Fish Survival in Aquariums vs. the Ocean

[skibum9884]

So, we get a lot of flak on here because the aquarium industry is responsible for destroying reefs, and plucking off the fish that reside there with the survival rate being arguably pretty low to extremely low.

While I don't have any data to back this up, I would expect that the survival rate of fish on the reef is very low due to predation and other factors.

Has anyone looked to compare survival rates of fish in the wild vs. captivity? I think this would be very interesting (although hard to accurately measure).

 

[darb85]

Actually, because few fish breed in captivity, thier Survival in the wild is much better.

 

[PaxRoma]

in his book I think Julian Sprung mentioned nowadays fish in captivity lives much longer life compared to wild fishes.

 

[JHemdal]

While I don't have a specific answer for you, I did just finished writing an article on "mortality rates in fishes in captivity" for Advanced Aquarist magazine. Here is an excerpt from the intro:

"All aquarists will lose animals; some will lose more than others. This mortality can be managed by preferentially acquiring certain species while avoiding others. Examining the mortality rate of fishes in captivity can also offer insight into the relative ability of the available husbandry methods to support aquatic life. Some new aquarists have unrealistic expectations of the mortality rates of their fishes. It is probable, that as new aquarists, their fish will experience a higher than normal mortality rate, yet even a few fish losses early on, can cause some of them enough frustration that they soon leave the hobby."


The key is to frame your question as a true rate, number of deaths over time. For example, you can say that the mortality rate of any fish is 100%. And it is, if you wait long enough (grin). Obviously, larval mortality is very high in wild fish. As they mature, the rate goes down.

I have done some studies tracking newly imported marine fish and found the 30 to 40 day mortality rate during this time to range from 0 to 60%. Typically "pet store fish" ran around 30 to 40% This spike in mortality rate is the big problem, certainly it far outpaces wild fish mortality for the same period.

Jay Hemdal

 

[skibum9884]

Interesting, this is what I was getting at. You say that normal mortality at the 40 day mark is 0-60%, probably the most common timeframe for mortality if it were shown as a distribution. So, if you were to extrapolate that and just guess that the expected mortality at the one year mark is say, 75%, I wonder what it would be in the wild.

Obviously there would be many factors, species of fish, age, size, etc, and it would be extremely difficult if not impossible to effectively measure.

My point however, is that a fish that dies in captivity is NOT always a fish that survives on the reef.


DISCLAIMER: this is not an excuse for responsible care for our beloved fish!

 

[ackee]

The length of time a fish survives in capitivity is largely irrelevant in connection with the survival of that species in the wild. As soon as a fish is removed from the wild breeding population it ceases to exist as part of that population. Suvival in captivity for only one year, or for 50 years, is of no consequence. Because mortality among larval and very young fish is extremely high, the removal of a small percentage of them has no real effect on the species. Removal of adults from the breeding population has more profound consequences.

The fact that a well cared for captive fish can outlive a wild fish is meaningless from a species survival perspective. A fish that is killed and eaten immediately is as much a loss to the species as one that lives happily in an aquarium for decades. The management of species survival has virtually nothing to do with the length of life of captive specimens, and everything to do with the numbers that are able to successfully reproduce in the wild.

 

[greenbean36191]

If you assume a 75% mortality rate for a one year period in captivity, then captive mortality rates are almost definitely higher than for fish of a similar age in the wild.

Most of the fish collected for the hobby are targeted as late-stage juveniles or sub-adults. By that point in their life, their age specific mortality should be dropping fast. In other words, if they've lived that long, there's a good chance of them living another year.

The problem is that there's really no good life history data on ornamental reef fish, so it's almost impossible to say how long they live in the wild or what the actual age-specific mortality rates are. That makes it hard to say with any certainty what their mortality curves even for the wild look like. Measuring age specific mortality rates in captivity is much harder still.

 

[syrinx]

I was involved in a study on the Cardinal (the bird). In the forest we studied, male birds had a average lifespan of two years-but the birds that were in suburban areas had three times that average. We stopped collecting data after 10 years and there was still one male alive. That being said- losses in the aquarium trade are so high, that a individual living 1000 times longer would not make up the spread. I am sure there are species we keep that are good shippers and would do much better statistics wise-but for the trade overall, we are at a deficit. Of course I don`t believe that our taking of fish is any diffrent than any other predator doing so.

 

[mm949]

i always say..u dont buy fish, you rent them....for how long, thats up to you

 

[buttons buster]

Some species do much better in captivity like seahorses for example

 

[NirvanaFan]

I agree with what has been so far. What if we take this one step further with breeding fish in captivity...

Take clownfish for example. My clowns have bred and I have raised 3 of the offspring and are getting ready to sell them. Once I have sold them, I have stopped 3 fish from being taken off the reef right? Now what if you factor the death rate from shipping into that? In order to sell 3 fish, a store may have to buy 4 or 5 fish (take them off the reef) in order for 3 to survive. Taking my 2 fish from the reef has now saved 4 or 5 right?


Note that my clowns were captive bred as well. I'm just trying to add some discussion.

 

[JHemdal]

Nirvanafan,

Sure - that logic holds up well in my opinion. But maybe you could take it a step further; if you've managed to bring three clowns through metamorphosis, it takes just a bit more effort to raise the majority of a subsequent batch - you are a lot closer to that than you might think; a slight change here, and a tweak there there will get you to that point. I raised my first skunk clowns back in 1986 - got 4 of them up. I didn't try again until 1991 and raised a dozen clarkii clowns. This year, I tried again, the mortality rate was near zero after the second day and I raised 150+ true percs. Just think what I could have done if I hadn't spent so much time between batches! Here is a link to information about the last batch:

http://microcosmaqx.typepad.com/jay_hemdal/2009/08/raising-clownfish-one-more-time.html


buttons buster - sorry, but I have to disagree with you that seahorses do much better in captivity than other species. While they can be raised in captivity by people with the resources to do so, a huge number of them die too soon in regular hobbyist's tanks due to improper feeding and problems with disease control.

