Pond Boss Forums INTRO Questions & Observations LM bass mortality vs. annual harvest

On my 9ac pond in Chester S.C., my friends and I fish the pond 4 or 5 days per week and release most fish. We have harvested approx. 90 lbs.of bass per year in the 12"-14" range. We catch 30 to 40 bass per week and release most fish.

The bass appear to be healthy and represent a good spread of year classes. Many 2 lb..to 4 lb.. bass and one 10lb.3oz caught this year.Water quality is good and established population of threadfin shad and BG is present. I do not have an over abundance of small stunted bass as would be expected with very little harvest. I am hesitant to harvest 50 plus lbs./ac or 450 lbs. annually. Is mortality due to catch and release compensating for not harvesting?

Your comments will be appreciated.

Al Allison

Al,

Sounds like you have a nice lake. I am not a pro but IMO If you are handling the LMB you catch with care, I doubt you are losing many do to your C&R practice.

FWIW Before making a decision to harvest more, I would start measuring length and weight of every bass caught and calculating the Rw/Wr. This will do two things. First, it will give you an idea as to how your fish are doing compared to a standard metric as well as get a good feel for percentage of fish in each size class. This should give you the info you need to make a more informed decision on whether you need to adjust your current harvest plan. Second, Rw/Wr data will provide the info you need in the future to monitor your fish growth to highlight changes in growth patterns.

Bill D.

Bill,
We use all barbless hooks and return fish quickly after hook removal. I have had the pond electro-fished several times and found the wr to be right at 100. I am not sure that my friends would be willing to weigh, measure, and record every fish-but we do an accurate count of all removed fish including BG' Thanks for your reply.

Al

Al,

If you are happy with your catch rates, size of fish, etc., why are you thinking about changing your harvest plan? IMO every BOW has it's own personality, carrying capacity, etc. There are no fixed numbers that work for every BOW...It all depends....

IMO I would tell your buddies that if they catch a large skinny bass (not right after spawn) to go ahead and harvest it as it is probably an older fish in decline and will just end up as a dead fish in the bottom of the pond anyway.

Just my 2 cents

al - you say "I am not sure that my friends would be willing to weigh, measure, and record every fish-...".

Weighing and measuring the bass will in most instances take the place of electrofishing and its associated cost. Both fishery methods provide essentially the same results. Electrofishing does provide an idea of the forage community available to the bass. However as the Wr on most of the bass drops lower than 80 you can assume the forage community is decreasing and in short supply, thus thinner body bass. Then more bass harvest is in order to allow the forage community to rebuild. So the choice is yours and your fishing friends whether to make measurements or pay for regular electro-fishing surveys.

The other parameter that relates to your bass harvest question is - What is the average secchi disk reading of your pond-lake? As the average secchi readings increase fewer bass per acre should or need to be harvested.
http://rmbel.info/how-to-use-a-secchi-disk/
http://www.secchidipin.org/makedisk.htm

Bill,

Greg Grimes has performed the electro fishing and provided my threadfin shad. The shad have survived for the past 3 winters and tilapia have been added for the past 4 years. The forage base including BG has remained abundant.

The secchi disk readings vary from 15" to 20" during the year and the pond is fertilized only by agricultural runoff and periodic visitation by geese. ph has averaged 7.4 to 8.4. I do remove any skinny bass but very few are caught.

From my last electro fishing in Oct 2014, all bass 10" to 16" averaged a Wr of 95 to 98- and 17 bass 16" to 20" averaged a Wr of 110 to 120.

However, we do catch and release approx. 1500 to 2000 bass a year and do not appear to have a trend to small stunted bass. The pond was initially stocked 9 years ago. I believe that release mortality may be accomplishing the same result as harvest. Thanks for your comments.

Al

Keep in mind that over time the death of LMB (by catch and keep or death due to catch stress)all target the fish that are apt to bite (catchable fish). See other threads on the heritability of catchability.I would suggest that you keep records and harvest fish (the skinny or oversized class)by electroshock as it does not target catchable fish.

More on catchability - the chart below shows a 50% reduction in catch rates over 3 generations.




THE CUTTING EDGE – SCIENCE REVIEW
By Eric West


Aggressiveness - it should have been obvious – it’s in the genes

Catchability, how likely a fish is to bite a lure, is a problem encountered by pondmiesters and is often referred to as aggressive fish vs. non-aggressive fish. It has been debated on several occasions on the Pond Boss Forum and articles have appeared in Pond Boss magazine concerning possible management options for fish that don’t bite well. So what are we missing that is so obvious about this aggressiveness trait?


