Pond Boss Forums MANAGING AN EXISTING POND Evaluating and adjusting fish populations Study- new stocker survival in existing pond

When thinking about how to increase the survival rate of newly stocked fingerling or advanced fingerlings when stocking them into an existing pond with adult predators I was asked by Greg Grimes to report on any studies I found. There are quite a few and I will check with Greg on that and figure out how to use the bits and pieces from them to post what we find.

I have posted several times on an existing expir. in which I am using blocking nets (feeding behind the net) to protect and grow out BG and RES .The idea was to protect them from large predators until they reached 6-7in. and spawned. That has worked well. I recently had some advanced fingerling (8in. feed trained) F-1 tiger LMB to add to the mix as part of the expir. The idea was to put part of them ( 33%) behind the net to let them adjust to the pond for 10 days+- before they had to face predation.

I have thought for some time that putting fingerling fish in an area with thick cover or other shelter was a way to increase their % survivability when stocking them into a pond with adult predators. Several hatchery biologists thought that would not help and even the nets would only help for a short time once removed. I think fish cages will work also.

In doing the above research I found a 2005 study that I would like to share because I think it will help any of us who need to or plan to stock into an existing pond with predators . I believe we can easily increase the % survival . I can not post the study but can post a few excerpts. Then we can have a discussion on it and its application to our ponds. I am not saying this study is correct in all its findings but I think the basic concept is sound and could benifit us ponders.

First the abstract.

Transactions of the American Fisheries Society 134:141–148, 2005 [Article] q Copyright by the American Fisheries Society 2005

A Laboratory Evaluation of Poststocking Predatory Losses for Cultured Largemouth Bass

J. WARREN SCHLECHTE,* ROBERT K. BETSILL, AND DAVID L. BUCKMEIER
Texas Parks and Wildlife, Heart of the Hills Fisheries Science Center, 5103 Junction Highway, Ingram, Texas 78025, USA

Abstract.—Stocking fish into preexisting fish communities is not always successful. Although
there may be many reasons why stockings fail, predation is perhaps the most likely reason. Reducing predation by allowing fish to become accustomed to their new environment before release (i.e.,habituation) may improve stocking efficiency. We evaluated the effect of habituation on predation of stocked, hatchery-reared fingerling Florida largemouth bass Micropterus salmoides floridanus (30–64 mm total length) in simple (i.e., open-water) and structurally complex (i.e., with vegetation
and cobble) habitats in indoor tanks.We found that fingerling largemouth bass survival significantly increased (P , 0.004) from 26% to 46% when fish were habituated in a predator-free enclosure for at least 15 min. Surviving fish spent most (95%) of their time in the structurally complex habitat. However, the survival of all fish stocked in structurally complex habitat did not differ from that of all fish stocked in open water (P 5 0.61). Although predation on nonhabituated, hatchery-reared largemouth bass approached 75%, we found that short-term habituation can enhance survival of stocked largemouth bass, as manifested by improved predator avoidance. This suggests that habituating fingerling largemouth bass before stocking may result in substantial increases in survival.

Some text.

Simpler strategies, such as habituating stocked
fish and stocking fish in suitable habitat, may be more cost-effective than rearing larger fish. Because hatchery rearing may exacerbate the problem of predation by decreasing innate behavioral skills used to avoid predators (Hossain et al. 2002; Davis et al. 2004), the concept of prerelease habituation of stocked fish has been investigated as a means of improving poststocking survival of several species, but its value for largemouth bass
has not been examined.

This is intuitively appealing and has theoretical support. Crowder and Cooper (1979, 1982) posited that predation success decreased as structural complexity of habitats
increased. Laboratory work by Savino and
Stein (1982) and Gotceitas and Colgan (1987)
showed that habitat complexity above 250 stems/
m2 decreased the efficiency of largemouth bass
predation on bluegills Lepomis macrochirus.

Observers noted that both green sunfish and
adult largemouth bass preyed on the stocked fingerlings,as anticipated. Predators were typically very aggressive and often actively attacked stocked fish. Fish stocked without habituation appeared disoriented upon release and were often eaten within minutes of release. Although predation was observed throughout the first hour of the experiment, most observers noted that the majority of the predation appeared to occur shortly after the
stocked fish were released.

Sublethal stress effects can result in decreased
predator avoidance, whether through biochemical
or behavioral responses (Olla et al. 1992; Kellison et al. 2000). Use of the predation bioassay (Kruzynski and Birtwell 1994; Berejikian 1995; Szendrey and Wahl 1995) allows one to quantify even subtle changes in a fish’s ability to adapt to a new environment. Sometimes specific mechanisms can be observed that might be linked to increased predation (Kellison et al. 2000). In this study, observers noted that hatchery-reared largemouth bass often remained where they were stocked for minutes, or until attacked. When attacked, nonhabituated fish appeared less deliberate in their movements
toward habitat.

