Resumen de Ontogenetic Habitat Shifts in Marine Organisms: Influencing Factors and the Impact of Climate Variability
Many marine animals must increase by several orders of magnitude in size as they grow from eggs or larvae to adults, and ecological scaling properties limit the size range over which certain habitats are exploitable. Many of these organisms therefore undergo one or more ontogenetic habitat shifts as they grow to maximize growth rates while minimizing predation risk. An understanding of the mechanisms that influence the timing and optimal sizes at these shifts is critical in managing both target and by-catch populations affected by fisheries. Here I summarize ecological processes that influence ontogenetic habitat shifts, including size-specific predation, size-specific limitations to habitat exploitation, and density dependence. I also consider how climate change may affect the variability in these processes. To illustrate the potential impact of climate variability, I present a simple model building on previous theoretical studies of ontogenetic habitat shifts. As a case study, I used the model to consider differences in the timing of the shift from pelagic to neritic habitats in populations of the loggerhead sea turtle (Caretta caretta Linnaeus, 1758), which are vulnerable to by-catch in different fisheries in the two habitats. Results of the model suggest that the optimal size at the pelagic-to-neritic habitat shift in loggerhead sea turtles may vary considerably over time. Generalizing these results, we must place our understanding of ontogenetic habitat shifts in the context of climate variability and recognize that the results of short-term observations and experiments may not be applicable at longer time scales.
