Foraging, swimming performance and morphology of semi-wild and hatchery-reared landlocked salmon juveniles

(Poster)

Raine Kortet
raine.kortet@uef.fi

University of Eastern Finland, Department of Environmental and Biological Sciences, Joensuu, Finland
,
Aurora Hatanpää
University of Eastern Finland, Department of Environmental and Biological Sciences, Joensuu, Finland
,
Hannu Huuskonen
University of Eastern Finland, Department of Environmental and Biological Sciences, Joensuu, Finland
,
Jukka Kekäläinen
University of Eastern Finland, Department of Environmental and Biological Sciences, Joensuu, Finland
,
Pekka Hyvärinen
Natural Resources Institute Finland (Luke), Aquatic population dynamics, Paltamo, Finland
,
Maria Vitelletti
University of Eastern Finland, Department of Environmental and Biological Sciences, Joensuu, Finland
,
Jorma Piironen
Natural Resources Institute Finland (Luke), Aquatic population dynamics, Joensuu, Finland

DOI: 10.17011/conference/eccb2018/108116

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The Saimaa landlocked salmon (Salmo salar m. sebago) in Finland is a critically endangered ecomorph due to the historical damming of rivers. The morph has been dependent on stockings of hatchery-reared juveniles for more than 40 years. Recently, various efforts have been taken to restore some of the earlier reproduction areas to return the natural life cycle. However, as the population has been reared in hatcheries over many generations and as the released fish generally suffer high post-release mortality, it is crucial to know whether domestication has affected the population’s fitness-related traits and to assess how the developmental environment affects salmon’s phenotype. In the present experiment, we studied the role of the early developmental environment in trait formation by comparing juveniles (0+ years) from three different backgrounds: 1) semi-wild fish from the River Ala-Koitajoki (stocked as alevins), 2) fish grown in standard hatchery rearing conditions and 3) fish grown in enriched hatchery rearing conditions. All the study fish originated from the same generation and had the same genetic background. We tested their capability of feeding on natural prey, critical swimming speed and studied their morphology. Our preliminary analyses indicate notable background-dependent variation in all the studied traits. Semi-wild fish consumed more natural prey items, had higher critical swimming speed and differed in their fin morphology, when compared to hatchery reared fish. The developmental environment seems to produce differences in key traits, but how this is linked to survival in the wild remains to be studied in the near future.

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INTRO:
In this study it is stated that information on the effects of domestication on fitness-related traits is important and that the effect of rearing environment on phenotype is assessed.
MERITS:
Experimental study with three different conditions with same origin and genetic background.
CRITIQUE:
As far as I can understand the first part of the quesiton is actually not addressed in the study i.e. how domestication is affecting fitness related traits. This may be due to the abstract not explaing the difference between the three environments or how the traits may or may not be related to fitness. So have the fish been semi-wild for a long period of time in the first treatment and thus are less domesticated as the other two types of treatments? The sample size of the experiment is not provided.
DISCUSSION:
It is hardly a surprising finding that environment has an imapct on genetically homogenous subpopulations of fish.

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INTRO:
The problem was expressed explicitly.
MERITS:
These type of studies are vital for stock assessment and to reduce post-release mortality.
CRITIQUE:
Aside from the traits studied, I think observed preferences should also be noted. Like food or microhabitat preferences (if there is any) since it may shed light on their key to survival in the wild.
DISCUSSION:
Identification of population fitness-related traits and assessing how the developmental environment affects their phenotypes is important because it opens answers to questions on evolution and survival. I do believe this study is worthwhile. However, I believe along the observation period, if there are observed preferences it should be noted since, it may indicate their adaptibility which hold also the key to their survival in the wild.

- - -
INTRO:
The Saimaa landlocked salmon is an endangered species and survives only with stocked individuals.

Semi-wild salmon differs in their prey selection, critical swimming speed and fin morphology to hatchery-reared salmon. Of this, the swimming speed is - to my knowledge - the most important finding.
MERITS:
I have litte knowledge of fish. I may not have understood how the fish was tested but I think the results seem obvious and also quite expectable given the literature: hatchery-reared fish usually has different fins compared to wild ones, they eat what they know (hatchery food) and might be much slower as they do not have to flee predators. I do believe that these differences are already known and therefore I dont see the novelty about the results.
CRITIQUE:
I am missing information about the set-up and the interpretation of the results. Also what the novelty about the results are.

DISCUSSION:
I believe that there is much to do for the Saimaa landlocked salmon and I am happy that these group addresses this. However, I believe that this work is just the beginning (or part) of a puzzle that will result in a nice conservation approach. I can imagine that there is more to this study than I can think of. However, the interpretation remains very open and leaves me a bit at a loss how the results help to conserve the salmon.