Pond Boss Forums MANAGING AN EXISTING POND Evaluating and adjusting fish populations Suppression of Sexual Maturity by Large Males in Non-Bluegill Lepomis

The presence of large male BG causing smaller BG males to delay reaching sexual maturity (the "90 lbs weakling getting sand kicked in his face" syndrome) has been well discussed both here at the forum and in PB Mag.

Dr. Frankenbruce and I were discussing horrible experiments we are conducting on sunfish and wondered if there are any studies or evidence showing a similar maturity delay caused by large males in other Lepomis species - specifically Redears, but info on this effect in any Lepomis in addition to BG would be interesting.

Wouldn't you expect that any Lepomis species that engages in colony nesting to exhibit the same traits. Have you checked the Neff studies? Is this a research request ? :p

Looks like a research request to me.

I would be interested too, I've been thinking about the redears we recently stocked. We have limited spawning areas available in our pond due to our heavy aquatic vegetation, this makes me wonder if the BG, or the RES will be the more agressive nesters in the few areas that they do spawn in and what kind of role delayed maturity might be seen due to the limited spawning areas available. Now "if" we end up with some mostly male RES/BG hybrids down the road, this might also help delay sexual maturity in subsequent younger male hybrids, BG, and RES. It's interesting to think what might happen in our pond now that RES have been introduced into the mix.

I thought there might be some interest. Good question Theo. Here is a start.

North American Journal of Fisheries Management 17:508-515, 1997

€> Copyright by the American Fisheries Society 1997

Male Reproductive Competition and Sex-Specific

Growth Patterns in Bluegill

TIMOTHY J. EHLINGER

Department of Biological Sciences, University of Wisconsin—Milwaukee


These findings support the hypothesis that intrasexual selection and competition among parental males for reproductive opportunities influence life history decisions and growth patterns in male bluegills. These conclusions are congruent with Jennings et al. (1997), who demonstrated experimentally that social interactions and size structure variation among male bluegills profoundly affects age of maturation, gonadal investment, and growth trajectory. The findings also parallel those for longear sunfish L. megalotis, where slow growth and small body size were attributed to early maturation (Jennings and Philipp 1992b). This contrasts, however, with studies of pumpkinseed L. gibbosus, where high juvenile growth rates correlated with early maturation (Fox 1994; Justus and Fox 1994). One possible reason for these interspecific differences is that both longear sunfish and bluegills are colonial nesting sunfishes (Cote and Gross 1993; Jennings and Philipp 1992a) with significant amount of male-male aggression involved in nest acquisition and spawning. Pumpkinseed nests are more dispersed and greater male attention is given to courting females and less to male-male aggression (Colgan and Gross 1977). If males must compete intrasexually, then body size may be involved more directly in nest acquisition
and reproductive success. Black ear tabs are flared during aggressive male-male encounters, and bluegills and longear sunfish have the greatest degree of sexual dimorphism in ear tab size within the genus Lepomis (Ehlinger, unpublished data).

Bluegill growth rates to maturation were greater for males than females in most lakes in this study . This difference between the sexes
is more pronounced than that reported for pumpkinseed in Ontario lakes (Fox 1994). One possible reason is that female courtship by pumpkinseed males may place very different constraints on the evolution of male life histories and growth trajectories. The payoff of delayed sexual maturation for a pumpkinseed male may not be as great as that for a bluegill, or may be entirely nonexistent.


Differences in Population Metrics between Bluegill and Redear

Sunfish: Implications for the Effectiveness of Harvest Restrictions

STEVE M. SAMMONS*
DAVID G. PARTRIDGE
MICHAEL J. MACEINA

North American Journal of Fisheries Management 26:777–787, 2006


Copyright by the American Fisheries Society 2006 DOI: 10.1577/M05-159.1


Most work on sunfish fisheries has focused on bluegill fisheries in natural lakes in the northern USA. However, substantial sunfish fisheries exist elsewhere in the country, particularly in large impoundments in the Southeast (Miranda 1999). Additionally, many of these fisheries contain redear sunfish, which have not been well studied. Redear sunfish composed as much as 66% of the annual sunfish harvest by weight in Tennessee reservoirs in 1998 (Malvestuto 1999). Given the popularity of sunfish fisheries in southeastern reservoirs, a more detailed investigation of their population dynamics is warranted.

