Abstract
AbstractIn fish populations with multiple age-classes of similar size and close proximity, interactions between age-classes may be an important source of density-dependent population structuring if there is a disparity in competitive ability, creating a competitive bottleneck. However, intercohort competitive interactions within a single year-class have rarely been investigated and may have implications for recruitment success. Bluefish Pomatomus saltatrix produce at least two cohorts (spring- and summer-spawned) of offspring each year, and juveniles of this species are abundant in the lower Hudson River estuary, New York, during summer and early autumn. Our objectives were to evaluate the potential for a competitive bottleneck between these spring and summer cohorts by assessing the cohort-specific growth, condition, and patterns of resource use prior to the autumn migration in 2008 and 2009. The size advantage gained by the spring cohort resulting from earlier hatching dates was maintained throughout bo...
Highlights
For temperate migratory fishes, achieving a minimum size and energy storage level during the summer may be required to survive the autumn migration and subsequent overwinter period
For juvenile Bluefish occupying the lower Hudson River estuary during the summer and early autumn of 2008 and 2009, our objectives were to evaluate the potential for a juvenile competitive bottleneck by comparing the energy content and growth and determining the degree of food and habitat overlap or partitioning between the spring and summer cohorts
Cohort Structure and Abundance A total of 788 juvenile Bluefish were collected from the Hudson River estuary during the summer and early autumn in 2008 (n = 310) and 2009 (n = 478)
Summary
For temperate migratory fishes, achieving a minimum size and energy storage level during the summer may be required to survive the autumn migration and subsequent overwinter period. According to the juvenile competitive bottleneck theory (Werner and Hall 1979), young fish of one species that exhibit a higher foraging efficiency than individuals of a competing species may force the competitors into an earlier ontogenetic niche shift than if the competitive interaction were not present. This competition can be revealed in a cost to growth and energy accumulation to the less efficient species, while potentially increasing the risk of predation to one or both species. Intercohort competitive interactions within a single year-class have rarely been investigated and may have implications for recruitment success
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