Pond Boss Forums MANAGING AN EXISTING POND Evaluating and adjusting fish populations Size Differences in Susceptibility to Extremes

This is a tough time of the year up North for RES. In the last month, the ice has melted on my pond 3 times and each time I have found a big, dead RES. All three were 8"-9" long and appeared stout and (other than being deceased) in good physical condition.

Bruce Condello informs me that last year in March, he lost a number of RES as well.

I know that different sizes of fish are more susceptible to environmental extremes. Large fish usually suffer first from low O2 levels and, IIRC, big cool water fish usually succumb to overly warm water first as well.

My question is whether or not large RES would be more prone to stress from cold water than smaller RES. The limited evidence I have gathered would tned to support this hypothesis. OTOH, small dead and dying RES in my pond could possibly be eaten by LMB and/or CC before I get a chance to see them, while the predators would have more trouble swallowing 8"-9" RES.

Your knowledge or thoughts?

I will see what I can find but keep in mind there is very little RES research.

They could have been dead and under the ice for a while. I doubt it is the freeze thaw - freeze thaw but rather just to cold for to long. That is not a loss of fat supplies but just to cold.

Theo, one of our local public lakes just south Lincoln had 25 RES wash up on the dam this week, last week the ice on that lake was "blown off" very quickly by high winds. My guess is that the wind mixed the water and super cooled the water column, this is what I think did the RES in.

I expect they were dead for some time before the thaws. The last two freeze-thaws (can't remember about the first) were preceded by bad supercooling events, 1-2 days of temps below 32 deg and high winds that mixed and cooled the pond but did not let it freeze quickly

Some info - no conclusions please.

]•FFECT OF WINTER KILL ON THE PONDS

Death of fish when oxygen is depleted and concentrations of carbon

dioxide build up beneath snow-covered ice is a common phenomenon

in the North Central States (Greenbank, 1945; Bennett, 1948b; Cooper

and Washburn, 1949). For the Marion County farm ponds information

on .occurrence of winterkill has been gathered from two sources: from

farmers and others who observed numbers of dead fish in ponds following

the breakup of ice, and from pond histories that indicate a sudden mass

disappearance of bass, of .bluegills, or of both. While in many cases there

is no evidence as to the time of year when such fish disappeared, heavy

mortality during the summer was observed by *he pond owners only once

(Pond 16) while winterkill was observed frequently. The chances of mass

mortality of fis•h being unobserved are probably greater in the win,ter than

the summer.

It appears that fish populations in 31 of the ponds suffered winterkill

(Table 6). In 15 ponds bass were eliminated but some bluegills survived;

in two ponds the reverse was true, with bluegills winterkilled while some

bass survived. The differential in mortality between these two species may

represent a difference in tolerance to low oxygen levels (though Cooper

and Washrburn, 1949, found none), but more likely it may represent

a difference in location within the pond during wintertime and ability

of some individuals to ioca•te and utilize pockets of water containing suf-

ficient oxygen for survival.

Complete kills of both bass and bluegills occurred in 18 ponds. Thirteen

of the 18 ponds also contained bullheads, and these always survived in

some numbers.

Some ponds winterkill repeatedly, as is shown by the frequency of some

pond numbers in Table 6.

T^BLE &--Known or suspected winterkills of fish in Iowa farm fish ponds

Species eliminated by kill Pond numbers

Bass, but not bluegills ..........................

3, 19, 19, 20, 24, 24, 29, 30, 32,

32, 35, 37, 40, 47, 48, 49, 49, 49,

50, 59

Bluegills, but not bass ..........................

3, 27

Bass and bluegills ...............................

9, 10, 11, 15, 16, 16, 16, 16, 20,

23, 27, 31, 35, 36, 39, 40, 41, 47,

49, 55, 56

Some bass and some bluegills ...................

94, 15, 25, 37, 45

Winterkill is believed to be a major factor in the lack of population

balance and success of Iowa ponds. The population remaining after an

incomplete kill is often very different than that presen.t before, and the

change is usually unfavorable for .angling (Bennett, 1948a). Of the ponds

which winterkilled, one-half had Ibeen listed as muddy with colloidal clay,

and one-third were known to have had low water levels going into the

winter season.



Data sources used for analysis of geographic variations in acute temperature preferences of fishes.

Redear sunfish, Lepomis microlophm'

Hill et al. (1975) Oklahoma 16.0-26.0

Still others, particularly the centrarchids, showed

occasional low thermal responsiveness. Fishes

continued to seek increased temperatures until

they succumbed due to physiological inability

to adjust to a rapid increase in temperature in

a steep gradient.