Redear sunfish growth has not been well described in the literature, but our results indicated that redear sunfish consistently grew
faster than bluegills in all systems. Redear sunfish grew faster than bluegills in all study areas, especially at older ages. Often, bluegill growth in length would begin to asymptote by age 4, whereas redear sunfish growth would not approach Linf until ages 6–8. Many studies from northern systems have collected bluegills as old as age 10–12 (Goedde and Coble 1981; Otis et al. 1998; Schneider 1999); however, we rarely
collected bluegills older than age 5 in our reservoirs. Ott et al. (2003) found few bluegills older than age 2 in a Texas impoundment and attributed this to fast growth
rates and associated high mortality rates. Bluegill harvest was assumed to be moderate because only 10– 12% of annual effort was directed at bluegills (Ott et al. 2003). However, Belk and Hales (1993) found bluegills as old as age 9 in a South Carolina power plant cooling lake where no fishing was allowed, so angling may affect longevity of bluegills, even at moderate rates of exploitation (Goedde and Coble 1981). In contrast to bluegills, redear sunfish older than age 5 were common in our study reservoirs, and fish as old as age 9 were collected in each reservoir. Fish longevity has been linked to natural mortality rates (Hoenig 1983), and the estimated natural mortality of bluegills was generally greater than that of redear sunfish in all three reservoirs. Other authors found that bluegill longevity was lower in populations with high fishing rates than in less-exploited populations (Goedde and Coble 1981; Drake et al. 1997).


Now the question is do RES more closely relate to BG or PS wrt this question. Dave Willis you out there -- you just made a comparison of RES and PS for the PB mag. One thing all seem to agree on is RES are not known to stunt in natural populations. RES do spawn in colonies but not as much so as BG.

Thoughts anyone ?

Ewest -- I've been reading the thread, but don't have anything more to add. Redears are too far south of me -- unless we all agree to meet periodically at the Condello Ranchette for daytime studies and nighttime "discussions?"

ewest - here is an intersting article in male BG growth rates. It might be intersting to start a thread on it.

http://www.blackwell-synergy.com/doi/abs/10.1111/j.1749-7345.2006.00063.x

Does this mean that Bruce is right with his all male BG ponds?

Both BG and PS have much higher reproductive rates than RES. How much influence does population crowding play a role in delayed sexual maturity/growth rates?

from the article:
(the above is in "uncrowded" ideal conditions)

Okay. Using the assumptions that 1) large males have an advantage (and presumably therefore delay maturation among immature smaller males by promoting competitive growth) in colony nesting Lepomis sepcies and 2) big ear tabs are more important for male-male spawning competition in Lepomis species with a hgih degree of sexual dimorphism (at least where it's wrt eartab size - and configuration?).

Accepting that PS are more solitary nesters than RES, what about sexual dimorphism in PS and RES eartab size/coloring? I do not recall seeing a great deal of eartab SIZE difference between male & female RES; IMO male RES have larger, more boldly colored "red" patches on their opercules. Is that right? And have we had a real good Redear sexing clinic here before?

As for PS sexing, I couldn't find sexed PS photos on-line. IIRC Dr. Dave had male & female PS photos in the article from 1-2 issues ago in PB Mag. I'll have to dig it our tonight.

Interesting assumption Theo, could an alternative assumption be that sexual maturation of male BG is simply a function of age and not size? Maybe maturing at age 2 on average? If so then highly crowded conditions with limited food sources one would expect to see much smaller mature male BG than in an uncrowded situation in which there is very high abundance of food available.

In my tanks the RES males "posture" towards one another. When one is trying to make the other back down he makes both of his gill flaps point outward at nearly 90 degrees and nudges forward in a menacing manner. The smaller male then retreats. I can see the red glimmer from the eartab even from above the tank.

Theo -- I scrambled just to find any pictures of pumpkinseeds that I could use. Bob had one and I had one, and neither of us knew the sex of the fish.

Here are a couple more things to throw in the pot. RES compete with BG for nesting spots (either RES or BG get the nest colony) but usually not mixed. Thus inter-species competition suggests that together large Male BG and large male RES suppress early maturation possibly in both species. RES use their rather large red edged ear flaps to warn other RES males and BG males and females to keep out. Noises like grunts or clicks are used by both as an identifier and I would guess that larger fish can make louder noises. Larger RES males will run off everything else from the nest area so during the spawn overlap with BG ( first BG spawn of the year here)the RES get first pick of the colony sites. The RES colonies nests I see are about from 4 to 15 nests while the BG use bigger colonies say 20 to 50. So the RES males must like fewer nests in a colony than BG.

