Interspecific Competition Heirarchy in Lepomis?

I debated about posting this query here or in the scientific section and flipped a coin.

My google-fu and other research methods have come up a bit short on this one. So, I'm looking for actual studies, data, or just anecdotal observations from keepers and anglers.

Obviously different species of Lepomis will feed on whatever they can, but they also have niches they excel in. Likewise, not all species overlap, but there are many places with 2 or more species sharing the same environment. These sunfish also all share the same cues for aggression, and the frequency of hybrids also reveals they definitely have similar breeding signals/behavior. Here in CT the only native sunfish are pumpkinseeds and redbreast. However, bluegill and some others have been introduced. While there are some fast moving streams where redbreast are dominant, the two native species have taken a back seat to the bluegill. I could be wrong, but this seems to be a combination of increased fecundity and perhaps higher levels of aggression (at least compared to pumkinseeds in terms of aggression). I'm not certain if the growth rates differ given equal conditions.

So out of curiosity, I'm wondering if there are any reliable hierarchic arrangements of Lepomis in terms of aggression, fecundity, growth rates, etc, and an overall competition hierarchy of groups of species when they all share the same body of water. I also wonder if there aren't any rock/paper/scissors type groupings!

Any feedback is appreciated. Of particular interest is any data for artificial populations (i.e., those groupings that don't occur normally) - especially ones with a large number of species. Any information about range limitations due to abiotic environmental factors is also interesting, as well as any news regarding the study of the radiation of lepomis into the various parts of north america. (Like I said, it was kind of a tossup which subforum to post this in).

Edited by IvanMike, 06 October 2011 - 04:59 AM.

I am wondering if it is not aggression that makes them seem to take over in their habitats, as I have not observed an overwhelming aggression in raising them in mixed tank conditions but simply perhaps they have an ability to out-breed and survive all the others in their habitat. How that might happen I do not know. More fertile? Higher numbers of young? Sieze or monopolize best breeding locations? Fry have a better 'hiding/avoidance' mechanism? Inherently better survival rates for fry? Perhaps far more complicated than just aggression.

Usil

Edited by Usil, 06 October 2011 - 06:25 AM.

There was a lot of research done on the subject of sunfish resource use, and how different species might intereact. For instance, see "Ontogenetic Habitat Shifts in Bluegill: The Foraging Rate-Predation Risk Trade-off", Earl E. Werner and Donald J. Hall,Ecology, Vol. 69, No. 5 (Oct., 1988), pp. 1352-1366, among many by Werner and Gary Mittelbach and other reseearchers.

There was a lot of research done on the subject of sunfish resource use, and how different species might intereact. For instance, see "Ontogenetic Habitat Shifts in Bluegill: The Foraging Rate-Predation Risk Trade-off", Earl E. Werner and Donald J. Hall,Ecology, Vol. 69, No. 5 (Oct., 1988), pp. 1352-1366, among many by Werner and Gary Mittelbach and other reseearchers.

I keep some, sometimes in mixed species assemblages. Rock-paper-scissors can apply.

Size always trumps when nobody is breeding or in feeding territory mode.

Breeders dominate nonbreeders. Territorial dominates non-territorial.

Territorial can be a function of habitat or food availability.

Warmouth and greensunfish become territorial when structure is heavy.

Bluegill will defend small food patches that are isolated. Very distinctive behavior associated with this.

Generally, species with more color on flanks, like with dollar sunfish and longears, are more aggressive. Stripes on operculum like with green and pumpkinseed I associate with aggressive species. Longear as a function of source are extremely variable so will not over generalize.


Order of woop-ass: dollar > longear; green > pumpkinseed > bluegill; pumpkinseed > redear


Habitat and temporal variation VERY important (i.e. warmouth are tough customers in heavy cover but wussies otherwise).

I don't know that you guys will have access to the papers, so I'll just put them here... If you find citations of others you would like to read, I am glad to get them for you and send via PM (this is for anyone, and I will say that I'm much more apt to act if I see "NANFA Member" over there under your name ). Google Scholar is a good place to start putting in your search terms, many times the papers will be linked. These citations you've seen so far are the classic papers for the topic in the journal Ecology. There are many more in other journals. If the topic interests you, I suggest you follow the peer reviewed lit. You can get opinions here all day long, but I'm not really sure that's what you're looking for.

If your interest is interspecific interactions and partitioning, these are two papers of interest to begin. I am hunting a lot of this down right now for intraspecific (such as the paper Bruce mentioned) for my next paper. So our timing is aligned

Todd

Edited by farmertodd, 06 October 2011 - 11:04 AM.