When raising hybrid striped bass in cages, several producers have reported sudden losses of hybrids when the water temperature rapidly decreased by several degrees in a relatively short period of time (Valenti 1989; A. M. Kelly and C. C. Kohler, personal observation). The rapid onset of cold temperatures has been reported as the cause of death in several species of fish (Verril 1901; Storey 1937; Galloway 1941; Gunther 1941; Ash et al. 1974; Coutant 1977; Mitchell 1990). It is believed that the lipid composition in the fish muscle plays a vital role in the ability of fish to adapt from one temperature to another (Hazel 1984; Greene and Selivonchick 1987; Henderson and Tocher 1987). Phospholipids are the class of lipids in which the most obvious changes occur. As environmental temperatures decrease, the invariable response is an increase in fatty acid unsaturation (Johnston and Roots 1964; Caldwell and Vernberg 1970; Hazel 1979; Cossins and Prosser 1982). Conversely, as ambient temperatures increase, phospholipid saturation must also increase to avoid excess fluidity. The dynamics of lipid composition of cells occurs in order to maintain a constant fluid matrix for enzymes associated with membranes (Greene and Selivonchick 1990). Different species of fish differ in their patterns of fat deposition and mobilization, which in turn affects the temperature range in which the species can grow and survive. For example, the Nile tilapia Oreochromis niloticus does not store excess lipids in the musculature but rather relies on visceral deposits that it is incapable of mobilizing at low temperatures, which results in high mortalities between 8°C and 6.5°C (Satoh et al. 1984). Viola et al. (1988) demonstrated that the common carp Cyprinus carpio, which is capable of mobilizing lipids from muscular and visceral deposits, is able to survive to 4.5°C under the same conditions.

The amount of unsaturated fatty acids in the muscle is believed to affect a fish's ability to tolerate lower temperatures (Hoar and Dorchester 1949; Hoar and Cottle 1952a, 1952b). In general, the tissue temperature of fish is within 1°C of the ambient water temperature (Carey et al. 1971; Reynolds et al. 1976). Physiologically, fish are affected by variations in water temperature in two ways (Hochachka and Somero 1984). First, temperature determines the rate of chemical reactions, and secondly, temperature dictates the point of equilibrium between the formation and disruption of the macromolecular structures in biological membranes. Structural flexibility, therefore, is a requirement for integrity of biological membranes (Hazel 1993). Cold temperatures constrain this flexibility and, as a result, stabilize less active conformations. The rate of increase in the ability of fish to tolerate higher temperatures usually requires less than 24 h at temperatures above 20°C, whereas the gain in resistance to lower temperatures is a much slower process, requiring up to 20 d in some species (Doudoroff 1942; Brett 1944). The rate of resistance to lower temperatures is governed in part by the rate of metabolism, which is depressed at lower environmental temperatures. The simulated cold front in this study resulted in higher mortalities
Diets influence the fatty acid composition in several species of fish (Henderson and Tocher 1987; Lovell 1989; Seo et al. 1994), and the ability of a fish to alter its lipid composition when placed in colder water is one factor that determines survival. For example, summer harvest syndrome is an anomaly seen in goldfish Carassius auratus when they are harvested in the summer and placed in tanks containing water that is colder than the pond water (Mitchell 1990). The death of these fish is thought to be a result of the fat that the goldfish consume or produce (Mitchell 1990). Goldfish with high concentrations of saturated body fat are less tolerant of temperature change than fish with high concentrations of unsaturated body fat. Similarly, rainbow trout Oncorhynhcus mykiss that have been fed diets high in saturated fats stiffen and die when placed in cold water (Mitchell 1990). In these fish, the fat apparently hardens in the colder water, causing the fat-impregnated muscles to stiffen and the fish to become exhausted and lose movement.

Although it has been hypothesized that temperature is closely linked to membrane composition, relatively few studies have been conducted to determine if a correlation exists between lipid composition and cold tolerance. This study was designed to determine the effect of a sudden temperature change (a simulated cold front) on striped bass, white bass, and their hybrids fed either a natural or prepared diet, as well as to determine their lower incipient lethal temperature. The association of fatty acid composition and unsaturated: saturated fatty acid ratios in these fish were examined with respect to their tolerance to cold.

We demonstrated that diet-induced muscle fatty acid composition directly affects cold tolerance of striped bass, white bass, and their hybrids. Fish fed fathead minnows had fatty acid ratios 10–25% higher than fish fed a prepared diet. When subjected to a simulated cold front, all groups of fish fed the prepared diet suffered high mortality (50–90%) whereas the groups fed the natural diet experienced zero mortalities. The LILT was also higher for fish fed the prepared diet.



