The first larval age and growth curve for bluefin tuna (Thunnus thynnus) from the Gulf of Mexico: Comparisons to the Straits of Florida, and the Balearic Sea (Mediterranean)

Abstract

Atlantic bluefin tuna (Thunnus thynnus) undertake extensive migrations throughout the North Atlantic Ocean, but spawn primarily in the Gulf of Mexico (GOM) and the Mediterranean Sea. Little is known about larval bluefin tuna (BFT) dynamics and growth despite numerous surveys conducted in the GOM. In this study, we describe age-length relationships for larval BFT using otolith increment analysis and compare somatic daily growth as revealed by individual increment widths from the GOM. Otoliths (sagittae) were aged from pre and post flexion larvae collected during multiple spring spawning seasons in 2000–2012 (259 larvae, 2.1–10.9mm body length, 0–15 daily increments). For the first time, larval growth from the GOM is compared to historical larval collections in the neighboring Straits of Florida and in the Balearic Sea. Our results indicate that growth for GOM larvae is significantly faster than reported from previous studies, indicating different growth strategies during the larval stages for the two spawning grounds. This new growth curve will be incorporated into the calculations of the annual larval index used in the management of this overfished species. Growth and its variability, are important drivers, integral in studies of larval ecology dynamics for BFT.