of july weekend) I might as well reel it in and go get a beer, because that’s the end of the fishing. I’m pretty sure my best fishing has been on Wednesday and Thursday, before the startup of the loud and noisy weekend. And that’s on a quietish part of a relatively quiet lake.

The only reason I’m mentioning this now is because I came across this story from my Science News Roundup:

The blare of human noise causes birds to pipe down and frogs to breed less frequently. Now, scientists have found a humanmade sound that has a far more colorful effect: The boom of a ship’s engine makes common cuttlefish (Sepia officinalis) change the complex swirls of skin hues, stripes, and spots that they use for camouflage and communication. …when researchers placed a loudspeaker near cuttlefish tanks and played the sound of an underwater engine, the animals swam more and changed colors more often. They also raised their first pair of arms, which are used to sense water movements, more frequently…The sounds of crashing surf had no effect, providing the first evidence that engine noise may stress the animals out.

The original story is here, in American Naturalist.

I would love to see a large number of large lakes shut down for boating. No motors. Eventually, of course, there will be no gas powered motors, with the shut down of fossil fuels. I promise you, when we start using quiet electric boats for fishing, the fishing will get better.

The strangest supposed “fish” yet?

I’m sure that several years ago a bunch of out of work “oceanographers” like the people here got board and started faking various “fish” that only they ever saw in the wild and only they ever photographed and that lived in the “deep” ocean where nobody could verify their existence. I assume this was a funny joke that got out of hand and now they’re stuck with having to come up with a new “fish” every so often to keep up the ruse. Here’s the latest, a fish with a see-through head:

For the first time, a large Pacific barreleye fish – complete with transparent head – has been caught on film by scientists using remotely operated vehicles at the Monterey Bay Aquarium Research Institute. The deep-sea fish’s tubular eyes pivot under a clear dome.

Man fishing for bluegills catches shark by hand instead

This is funny:

Just so you know, he was not fishing for “bluegills” This is a bluegill:

A nice bluegill
A nice bluegill

Bluegills live in fresh water and are like “sunfish” and “pumpkinseeds” and “crappies” etc. all of which are in the bass family.

Bluefish live in the ocean and roam along littoral regions in large schools. This is what large bluefish look like:


Of course, when one is fishing for bluefish, there is always the possibility of catching the fish that eats them, such as striped bass. Like this:


The striped bass is not in the “bass family” referred to above. Striped Bass are Moronidae, bluegills, largemouth bass, etc. are Centrarchidae.

Anyway, sometimes you catch a shark.

Japan Nuclear Disaster Update # 37: Glow in the dark fish, and the meaning of “Power”

As a result of our last posting on Fukushima, we had a discussion initiated by commenter Daedelus2u about radioactive istopes of Cesium becoming concentrated in fish. I thought I’d take this opportunity to expand on that discussion a little. This relates to the possibility that radioactive elements spilled or spewed from a nuclear reactor site (as per normal or following a meltdown and China Syndrome, as in the case of Fukushima) can become part of our diet especially in fish, and how much concentration of radioactive isotopes we might expect.

Continue reading Japan Nuclear Disaster Update # 37: Glow in the dark fish, and the meaning of “Power”

World’s Largest Fish that is not a whale* on film!

This sucker was filmed in the Gulf of Mexico swimming among the oil rigs!!! It propelled itself with undulations of its dorsal fin and looks a lot like a sea serpent. In fact, it is said to be “the origin of the sea serpent myth” but I’m not quite sure what the difference is between being “the origin of the story of a 30 foot long fishy snaky thing with an undulating dorsal fin” and being a “30 foot long fishy snaky thing with an undulating dorsal fin” …

Continue reading World’s Largest Fish that is not a whale* on film!

“I only fish for the fishing, not the catching”

There are two lies you will hear from anyone who is into the sport of angling. 1) “It was THIS BIG!” and 2) “Catching fish isn’t the point. It’s the experience of fishing that matters.”


The Mocking Bass. For four years this fish watched me cast lures and live bait from the end of the small dilapidated dock in the lagoon behind the cabin, without ever showing interest in what I had to offer. Two weeks ago I dropped a plastic worm on his head. The worm slid off and rested on the bottom. The mocking bass reoriented towards the worm and took a sniff. I jiggled the worm. And, BANG. He took the bait. My drag was set to medium, so WZZZZZZZZZZZZZZZ .. he took off across the lagoon. I tightened the drag a little because he was running into brush and he turned direction and jumped. But I kept the rod tip up and used his jump to bring him in. He ran back and forth across the lagoon two more times and then headed out. WZZZZZZZZZZZZZZ against the harder drag with his last bit of strength, and one more jump. Then I brought him in, letting him struggle and tire a little more because they always manage to pull off that one last bit of resistance, the one where you lose most of the big ones. I got on my knees and pulled him out just as he got near the dock… And that fish was THIS BIG!!!!!
Continue reading “I only fish for the fishing, not the catching”

Hybrids of Blind Fish Can See

The loss of sight in cave dwelling species is widely known. We presume that since sight in utter darkness has no fitness value, the mutation of a gene critical to the development of the sense of sight is not selected against. Over time, any population living in darkness will eventually experience such mutations, and these mutations can reach fixation.