Fish deaths due to cold temperatures have frequently been reported. It is generally believed that deaths arise from the rapidity of dropping temperatures whereby the fish are unable to acclimate to the lower temperature despite being within their biokinetic range. It is consequently critical especially in autumn to feed fish of the genus Morone, and possibly other genera, a diet that is relatively low in saturated fats when they are confined to surface waters in cages or pens.

Clearly diet affects ability to survive rapid temperature drops. I have no idea how diet might vary, large vs. small RES, in the pond.

The ice is coming off at our pond, so far I have seen 3 dozen 2-3" BG floaters. One of those that I picked up last night looked like it had been dead less that an hour. Some of the other ones looked like they had been dead much longer. The good news is that there are large numbers of 1-2" BG along the north shore sitting in shallow warmer water, it was fun watching them swim around. I even saw one bullfrog last night too. I suspect that if we had a sifngifcant winter kill, bodies will start popping up in the next 2-3 days.

FWIW, I've had an indoor tank that I'm holding RES in. I didn't have time to feed train this group so they've been kept in 45 degree water. There are a couple of dozen fish that are 7.5 inches and greater that have had ZERO mortality. The little ones however, that range from 2-4 inches I've lost about 30 of the 300 or so that are in there. I couldn't tell if this was because of size susceptibility differential, or if it was simply because the littlest ones have the least calorie reserve from which to draw.

I feel like I recall being told by our local biologists that the smaller redears have the highest cold water mortality. I don't have any data or studies to back this up though.

I know nothing about ice i live in Myrtle Beach, South Carolina.But couldnt you pump the some O2 by cutting a hole in the ice??JUst woundering.

MbBass, I don't think we're so much concerned with O2 levels. We're trying to determine how redear sunfish tolerate cold water, since they are somewhat of a "southern" species.

As far as my intent, that's correct Bruce.

O2 would not have been a problem.

The points above.

Low DO is one of the main causes of cold water fish kills.

Centrarchids (RES are a member) are more likely to have cold water problems than many other species. Their avoidance methods are poor.

The material on cold temps in the bottom half of the post is to show how fish die from cold water.
The rapid onset of cold temperatures has been reported as the cause of death in several species of fish.It is believed that the lipid composition in the fish muscle plays a vital role in the ability of fish to adapt from one temperature to another . Due to cellular dis-function from low lipids the fish lock up stiffen and heart and respiration stop.

IIRC small fish die in winter by starvation in yoy/small fish (not enough lipids stored)while large fish die from thermal lock-up of cellular activity due to low lipids . The other alternative is death from low DO.

I am not through checking. If I have to guess now I think the large RES died from thermal cell lock-up from cold followed by rapid change in temps and poor ability to avoid the problem . One does not exclude the other. The small RES may have starved and the large RES locked up , one or the other or nither.

More

The dynamics of lipid composition of cells occurs

in order to maintain a constant fluid matrix for

enzymes associated with membranes (Greene and

Selivonchick 1990). Different species of fish differ

in their patterns of fat deposition and mobilization,

which in turn affects the temperature range in

which the species can grow and survive.



the ability of a

fish to alter its lipid composition when placed in

colder water is one factor that determines survival.

In these fish, the fat

apparently hardens in the colder water, causing the

fat-impregnated muscles to stiffen and the fish to

become exhausted and lose movement.



Physiologically, fish are affected

by variations in water temperature in two

ways (Hochachka and Somero 1984). First, temperature

determines the rate of chemical reactions,

and secondly, temperature dictates the point of

equilibrium between the formation and disruption

of the macromolecular structures in biological

membranes. Structural flexibility, therefore, is a

requirement for integrity of biological membranes

(Hazel 1993). Cold temperatures constrain this

flexibility and, as a result, stabilize less active conformations.

The rate of resistance to lower temperatures is governed

in part by the rate of metabolism, which is

depressed at lower environmental temperatures.

I just read Dr. Dave's current PBMag article on Winter Aeration and am anxious to see the conclusion in an upcoming issue. It could be very pertinent to this.

Theo -- yesterday, I gave copies of the article to the grad students pictured. I told them they were now OBLIGATED to get research results into Pond Boss before any other outlet.

Theo and all, In addition to what ewest has provided regarding lipids in muscles and those fishes reaction to cold temps, I think there is the issue of inherent genetic tolerance to cold or heat that is specific to each species, subspecies, race or cline. Cold tolerances of individuals could be tied physiologically to the lipid issue. A good fish physiology textbook may help with this topic.

Many of us are aware of the relative intolerance of Florida bass to extended cold temperatures of northern ice covered waters. To take this concept even further, we are all familiar with what happens to tilapia and threadfin shad when water gets too cold for them. Tropical fish probably have the same or similar physiological reaction to the cold. What ever this mechanism is, I am pretty sure it has a lot to do with the winter mortality of a few of your larger RES.


