Effects of temperature on energetics and the growth pattern of benthic octopuses

In octopus, growth trajectories have implications for survivorship, adult size and fecundity. Many species exhibit a 2-phase growth pattern starting with rapid exponential growth before shifting to a slower (commonly power) growth rate. Based on the concept that energy conservation enforces this threshold, we developed a temperature-dependent model which incorporates the energy balance between food intake and expenditure in growth and metabolism. We employed the model to investigate growth patterns occurring at different temperatures for 2 octopus species, Octopus ocellatus and O. pallidus. Model projections were consistent with laboratory data and suggest that increases in temperature as small as 1°C could have a significant influence on cephalopod growth, affecting the threshold body mass by up to 15.5% and the body mass at 100 d by up to 62.6%. Sensitivity analyses suggest that threshold size is more sensitive than threshold age to any given change in parameter values, and that metabolic rate has the greatest influence on the growth threshold. This model provides a basis for predicting individual growth trajectories and consequential population structure of natural octopus populations. This type of analysis also has the potential to predict optimum conditions for a species and could be a powerful tool for predicting how climate change might affect species distribution as well as population structure and abundance.