Astyanax mexicanus: Top is the surface, sighted form, bottom is the cave-dwelling, blind form. From the Jeffery Lab.

Beyond this, we may hypothesize that a mutation “turning off” sight could be beneficial. By definition, an adaptation (such as sight) has a cost. When a trait that is adaptive is no longer adaptive, individuals with that trait “turned off” should experience an increase in fitness. It may also be the case, however, that such an increase in fitness is so small that it may be irrelevant. This line of thinking needs further investigation and what one finds in such an investigation may vary a lot from system to system. For example, a mutation that simply causes a particular protein to no longer be produced in what would have been a small quantity would save the individual with that mutation the use of a few tens of thousands of amino acids over some fixed period of time. This would have very little fitness value. But if a system is exploitable by a pathogen — such as a receptor site on a cell used by a common virus — turning that gene off may have enormous benefits. But this is a bit of a digression from the research at hand.

Borowsky, in his paper “Restoring sight in blind cavefish,” provides a test case for how we think evolution works. In Mexico, the species Astyanax mexicanus, is known to exist in 29 distinct populations. Genetic studies indicate that the turning off of the sense of sight in these fish has involved a deleterious (as in loss of function) of genes in at least three different lineages, or to put it a different way, sightlessness has evolved three or more separate times in these Mexican blind cavefish.When Borowsky cross breeds some of these cavefish, crossing them between these populations, he gets a certain percentage of fish that have functional, if not fully developed, eyes.This should not be at all surprising. Several different genes are involved in the development of sight, so by cross breeding strains that have experienced mutations in different genes, one would expect a certain number of offspring to have a set of functioning genes sufficient to make the sense of sight develop at least to some extent. When Borowsky breeds the blind cavefish with the non-blind version of this fish (“surface fish”) he gets restoration of the sense of sight in all of the offspring.

F1 hybrids between surface fish and cave fish have smaller eyes than surface fish, but are fully visual, even into adulthood … Thus, one surface allele at each of the population-specific eye loci is sufficient for restoring vision.

This is also expected, although not necessarily inevitable (This depends on the dosage required for each genetically coded step in the development and function of sight).

It seems to me that one could test the hypothesis mentioned above that turning off any fitness-free gene is adaptive. If simple production of unused proteins is costly, the rate at which particular genes are found to be turned off should be correlated with that cost. Perhaps the genes coding for longer proteins, or proteins that are produced more often in a particular system, should be more likely turned off. Or, some measure of the total mass of amino acids turned into proteins when a gene functions, should be correlated to the likelihood of having a gene turned off. At a most basic level, one would need to show that the mutant genes are in fact turned off and are not simply producing a non-functional protein.In short, this study (and others by this and other research teams) demonstrates in empirical reality what is expected from commonly held evolutionary theory. Creationists often cite blind cave dwelling organisms as evidence against evolution, because, they say, it is “devolution.” This point of view is absurd, and relies on a teleological view of, in this case, teleost (bony fish) evolution.

Darwin wrote about cave blindness and disuse, and through various observations notes the potential complexity of the problem:

It is well known that several animals, belonging to the most different classes, which inhabit the caves of Styria and of Kentucky, are blind. In some of the crabs the foot-stalk for the eye remains, though the eye is gone; the stand for the telescope is there, though the telescope with its glasses has been lost. As it is difficult to imagine that eyes, though useless, could be in any way injurious to animals living in darkness, I attribute their loss wholly to disuse. In one of the blind animals, namely, the cave-rat, the eyes are of immense size; and Professor Silliman thought that it regained, after living some days in the light, some slight power of vision. In the same manner as in Madeira the wings of some of the insects have been enlarged, and the wings of others have been reduced by natural selection aided by use and disuse, so in the case of the cave-rat natural selection seems to have struggled with the loss of light and to have increased the size of the eyes; whereas with all the other inhabitants of the caves, disuse by itself seems to have done its work.[On the Origin of Species…, 1859, pp 137-138]

You might be wondering how these fish got into these caves to begin with. I can’t describe the exact process for the fish studied in this paper, but there is a general way in which this can happen. Underground lakes or streams in caves may be connected to each other during less arid periods, in some cases running from the deeps of large lakes that later try up almost entirely. In this way, a continuous population in a river or lake is broken into relict populations that are separate from each other and perhaps living in habitats that are different from the original, continuous habitat, and possibly different from each other as well. Under these conditions evolution’s just gotta happen.

BOROWSKY, R. (2008). Restoring sight in blind cavefish. Current Biology, 18(1), R23-R24. DOI: 10.1016/j.cub.2007.11.023