Pond Boss Forums INTRO Questions & Observations Post spawn relative weight

Hi everyone..very informative site...Okay the quick version to this is that I just joined a club that has a 400 acre(actually 2 twin connected)200 acre shallow resevoirs with 2-4 ft highly vegetative flats surrounding 6-10 channels and clear water in southeast Texas what I call a marsh resevoir with levees...I've fished it twice and have caught a bunch of 8-12" skinny bass..I got the report from a 2001 electro study done in may that showed a relative weight of LMB to be 58%...bluegill relative weight of 153!the analyst of the study blamed the low relative weight for the bass on post spawn condition and recommended 15k woth of bass and threadfin stockings which I think they did 2 years ago...It sounds a little fishy to me based on my anectdotal fishing results and everyone is complaining about the fishing..58% seems very low..can this be from post spawn..seems way to low for that..seems like a crowded bass trophy bluegill fishery that needs some serious intervention..a food problem or "hard to get at"(vegetation) food problem seems more likely than a need for more fish..I know this is complex but we are not in the club for bluegills no matter how big.this resevoir is 30years old and has produced numerous 10+ fish and some 12- 13's.What do you guys think?Bob do you service the entire state? any info would help..thanks..Kelly

Kelly, I agree with your thinking. Post spawn could cause maybe a 10% drop in Wr, so they might have been 65% or so, still skinny. Run them again you can do that every time you fish. The most accurate way to perform Wr is throughout the year and then take average. I think your right remove smaller bass and increase forage instead of stocking more bass.

thanks Greg.It did not seem that the weights would be that low just from spawning..plus male are in the equation too..The survey analyst semmed to rely completely on PSD(proportional stock density) to make his recs and ignored relative weights..the calcualed PSD for this lake bass:65...bluegill 55...however only 60 bass were obtained in the entire 400 acre resevoir and about the same number of bluegill(1-2"BG were rare)...Is this an adequate sample size? and how helpful is the calculation of PSD's considering the very low relative weights..I don't see a lot of discussion related to this index(PSD)on this discussion board as it relates to pond management..thanks .Kelly

Good morning, Kelly. I now see why there is some confusion on the part of your management folks.

Let me back up, and start with your original question. Based just on your relative weight information, I immediately thought of just the same response that Greg gave you. [I didn’t answer, as I thought one of the southern biologists should be working with you. :-)]

However, you now have complicated the “puzzle” with your high PSD value. Yes, that is indeed a darn important piece of information. The biologists that frequent this board don’t talk about it much, probably because it starts to get complicated. Actually, one of the cool things about this website is that PSD would even come up!! Sure makes it fun!!

Anyway, PSD is short for proportional stock density. What it does is put a number on the size structure (length distribution) of your fish population. For largemouth bass, it is the percentage of 8 inch and longer bass that also exceed 12 inches (for bluegills, it is the percentage of 3 inch and longer bluegills that also exceed 6 inches). So, a low PSD means the population is dominated by small bass, less than 12 inches long. A high PSD means it is dominated by larger bass.

When I analyze a pond, I like to know relative weight values, PSD values, and I also very much want to see what we call catch per unit effort. In this case, it would be how many largemouth bass they caught per hour of electrofishing. Relative weight tells me if fish are fat or skinny (crowded? Plenty to eat?), PSD tells me size distribution (quality), and catch per hour also provides some information on abundance (many, few, moderate).

In your situation, you first told us a very low Wr value for bass, and then the high Wr for bluegills. That does indeed sound like a classic example of a high density, crowded bass population that is producing some dandy bluegills. As Greg said, even with the post-spawn decline in bass condition, bass should not be that skinny unless they are crowded. However, such a bass population normally would have a PSD of 10 or 20, not 65! So, I can indeed see the source of confusion in your management report. I suspect your impoundment is somewhere in the phase of shifting. Perhaps it used to have better bass, but they are becoming crowded, but there obviously still are quite a few bass that exceed 12 inches (65% in that last sample).

What bothers me about your last comment was that you seemed to infer that the catch per hour of largemouth bass by the electrofishing boat was low. Did they happen to report that in your report?? If so, post that number for us.

Also, did they perhaps report a relative stock density (RSD) value?? PSD by itself generally is not all that sensitive. Were the bass over 12 inches, but nothing over 13 inches?? OR, were there 15 inch, 18 inch, 20 inch bass?? Did they perhaps report an RSD-P value or a RSD-15 value?? If so, we could help interpret that for you if you would post that value in a response.

So, right now, all the “pieces” of your puzzle don’t fit well together. That’s why I first said I could understand some confusion on the part of your management report.

Perhaps we can do two things. First, answer my last couple of questions above if possible, and let’s see if there is a little more information in that report that we can use.

Secondly, let’s hope Greg is still watching or that Bob Lusk happens to come on line. Their input might really help. I’ve never worked in far southern waters, and their expertise would be helpful.

Ok, how’s that for long-winded???

