Body mass, temperature, and depth shape the maximum intrinsic rate of population increase in sharks and rays

Abstract

AbstractAn important challenge in ecology is to understand variation in species’ maximum intrinsic rate of population increase,rmax, not least becausermaxunderpins our understanding of the limits of fishing, recovery potential, and ultimately extinction risk. Across many vertebrates, terrestrial and aquatic, body mass and environmental temperature across important correlatesrmaxacross species. In sharks and rays, specifically,rmaxis known be lower in larger species, but also in deep-sea ones. We use an information-theoretic approach that accounts for phylogenetic relatedness to evaluate the relative importance of body mass, temperature and depth onrmax. We show that both temperature and depth have separate effects on shark and rayrmaxestimates, such that species living in deeper waters have lowerrmax. Furthermore, temperature also correlates with changes in the mass scaling coefficient, suggesting that as body size increases, decreases inrmaxare much steeper for species in warmer waters. These findings suggest that there (as-yet understood) depth-related processes that limit the maximum rate at which populations can grow in deep sea sharks and rays. While the deep ocean is associated with colder temperatures, other factors that are independent of temperature, such as food availability and physiological constraints, may influence the lowrmaxobserved in deep sea sharks and rays. Our study lays the foundation for predicting the intrinsic limit of fishing, recovery potential, and extinction risk species based on easily accessible environmental information such as temperature and depth, particularly for data-poor species.