Pond Boss Forums INTRO Questions & Observations Bluegill

I have three questions about bluegill

1 How many can you safely harvest out of a 25 acre lake a year?
2 How big should a blue gill grow in a year?
3 How long will a bluegill live?

#1. As many as you can catch!

John, a serious question deserves a serious answer.
I am unable to advise on a lake of this size, but there are experts on this board that are well qualified to address your problem.
They have been very helpful me in small pond management.
I’m sure they will chime in.
Good luck.
George Glazener

I am not an expert but....

1. This depends on a lot of factors like your goals, pond fertility, predator density, etc. If you provide more info, one of the experts may chime in with their recommendation.

2. This is variable. Under normal conditions they should be about 2" inches after the first year. After the second year, they should be 4-5". You can expect another 1-2" of growth in the third year. With some management (feeding, etc) you can greatly increase these numbers. Consequently, if the population is overcrowded, you will have less growth. Do a search on this site for BG growth. It is way more complex than I ever imagined.

3. Avg lifespan of a bluegill in an aquarium is around 7 yrs. 13 year olds have been documented. Of course, in a pond, the vast majority are eaten in their first year.

I hope this helps.

JAM :

JayMan is right . Many factors go into proper harvest rates . Size and life expectancy also are determined by several factors. JayMan noted some of them. One I want to additionally point out is location . Location often determines growth rates , feritility of the pond , growing season , types of fish that can survive and how the pond is managed for DO {oxygen levels in the water}, wintering {ice over} and a host of other matters. Please see the first site below for info on Indiana . On pg. 7 it has info on BG in southern Ind. where you are located. This site also has some good general info but according to CB1 some of it is dated. The second site is to a dicussion about BG growth in CB1's pond over the summer.

http://www.in.gov/dnr/fishwild/publications/fsmgt/fishmgt.pdf

http://www.pondboss.com/ubb/ultimatebb.php?ubb=get_topic;f=20;t=001625

While many of us in the south can , as bobad implies , take many BG often as many as we can catch , up north is different. I read an article in In Fisherman mag. some time back that warned against fishermen up north { infertile waters and slow growth rates} taking to many large male BG off the nests. It pointed out the dangers of that practice on the populations size and quality. There are many on this fourm who can give good advice for your area . ewest

Usually this question would be posed for one of two reasons.

1. Management purposes--in order to influence size structure or population dynamics of bluegill, competing species, or predator species that utilize bluegill as forage.

2. Dinner table management--the person posing the question likes to eat bluegill.

I think that if you fall in the latter category, then a good way to protect your population would be to identify a group of fish that you can put heavy pressure on. Using this forum, you could learn to ID bluegill by sex and pressure females, or you could pick a slot, such as 6-8 inches, and harvest these fish. I believe that in a body of water this large that if you kept only females or 6-8 inch fish, then you and several friends could harvest as many fish as you can catch without guilt or danger to the population.

If you fall into the former category, then the question is considerably more complex and might be better answered by Greg, Bill or Cecil.

Annual growth of bluegill and their maximum age are together linked by geographic and climatological factors. In warmer climes bluegill can grow to six inches in the first year and as much as nine inches by the second year. In cooler areas this could take as many as six years to reach the nine inch size. Around here a bluegill that reaches age-10 is an old warrior, but a fish this old would be unheard of in south Georgia or Florida. In Minnesota an age-10 fish might have some pretty good years left in him. Some people believe that cold blooded animals such as fish, age as a function of degrees in excess of freezing multiplied by the number of minutes spent at said temperture. This has also been a subject of speculation on this forum. Good question--vague answers. Sorry about drifting a little bit.

John - Simple questions - but complex answers. Nature and its ecosystems are rarely simple; this includes dynamic fish populations. Your questions could be answered in several different ways depending how one interprets the question. As Bruce mentions, harvest numbers will depend a lot on the long term GOALS for the pond's total fishery.
For example
1. What do you mean by safely? Safely in terms of what goal for the fishery? Most will assume you mean without upsetting the overall balance and keep the fishery with a "good" or "normal" number of all sizes of prey and predators. The type of predators, trash fish and mix of panfish (prey species) will also affect the number harvested. If perdators are not managed or harvested, then this will eventually affect the number of harvestable bgill at any given time.

As others eluded to, Fertility of the pond also affects how many fish it produces a year to replace mortality -natural and harvest.

2. Bgill growth per year is determined by fertility and density of fish. Too many fish result in too many "hogs" feeding at the trough and food supplies run short thus slowing fish growth. How much bgill "SHOULD" grow per year may not be truly what occurs due to NUMEROUS factors - to name a few: fertility, fish density, genetics, forage diveristy, zooplankton populations (food chain), water chemistry, trophic conditions, amount or percentage of bottom that is anoxic.