The biggest question is whether
the improved survival comes from reduced stress
because the prey are given time to recover from
the stocking or whether learning is occurring. Given the observational data, it appears that the most likely explanation is that stocked fish are initially too stressed to actively avoid predation. Alternatively, it is possible that antipredatory conditioning (Brown and Smith 1998; Kellison et al. 2000) occurred during habituation. Cues may have been visual or chemical. Understanding how habituation
improves survival could both improve the technique and suggest when and where it would be
successful.

In general, it appears that complex
habitat can provide protection from predators, but when the predator is a conspecific, the risk can also be high, because that is where predators also prefer to reside. Future research should focus on whether fish must be stocked in complex habitat in natural conditions. We documented significant improvement in survival
with only a 15-min habituation. Fish that are
stressed and not allowed a period of habituation
are likely to suffer much higher mortality when
stocked in areas with high predator densities. Obviously, mitigating these losses by holding fish within a predator-free enclosure before release has the potential to improve stocking efficiency.

Holding stocked largemouth bass in predator-free enclosures for 15–60 min seems practical. Given the promising results in the laboratory, future research in more natural settings
should begin to address whether deploying a predator- exclusion cage and habituating stocked fish for upwards of 15 min would be a practical and inexpensive way to improve survival of stocked largemouth bass. Likely, this minor change in stocking largemouth bass will substantially increase short-term survival at minimal cost.

Fascinating study...and I have witnessed first hand what happens when HSB are introduced into environments with LMB present. It can be quite a massacre. One secondary point, which I would assume should be factored in, would be the time of day at which release occurs. Knowledge about the types of predators present and the preferred time of day in which predation occurs could be used, along with structural complexity and environmental habituation, to increase survival rate of stocked fish.

ewest,

Interesting topic--this could prove to be a real cost saving--when I add new fish--I drain about half of the water out of the transport container--fill with pond water and wait about 30 min before release--try to release in several spots with good cover--

Increasing the survival rate of fingerlings would be a real benefit to pond managers. Good job--looking to your future post

Thanks--Tentmaker

I have observed that upon stocking of sub adult and adult fish, they seem to "go exploring" the perimeter of their new environment. Most of the juveniles don't make it very long.

Livestock do the same thing.

I recently talked to a deer rancher who told me when he changes deer from one pen to the other, they are initially confused and explore the limits of the pen or the perimeter. However, placing a downed tree in the pen initially attracted them to the cover. These deer had never known free range but were pen raised to improve genetics for breeding purposes. The pen fences are lined with black plastic mats to keep them calm. I have always that all animals are attracted to structure or just something different. Even humans.

I believe that introducing stockers into a complex habitat of cover should let them get their bearings and decrease initial predation. However, sooner or later, like all children, they gotta come out and face the real world.

Could water temperature play a role in survival?

What about stocking in the coldest part of the season? Bass are lethargic and don't eat as much?

I am sure other factors play into this such as, transporting fish at that temp, and not all predators are lethargic at lower temps. But it would seem that it would at least help with predation of LMB on fingerlings.

I keep a small bass in an aquarium and when I add his baitfish to the tank, the bait fish don't even realize he is a threat, the first 20 minutes the fish are just darting around frantically and sticking together, a lot of times they hang out in front of the bass's mouth or in his line of fire.

It take about an hour to figure out the surroundings (10 gallon tank), and one chase from the bass to realize they are food and see him as a threat.

Thanks for the great article.

Good points all!! From what I have gathered so far there seem to be a number of factors like type and size of predator , time of day stocked ,amount and length of light left in day , water temp. ( predator metab./time of year), thickness of cover, size of stockers and their conditioning as to predators (have they seen them before)and others. Bruce I have seen the same slaughter wrt new stocks of small BG ,RES, tshad, trout and tilapia and it is not a pretty sight if you are paying for the new fish. ewest

ewest - very interesting subject.

I share common experiences of other respondents that have observed their stockers being decimated by predator fish, and therefore have pursued the objective of acquiring adult stockers, as opposed to holding pens and conditioning techniques.

Holding pens and conditioning techniques in small ponds are not practical for myself, and perhaps others as well.

It would be interesting to see a “quick and dirty” economic analysis of cost of “growing out” stockers vs. the holding pen/conditioning approach.
Bruce Condello and Todd Overton have discussed in the past, percentage predation loss vs. size of fish stocked.

