Pond Boss Forums MANAGING AN EXISTING POND Evaluating and adjusting fish populations Fish Weight Monitoring

After reading a Lusk article on this a couple of years ago, I've been monitoring fish weight for about a year, and have noticed that last year all fish were above the relative weights shown on this site. But this year only the 15" Bass are above relative weight. Longer than 15" the fish drop to 70-90% of relative weight. I'm not clear though on what fish should be taken out - the larger ones or the smaller? We're fishing all we can, and mostly preferring the larger ones for obvious reasons. Should we make more effort to get the smaller ones out too? The lake is about 35acres Soil Conservation (similar to Otto's recent article about silting), and although we're in a drought it's holding up at normal summer levels. Thanks!

If I understand correctly (a big if), I'd say there's plenty of forage fish the right size for 15" bass to utilize efficiently, while larger forage is sparse.

Possible corrective measures would include:
-thin the larger bass (thin the thin ones first, keep the fattest/fattest growing)
-thin the smaller bass, in the hope that more forage will grow to a larger size (sounds like a poor argument to me)
-adjust the forage base to have larger meals available for large bass

WRT the third option, what forage fish do you have currently?

It would help to know the size distribution of bass in the population. If you catch 20 fish how many are 8-12 inches,12-15 inches and longer than 15 inches? An excellent proportional size distribution (PSD) for fish over 12 inches is 60. An excellent proportion longer than 15 inches is 10 to 20. Thin where you have a surplus in that size group.

Dick - For all the novices here you should explain PSD (proportional size distribution). Mention how it is determined, what are the common range of values and discuss what or how many bass in each size class that you consider to be a surplus. Better yet write up an article about PSD and submit it to Bob Lusk as editor of Pond Boss Mag. Lusk is always looking for additional articles. If you provide a decent and informative post on the topic, I will include it in the Archives Section.

I would also like to be updated on your concept of Proportional Size Distribution as an evaluation device.

novice here...out of 20 fish an excellent PSD for fish over 12-inches is 60......60 what?, percent? yes, please explain in laymen's terms, and thanks for bringing in a new perspective.

Fisheries Techniques 2d pg. 468. PSD = Proportional Stock Density = [ # of fish > or = minimum quality length divided by # of fish > or = minimum stock length ] X 100. See also Relative Stock Density = RSD which is the % of fish of any designated length-group in a sample. Without getting to complicated these have been refined to 5 catagories , stock , quality, preferred ,memorable and trophy lengths. Table 15.2 has these for 39 taxa.

This is the only AFS study using the words " proportional size distribution ".

Black Bass Length Limits by Design: A Graphic Approach

The bass proportional size distribution presented
in the wing graph is similar to the proportional
stock density (PSD) concept of Anderson 1976 .
Had we chosen CPUE of bass 8 in and
longer as the JV-axis and CPUE of bass 12 in and
longer as the X-axis, the slope of a line from the
origin to a given point would equal the PSD for
that population. The PSD is a useful concept for
fisheries management, especially as related to angler-
caught fish; however, we have found that PSD
based on electro fishing data can be overly sensitive
to annual changes in recruitment. A large increase
in abundance of 8-in bass can inflate the denominator
of the PSD equation and thus reduce PSD
substantially, even though the abundance of larger
bass remains unchanged. Therefore, we agree with
Dent (1986a) that PSD information should be used
in conjunction with CPUE data by si/e-group. Another
limitation of PSD is that it does not include
largemouth bass less than 8 in. The product of
total bass CPUE and PSD is of little value by itself.
Total bass CPUE and the CPUE of bass 15 in and
longer is much more useful. The larger bass are
needed to sustain population biomass, predatory
pressure and the quality of fishing.

I have some mixed emotions about PSD. It ignores an awful lot of the total bass density (8 in. or less) which can have the biggest effect on forage and thus the greatest potential damage on predator/prey relationships or pond balance. However, in a BOW with a good bass distribution, most of those smaller ones wind up as "bait for the biguns" with very little proportional recruitment. Compound the creel survey problem with the fact from studies that about 50% of the bass in a population never bite a hook. Electrofishing tends to favor the smaller, dumber bass that hang out in skinny water.

