Filial cannibalism by largemouth bass (Micropterus salmoides): a three-decade natural history record from a small northern temperate lake

Abstract

We observed cannibalism by juvenile and adult largemouth bass (Micropterus salmoides) on their young-of-year (YOY) over nearly three decades (1984–2012) in a small temperate lake located in the Upper Peninsula of Michigan, USA. Largemouth bass are consistently the only fish species in the lake, necessitating the importance of studying filial cannibalism as a valuable energy source although it has potential consequences on recruitment and overall population structure. Annual whole-lake population estimates of juvenile and adult bass ranged 91–460 individuals, and these oscillations had significant differences between periods of higher and lower densities. Captured bass >150 mm in total length were individually tagged and had their stomach contents analyzed before being released. Despite significant differences in population estimates, we found no relationship with cannibalism. Additionally, we found no apparent patterns relating cannibalism to day of year, water temperature, or recruitment rates. We also found no differences in cannibalism or the size of consumed YOY between juvenile and adult bass. However, we found that recaptured individuals who consumed YOY bass on two or more occasions had significantly longer total length than individuals who consumed YOY bass one time or not at all, which provides additional evidence of dietary specialization as previously found in this population. Notwithstanding these patterns in cannibalism and the potential energetic benefits that it provides, we could not discern the effects of it on either individual growth rates or consequential changes in recruitment and overall population size. Regardless of the ever-present pressure of filial cannibalism, the population sustained recruitment across the whole study period.