Using length–mass relationships to estimate life history: an application to deep-sea fishes

Abstract

Length–mass relationships, while often overlooked, form the basis of many fisheries science applications. Fisheries-independent research surveys compile large databases of biological data that could hold a wealth of information regarding species’ life history, which, for many, are data deficient and infrequently sampled. A flexible model using permutations of a broken stick and variance shift was applied to length–mass relationships to evaluate changes in the mean or variability of mass-at-length using data from deep-sea fishes and focusing on particularly poorly known deep-sea chondrichthyans. Changes in body shape and (or) in the scale of variability around mean mass-at-length were estimated for most species (94% of data sets examined). Such changes seemed likely to be correlated with biological factors, such as the onset of reproduction; 70% of length estimates for a variance shift correlated with the expected length-at-maturity. The model presented here could be applied to any fish where length and mass data are available, providing a way to estimate, validate, and investigate biological factors in species where macroscopic evaluations are unavailable or difficult to estimate.