Life history trade-offs in Anadromous Burbot Lota lota (Linnaeus 1758) from Rickleån and Sävarån, Northern Sweden

• Main Author: Sandberg, Mikael
• Format: Text
• Language: Swedish; English
• Published: 2015
• Subjects: Fisheries and aquaculture - General aspects; Aquatic ecology; Life sciences; Burbot; Lota lota; Northern Sweden; lota
• Online Access: https://stud.epsilon.slu.se/8638/7/sandberg_m_160208.pdf

Anadromous burbots Lota lota (Linnaeus 1758) from two similar rivers in the Gulf of Bothnia area, Sävarån and Rickleån, Northern Sweden, were compared. The aim was to test for and explain differences in ecology. Spawning burbots in Sävarån were smaller, younger, grew slower and were more densely populated. The positive correlations between individual size, and gonad- and liver indexes which were found in Rickleån, were weaker or absent in Sävarån. The positive correlations of rapid growth in regard of liver tissue growth and K, were weaker in Sävarån than in Rickleån. K in Sävarån were not correlated with individual size, and were also lower in general, than in Rickleån. The majority of spawning burbots had empty stomachs, 73 % in Sävarån, and 58 % in Rickleån. “Rest year” strategies, which were correlated to both organ (except gonads) indexes, and K, where common in Rickleån, but almost absent in Sävarån. Almost all burbots, even those smallest, found in the stomachs of bigger individuals, where fully mature with high gonad index. The size group histogram and normal probability analyses, indicated that there were large numbers of even smaller individuals present at the spawning sites in Sävarån, not possible to sample with the gear used. As a whole, burbots in Sävarån exhibited precocity, favouring early spawning on the expense of growth and/or higher fecundity in future spawnings. I also found that many of the differences confirmed between the populations, were also present within both populations, between males and females. Males exhibited a more precocious reproduction, while females exhibited a more delayed reproduction. [1] The differences between the populations in age at spawning, individual size, growth, allocations to different organs and foraging, were presumably due to both a) trade-offs favoured by selection due to differences in mortality related to human harvest, and b) density-dependent effects [2]. [2] The population densities differed, assumably due to two abiotic factors, a) higher summer ...