Assessment of nutritional condition in crustaceans: a review of methodologies and guidelines for applying inexpensive and wide-ranging indices to the spiny lobster Panulirus argus (Latreille, 1804) (Decapoda: Achelata: Palinuridae)

Abstract

Abstract The review explores the current diversity of methods used to determine the nutritional condition of crustaceans and to provide evidence that standardization is needed to make results comparable among the increasing number of studies in this field. The advantages and disadvantages of inexpensive and wide-ranging indices are discussed with respect to the blood refractive index (BRI) and the effectiveness of the total weight/carapace length relationship based on their application to the spiny lobster Panulirus argus (Latreille, 1804). Also reviewed are the environmental factors that impact metabolism based on the nutritional condition concept and the nutritional condition itself. Ocean acidification, temperature, salinity, dissolved oxygen, and noise have been the most studied factors impacting nutritional condition in crustaceans, usually under controlled (laboratory) conditions. Methodological aspect could be nevertheless one of the most important factors affecting nutritional condition estimations. More than twenty methods have been applied to determine nutritional variations in crustaceans, all then following different techniques, procedures, and instrumentation. These differences make results almost impossible to compare. BRI determined by a hand-held refractometer, usually inexpensive, is a good option to standardize studies so that the results from different species and different regions can be comparable; other methodologies could nevertheless be used in combination. Laboratory studies, which typically use few individuals that are exposed to extreme and usually non-natural conditions, show limited results. Emphasis should be placed on field studies that integrate the effects of several environmental factors.