Jay Hemdal

 

[NirvanaFan]

I agree that raising clowns is fairly easy. There are many species that can be bred in our hobby. I'm not advocating pulling a lot more of every fish from the ocean to try to breed (like moorish idols). But, putting some species into the hobby could actually increase population of some fish. I don't want this to get policital, but I'd be willing to bet that if Oman clowns were allowed to be collected, the population of them would actually go up.

I had 4 from my first batch, but I went on vacation and I lost one in a cooler coming home from my friends house who was watching them. I left his house with 4 and arrived at my house with 3. I have no idea where the 4th dissapeared to. My clowns haven't been laying lately because of some things, but I do plan on raising the next batch when they do lay them.

 

[hk855]

I read some papers on mortality rates of reef fishes and general population dynamics this last semester. Damsels are some of the best studied and a good representative of many aquarium fish but definitly not all. In their first year mortality is quite dramatic, in the 90% range or so. After this it drops to 5-10% the next few years untill they reach maturity. The first breeding year they experience increased mortality to 20% or even higher, then it drops back down. So the smallest fish is the best to take as far as having minimal impact on numbers, yea pretty obvious. With reef fish the main factor for survival is habitat and removing one fish opens an area for new young to settle. This young fish would have something like 99% mortality had that older fish not been removed because it simply wouldn't have a place to hide.

As far as large fish are concerned a female in her 5th breeding year(horible fish to remove from the pop) will have a much higher chance of her fry returning to the reef after development than a first year female. A small increase in size has a large impact on egg production, like double the size 10 times the eggs. Further the eggs she produces are healtier and stand a better chance of fry survival than a younger female, lipid content is better mainly. Species with slow growth and long lives are dramaticaly impacted by this while faster growers with short lives are not as much.

This could be why you see better results from your later attempts at rearing young. JHemdal how old were your clowns at different attempts? Experience is probably the biggest factor in captivity but you could also have been getting better eggs in your later attempts. So when your new pair breeds and you can't raise any fry it's not always your fault, just use it as experience so when you get good eggs they will have the best conditions. Also when you see your fish spawn one day it may not be worth it to rush into collecting the eggs and throwing together a setup but be patient and rear the second spawning with some planing.

 

[carnut]

While I do beleive a well treated fish will live longer in your aquarium, do to care and the loss of natural stress of trying to survive, I believe it's the loss at the LFS that the general public sees that causes the belief that we are doing the planet wrong.

 

[preef]

The length of time a fish survives in capitivity is largely irrelevant in connection with the survival of that species in the wild. As soon as a fish is removed from the wild breeding population it ceases to exist as part of that population. Suvival in captivity for only one year, or for 50 years, is of no consequence. Because mortality among larval and very young fish is extremely high, the removal of a small percentage of them has no real effect on the species. Removal of adults from the breeding population has more profound consequences.

The fact that a well cared for captive fish can outlive a wild fish is meaningless from a species survival perspective. A fish that is killed and eaten immediately is as much a loss to the species as one that lives happily in an aquarium for decades. The management of species survival has virtually nothing to do with the length of life of captive specimens, and everything to do with the numbers that are able to successfully reproduce in the wild.

Well said.

 

[lordofthereef]

Actually, because few fish breed in captivity, thier Survival in the wild is much better.

Survival rates and reproduction rates/abilities are two different things. The length of time the specific specimen is expected to live in the wild versus in our tank is what is being referred to here.

 

[skibum9884]

yes, obviously reproduction rates will be diminished in captivity and not contribute to a wild breeding population......

 

[Sardaukar]

The length of time a fish survives in capitivity is largely irrelevant in connection with the survival of that species in the wild. As soon as a fish is removed from the wild breeding population it ceases to exist as part of that population. Suvival in captivity for only one year, or for 50 years, is of no consequence. Because mortality among larval and very young fish is extremely high, the removal of a small percentage of them has no real effect on the species. Removal of adults from the breeding population has more profound consequences.

The fact that a well cared for captive fish can outlive a wild fish is meaningless from a species survival perspective. A fish that is killed and eaten immediately is as much a loss to the species as one that lives happily in an aquarium for decades. The management of species survival has virtually nothing to do with the length of life of captive specimens, and everything to do with the numbers that are able to successfully reproduce in the wild.

That is why I will always try to buy captive bred whenever I can (clowns, dottybacks, etc) and always try to avoid buying anything but juvies when I can. Its why I will also be willing to pay a little more for a fish caught from a place that practices responsible harvesting, like Aussie and Hawaii. The same goes for coral frags from other hobbyists and aquacultured colonies vs wild collected corals.

 

[vitz]

if i'm not mistaken, most pairs of any wild animals, over long time intervals, replace themselves with one pair-i.e.-populations remain stable, static, and in balance-with or without minor fluctuations of 'bumper crop' years (e.g. an increase in deer populations from high grain resulting from good rains one year, leading to an increase in lions, which ultimately lead to less deer surviving in years following )

one pair of damsels can lay tens of thousands of eggs in the course of a typical lifespan, resulting basically in ONE PAIR surviving to replace the original pair- how is this any worse OR better than keeping a damsel alive for 3-5 yrs, or longer, in an aquarium ?

imo-the whole debate is a non-starter