All of that means that we can only make guesses, albeit educated guesses, if we use a snapshot approach to decision making. Jimbob is doing it right by keeping an ongoing record. If it were me, and it's not, I would eliminate fish with a low WR. That would tend to indicate an out of balance condition for that size in the total bass distribution. It is symptomatic of overeating the forage base that the low WR predators prey on.

Jimbob, all of those six bit words say that you have too many bass in a given size range compared to the appropriately sized bluegill they need to stay healthy. Yeah, they can eat smaller ones but have to expend more energy to get them. They can durn sure overeat their prey and cause a problem. Eat the ones that are of low WR and don't ever release a bass under 12 inches back into the pond.

Good advice. In conjunction with the PSD/RSD method (which uses creel (catch) surveys) include good visual analysis and seine surveys (keep records - size and weight and #s - RW ) and an occasional shock survey ( CPUE = catch per unit of effort in ES surveys) and you will have a very good system for assessing this problem.

This combo of methods compensates for the potential for error associated with each of these tools as noted in the above quote and as mentioned by Dave.

One word of caution with using just the RW (skinny looking fish) method. Time of year makes a big difference. A 110 % RW female in Feb. may be an 85% RW female 3 mths later. Same for males who just spent a mth nesting and guarding yoy.

VERY important point on the seasonal changes in relative weight, Ewest!!

Ewest asked me to "clarify" the Proportional Size Distribution vs. Proportional Stock Density issue. I guess this is most important for you pondmeiseters who REALLY care.

PSD was originally called proportional stock density by Dr. Anderson when he created this index back in the early 1970s (I was still in high school). Over the years, within the fisheries profession, there has been some discussion that stock density is really not measured. Instead, we are measuring size structure or size distribution. So, we have been toying around with changing the proportional stock density name to something else, perhaps proportional size distribution (which was suggested by Dr. Anderson).

Again, for those of you who REALLY care, PSD often does reflect density in ponds, but not always in larger water bodies.

So, functionally, none of this really matters to those of you who calculate PSD. Nothing has changed, and life goes on. It's a great tool.

By the way, I encourage all of you to welcome and engage Dr. Richard Anderson on this forum. Dick is retired, and should have LOTS of time to help everyone, right Dick?? Seriously, in my classes, I call Dick the "father of the rebirth of fisheries management." He did SO much for our profession! Plus, he's a great guy.

Thanks Dr Dave for pointing that out. I was not aware that the post above was by the Dr. Richard Anderson. I have many of his publications and he has been a big contributor to my education in regards to my knowledge of fisheries. We all should be very honored AND PLEASED to have Drs Willis and Anderson participating on this forum. They can help all of us learn more about the fish communities of our ponds and lakes. Thank you for your insight and the time that you spend with us.

Thanks Dave. AND WELCOME DR. ANDERSON we are indeed glad and privileged to have you join us. I think you will find this an enthusiastic bunch of pond nuts who need guys like you and Dave and Bill and Bob to help us along the journey.

Note that in the study quoted above it credits "Anderson (1976)" with the PSD concept development.

Greetings, Dr. A!

It is an honor to have someone here who so impresses someone who so impressses us.

Ah, Bill -- you're my hero with your broad knowledge base!

I'm always glad to help others learn more about their water resource or ponds. Education is key to better pond management.

