Atlantic Bluefin Tuna (Thunnus thynnus) Biometrics and Condition

Abstract

The compiled data for this study represents the first Atlantic and Mediterranean-wide effort to pool all available biometric data for Atlantic bluefin tuna (Thunnus thynnus) with the collaboration of many countries and scientific groups. Biometric relationships were based on an extensive sampling (over 140,000 fish sampled), covering most of the fishing areas for this species in the North Atlantic Ocean and Mediterranean Sea. Sensitivity analyses were carried out to evaluate the representativeness of sampling and explore the most adequate procedure to fit the weight-length relationship (WLR). The selected model for the WLRs by stock included standardized data series (common measurement types) weighted by the inverse variability. There was little difference between annual stock-specific round weight-straight fork length relationships, with an overall difference of 6% in weight. The predicted weight by month was estimated as an additional component in the exponent of the weight-length function. The analyses of monthly variations of fish condition by stock, maturity state and geographic area reflect annual cycles of spawning and feeding behavior. We update and improve upon the biometric relationships for bluefin currently used by the International Commission for the Conservation of Atlantic Tunas, by incorporating substantially larger datasets than ever previously compiled, providing complete documentation of sources and employing robust statistical fitting. WLRs and other conversion factors estimated in this study differ from the ones used in previous bluefin stock assessments.

Relationship between weight and linear dimensions of Bluefin tuna (Thunnus thynnus) following fattening on western Mediterranean farms

“…Having new biometric relationships involving these dimensions may facilitate a deeper understanding of the fattening process of captured tuna in farms, but also a better definition of the physiological condition of wild tuna from biometrics. The validity of a specific equation relating weight and length for ABFT, depending on physiological condition associated to different factors (geographical location, season, spawning period, etc) has been a matter of controversy [ 17 , 18 ]. The idea of considering other dimensions in addition to length is not new, since conversion equations including length and height have been introduced before [ 10 ].…”

Review of Recent Studies on the Absolute and Relative Growth of Atlantic Bluefin Tuna: Similarities with the Pacific Bluefin Tuna

“…The evolution of K throughout the year is studied by means of the samples used in the present work. The results have been compared with K values obtained using the monthly L-W equations of Rodríguez-Marín et al (2015) for a fixed value of straight fork length (SFL)= 220 cm.…”

“…On the capture of the largest PBFT captured to date published by the Japanese press (information contrasted with Japanese scientists), a comparison of length-weight relationship of PBFT (Shimose et al, 2009) has been established with several lengthweight models of ABFT (Parrack and Phares, 1979;Rodríguez-Marín et al, 2015). The purpose of this comparison is to determine which best fits the data of the largest ABFT and PBFT captured.…”

“…Table 5 and Figure 5 show two length-weight relationships for ABFT and PBFT (converted to round weight). Parrack and Phares (1979) model was discarded by the ABFT evaluation group in 2014 and Rodríguez-Marín et al (2015) was the adopted model. Table 5.…”

“…Of these, 32 contain 43 growth equations. In relation to length-weight relationships, report 37 articles with 57 equations Rodríguez-Marín et al (2015). publish 12 monthly and 2 population equations (western and eastern stocks).…”