A QUALITATIVE APPROACH TO MANAGING SHELLFISH POPULATIONS - ASSESSING THE RELATIVE IMPORTANCE OF TROPHIC RELATIONSHIPS BETWEEN SPECIES

Simple qualitative models are applied to investigate aspects of how ec ological interactions between a variety of predators and competitors o f shellfish can be used to assist with the development of resource man agement policies. The modeling approach illustrates how typically comp lex interspecific interactions which vary with species and shellfish l ife stage can influence shellfish populations. Model results show the importance of managing shellfish predators, as well as selected groups of fouling species that may function as larval predators or competito rs or both with juvenile shellfish life stages. While the modeling app roach is limited by the lack of estimating intensities of interspecifi c interaction, it allows first-order insight into the relative importa nce of different types of interactions on shellfish populations and wh ich variables are likely to be the most important in affecting shellfi sh abundance. Coupled with rigorous experimental hypothesis testing, t he qualitative modeling approach provides assistance regarding which l ife stages of a shellfish species or interacting species needs to be m anaged in order to maximize shellfish productivity. Examples using the eastern oyster (Crassostrea virginica) are given.