Theo, as you mentioned, RES were originally a primarily southern species that probably posess some or a moderate cold tolerance. As with most genetically determined physiological (and usually physical) features there is almost always some variation of the genetic trait among individuals within a population that includes a specie through cline. Selective breeding (natural or artificial) can select for cold tolerance which I am pretty sure is what has happened in the RES that are now established permanent residents of southern Michigan.

Theo what I think you are seeing is the process of natural selective breeding for cold tolerance of your RES. I am pretty confident that the original stock of RES in your pond came from AK or further south. These fish as a group are probably only moderately cold tolerant. Within this group is a temperature gradation range in the shape of a bell curve for the genetic trait of cold tolerance i.e. a few that are intolerant, most that are moderately tolerant and a few that will tolerate the coldest allowable by the genetic make up for that species or race. I think the mortalities that you are seeing are those most intolerant and maybe a few close to that end of the spectrum.

I think if you would have gotten your RES from an established breeder using long term brood stock and further north say mid-Ohio or southern MI you would not be experiencing as many mortalities because a lot of the intolerence to the cold would have been over time been bred out of the population .

Postscript to Dr. Dave and his "crew". When summarizing the winter aeration data be sure to check out
Lackey and Holmes 1972. Evaluation of two methods of aeration to prevent winterkill. Prog. Fish. Cult. 34(3):175-178.

Miller, Mackay and Walty 2001. Under ice water movement induced by mechanical surface aeration and air injection. Lake & Reservoir Managmt 17(4) 263-287.

Miller, and Mackay 2003. Optimizing artificial aeration for lake winterkill prevention. Lake & Reservoir Mgmt 19(4):355-363

That is an encouraging thought, Bill - that natural selection should make RES Winter losses lessen over time. I hope.

Good job Bill . I was attempting to explain the how and what and you did the why. Theo I think I would keep my eyes and ears open for a source of a few RES from as cold a clime as I could find to help that natural selection along. Tub life from a young age may also be limiting the cold selection process a little.

Thanks, Bill. Did not have the 1972 publication. Have talked with Miller on the phone a couple of times about this.

That shouldn't be a factor with this Winter's dead RES, but it certainly could be with the new pond in the future. The first 20 RES that are going into it have spent the last 2 Winters indoors (with, for some reason, 0% mortality).

I am planning on moving most of the adult "battle hardened veterans" I catch in the old pond into the new one this year. Still, any RES spawn that occurs in the new pond this year will be predominantly/only from the basement-dwelling warm water wimps. So they should be the biggest gene-pool influence on the new pond's RES. It will be interesting to see if any significant (i.e. big enough to rule out pond versus pond differences being the cause - that could be difficult) differences in RES mortality between the 2 ponds occurs in the future.

Sometimes I am sorry that limits exist, but if the envelope wasn't there, we couldn't push it.

Well, I lost 2 more big RES today, and 8 incher and the biggest Redear I have ever seen, 10 3/4" and 15 oz.
This was after yet another supercooling weather event - 15" of snow melting with some added cold rain over 3 days.

That makes me really sad to hear. If you're like me there was a little pain in the pit of your stomach when you saw that bigger one.

Come on spring!

*+^*%$) *#$&U#@)_ !!! - -

Yes, this "Thermal-Shock Sampling" leaves a little something to be desired.

Bright Side: Bruce, if they don't all die, I ought to have those 12" Redears ready for you to catch in about a year.

Just bumping this thread because I lost two large 11"+ RES recently at ice out, this was shortly after a rapid snow melt that brought the pond up 8" in two days, probably a rapid temperature change cooling the water. The two RES that I lost were very likely pellet trained and eating a diet of Aquamax. Was this a muscle fat issue related to diet and rapid cooling?



As a side note it appears that I had very good winter survival of late hatch YOY RES in the 1" to 1-1/4" size.

I've always felt larger fish are more sensitive to rapid temp changes and to anoxic conditions in winter, and there's a lot of literature that backs that up. (Not saying you had anoxic conditions.)

For me the main reason for your redear loss was you are at the northern edge of your range and ponds tend to cool faster than larger deeper bodies of water.

A few years back a fish farmer in Ohio lost a lot of smaller perch when he got an early spring snowfall of 21 inches. He's convinced it was due to the rapid chilling of the water. And yellow perch are quite hardy!

Have any of the anglers here noticed that larger trophy size fish tend to hang much deeper in the water column in lakes and reservoirs than there smaller counterparts? I'm convinced that is due to more stable water temps among other things.