The new study is titled Recreational Fishing Selectively Captures Individuals with the Highest Fitness Potential by David A. H. Suttera, Cory D. Suskib, David P. Philippb, Thomas Klefotha, David H. Wahlb, Petra Kerstene, Steven J. Cooke, and Robert Arlinghaus , in Proceedings of the National Academy of Sciences. doi: 10.1073/pnas.1212536109 , October 26, 2012. This study, using the same genetic line as the first study noted above, found that the trait “catchability or vulnerability to angling” positively correlates with 1) aggression, 2) intensity of parental care, and 3) reproductive fitness.

THE CUTTING EDGE – SCIENCE REVIEW

By Eric West

Mixing Largemouth Bass sub-species, catchability and other questions

Mixing the two sub-species of largemouth bass (Florida - FLMB and Northern - NLMB ) to achieve the result of bigger fish while retaining good catch rates has been a goal of many a fisheries manager for years. Now we have another scientific point of light , titled Subspecies Composition of Angled and Electrofished Largemouth Bass in Texas Reservoirs , Dijar J. Lutz-Carrillo, and Spencer Dumont in Proceedings of the Annual Conference of the Southeast Association of Fish and Wildlife. Agencies 66:75–81, 2012 Proc., to add more knowledge to the equation

The study’s results provide biologists with a provocative concept that, in southern waters (natural integrated zone of FLMB and NLMB), FLMB likely are more difficult to angle than NLMB, but the phenotype (genetic trait) of reduced angler susceptibility (catchability) is mitigated (reduced) by introgression (genetic mixing), even at low levels of NLMB genes

While many factors may function concurrently to determine angling susceptibility, including fishing pressure, naivety of individual fish, learned lure avoidance, and stress from catch and release , we now know that catchability is a genetic and heritable trait as was previously discussed in earlier Cutting Edge articles ( see Garrett (2002) and Philipp et al. (2009) ).
See the table 1 below from the study which provides some eye catching numbers. A few that quickly got my attention. Even when there were roughly twice as many NLMB in the survey as FLMB the cross population showed almost 50% Florida genetics. In one instance where there was roughly 15 times the number of NLMB as FLMB the cross population showed 29% Florida genetics. The number of crosses in the tests far out numbered either FLMB or NLMB. I bet if you look you can spot a few more.

Note that when pure FLMB were removed from the dataset numbers (leaving only crosses with high levels of FLMB genetic influence) the trait of reduced catchability disappeared. Stated differently the addition of only a small amount of NLMB genetics caused poor catchability to disappear.

One interesting aspect of this study is the incorporation of a substantial amount of information from unpublished Texas Parks and Wildlife Department studies.
Assuming the electrofished collections were a reflection of the true composition of the population these results suggest that FLMB were more difficult to angle than expected based on their frequency in the population and that NLMB were angled at expected rates. Thus, in a scenario where both subspecies exist in equal proportions, we would expect FLMB to be more difficult to angle relative to NLMB.

Electrofishing has been the preferred method for collecting non-biased samples of largemouth bass for genetics studies over the last three decades and while capture rates may differ among seasons and throughout the day, no bias in the collection of either subspecies has been observed in numerous studies. Additionally, one study reported that largemouth bass collected using rotenone and electofishing from impoundments exhibited no differences in genotype frequencies.




In two lakes fish with high levels of FLMB influence (crosses and FLMB) were collected at significantly greater rates by electrofishing than angling. However, when the pure FLMB were removed from the dataset (leaving only crosses with high levels of FLMB influence) these differences between gear types disappeared. This suggests that the initial differences between gear types was skewed by the disproportionate number of FLMB collected by electrofishing and that crosses, even with high levels of FLMB influence, were collected at expected rates. Therefore, if FLMB and crosses with high FLMB influence were present in equal proportions, it would be expect that FLMB would be more difficult to angle than the crosses.
The distribution of LMB subspecies and their crosses are not identical; however, habitat preferences and distributional patterns appear to be more similar between the subspecies in southern impoundments than elsewhere. This I suggest is because the southern region is where FLMB and NLMB naturally coexist and cross leaving high populations of crosses.
It appears that the introgressed fish( FLMB/ NLMB crosses of all % , F-1 through Fx predominate and trend toward greater FLMB gene expression (see trophy fish comment below) .
Trophy fish (≥13 lbs.) from introgressed populations are represented disproportionately as non-introgressed FLMB relative to the frequency of FLMB in the general population ( TPWD, unpublished data). Thus, in an appropriate environment, genetic composition appears to be a critical component of maximum size in largemouth bass. While most of the differences in growth and maximum size between these subspecies are likely due to intrinsic physiological differences, behavioral differences, such as reduced angling susceptibility, may also play a role. FLMB that are potentially less susceptible to angling would be removed from populations at reduced rates relative to non-introgressed NLMB or crosses, allowing a greater proportion of FLMB to reach an older age and greater size. However I recall TPWD data also showing many of the share-a-lunker fish were high FLMB percentage crosses.