I am well aware of increasing cost of high percentage fish food, but can only speculate on the amount of feed and intensive management and labor costs of growing out adult stocker fish on a commercial basis.

My first stocking of 3-5 HSB stockers in 2001 was an expensive learning experience.

I was advised by the fish re-seller that the HSB were an open water fish and too fast for LMB to catch them, and not to worry about predation….. :rolleyes:
I likely had less that 15% survival after observing a LMB feeding frenzy in the middle of the pond.

I suspect the cost per fish of the recent 8-10 HSB stockers were less than the cost of the 2001 stockers…

The only fish farms that are “growing out” adult stockers that I am aware of are Bruce Condello and Todd Overton. Perhaps they might chime in on the economics involved without divulging their trade secrets?

http://www.pondboss.com/ubb/ultimatebb.php?ubb=get_topic;f=5;t=000199

01-06-05 Bruce Condello:
"I’d estimate risk of predation from largemouth as follows:

5 inch wiper--80% over one year in presence of LMB
6 inch wiper--65% over one year in presence of LMB
7 inch wiper--45% over one year in presence of LMB
8 inch wiper--15% over one year in presence of LMB
9 inch wiper--negligible mortality.

No scientific data to back this up. Just knowledge about existing ponds in which I've seen fish such as this stocked in ponds around here."

01-06-05 Todd Overton wrote:
"Here are my thoughts. We raise HSB on our farm, and have a good idea of survival rates respective to LMB predation. Here's what size HSB would guarantee good survival rates with respective bass population:

3"-5" HSB with 4"-6" or smaller LMB population
5"-7" HSB with 12" or smaller LMB population
6"-8" HSB with 15" or smaller LMB population"

Pardon the long post – now back to Turkey Day….
Have a Happy Thanksgiving – we have much to be thankful for.

George Glazener

George :

Great post !! Thanks for the prior ref. post. Most of the studies in this area ( the ones found so far) are based on the question you raised and are raised by biologists looking to improve stocking vs $ on public lakes. As a result they are looking at what size of stocker and when and how to get the best result for the $ invested. They do use larger (sub adult)advanced stockers in some of the studies . Even with larger stockers ,depending on predator size, there is still the initial massacre just not quite as bad ( like your 3-5 in. HSB exp.). It is a numbers game and the point is if we can find a way to stop or reduce the initial (1st couple of days massacre) then we will be working from a much larger base for survival for year one. It looks like in some cases 40-75 % losses occured in the first day. For those wondering there are some studies on the topic on other types of fish with the same type of questions. ewest

Happy Thanksgiving to all we are very blessed indeed !!!

thanks Ewest. I appreciate that but also would like detials of enclosure, PB article? I have similiar story with 8 inch grass carp. I've seen them jump clear out of the water with a bass right behind.

Of course when we stock threadfin shad it is just crazy the frenzy that happens. As somone noted sagree twmp makes significant diff. It does seem shad predation is significantly less when we arrive by 9 am than in the afternoon. The am run is not as crazy and I tell clients this but some want to be there after work so "the client is always right" an then they wonder if enough shad made it through to start a spawn but usually they do establish to sptie this massacre.

Greg :

I am getting together a number of articles, not just the one mentioned, to email to you wrt your question on stocking sizes/survival and %. I will go ahead and send them but I have not finshed and there are a number of different points/info spread out through the articles. It would be good to pull the points together in an understandable manner. ewest

Greg :

Sorry I misunderstood your post. :rolleyes: You ask about the enclosure and I thought you were talking about the enclosed (discussed) study.

Part of the study was in the lab so the type of enclosure was not applicable to ponds. The rest of the study was lake observations where thick brush to thin brush to open water was observed.

I have placed thick brush in several coves and use a blocking net on one cove in our ponds.

I have thought about an easy portable way to make a safe area and enclosure to shelter fish as per the article. My idea is to buy 4 pieces of rigid plastic fencing/net 6 ft. long by 4 ft high. with 1/4in. holes (much like a std. seine net). It is fairly cheap about like seine net. Then attach to the bottom w/ epoxy and or plastic ties about 4 8in. tent stakes to each piece. ID the location to be used and in 3 ft of water add brush around an open area of 8 x 8. When ready to stock then stick the 4 panels into pond bottom in open area to form an enclosed square and use D rings to attach top of 4 panels to each other. All the enclosure has to do is keep out big fish for a short time (+- 1 hr.). After your selected time is up take off D rings pull up panels and add some brush to the open area and you are done. I think this could also be done with a 40 ft standard seine and 4 stakes. Use stakes to form corners of area and place seine around them and tie end poles of seine together. After selected time remove seine and add brush to open area. I am sure there are other ways as well. ewest

I've been thinking of placing a net across an open area, place brush and feeder; the net will not allow the fish out until rain causes the water to rise about a foot and they can escape to the pond around the sides of the fence.

