Unique Experimental Sunfish Assemblage

Could water temp. and food availability be the reason that Pumpkinseeds are doing so well and Redears are not?

My guess it food availability. Mollusks (pond and rams horn snails and fingernail clams), that normally provide an alternative for both species when they co-occur with bluegill, dropped out very early. If memory serves, then pumpkinseed better suited for targeting smaller prey that do not require heavy pharyngeal teeth to process. The pumpkinseed also seem more adept at feeding on insects falling on water surface. Would be an effort to measure but redear seem to operate at greater depth than the pumpkinseed.


For fun I might provide rams horn snails of various sizes and see how everyone reacts. I could also check Missouri river and look for a heavier shelled snail species that might be able to persist with both shellcrackers and possibly provide redear with a something they can handle better than pumpkinseeds can. I was very surprised the snails dropped out completely but I do not know what is going on at greater depths (>6').

Pseeds are usually mollusc specialists in New England ponds, with better pharyngeal jaws for handling them than bluegills. Bluegills are better at picking small prey like Daphnia out of the water. All sunfish species are opportunists, of course, with varying degrees of success.

In this situation the pumpkinseed may be a generalists using resources that otherwise would be used by bluegill. Redear are doing what, I do not know. Regardless, redear are either growing slower and / or not living as long and it appears largely food dependent.

My guess it food availability. Mollusks (pond and rams horn snails and fingernail clams), that normally provide an alternative for both species when they co-occur with bluegill, dropped out very early. If memory serves, then pumpkinseed better suited for targeting smaller prey that do not require heavy pharyngeal teeth to process. The pumpkinseed also seem more adept at feeding on insects falling on water surface. Would be an effort to measure but redear seem to operate at greater depth than the pumpkinseed.


For fun I might provide rams horn snails of various sizes and see how everyone reacts. I could also check Missouri river and look for a heavier shelled snail species that might be able to persist with both shellcrackers and possibly provide redear with a something they can handle better than pumpkinseeds can. I was very surprised the snails dropped out completely but I do not know what is going on at greater depths (>6').

Thats a good idea about introducing mollusks to the experiment.....I know very little about mollusks, are their any natives that could be introduced?

Edited by wargreen, 04 July 2011 - 01:06 PM.

Thats a good idea about introducing mollusks to the experiment.....I know very little about mollusks, are their any natives that could be introduced?

Buttloads of local options but those in stream that quarry drains into are of the small stream type. I have never seen those establish populations in ponds or quarries. Quarry had several mollusks species at time of introduction. All appear to have dropped out or in such low abundance that I can not find any. Examples were fingernail clams, pond snails Physa sp., and ramshorn Heliossoma sp..

... pumpkinseed males spawn on the other side of the quarry with distances of approximately 30 feet between nests. Females of redear and pumpkinseed, when not associating with males, move about as single species shoals...

Most nests I have seen have distances of only 3 feet between nests. I have also observed females move about as a shoals, especially those that are mature and gravid.

Most nests I have seen have distances of only 3 feet between nests. I have also observed females move about as a shoals, especially those that are mature and gravid.

Quarry offers only a very narrow strip of nest sites in just a few locations around perimeter. Now that quarry has become saturated males nesting much closer (about often within 3 feet of each other). Closer proximity may also be a function of stunting. Largest males are barely 4" while previously males often exceeded 5". Males and females seem to last only one breeding season then drop from population. It is as if they are burning themselves up.

Female pumpkins in quarry also move about in small loose shoals. Redear may or may not and ripe warmouth move about singly.

This is still going on. All three sunfishes are present although stunting among both redear and pumpkinseeds is very evident. Snails appear to no longer be present. Individual size of warmouth is likely the largest I have seen of any warmouth population. The numbers of warmouth are not evident by observing from shore but when snorkeling they easy to find and appear to have high condition factors. The really cool stuff involves the two pelagic species; brook silversides and red-fin shiners. Both can be seen at surface from shore and former appears to be uniformly distributed seldom more than a couple inches down while red-fin shiners operate mostly more than a foot below surface. Red-fin shiners are possibly more concentrated around perimeter yet they do come up to feed as they chase algae mats brought to surface by oxygen bubbles. The silversides appear to have home ranges that might even be territories well away from structure. I would very much like to make estimates on biomass and growth rates of these species. Very soon reproduction will begin for 2013 season. Male sunfish seem to be working out pecking order among themselves when home ranges overlap.