The role of compensatory dynamics and influence of environmental factors across multiple spatial scales in structuring fish populations

Phillips Christian Perry, Purdue University

Abstract

Inter-specific compensatory interactions such as competition and predation have potentially strong influence in structuring populations. Compensation occurs when increased abundance or vital rates of one population leads to a negative response in the abundance or vital rates of another population. However, if the benefit imparted to all populations when environmental conditions are favorable overrides the effects of biotic interactions among populations, then populations could be described as more strongly influenced by environmental suitability and bottom-up processes. The purpose of the first part of this study was to compare the population metrics of relative abundance, relative condition, and length-at-age across multiple fish species collected from the glacial lakes of northern Indiana in order to determine if across-lake differences among populations are structured primarily by compensatory processes such as competition and predation or by bottom-up processes such as primary productivity. The mostly positive relationships revealed by inter-specific correlations among the population metrics indicated the dominant roles of environmental suitability and bottom-up processes in structuring these populations. Thus, within this study region, the role of compensatory dynamics is thought to be secondary to processes such as primary productivity and habitat quality in structuring populations. While traditionally investigators of lake fish populations have focused their attention on in-lake features such as surface area, depth, and shoreline complexity, more recent investigations have integrated factors operating at multiple spatial scales. The purpose of the second part of this study was to determine the relative influence of environmental variables from multiple spatial scales on the three population metrics. With one exception, the contribution of the environmental variables toward explaining variation in the population metrics was nearly equally spread across the three spatial scales. The exception was length-at-age which was better explained by environmental variables from the landscape spatial scale. No single environmental variable from any given spatial scale explained a significantly greater proportion of the variance associated with the population metrics than other environmental variables. The fact that variance in population metrics was explained by factors from multiple spatial scales indicates that management of fish populations should not be restricted to just one scale. Rather, when assessing and managing fish populations managers should consider the influence of factors operating at multiple spatial scales.

Degree

M.S.

Advisors

Hook, Purdue University.

Subject Area

Ecology|Environmental Studies|Aquatic sciences

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