Dave

Dave, I wish I could convey my point in writing as well. Great points! I wish I could say what I mean instead of trying to write it. Here goes, I used to always run PSD, it seemed to confuse the lakeowner and now I put much more emphasis on Wr. I think RSD would be much better and I think I might start running them again for clients I have had for several years. ALso I use CPUE to help indicate productivy. However if you are shocking an 8 acre pond and get 65 bass in 20 mins does this mean anything if they are all less than 2 lbs?

One problem with PSD for bass is that quality status is 30cm (11.8"). I have tons of stunted bass ponds that would be high PSD with 85% of the total bass pop between 12-14 inches. So if I report a good PSD yet all they catch are skinny low Wr bass it confuses them.

In the case with Kelly (having not thought this out too long b/f posting) he could have tons of 13" bass that could inflate PSD to 65. Am I thinking right? I see your point RSD would be better.

I report to my clinets a size class distribution histogram. I also include a typical one for bass crowded, another for balanced and another for trophy bass pond. They can see how their pond fits in. The bass heavy pond, maybe like Kelly would have lots of bass above 12 inches but few above 16 inches, make sense.

Thanks, Greg. I think we are on exactly the same thought track.

It's very interesting to know that you find crowded populations where the bass still make it a few inches over that 12-inch break. In our Midwestern work, that's not as common as it apparently is for you, so that's a good lesson you've shared with me. I suspect it's probably just an artifact of the northern latitude. We don't get the maximum size on largemouths, either. If we can produce an occasional 5 pound largemouth in the ponds, that seems like the trophy fish up here.

I also was interested in your observation on cpue being an indicator of productivity for you. Good thought. Again, I just have never worked on any infertile ponds (infertile soils). All my work has been in the plains, and I guess those soils are just consitently more fertile. If I had to work on a Kansas or a South Dakota pond, then catch per hour means a lot. If it is 100 8-inch and longer bass per hour of night electrofishing, I can just about predict slow growth, a low relative weight and low PSD/low RSD. If it's 10 or 20 per hour, then we'll see the bigger bass that are growing faster and in better condition. Anyway, that's why I like CPUE, but it's probably because of a limited fertility range. Very interesting. Some day, I'll have to take you up on your offer of a visit to the south, and see some of your ponds. Famous last words, probably. :-) Always too busy.

Anyway, thanks for posting again. Hopefully, Kelly will read this and find it helpful.

Dave

Greg, What the dickens is a CPUE? Got any more fizzlegidgets up your sleeve?

thanks for the replies..hard to solve the puzzle without all the pieces..unfortunately, the catch per hour rates were not given..I do know they completed the study in a day(400 acres) including seining the boat ramp..not sure if that is a reasonable time spent or not..Dave, I think the fishery in a transition may fit with a trend toward stunting..the distibution of bass was a large proportion at 12-13" and a drop off between 15-18" and then 5 or 6 bass 22" -24" with one 28"..no relative weights given for each length class...My main concern with the study was that it completely blew off the 57% Wr number and then they just recommended stocking and forage without any further management option..It just seemed very incomplete and I think you guys are confiming my suspicions that more study needs to be done..and with a different company..this bass club used to be famous for producing large bass and there is still quite a waiting list to get on it..the fishing to me is just not what it should be and I am interested in helping the members find answers..thanks..Kelly

Good morning, Kelly. Sounds like you have a good handle on it. Post-spawn largemouths from a healthy population should drop into the 80s post spawn, not the 50s.

I think I'd go right back to the top of this string, and take Greg's advice -- start a selective harvest program for those smaller largemouths.

A 28 inch largemouth -- we can only dream of those up here!!

Dave

Dave intresting the diff. in north vs. south. I have had several ponds with bass stunted 15-16 inches. In fact Ray Scott had a harvest plan a few years ago to harvest his overabundance of "skinny" three pound bass, a problem most pondowners would like to have. Davidson CPUE is catch per unit effort, sorry about that.

Greg, assuming a unit to be a fisherman, I see how it could be skewed. Too many variables.

Dave D, it usually means the amount of fish caught per time of electorfishing. A pond full of stunted bass could equal 80 bass/hr but is that a good pond? I have used the CPUE to get how many POUNDS of bass/hr and it seems to indicate how productive (how many pounds) the pond can sustain in bass.

dave and greg, this is the most interesting and informative post i've read in a long time. thanks for the information. jb

I agree. Very interesting stuff.

I am interested in the answer to the question of whether a person and maybe one assistant can adequately sample a 400 acre resevoir in a day..say 8 hours....60 bass were obtained total, but if I fished for 8 hours I might catch 20.I'm just trying to get a ballpark answer with unfortunately not all the facts..how long would it take to run say a 10 acre facility and what do you guys consider an adequate sample size?..Is there a formula for hours/surface area that is an acceptable standard to consider the pond adequately sampled?

I think that I missed something. Exactly in what way is relative stock density different from proportonal stock density?
-Scott

Scott -- I don't want to make this too complicated. :-) To be factually correct: proportional stock density is just one type of relative stock density. I didn't want to further confuse this discussion with jargon used by fisheries biologists. I recall your dad saying one time that you were thinking about a career in fisheries. If you want, send me an e-mail with your mailing address. I'll send you a technical review paper that explains the history of proportional stock density and relative stock denisty. We just use those indices to quantify (put a number on) size structure of fish populations. It's the kind of thing taught in university classes in fisheries management.