Because RES are larger fish , don't stunt , compete with BG for the prime colony nest sites , spawn in colonies and use their ear flaps as they do I lean toward them being closer to BG wrt male maturation than to PS. Because RES do seem to be less colony nesters than BG , I have seen no info on RES reproductive strategies ( such as BG with solitary nesters , cuckholders and sneekers) then that would argue towards more like PS. It is interesting however that some large prime male BG are solitary nesters which some times nest with the colony (from the Neff studies) which to me puts them closer to RES.

One more point. Is the spawning strategy of RES , PS and BG conditioned or genetic and at what point in the species development did it occur ? If genetic then note the chart below from the thread (thanks Theo) and see how closely related the three are.

Longhaired Hybridization
http://www.pondboss.com/cgi-bin/ubbcgi/ultimatebb.cgi?ubb=get_topic;f=20;t=002154;p=

TEMPO OF HYBRID INVIABILITY IN CENTRARCHID FISHES

(TELEOSTEI: CENTRARCHIDAE)

DANIEL I. BOLNICK1, AND THOMAS J. NEAR





I will keep looking.

Interesting idea. Sounds reasonable.

Could smaller RES nesting colonies be due to lower RES population numbers?


Perhaps colony nesting, large sunfish size, and the importance of being a large male (with subsequent suppression of maturity in small males) go together for Lepomis. Even though RES and PS are supposed to be more closely related to each other than to BG, these traits could have been passed down from the ancestral sunfish (a mythical "L. antiquatus", located at point 7 on the gene chart above). Do colonial nesting and large size go together in other sunfish? If true, most of them should be less prone to colony nesting than BG and RES, since those are the two physically largest species.

"Even though RES and PS are supposed to be more closely related to each other than to BG, these traits could have been passed down from the ancestral sunfish (a mythical "L. antiquatus", located at point 7 on the gene chart above)."

Yes or they could have easily developed after the branching through a genetic adaptation process that related to larger lepomis only. Then even after that the BG developed the other spawning/survival adaptation of cuckholders/sneekers/solitary nesters.

"Could smaller RES nesting colonies be due to lower RES population numbers?"

Yes but why if they are colony nesters would they opt for less nests which is counter to the purpose. It could relate to a smaller # in a given drawing area (the distance RES will move to find a nest site) in conjunction with not wanting more empty nests around them for other species to use or to defend more nests/area than are needed.

I will check on colony nesting in other lepomis.

You're a good man, Charlie Brown!

More info. I strongly suggest that you save the link below (Sunfish Culture Guide) as it is a great summary and index of most every study topic on lepomis.


Gross, M.R., and A.M. MacMillan. 1981. Predation and the evolution of colonial nesting in bluegill sunfish (Lepomis macrochirus)


A male sunfish will construct a nest in shallow water by sweeping a depression in the sand or gravel with undulations of his caudal peduncle. The nests of bluegills consist of depressions 2-6 in (5-15 cm) deep and about 12 in (30 cm) in diameter, constructed in water 1-5 ft (0.3-1.5 m) deep (Becker 1983). Bluegill and most other sunfish are colonial nesters, constructing nests in densely packed aggregations (Gross and MacMillan 1981). Different species, i.e., bluegill and redear sunfish, can frequently be found nesting together in the same colony (Childers 1967). However, the warmouth (L. gulosus) are more solitary nesters (Childers 1967). A bluegill colony is usually comprised of 40 to 50 nests within a radius of 20-23 yd (18-21 m) (Becker 1983).

Sunfish Culture Guide
Editors
Joseph E. Morris, Iowa State University
Charles C. Mischke, Mississippi State University (formerly with Iowa State University)
Donald L. Garling, Michigan State University

http://idea.exnet.iastate.edu/pdf_pubs/sunfish_culture_guide.pdf

I can tell there is still alot I need to learn on this issue.

http://www.blackwell-synergy.com/doi/abs/10.1046/j.1095-8649.2003.00033.x