Factors for numbers 1 and 2 are closely interconnected.

3. The life span of bgill as in many fish is dependent on heat units per year and how dense the year classes are of each species. Normal (whatever ever that is) bgill life span in your pond should be very close to what Bruce suggested. But a lot of variables will affect the life span.

You are dealing with a living animal (bgill) that is succeptable and vulnerable to all the surrounding environmental influences of Mother Nature. It is very hard to give you definate or specific answers because it always depends on numerous things the fish are subjected to.

There will be conditions and exceptions in every answer someone gives you.

In general, numerous fishery studies have shown that 20% to 35% (upto45%) total mortality of the adult (5"+) bgill occurs each year in public waters. Fishery managers strive for a harvest of around this number (abt 30%). But to arrive at this number one has to have an estimate of the total bgill present that are 5"+.

As Bruce notes, harvest of the bgill can be done so it skews the sizes of the remaining bgills to result in an A. average bgill fishery (normal blend mixed sizes), B. a propensity of smaller sizes (few greater than 8") or C. a trophy fishery (lots of big ones above 8").

In gerneral, if you have a normal balance of bgill sizes, I think that the smaller bgill you will accept as keepers the more fish you will be able to "safely" harvest each year. The reverse is also true the larger the minimum keeper size, the fewer you will be able to "safely" harvest per year. This is due to the natural or normal size structure of fish populations: more of the smaller sizes, decreasing numbers of each larger size class up to fewest numbers of the oldest, largest fish.

Before I commit a guess or recommendation of a SAFE number to harvest per year I would like to know your average, minimum and maximum secchi disk readings for the pond. Secchi disk values will provide me a relative value of the pond's productivity

I want to thank you all for the information you have all provided me. I now have to make a little confesson. I am the lake manager of a lake in southern Indiana. I have been given this responsibility about 5 years ago. We have been putting cover in the lake and have 8 diffusers going all summer long with oxygen and temperature checked once a month from top to bottom every five feet. I have a few guys that I think are taking advantage of the lake. One said that in mid July that they have take out over 3000 bluegill this year and another I have seen throw away three five gallon buckets of fish remains on one fish outting. I am really concerned of an over fishing problem on the bluegill. To me the bluegill are all to small 5-7 inch range. I have to say that I have seen three red ear this year 15/16 oz. one pound and one pound 2 oz. I know that there are some big gills in the lake but I am trying to get bigger ones in the lake. I am just trying to get all the information that I can to try and get them to back off a little bit.

When doing DO and Temp measurements are you taking secchi disk readings? They can also provide valuable information.

Intensive fishing pressure and an overharvest of the bgill without any selective harvest or harvest limits, will in the not too distant future, result in decreasing the average size of bgill caught or harvested. You might be already seeing some of this occurring. It happens in lots of public access lakes. Soon anglers will be complaining about always catching too many small bgill. "Where are all the big bgill we used to catch?" In the near future, the over harvesters can be thanked for the changing size structure of the bgill population and the relatively poor quality of the panfishing.

Bill,

I'm a little puzzled . What do you mean by "minimum" secchi disk reading? In addition, can you cite a reference that explains the correlation between secchi disk readings and pond productivity?

Thanks

Russ

John -- what can you tell us about your largemouth bass population?

John, one other question. What means do you have to control harvest? What rules or regulations is it possible for you to set and enforce?

Russ - As of today I do not know of a good reference which correlates secchi disk with specific pond productivities. My textbook references only deal with generalities. This is probably because there are several reasons for a reduced secchi disk reading besides the influence of plankton. Thus it is hard to consistantly and accurately predict producivity due to secchi values alone. Secchi readings are just ONE way to generalize the relative productivity. If one has consistantly high secchi values the producivity is likely to be low and fish biomass low compared to one with reduced secchi readings providing both water bodies are relatively similar.

I am starting to collect some information on this topic but it is in the beginning stages. North American Lake Management Soc has secchi disk readers participating throughout N.America.

Minimum secchi disk reading is just the lowest value among a series of readings obtained from a pond.

Norm brings up a very, very important point. Trying to get cooperation for control of fish harvest or monitoring the annual harvest from a few unwilling fishermen could be very difficult,if not an impossible task.

