Enhancing fish diet analysis: equations to reconstruct Themisto gaudichaudii and Euphausia lucens length from partially digested remains

Abstract

Themisto gaudichaudii and Euphausia lucens are important prey of several fish and squid species of commercial value in the southwest Atlantic Ocean. Although allometric relationships linking size and weight can be used to estimate prey biomass, size is often difficult to obtain as they are usually partly digested. The objective of our work was to provide length–length relationships to estimate body size of both crustaceans from their remains in fish stomachs, as a first step to estimate their weight. Measurements were performed on intact specimens collected in the field. Each of the body dimensions analysed (eye height and width for T. gaudichaudii, and carapace length and eye diameter for E. lucens) was significantly related to total length in both species. Thus, they appear to be highly reliable predictors of original size and can potentially aid in the identification of crustacean remains, allowing a more accurate analysis of digested contents.

Keywords:

• Prey size reconstruction
• zooplanktonic crustaceans
• fish stomach contents
• southwest Atlantic Ocean

Published in collaboration with the University of Bergen and the Institute of Marine Research, Norway, and the Marine Biological Laboratory, University of Copenhagen, Denmark

Published in collaboration with the University of Bergen and the Institute of Marine Research, Norway, and the Marine Biological Laboratory, University of Copenhagen, Denmark

Acknowledgements

We are indebted to Dr Gustavo Macchi, head of the Merluccius hubbsi Assessment Program of INIDEP for the collection of samples. We also thank the crew and technicians of the R/V Eduardo Holmberg for their assistance during cruises. This study was partially supported by funds from a PhD fellowship from the Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET) to BT, CONICET PIP no. 00815 and Universidad Nacional de Mar del Plata (UNMDP) Proj. 15/E483. This is INIDEP contribution no. 1754.

Notes

Published in collaboration with the University of Bergen and the Institute of Marine Research, Norway, and the Marine Biological Laboratory, University of Copenhagen, Denmark