Overcompensatory response of a smallmouth bass (Micropterus dolomieu) population to harvest: release from competition?

An intensive seven-year removal of adult, juvenile, and young-of-the-year smallmouth bass (Micropterus dolomieu) from a north temperate lake (Little Moose Lake, New York, USA) resulted in an increase in overall population abundance, primarily due to increased abundance of immature individuals. We developed a density-dependent, stage-structured model to examine conditions under which population control through harvest could result in the increase of a targeted species. Parameter values were derived from a 54-year data set collected from another north temperate lake (Lake Opeongo, Ontario, Canada) smallmouth bass population. Sensitivity analyses identified the demographic conditions that could lead to increased abundance in response to harvest. An increase in population abundance with harvest was most likely to occur when either (i) per capita recruitment at low levels of spawner abundance was large, juvenile survivorship was high, and maturation of age-4 and older juveniles was moderately high or (ii) per capita recruitment at low levels of spawner abundance was slightly lower, yet the maturation rate of age-3 juveniles and adult survivorship were high. Our modeling results together with empirical evidence further demonstrate the importance of overcompensation as a substantial factor to consider in efforts to regulate population abundance through harvest. Des captures intensives pendant sept ans des adultes, des juveniles et des jeunes de l'annee d'achigans a petite bouche (Micropterus dolomieu) dans un lac de la region temperee nord (lac Little Moose, New York, E .-U.) ont eu pour effet un accroissement dans l'abondance globale de la population, principalement a cause d'une augmentation de l'abondance des individus immatures. Nous avons elabore un modele dependant de la densite et structure en fonction des stades afin d'evaluer les conditions sous lesquelles un controle de la population par la recolte peut entrainer une augmentation de l'espece ciblee. Les valeurs des parametres ont ete tirees d'une banque de donnees couvrant 54 annees et provenant d'une population d'achigans a petite bouche d'un autre lac de la region temperee nord (lac Opeongo, Ontario, Canada). Des analyses de sensibilite ont permis d'identifier les conditions demographiques qui pourraient mener a une abundance accrue en reaction a la recolte. Une augmentation de l'abondance de la population en reaction a la recolte va plus vraisemblablement se produire quand ou bien (i) le recrutement par individu aux faibles densites de reproducteurs est important, la survie des juveniles est elevee et la maturation des juveniles d'age 4 ou plus est moderement elevee ou alors (ii) le recrutement par individu aux faibles densites de reproducteurs est un peu plus faible, mais malgre tout le taux de maturation des juveniles d'age 3 et la survie des adultes sont eleves. Les resultats de notre modelisation combines a des donnees empiriques demontrent de plus l'importance de la surcompensation comme facteur important a considerer lorsqu'on tente de controler l'abondance d'une population par des recoltes. [Traduit par la Redaction]
Introduction Optimizing resource use and maximizing productivity are common management objectives of harvest, but reducing abundance levels of undesirable species is another objective less frequently considered. Although harvest can be [...]