Kelly -- We'll need Greg to respond fully to your question about electrofishing samples. I don't know what to expect in a southern, infertile water body. He's been good about helping us with this discussion, so hopefully he'll spot this.

However, I can give you some generalities. If a person went electrofishing for eight hours and only caught 60 bass, that would be a very low catch in all places in which I have worked. In fact, the muddy Kansas reservoirs (no aquatic plants) on which I used to work had at least that many bass, and those were very low population densities.

If I went to a SD impoundment of 400 acres, we certainly could get a very good electrofishing sample in 8 hours with 2 people.

Now, here I go again with the complications! There are so many factors that affect electrofishing that I could write pages on it. Let me mention a couple. First, water clarity has a big inluence on sampling. It sounds like you have very clear water. If so, we often find that we need to electrofish at night (after dark) to get the best sample in the least time in such waters. Maybe Greg could comment on this as well. A second example: season has a big influence on our sampling. In spring or fall, when water temps are in the 60s F, more bass are near shore, and we get our best samples. If you shock during the summer when water in up to the 80s, then you tend to catch a lot fewer fish, and you tend to catch mostly smaller ones, and fewer big ones.

OK, your other questions: 'How long would it take to run say a 10 acre facility' -- Usually an hour or two of electrofishing is plenty on a 10 acre pond.

'What do you guys consider an adequate sample size' -- we argue about this all the time. I'll bet 60 fish would tell you a lot in many cases. I usually try for at least 100, but that's just a number, and it's affected by so many things. I would be interested in Greg's response to this as well.

'Is there a formula for hours/surface area that is an acceptable standard to consider the pond adequately sampled' -- No, I've never seen anything like this. It really depends on our objectives. If we are asking a simple question (what is the bass size structure?), then it takes less sampling. If we are doing in-depth work (has growth changed), then we often will want a bigger sample size.

Dave

Dave,thanks for the info......So to perhaps sum up what may be happening in this "pond"...A relatively high PSD exists(scewed on the 12"-13" side) in the presence of an extreme Wr only on a temporary basis and I'm guessing with time if no nutritional changes are made there will be a further decrease in the PSD with a shift more toward 10"-11" bass and perhaps continued presence of a few large individual bass that are able to feed on the overpopulated smaller bass..Do you think thats the overall gist of whats going on?thanks again..your input will definitely help me when I research qualified fishery management companies and hatcheries in the future...Kelly

Dave, This would make a very interesting article for your next magazine article. Now, if someone would just tell me how to catch fish instead of counting them............

Kelly -- yes, I think that is the gist of it, but with one small exception. Based on Greg's experience, the bass may actually "stay stunted" at lengths a little above 12 inches.

It would be interesting for you to weigh some of the bass you catch pre-spawn, post-spawn, during midsummer, and then fall. Greg has the calculation for relative weight on his company's web page. If you can't access that, I can send you the information. Anyway, you can track your own relative weight values over time for bass you catch by hook and line, and then watch the relative weight increase if you start a removal program. The key for year-to-year comparisons is always to always look at relative weight values from a similar time of year.

I don't know if I need to say this, but I'm uncomfortable sounding like too much of an expert without seeing an impoundment or doing some sampling. There's nothing like actually being there. See my point?

Dave -- thanks for the input!! Much appreciated (ideas are always needed!). Bob is going to run "part 2" of the smallmouth bass article in the next issue. I'll run this idea by him for a future article.

Dave

DW you would fit in just fine doing this southern work. I agree with what you said. Clarity makes alot of diff. However I rarely shock at night. ALso I do spring and fall sampling b/c your right high temps equal less big fish.

This may sound arrogant but I can usually tell the poulaiton dynamic in simple bream/bass pond within five mins after we start shocking. It is very obviuos if bass heavy. I will get lots of little bass and few or no intermediate bluegill. However we will sample for about 30 shock mins for 5 acre pond. The client wants me to cover evey nook and cranny and I try to do that since they are paying the bill.

So I guess Kelly I'm saying yes they could shock a 400 acre lake in 8 hrs but I can not see how they could not get more than 60 bass. I average about 75/hr. ABout sample size I try to get as much as possible by sampling all the diff habitat types. However I have only felt I did not get enough for an accurate assesment a few times, even if I had just a few. Looking at other species besides bass will also fill in the puzzle and help in the big picture.

Also what Dave said is true they will not get shorter just remain at 12 inches and if nothing is done Wr will continue to drop. Wr is good to track over time.

Dave check this out I just got hired to shock a 4,000 acre lake in Orlando. How long will it take me to properly analysis this?? I have only done 5 over 100 acres so it will be interesting. I under bid the job but looking forward to seeing this one.

Thanks for sticking with us on this one, Greg. Appreciate it.

Man, can I come and see that sample in Orlando?? I've never handled a bass bigger than about 9 pounds!!

4,000 acres: no problem. 12 stations at about 15 minutes each. You'll know exactly what is going on, right??

Dave