Can fish live shorter lives in larger groups / hierarchies?

[Zionas]

Is it possible that some species of fish live shorter lives when in a larger group / hierarchy (compared to being kept in pairs / alone)? As in the stress of the pecking order especially if they’re not the dominant members of that hierarchy makes them less likely to live relaxed and reach their full lifespan potential?

Like groups or harems of damsels, Anthias, Tangs, Clowns, certain angels and butterflies, wrasses, Chromis, any fish really.

 

[xxkenny90xx]

I wouldn't think so since that's how most of them live naturally in the wild. If anything being in a group should be more relaxing since they don't have to worry about being targeted by predators as much.

Why do you ask?

 

[Zionas]

I read another post (forgot where) that said for Chromis the stress of being lower on the hierarchy can shorten their lifespans though still “normal” for a fish in that part of the hierarchy. Also read somewhere on this forum that the stress of Anthias being in a rigid hierarchy might take a toll on their lifespan.

 

[xxkenny90xx]

Interesting. I would think in the wild they would have longer lifespans in groups due to being safer. But it does make sense that the dominant fish will get the most food and be the healthiest. Not to mention its typically the strongest that becomes dominant fish in the first place.

So imo it stands to reason that yes, the dominant fish should live the longest. Were these articles you were referring to or just threads? I'd be interested in reading them if they're articles and you come across them again.

 

[Zionas]

They’re just threads on the forum. I wish I had an article to show you, I’ll probably look for one.

 

[mort]

It's definitely true that being part of a harem can shorten the life of some fish and cause stress but it's a natural process and why the species evolved.

If you use anthias as an example, they group for protection in numbers. In these groups there is constant bickering and defending by the males as he tries to maintain his little harem (it appears females can fluidly move between males but each male defends a rough area within the larger anthias grouping). The male breeds with his harem and is constantly having to defend it which is why they don't tend to be that long lived, they simply become warn out and this is where the next dominant female senses the chance to become dominant and initiates a sex change.
The same happens within wrasses and dottybacks where it is the end goal to become a male and father the next generation.

You can basically sum it all up with Darwins survival of the fittest. If you live in a group it might bring safety in numbers meaning your less likely to be picked off by a predator but conversely you have to maintain your place in the hierarchy and compete with the others for resources. It's no wonder why more solitary species tend to be longer lived.


In our tanks anthias can definitely live longer on their own without the pressure from other conspecifics. We see this when a group has been whittled down to one and often it last longer but it's also true to say that a lot of anthias species just won't feed or acclimate very well unless kept in a group.

I've had experience of dottyback males breeding themselves to death when kept in harems, the same with bangaii cardinals and other species who exude a lot of parental care.

At the end of the day you have to sum up how much keeping a fish in a more natural way improves the life of the fish and counter that against life span. Some fish that live in groups in the wild are hard to maintain as groups in aquaria and do brilliantly on their own (like tangs), living a very long life.

 

[Paul B]

This is true. I know pipefish have problems in groups in a tank because they don't normally live in groups in the sea. Bangai Cardinals also have problems in groups in a tank even though they do live in groups in the sea.

Anthius also. I assume in the sea they have much more room. It's like if you had to live with a big family in a small house. That is always a problem.

 

[Zionas]

That’s really interesting. I wonder for Anthias and Bangaii Cardinals how long they can live if only maintained singly or no more than a pair.

 

[mort]

Single lyretail anthias can easily live 5 years + from my experience. Single bangaii's at least 4 years but if you keep a pair the male can wear itself out in a couple of years if breeding constantly.

 

[Zionas]

That’s interesting. How long have you had single Lyretails or other species live for? (What would you say is the norm?) Do single Lyretail females usually end up becoming male?

 

[mort]

That’s interesting. How long have you had single Lyretails or other species live for? (What would you say is the norm?) Do single Lyretail females usually end up becoming male?

The singles were in old customer and maintenance tanks, so not sure how old exactly they were but 4 or 5 years at least.
Single females can change sex but they normally don't as there is no stimulus to do so. If you had two females them one would likely change unless the tank was very large. I don't think sex really has any relation to how long they live if you keep them singly though but perhaps you have to knock a bit off as it takes a while for males to form.

 

[Zionas]

That’s interesting to know.