Effect of population density on diel activity and growth in stream-dwelling Arctic charr Salvelinus alpinus

• Main Author: Fingerle, Amy, 1988-
• Other Authors: Háskólinn á Hólum
• Format: Thesis
• Language: English
• Published: 2014
• Subjects: Fiskifræði; Líffræði; Meistaraprófsritgerðir; Bleikja; Fiskirannsóknir; Arctic; Arctic charr; Salvelinus alpinus
• Online Access: http://hdl.handle.net/1946/20592

Intraspecific competition plays a significant role in shaping how animals use and share habitats in space and time. However, the way individuals may modify their diel activity in response to increased competition has received limited attention. I used juvenile (age 1+) Arctic charr Salvelinus alpinus as a model species to test the prediction that individuals at high population density will increase their activity rate and distribute their feeding activity over a greater portion of the 24 h cycle. Individually-tagged fish were stocked in semi-natural stream enclosures at low (2 fish/m2) and high (6 fish/m2) density. During each of two 2-week experimental rounds, I noted the identity of all active fish within each enclosure every three hours over seven 24 h cycles. In high density enclosures, fish were more active and distributed their activity over a greater portion of the 24 h cycle, resulting in increased activity specifically at crepuscular times of day. Fluctuations in water temperature, light intensity, and water depth affected the probability of activity at both high and low density, which suggests that an interplay of ecological factors shape diel activity patterns. Individual growth rates were unaffected by population density, with fish at high density maintaining growth despite increased competition. This study demonstrates that individuals exhibit a degree of behavioural flexibility in their response to changes in ecological conditions and that intraspecific competition can cause animals to modify temporal aspects of their activity to ensure access to resources and maintain growth. Samkeppni innan tegunda gegnir mikilvægu hlutverki í mótun þess hvernig dýr nota og deila búsvæðum í rúmi og tíma. En hvort og hvernig einstaklingar breyta dægursveiflum í virkni sinni til að bregðast við aukinni samkeppni hefur lítið verið rannsakað. Ég notaði bleikjuseiði Salvelinus alpinus til að prófa þá tilgátu að við háan stofnþéttleika myndu einstaklingar auka virkni sína og dreifa fæðunámi yfir stærri hluta ...