Influence of the habitat on the potential for cannibalism and population dynamics in stream-dwelling European grayling (Thymallus thymallus L.)
Cannibalism can have major influence on fish population dynamics. A prerequisite for cannibalism is that the cannibal and the potential victim meet, and besides density effects, the encounter rate between cannibals and their victims is therefore also largely dependent on habitat use and habitat hete...
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| Format: | H1 |
| Language: | Inglés Swedish |
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SLU/Dept. of Wildlife, Fish and Environmental Studies
2010
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| Subjects: |
| _version_ | 1855570298174177280 |
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| author | Lindström, Carl-Johan |
| author_browse | Lindström, Carl-Johan |
| author_facet | Lindström, Carl-Johan |
| author_sort | Lindström, Carl-Johan |
| collection | Epsilon Archive for Student Projects |
| description | Cannibalism can have major influence on fish population dynamics. A prerequisite for cannibalism is that the cannibal and the potential victim meet, and besides density effects, the encounter rate between cannibals and their victims is therefore also largely dependent on habitat use and habitat heterogeneity. In this study I quantified and compared the potential for cannibalism in stream-dwelling European grayling populations in three rivers in Jämtland by means of habitat classifications. I also analyzed population dynamic consequences of varying the potential for cannibalism in terms of intensity, using a physiological structured population model. Findings based on habitat characteristics were that the potential for cannibalism is in general not favourable in these types of streams. However, some sections had optimal conditions for cannibalism. The population dynamic model predicted that cannibalism can regulate the dynamic if sufficiently intense. It might also induce population cycles, and a fishing mortality will increase the destabilizing effect. It is the younger cohorts that drive the cycles by delayed density regulation. Cannibalism can be important to take into consideration in management actions. Hence, sections with favorable conditions for cannibalism also has a capacity for high fish production, and can thus be important as a source to less productive areas of a watercourse. Cannibalism can therefore indirectly decrease the fish density in more sections than in the few sections with favorable conditions for cannibalism. Moreover, if a population has fluctuating dynamics, some years the population will be dominated by young individuals, which not is desirable for watercourses used for sportfishing.
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| format | H1 |
| id | RepoSLU1375 |
| institution | Swedish University of Agricultural Sciences |
| language | Inglés swe |
| publishDate | 2010 |
| publishDateSort | 2010 |
| publisher | SLU/Dept. of Wildlife, Fish and Environmental Studies |
| publisherStr | SLU/Dept. of Wildlife, Fish and Environmental Studies |
| record_format | eprints |
| spelling | RepoSLU13752012-04-20T14:13:54Z Influence of the habitat on the potential for cannibalism and population dynamics in stream-dwelling European grayling (Thymallus thymallus L.) Habitatets betydelse beträffande potentialen för kannibalism och populationsdynamik hos strömlevande harr (Thymallus thymallus L.) Lindström, Carl-Johan cannibalism European grayling Thymallus thymallus habitat mapping Jämtland population dynamics recruitment size structured population model stream environment Cannibalism can have major influence on fish population dynamics. A prerequisite for cannibalism is that the cannibal and the potential victim meet, and besides density effects, the encounter rate between cannibals and their victims is therefore also largely dependent on habitat use and habitat heterogeneity. In this study I quantified and compared the potential for cannibalism in stream-dwelling European grayling populations in three rivers in Jämtland by means of habitat classifications. I also analyzed population dynamic consequences of varying the potential for cannibalism in terms of intensity, using a physiological structured population model. Findings based on habitat characteristics were that the potential for cannibalism is in general not favourable in these types of streams. However, some sections had optimal conditions for cannibalism. The population dynamic model predicted that cannibalism can regulate the dynamic if sufficiently intense. It might also induce population cycles, and a fishing mortality will increase the destabilizing effect. It is the younger cohorts that drive the cycles by delayed density regulation. Cannibalism can be important to take into consideration in management actions. Hence, sections with favorable conditions for cannibalism also has a capacity for high fish production, and can thus be important as a source to less productive areas of a watercourse. Cannibalism can therefore indirectly decrease the fish density in more sections than in the few sections with favorable conditions for cannibalism. Moreover, if a population has fluctuating dynamics, some years the population will be dominated by young individuals, which not is desirable for watercourses used for sportfishing. Kannibalism har stor potential att påverka fiskpopulationers dynamik. En förutsättning för att kannibalismen skall kunna ha någon större betydelse är att lekområden, yngeluppväxtområden och vuxenhabitat antingen överlappar eller finns i nära anslutning till varandra. Syftet med denna studie var att undersöka och jämföra tre vattendrags förutsättningar för kannibalism hos strömlevande harr i Jämtland, baserat på yngel- kontra vuxenhabitatens lokalisering samt kvalitet med hjälp av fältbaserade habitatklassificeringar. För att undersöka hur dessa förutsättningar kan tänkas påverka populationsdynamiken gjordes även analyser med hjälp av en fysiologiskt strukturerad populationsmodell. Resultatet från habitatundersökningarna visade att även om det finns sektioner som har optimala egenskaper för kannibalism, så är goda förutsättningar för kannibalism inte vanligt förekommande i denna typ av vattendrag. Den populationsdynamiska modellen visade att kannibalism kan reglera dynamiken även om graden av kannibalism är låg och kan framkalla mer eller mindre regelbundna populationsfluktuationer. Ett uttag via fiske ökar den effekten ännu mer och det är de unga kohorterna som skapar cyklerna genom fördröjd täthetsregleringen. Kannibalism kan vara viktigt ur förvaltningssynpunkt även om det inte är så vanligt förekommande. Sträckor med goda förutsättningar för kannibalism har vanligen även kapacitet för hög fiskproduktion och kan således vara viktiga som källa till mindre produktiva områden av vattendraget. Kannibalism kan följaktligen minska fisktätheten på fler lokaler än på de få sektioner som har gynnsamma förutsättningar för kannibalism. Dessutom, om fluktuationer förekommer så kommer populationen vissa år att domineras av unga individer, vilket inte är önskvärt om vattendraget utnyttjas för sportfiske. SLU/Dept. of Wildlife, Fish and Environmental Studies 2010 H1 eng swe https://stud.epsilon.slu.se/1375/ |
| spellingShingle | cannibalism European grayling Thymallus thymallus habitat mapping Jämtland population dynamics recruitment size structured population model stream environment Lindström, Carl-Johan Influence of the habitat on the potential for cannibalism and population dynamics in stream-dwelling European grayling (Thymallus thymallus L.) |
| title | Influence of the habitat on the potential for cannibalism and population dynamics in stream-dwelling European grayling (Thymallus thymallus L.) |
| title_full | Influence of the habitat on the potential for cannibalism and population dynamics in stream-dwelling European grayling (Thymallus thymallus L.) |
| title_fullStr | Influence of the habitat on the potential for cannibalism and population dynamics in stream-dwelling European grayling (Thymallus thymallus L.) |
| title_full_unstemmed | Influence of the habitat on the potential for cannibalism and population dynamics in stream-dwelling European grayling (Thymallus thymallus L.) |
| title_short | Influence of the habitat on the potential for cannibalism and population dynamics in stream-dwelling European grayling (Thymallus thymallus L.) |
| title_sort | influence of the habitat on the potential for cannibalism and population dynamics in stream-dwelling european grayling (thymallus thymallus l.) |
| topic | cannibalism European grayling Thymallus thymallus habitat mapping Jämtland population dynamics recruitment size structured population model stream environment |