Thanks so much for the kind words from all of you. I only recently became aware of Pond Boss thanks to Dave Willis (the best fishery professor in the country for my money). I am impressed with the quality of information in the magazine and in this forum. Sorry for the confusion about the terminology for PSD. I do hope to prepare an article for PB explaining the relationship between structure (what you can see) and dynamics (rates of recruitment, growth and mortality). PSD is sensitive to changes in recruitment. When high recruitment lowers PSD it is an early warning to increase harvest of 8 to 12-inch bass.
Dave Davidson--in my experience small bass do not exert the most important effect on forage. They may consume numbers but not much weight. Female bluegill in a balanced population are in good condition and spawn repeatedly. High numbers of young recruit to age one. A high mortality of age-1 and 2 bluegill is needed to reduce density and maintain growth. It is rare to find a bass population with a surplus of 12 to 15-inch fish. The most common structure is low PSD of stunted bass. With selective harvest and educated catch and release, most fish of quality size (>12 inches) are caught repeatedly.
Jimbob--you made me happy to read about maintaining records on relative weight. It is not easy to get good data on lively fish. Look for trends in the data. Look for fish in good condition in the fall. You are right on to evaluate RW as a function of length. It is another measure of structure to help decide should I keep this fish or put it back.

I think I understood everything but this one statement. I'm sure it's a misinterpretation on my part, but it seems like all of the ponds around here have tons of 11-13.5 inch LMB. What am I missing here.

WOW - Dick presented some very valuable advice. Read and re-read his posts carefully. At times he may be presenting information above the understanding of many of the readers.

Dick you may have to dummy down or simplify some of your presentations. There are many people here who love fish and fishing, but I am pretty sure that there are very few people here with technical fish backgrounds. However they seem to be eager to learn.

I look forward to every article that you have time to create for us in Pond Boss Magazine. Each article will give you an opportunity and the space to explain and expand on each topic. It is really great news that you may be publishing in PB Magazine. Many Thanks for all your effors while you are with us.

Welcome to PB Dr. Anderson but I didn't think professional fish squeezers made enough money to retire!

Doc Anderson, welcome to PB and Cody is right. There are a bunch of us Texans here and you really would do us a favor by dumbing it down to somewhere just above "See Spot Run".

Although my experience is very limited compared to yours and certainly influenced by an 8 year drought, those of us with relatively small bodies of water have way too many small bass eating us out of house and home. We have a lot of previously 5+ acre ponds with, effectively, an acre or 2 of reasonably shallow water, a bluegill shortage and skinny bass. Things being what they are, the bass are still spawning. I have evidently let my drought mentality influence my posts.

A lot of us have a different experience than you on catching the >12 inch bass. If we fish over twice per year, the bass get so hook shy that we may or may not catch anything that trip. Management and maintenance of bass becomes a real character builder.

BTW, I agree about Doc Willis. I prefer professionals and PhD's who repeatedly say "We just don't know.".

BTW, what is the Tx, Mo, Wi? That's a pretty good travel area. Are your Grandkids scattered that far?

Bruce , with reluctance to attempt to interpret for others D. Anderson's post , this is what I think he is telling us wrt PSD IN A BALANCED POND. Please correct me if this is wrong.

By definition a BALANCED POND does not have to many of any size LMB , but especially not 12-15 inch LMB. It is much more common to find unbalanced LMB stunted ponds with to many 8-10 in. stunted LMB. If BG are healthy and producing normally you need small LMB to crop the BG numbers. While the function of small LMB controlling under 3in. BG numbers is important it is not the biggest foraging factor effecting the total mass (standing crop) of fish in the pond. In a balanced pond if you start to see high LMB recruitment lowering PSD then it is an early warning of LMB stunting so start thinning that size and you can manage the situation.

Here is the wow factor condensed. Not only is PSD a tool for assessing your pond population it is a very good management tool to use to avoid a LMB stunted pond. That is use it as a pro-active tool to create a better pond - not just to assess the situation. Like a map don't just use it to tell that you are lost but use it to help you get where you want without getting lost. Our collective problem is in keeping a balanced pond population.

Drs. A or W , Bill or Bob how close is this assessment?

Ewest -- I was hoping that Dick would answer. You're right on target.

OK, I was having a little trouble putting 2 and 2 together. It makes perfect sense now. I failed to link the beginning of the paragraph with that statement.

I hate it when stuff goes over my head.

Dr, Anderson,

Welcome to the group! I have read and studied several of your articles especially the one on Length, Weight and Associated Structural Indices. I used those formula to create a simple spreadsheet to calculate relative weight. I also keep extensive catch records and chart my relative weights. I look forward to your contributions here.

Frank
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