Looking for references for fish "dwarfing"

Mika · Post by **Mika** » 12 Mar 2006, 15:01

Common belief is that fish are able to dwarf its size to limits of surrounding.This is true to some extent. In Finland, it is well-known that Perca fluviatilis can be found from very small swamp ponds also. There is very limited recources of food and density of population is high. They are stunned and even at old age very small at size.These fishes and phenomenon is called " thousand brothers" by fishermen.

Are any scientific paper and references where fish dwarfing has been studied? IÂ´m hoping to write an article about theme and need good scientific back-up.

drpleco · Post by **drpleco** » 12 Mar 2006, 15:51

In the US, studies have shown that trout vary their ultimate size based upon food supply and water temp. Lake trout in some northern lakes can develop two different sizes; large fish that eat fish, and small fish that eat planton. These fish, reportedly, are all born the same. This phenomenon also happens to rainbow trout. Brook trout in the US commonly get "stunted" in small streams that lack predation. The fish are able to breed easily and overpopulate the stream. When this happens, few or none of them get large. I don't know if this is because of a lack or food, or the fish "making" themselves smaller. I suspect the former.

I don't have any refs. for you, but hopefully this will give you some ideas to pursue. Good luck!

Andy

Post by **Silurus** » 12 Mar 2006, 16:01

Would this help?

Trudel, M, A Tremblay, R Schetagne & JB Rasmussen, 2001. Why are dwarf fish so small? An energetic analysis of dwarfism in lake whitefish (Coregonus clupeaformis). Canadian Journal of Fisheries and Aquatic Sciences 58: 394â??405.

Sympatric populations of dwarf lake whitefish (Coregonus clupeaformis) (DLW) and normal lake whitefish (NLW) commonly occur in north temperate and subarctic lakes. DLW have a much lower growth, mature earlier, and have a shorter life span than NLW. Furthermore, they are usually not found when cisco (Coregonus artedi) are present, possibly due to competitive exclusion. In this study, we compared the energy budget of DLW, NLW, and cisco using food consumption rates estimated with mass balance models of chemical tracers (i.e., mercury and radiocesium). These chemicals are globally distributed and can be readily detected in fish and their prey. Our analysis showed that the energy budget of DLW and cisco was similar. DLW and cisco consumed on average 40â??50% more food than NLW. The conversion efficiency of DLW and cisco was two to three times lower than that of NLW. These results suggest that DLW and cisco allocated a larger fraction of their energy budget to metabolism than NLW. Our analysis also suggests that the earlier maturation and shorter life span of DLW and cisco may be due to their higher metabolic rates.

Post by **Birger** » 12 Mar 2006, 17:44

These brook trout(Salvelinus fontinalis)are introduced but it is interesting how quickly they have adapted.

I also know of a lake in Jasper National Park(where I grew up) that has full grown lake trout(Salvelinus namaycush) introduced years ago to an alpine lake that are 20 cm long and sustaining their population,these fish usually can get huge, the abscence of something in the food chain is to blame.

If you want a news article on these I can copy it for you when I find it.

On the other end of the scale I could take you to a lake in Jasper that has monster rainbow trout due to a overabundant food source.

Years ago they would play god in the parks,now they are learning to leave well enough alone.

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This is the outlet creek where the little brookies spawn(can be observed),the stream is one to two metres wide,and very shallow.

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A few more shots of the small shallow lake,look for the fish in the lowest picture.

Not really good documentation but hope you find this interesting
Birger

Mike_Noren · Post by **Mike_Noren** » 12 Mar 2006, 17:53

Silurus wrote: Sympatric populations of dwarf lake whitefish (Coregonus clupeaformis) (DLW) and normal lake whitefish (NLW) commonly occur in north temperate and subarctic lakes.

I suppose everyone already knows this, but several of the presently recognized species of whitefish are possibly species complexes. In other words, the dwarf form may well on closer scrutiny turn out to be a different species.

EDIT: And indeed, this is also the case with arctic charr. Not, though, perch (to the best of my knowledge).

Post by **Silurus** » 12 Mar 2006, 22:11

Some more references...

Jobling, M & T-G Reinsnes, 1986. Physiological and social constraints on growth of Arctic charr, Salvelinus alpinus L.: an investigation of factors leading to stunting. Journal of Fish Biology 28: 379-384.

When stunted (runt) Arctic charr, Salvelinus alpinus, were reared together in small groups growth rates were low. Contrary to expectation, there did not arise a rapidly growing despot within each group. It is suggested that the narrow size range offish within groups prevented the rapid formation of clear-cut dominance hierarchies. Fish reared in isolation had significantly higher and more variable rates of growth than those held in groups, demonstrating that social interactions between individuals were responsible for growth suppression of grouped-reared fish. There were no significant differences in growth rates between fish allowed visual contact with conspecifics and those held in visual isolation, indicating that visual contact is insufficient to cause growth depensation in Arctic charr. Despite the fact that growth rates of stunted (runt) Arctic charr improved when they were held in isolation, the growth rates recorded were substantially lower than those of normal individuals reared under hatchery conditions. It is concluded that physiological (genetic) factors are important in the determination of the slow growth rates of stunted (runt) Arctic charr and that this trend is exacerbated by social interactions with more rapidly growing siblings.

Ylikarjula, J, M Heino & U Dieckmann, 2000. Ecology and adaptation of stunted growth in fish. Evolutionary Ecology 13: 433â??453.

Dwarf individuals are observed in many species of freshwater fish. This paper studies the potential causes of such stunted growth. We present a model which describes the effect of growth conditions on the age- and size-structure of fish populations. The model parameters are chosen to characterize a Eurasian perch population. Two possible causes of stunting are identified: resource limitation and size- or age-dependent survival probabilities. While the former mechanism often arises from intraspecific density dependence, the latter is of particular relevance in the context of interspecific interactions and fishing. After evaluating the immediate ecological consequences of these factors, we examine the potential for life-history adaptations in stunted fish populations. Interactions between the ecological and adaptive mechanisms of stunting are shown to be intricate: not only does the age at maturity of individuals affect their growth trajectories, but, in addition, alterations in growth conditions can result in different adaptively stable ages at maturity. We show that such adaptive responses can either alleviate or amplify stunting caused by ecological factors. Life-history adaptation may also lead to the persistence of stunting when ecological factors alone would allow for normal growth. An appreciation of the interplay between ecological and adaptive factors therefore is critical for understanding the causes and mechanisms of stunted growth.

Mika · Post by **Mika** » 14 Mar 2006, 07:14

Thanks to everybody for input.

Ylikarjula, J, M Heino & U Dieckmann, 2000. Ecology and adaptation of stunted growth in fish. Evolutionary Ecology 13: 433â??453.

Funny, that two of these scientist are from Finland too!
I found pdf of that paper
http://www.iiasa.ac.at/~dieckman/reprin ... al1999.pdf