Well we are now one step further along the road to understanding FLMB and NLMB and their crosses. While it is early in the process most fisheries scientists now agree that FLMB can grow larger and are harder to catch. This study is the first to show that with a few NLMB genes in the population (individual) that the dreaded trait of reduced catchability can be greatly diminished. This was suggested in some of the early studies but not isolated in crosses as has been done here. You might, if you are in the south (natural integrated area) , consider adding a few NLMB to your FLMB only waters to improve catchibility. At low rates the NLMB genes don’t seem to reduce growth and size in the crosses.

Look for threads here on catchability. The info is here as is the research.



Here are a couple with links

http://forums.pondboss.com/ubbthreads.php?ubb=showflat&Number=274175&page=1

http://forums.pondboss.com/ubbthreads.ph...true#Post200220

http://forums.pondboss.com/ubbthreads.ph...true#Post260622

Very good information provided by ewest. Your secchi disk readings of 15"-24" indicate an ample plankton community and fertile water assuming the water visibility is due to algae and not primarily suspended sediment. Fertile water suggests the pond produces more fish and bass pounds per acre and resulting in a higher carrying capacity.

Eric,
Thanks for the reply!

Am I to interpret from this info that as a pond ages the genetics of the fish population gets "stale" so to speak and thus the catchability of the fish population also reduces significantly.

The implied solution to reduced catchability overtime is to periodically introduce a different genetic population including northern strain LMB and maybe some F-1. Now, I may have over-simplified things- but am I on track?

How often would you introduce new NLMB or F-1 to retain good catch rates?

Thanks again,

Al

Bill,
The pond alkalinity has been 60 to 80 and ph varies around 8.o. I do occasionally have ph approaching 8.5 to 9.o in the summer. I have extended vegetation buffers from agricultural operation to over 200'.

I do have some turbity after heavy rains but plankton bloom maintains from run off. I have not fertilized and have never had visibility over 24".

Thanks for you input.

Al

Eric, thanks for posting that study and the links that I had forgotten. Somewhere around here I still have the printed copy of a University study that you provided at our first PB get together at D/FW Airport. What University was that?

I am reminded that our first meeting of fish junkies was a long time ago when we first got the opportunity to look each other in the eye and form some long lasting friendships. What year was that?

Here are the meeting reports from summer 2005 DFW meeting.

http://forums.pondboss.com/ubbthreads.php?ubb=showflat&Number=92439#Post92439

DD1 not sure which study as there were several.

Yep, that's the first time any of us had ever met. I knew Lusk from a TAMU pond conference in san Marcos but met Otto and the rest for the first time. I remember several of those guys. James Holt is on the far right.

Lusk snookered me into "arranging" everything.

Eric, it was a University study; maybe Auburn. They stocked a pond with some small bass and let them grow. Then they fished and tagged those that bit. They kept records and later drained and transferred fish to other ponds based on experience with them. Those that bit and those that didn't went to different ponds. They went through several iterations like that and surmised that catchability seemed to be a trait that was probably generic.

If it was my pond, I'd remove a higher number of fish per acre than what you are doing now, and a higher % of 10"-16" fish. You will see faster growth on the LMB, and eventually heavier LMB. To me the WR that you saw in 2014 is indicative of a large smaller LMB group, and they will be targeting the smaller forage fish. I'd prefer to see the WR of the smaller LMB in the 120 or better range.

Once you see low WR on the LMB, it will take a few years to recover. What is the WR of the LMB in those size classes this year?

I agree with esshup. Try and stay proactive in bass removal. Once you see lower Wr values the bass predation is overactive and ahead of the forage population. Trying to 'play catch up' is difficult to get forage back to where it is balanced for growing larger bass and keeping the bass machine trending toward fat fast growing big bass.

You can have the electroshock boat take out a lot of skinny LMB as a tool.

Dave that would have been a TPWD study I think. I will try and locate it.

One thing to remember. When you start culling, you will be darn lucky to catch enough to meet your goals. But, you certainly have to try.

This thread has me a little confused. I keep going back to the original post. The current harvest plan seems to be working. The concern seems to be there is not an "over abundance" of stunted bass. So the question is (I think! ) is the reason he does not have an over abundance of little bass that his C & R plan is killing a lot of the bass he is catching?

C&R could be causing some mortality. I doubt C&R is causing significant mortality if the anglers are experienced and reasonably careful handling hooked bass. Other things could be happening to help maintain a balance or reduce numbers of smaller bass. If the system is productive and some big bass are present they may be cropping a measureable amount of smaller bass. The pond may be productive enough that food is still plentiful and the LMB have not overpopulated yet. Other factors may be causing reduced recruitment. Numerous possibilities to explain the current status of the fishery.

Based on the assumption that Greg has surveyed the lake and said remove 90lbs of LMB per year in the 12 -14 inch slot - - then that is good advice in order to prevent the described concern. I would remove them by electroshock culling the skinny ones in order to help reduce the potential catchability problem.