Ok guys thanks for all the input. As for as the Secchi Disk I have not taken any reading with one. We are having an algae bloom going on and am fighting a Colonial and a Blue Algae. We tried to put 3200 pounds of alum in this year in April to settle the algae to the bottom. It worked for a while but had to resort to Cultrine Plus spot spraying to kill it off. The lake is clearer this year than last. The question on the Largemouth Bass we have a 13-16 inch slot limit on those. Since implementing that rule the bass are getting bigger and look real healthy. As far as enforcement it is an honor system. There is no way you can enforce this on this lake since some days it gets fished and some days it may not. I tried once to get the guys to fill out a creel sheet for size, weight and numbers but only a few would do it.

How did you acquire your alum?

Bruce,

Did you know it's readily available from any Chemical supply listed in the yellow pages? A lot cheaper than the one in pellets that Haliburton sells too.

Bill,

Thanks for the explanation. Given the small size of my ponds, I only take one reading. Now I'm curious to see the results of multiple measurements.

Russ

John -- here is the reason that I asked about the largemouth bass management program. I'll try to keep this short, although it can be a complex subject. Also, pardon me if I sound like I am lecturing -- I'm aware that you are a lake manager and mean no disrespect. :-)

Fishery biologists typically apply a protected slot length limit (in this case, 13-16 inch largemouth bass must be released) to a higher density, slower growing bass population. The goal is to reduce abundance of smaller bass, increase their growth rates, and increase/improve the size structure of largemouth bass in the impoundments. This can be a VERY effective tool in small impoundments where the management goal is production of larger bass, and it sounds like it has been effective for you.

However, there is also a trade-off on bluegill sizes when you use this protected slot length limit. Many people, and you'll hear similar comments on this forum, believe that larger largemouth bass better control bluegill populations through predation on intermediate size bluegills (say 4-6 inches). It makes common sense, but it is not correct. High density bass population with lots of small bass (< 12 inches) really think the small bluegills. That's what creates a high quality bluegill population.

Ok, so here's my long-winded point. By successfully using the protected slot length limit on largemouth bass, you should expect a decline in the average size of bluegills in your impoundment. Don't get me wrong: angler overharvest can certainly affect the size structure of your bluegill population, and I'm not excluding that problem. However, your management strategy is designed to increase the size structure of bass at the expense of the size structure of bluegills.

The fishermen that would not fill out the creel or catch forms are very likely the ones who are doing the most damage to the lake's fishery. They are the least honorable, and most greedy and selfish of the anglers. They are the ones to be watched most carefully for overharvest violations.

Russ - FYI - To elaborate / explain, one secchi reading at a central location during each date is usually adequate. My reference to "minimum reading" is the shallowest depth reading of all the readings taken during the entire openwater season. Secchi disk readings can sometimes vary at different locations on the same date due to plankton patchiness or turbidity inflows. But this is not what I was referring to by minimum reading in the above post.

Bruce we get our Alum in 50 pound bags form Ulrich Chemical in Evansville, Indiana. The more bags we buy the cheaper it is. When we bought 65 bags it was $12.00 a bag. Fifteen bags were $13.25 a bag. If you use it where a respirator and a pair of goggles.

Dave I understand what you are saying. We were told to do put the slot limit after Aquatic Control came and shocked the lake and did a survey for us back in 2001. At that time all we were catching were ones under 12 inches. Since then we have been seeing a bigger and a better quality of Bass. That is a thought about harvesting some of the bigger ones and leave a few little ones. Personally I do like Jimmy Houston does kiss and release.

John -- I once asked Greg Grimes on this Forum about management of private waters for big bass vs. large bluegills. He said that about 90% of his customers wanted the big bass, and only about 10% were willing to sacrifice quality of bass to get big bluegills. So, your largemouth bass slot limit is likely the most popular choice.

JOhn to state in another way what Dave said. It appears the harvest of bass has worked to increase aveargae bass size. It also has done what Dave mentioend it has lowered the average size of your bluegill. Youi mentioned mostly 5-7 inch. Why did the bluegill size go down, easy becasue you have more. So is it bad they guys are taking out this many, probably not if you want to increase bluegill size but yes if you want to continue to produce bass food. Once again it boils down to goals.

Dave I did say that and it is true most clients want to produce big bass and do not really care if average bluegill size is lower. However most lakes have the opposite they have too many bass b/c in I deal with city folks that have property in the country and they never take out enough bass.

The grass is always greener too it seems. Earlier this year we shocked several good bass out of a 2 acre pond. I commneted most of my clients would be super happy with this, guess what he likes catchin' slab bluegill and was tired of all the 5 inch bluegill and few big ones. SOld him some bass from a client that had too many, problem solved. I guess this is what keeps us busy

"Something which is a smelly mess in one field is valuable fertilizer in another!" - Robert A. Heinlein