Fertilization is the first major determinant in reproductive success in free-spawning invertebrates. A spatially-explicit, 3D, diffusion and fertilization model was used to explore the effects of spatial distribution, rate of gamete release and population structure (density and sex ratio) on the larval production of benthic free-spawners. The results of the simulations indicate that high population density, spatial aggregation and high rate of gamete release significantly increase the overall larval production in large populations. Moreover, in a population undergoing even mild fishing pressure, the model predicts a very strong decrease (90%) in larval production. This evidence of sperm limitation suggests that recruitment in some heavily exploited populations of free spawners rely on either natural or human induced refuge populations that act as reservoir for larval production.
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