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

Abstract

This study aims to clarify some aspects of the growth of Atlantic bluefin tuna, Thunnus thynnus (L.), (ABFT) mainly regarding parameters of the growth equation and of relative growth, in this case length-weight relationships. There is a great volume of literature on these matters and there is a danger that the resulting confusion may give rise to mistaken decisions.In spite of the publication of 55 articles on absolute growth (FL > 50 cm), which contain a total of 43 growth equations, no consensus has yet been reached within the ABFT assessment group (AG) of the SCRS on parameters such as L max and L ∞ . The results of the present study indicate that the L ∞ = 314.9 cm of the growth equation used for the western stock by the AG from 2010 (Lt= 314.9 [1-e -0.089 (t + 1.13) ]), which was discarded in 2016, lies within the confidence limits of the maximum Ls presented in this study (L max = 321.4±8.7 cm), confirming that this equation fit the biology of the ABFT growth, and does so even better than that adopted in 2016 for the western stock, whose L ∞ = 271 cm is statistically different from L max . There is a similar situation with regard to the length-weight relationships. 38 articles (FL > 50 cm) have been consulted containing a total of 71 equations, but in spite of this the models adopted by the AG in 2014 underestimate the weight of spawners (> 2 m) by up to 23%.The coincidence of the length-weight model for the ABFT western stock, discarded by the AG in 2014, with that of Pacific bluefin tuna, Thunnus orientalis (T & S), (PBFT) indicates that both species must have the same growth, something that is not surprising since both were the same species until 2003. Other coincidences, such as the trend of condition factor K in adults and the growth in the first months of life, could ratify it.In the Pacific Ocean, where far fewer growth studies have been made on PBFT than on ABFT in the Atlantic and Mediterranean, the management of growth models for the purposes of stock assessment in the International Scientific Committee (ISC) makes more sense than that carried out by the SCRS on this matter.

Importance of the Lunar Cycle on Mesopelagic Foraging by Atlantic Bluefin Tuna in the Upwelling Area of the Strait of Messina (Central Mediterranean Sea)

“…The study period (March–June) was not precisely the peak feeding season for adult bluefin tuna, since this peak usually occurs after spawning (July–November). According to Cort and Estruch [ 89 ], during this period the condition factor (K) increases progressively. Therefore, it would be useful in the future to extend this dietary study to the peak feeding season of bluefin tuna in the Strait of Messina and adjacent areas, comparing the results in relation to the lunar phases.…”

A review of giants: Examining the species identities of the world's heaviest extant bony fishes (ocean sunfishes, family Molidae)

“…The next largest teleost is the blue marlin (Makaira nigricans), which reaches 820 kg. Some other Thunniforms may grow to 600–800 kg .” The largest record of a blue marlin Makaira nigricans (Lacépède 1802) we could find in the scientific literature is 906 kg (Nakamura, 1985; Shimose et al ., 2009), and the largest Atlantic bluefin tuna Thunnus thynnus (Linnaeus 1758) is 1056 kg (Cort & Estruch, 2019; Di Natale et al ., 2017). In the game fish database of the International Game Fish Association, the heaviest bony fish recorded (as of February 2022) was black marlin Istiompax indica (Cuvier 1832) at 707.61 kg (IGFA, 2022).…”

“…Legends of giant sea creatures often differ from actual biological findings (Boulêtreau & Santoul, 2016;Cort & Estruch, 2019;Francis et al, 2019), and misinterpretations about animal sizes appear in both the scientific literature (e.g., McClain et al, 2015;Sawai et al, 2020) and the media (e.g., Boulêtreau & Santoul, 2016;Roach, 2003). One group of marine giants, the ocean sunfishes (Tetraodontiformes: Molidae), are likewise associated with various historical and contemporary legends of massive body size (Sawai, 2017a,b).…”

“…Apart from the novelty of records, the maximum body size of an organism is an important biological factor that is fundamental for understanding the life history of a species (Boulêtreau & Santoul, 2016; Cort & Estruch, 2019; Freedman & Noakes, 2002; McClain et al ., 2015). It is therefore a relevant question if all Mola and Masturus species attain similarly large sizes, or if any grow larger (heavier) than others.…”

Effects of Age, Fulton’s Condition Index (K) and Muscle Fat on Total Mercury Content in Raw, Pre-Canning and Canned Samples of Atlantic Bluefin Tuna (Thunnus thynnus)

“…The term "bluefin tuna" indicates three species which are very similar to each other. In particular, the two northern hemisphere species [2] were recently unified as "Northern bluefin tuna" [3]. Therefore, in addition to the current "Atlantic bluefin tuna" or Thunnus thynnus [4], we can then consider the restored "Pacific bluefin tuna" or Thunnus orientalis [5], as well as the southern hemisphere congener, the "Southern bluefin tuna" or Thunnus maccoyii [6].…”