Thanks Todd, you found two of the better ones.

Thanks for the replies. Those were good papers Todd - two of the better researched relationships that I've seen (as in the papers are excellent, and also as in this information is some of the more readily available).

I'm not 100% convinced that the presence of spangling/color is indicative of aggression, but then again, I'm coming from a cichlid background. When I see a fish like the longear that is more elongate and has a high level of spangling I instantly think "riverine". Of course the habitat of the longear doesn't always bear this suspicion out, and of course the slightly larger mouth and somewhat more elongated form would also indicate a picsiverous nature (as in the green and to a lesser extent, the longear).

Keep 'em coming.

Edited by IvanMike, 06 October 2011 - 02:35 PM.

Ivan,

I read your original post again (several times now). You are asking for a lot of very different info that needs to be more focused otherwise you will overwhelm.

Fecundity when controlling for female size is inversely related to egg size. Species with smallest to largest egg diameter are approximately orange-spotted sunfish, warmouth, bluegill,green sunfish, pumpkinseed, redear, redspotted sunfish and spotted sunfish, dollar sunfish,longear sunfish and redbreast sunfish. Diameter does differ between populations of same species. Larger female size can also compensate for larger egg size.


Growth rate is generally faster for species that ultimately achieve largest size but early growth is often faster for those hatching from larger eggs.

After reading the original post, it made me think of the research done at the Kellogg station in the mid-eighties. Not surprised when those two papers showed up right away. A lot of centrarchid interaction work was done there.

I have two thoughts:

1. Interactions in the wild are not the same as in an aquarium. In the wild, the different species have a much greater opportunity to find their optimum habitat. In an aquarium, even a very large one, they are forced into much more interaction on "neutral turf".

2. I have always thought habitat rules; where habitat is optimum, that species will dominate. In a waterbody with multiple habitats, the species will seek their comfort zones and different species can dominate different areas or at different life stages. I don't have a specific study to fall back on, its just my sense after all of my reading and observation.

Then I start thinking about fecundity, growth rates, etc. and my head starts to hurt. Lets not forget range, too. Where I live, we are at or nearing the northern edge of some species (Red Ear, Orangespot) and well placed for pumpkinseed and bluegill. What role will that play?

Recently, I had an adult male bluegill and an adult male pumpkinseed in a 180 gallon aquarium. For a period of time, say 6 weeks, the bluegill would beat the tar out of the pseed. Then, the pseed would color up and dominate the bluegill. When I would get ready to separate them, and they would switch dominance. As they grew older, the pseed finally became fully dominant, and I had to separate them.

I know this didn't really answer anything, but this is a great question.

I agree that I'm asking for a lot, and double agree that interactions in a captive setting are not = to interactions in the wild (as interactions in an artificial grouping in an outside pond - even with a variety of zones and food items do not = interactions in the wild "normal" state).

Likewise, preferred zones, prey items, egg size, number of spawns, tendency to hybridize, and tendencies for the presence of one lepomis to affect the other (e.g., bluegills rarely stunt in the presence of redears, bluegills are kept small in the presence of greens, etc) all come into play.

That said, I tend to treat these things holistically and think It's a mistake to focus on one piece of the puzzle to the exclusion of the other factors. True, this can overwhelm a person, and when experimenting one must control all other variables (as best they can), but I enjoy the big picture. As it stands we have some pristine settings where the centrachids are all natives, many settings where introduced species (such as the ubiquitous bluegill) have changed the dynamic, and the even more artificial groupings in aquaria and backyard ponds. All of these interest me for varying reasons, and I think that taken together they give a clearer picture of the potential relationships between Lepomis.

As always, YMMV.

Edited by IvanMike, 07 October 2011 - 03:04 PM.

Don't get me wrong, I love the big picture too. You posed a great question. This is a great discussion topic. It takes me out of my comfort zone, which is a good thing.

I was never good at doing a DOE past three variables. This seems too complex to get a good handle on an answer that might arise and later be toppled by another observation not taken into account or data found to be incorrectly binned somewhere.

Usil

I was never good at doing a DOE past three variables. This seems too complex to get a good handle on an answer that might arise and later be toppled by another observation not taken into account or data found to be incorrectly binned somewhere.

Usil

Lol - welcome to science! Every good theory gets toppled by a better one sooner or later. I always find more evidence that causes you to re-evaluate your past conclusions to be stimulating.