Otolith chemistry in stock delineation: A brief overview, current challenges and future prospects

- Brief overview of otolith chemistry in stock delineation.
- Main achievements of otolith chemistry to identify fisheries management units.
- Current challenges of otolith chemistry in population structure studies.
- Suitability of combining multiple complementary techniques to resolve stock structure.
- Future perspectives on otolith chemistry to address fishing management requirements.

Otolith chemistry has become a key tool to identify and delineate fish stock units. Its successful application as a natural tag in stock discrimination studies is based on the ability to distinguish among different groups due to variation in otolith chemical composition. Here, we briefly summarize the history and the development of otolith chemistry in general and their application in stock delineation studies in particular. A short overview of the major achievements in stock identification using otolith chemistry is provided whilst covering the evolution in methodological and analytical approaches over the last decades. Current and future challenges and research gaps are outlined focusing on the need to provide accurate stock structure estimates for management purposes. Overall, there is still large room for improvement regarding how we overcome these challenges and supersede the current gaps in population structure and connectivity studies using otolith chemistry. The most favorable and practical directions for future research are discussed, and include marker integration, new technological and statistical approaches that may contribute in further advancing otolith chemistry and its application in stock delineation. Ultimately, the continued development of holistic approaches combining otolith chemistry with different and potentially complementary techniques is clearly the course of action to promote interconnection between management actions and biological processes, and unambiguously resolve stock structure and scientifically underpin fisheries management.