BM :

Thoughts like yours are what started me toward the blocking net approach and it has worked well. The only thing I would warn you about is to get the predators out before you put in fish. Remember that the net/fence works both ways -- it can trap fish in with predators or keep the predators out depending on if the predators get inside the net. ewest

This a duplication of a post that I created under the heading Corrective Stocking. I include it here because is related to this topic.

Corrective stocking can involve stocking of fingerling fish into an existing fishery. A recent study at Texas Parks and Wildlife (J. of Fisheries Management 2006) looked at prerelease habituation as a way of improving the post stocking survival of fingerling LMB (1.2"-2.0"). Prerelease habituation is defined as allowing fish to become accustomed to their new environment before release.

The study found that in ponds, habituation for 60 minutes before release significantly reduced predation of the fingerling bass. The study found that if fingerlings were released directly into complex habitat, prerelease habituation did not greatly affect the amount of predation during the first 24 hours. Complex Habitat was defined as having or containing 250 stems per square meter.

The study was performed in 0.5 ac ponds and EACH TEST LASTED JUST 24 HRS. To test the effects of habituation, researchers constructed predator exclusion cages (2’diaX4’tall cylinders) using netting (1/8",3mm) with a floatation ring on top. The cage bottom was open with a lead line sewn around the lower edge to hold it onto the bottom so fish could not escape. The LMB fingerlings to be tested were MARKED and held in each cage for 60 min before release, whereas control, unmarked, fingerlings were directly released into the pond remotely away from structure. Structurally complex habitat consisted of a cluster of 6 ft tall Fraser fir trees and bamboo stalks encompassing 100 sq ft. Test fingerlings were released directly into the dense habitat. At the end of each 24 hr test, the pond was seined and then drained.

Survival of fingerlings after 24 hrs into an open pond ranged from 13% -25% whereas survival of fingerlings with habituation or complex habitat ranged from 17% -38%. Dense habitat provided some refugia for fingerlings in the first 24 hrs and reduced predator efficiency. Further research should focus on: 1. what habitat types and the density are best for reducing predation and 2. what would the survival rate of fingerlings after a longer study period, such as 1 to 6 months.

Predators were stocked into each study pond. On a per acre basis in each pond, predators consisted of 200 LMB 4"-7.8", 70 at 7.9"-11.8", 20 at 11.8"-15.7" plus 100 green sunfish 3.9"-7.9", plus 20 white bass 3.9"-11.8" plus 6 FW drum 6"-11.8" for a grand total of 416/acre. Four hrs before the LMB fingerlings were stocked common carp fry were stocked into each pond as food for fingerlings.

Here is the link.
http://www.pondboss.com/cgi-bin/ubbcgi/ultimatebb.cgi?ubb=get_topic&f=8&t=000124

Update - need to find the additional article and include it here.

Results : From the PB mag article.

Blocking Nets ;
A Hatchery Pond Inside a Pond

Step two called for more intermediate coppernose bluegill along with six to eight inch advanced genetics, feed-trained largemouth bass to be placed behind the net. Why, you ask, did you put the bass in there with the bluegill? A good question. In these lakes small bass are a prime food source for the larger bass. Being aware of this I researched and found two articles of note concerning the need to habituate small bass to avoid excessive initial predation. The articles are entitled A Laboratory Evaluation of Poststocking Predatory Losses for Cultured Largemouth Bass by J. WARREN SCHLECHTE, ROBERT K. BETSILL, AND DAVID L. BUCKMEIER from The American Fisheries Society Transactions of the American Fisheries Society 134:141–148, 2005 and Initial Predation of Stocked Fingerling Largemouth Bass in a Texas Reservoir and Implications for Improving Stocking Efficiency by DAVID L. BUCKMEIER, ROBERT K. BETSILL, AND J. WARREN SCHLECHTE from the American Fisheries Society North American Journal of Fisheries Management 25:652–659, 2005. These studies, one from the lab and one in the field, found that predation greatly affected post stocking survival of fingerling largemouth bass. They revealed estimated losses of stocked fish to predation in the initial period after stocking at high rate ranges from 27.5% to 75 %. Fingerling largemouth bass survival significantly increased when the fish were allowed to habituate in a predator free enclosure for a short period of time. The study showed this short-term protection enhanced survival because it resulted in improved new fish’s awareness of existing predators and sharpened their instinctive avoidance skills.