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The Atlantic bonito (Sarda, family Scombridae) is a pelagic species and one of the most exploited small tuna species. Despite its economic importance, biological information is scarce with no associated management directives. In this study, using a population genomic approach resulted in a lack of panmixia of two genetic pools with different effective population sizes (east central-tropical Atlantic and northeast Atlantic-Mediterranean) and an intermixing zone in Atlantic Morocco. The absence of genetic heterogeneity between the locations in Atlantic - Mediterranean transitional zone adds new evidence that challenges the Strait of Gibraltar as a phylogeographic barrier for marine pelagic species. These results are proposed to the ICCAT Commission to establish management areas for this species, although they are not consistent with the recently adopted pelagic ecoregions. Finally, a panel of highly informative SNPs was developed for efficient and low-cost population assignment and the analysis of unresolved population structures.

The shape of sagitta otoliths was used to compare individuals of little tunny (Euthynnus alleteratus) harvested on board commercial fishing vessels from the coastal areas along the Eastern Atlantic, including the Mediterranean Sea. Fish sampling and selection was designed to cover possible seasonal changes and tuna size. The research encompassed both morphometric and shape analyses of left sagittal otoliths extracted of 504 fish specimens. Four shape indices (Circularity, Roundness, Rectangularity, and Form-Factor) were significantly different between two groups, showing a statistical differentiation between two clear spatial units. The degree of divergence was even more pronounced along the rostrum, postrostrum, and excisura of the generated otolith outlines between these two groups. One group corresponds to the samples from the coastal areas in the Northeast Temperate Atlantic and Mediterranean Sea (NETAM Area) and a second group from the coastal areas off the Eastern Tropical Atlantic coast of Africa (ETA Area). This study is the first to use otolith shape to differentiate tunas from separate spatial units. These results could be used to re-classify previously collected samples and to correct time series of data collected.

This document is the final report of the third year of the short-term contract of the Small Tuna Year Program by ICCAT, with the objectives of: a) conduct additional sampling aiming to fill the specific gaps of the biological samples for estimating the growth and maturity parameters for BON and LTA; b) estimate the referred parameters for both species, and preliminary provide preliminary results for WAH; and, c) refine the sampling and stock structure analysis for BON, LTA and WAH. A total of 374 individuals were collected: 145 of BON, 139 of LTA and 90 WAH. Initial target size class was accomplished only for BON in the Mediterranean. Small individuals are need in the Northeast and no samples were obtained in Southeast Atlantic. For LTA, total target sizes were not completely achieved in any case. However, preliminary results were obtained for growth and reproductive parameters. For BON, with samples arrived from Morocco, no genetic differentiation was detected, and the hypothesis provided in the previous contract is maintained. The population genetic analysis of WAH presents a scenario of homogeneous distribution.

Maturity ogives are usually estimated using different methods, including macroscopical and microscopical maturity data. Differences in maturity ogives estimations are found for species and by area/stock. So those differences may be a consequence of the use of different methodological techniques (criteria) or due to different spawning tactics. Taking this into account is essential to guarantee that the maturity criteria for each species are consistent across the laboratories and countries involved in stock assessment. The objective of this document is to show a large amount of detailed photos (macro and microphotographs) of the different gonad stages of Auxis rochei, Sarda sarda and Euthynnus alletteratus, for females and males, which will be an enhancement to the descriptions of maturity stages given in the maturity tables.

This study provides information on some biological aspects of Euthynnus alletteratus from the western Mediterranean (Spanish coast) and in the Atlantic Ocean (south of Iberian Peninsula). A total of 1266 individuals were measured between 2003 and 2017. The L-W relationship was calculated with W equal to 0.01242 FL3.058 . Histological analysis of the ovaries and the monthly variation of the gonadosomatic index for both sexes suggested that the spawning season for Euthynnus alletteratus in the western Mediterranean Sea takes place from June to August. The lengths at first maturity (L50) were estimated to be 50.1 cm and 43.4 cm FL for female and male, respectively. Age at first maturity (A50) was calculated.

This study assesses the stock structure of Atlantic bonito (Sarda sarda) using the mitochondrial control region as a genetic marker. About 615 individuals distributed in seven locations were analyzed. Two of the locations were in the Mediterranean Sea (MD/BIL95) (Spain and Tunis), three in the northeast Atlantic (AT-NE/BIL94B) (Portugal, Tunis, Morocco and Mauritania), and one in the southeast Atlantic (AT-SE/BIL97) (Côte d’Ivoire). All these samples were obtained thanks to the participation of all authors in two Small Tuna Research Programs funded by ICCAT. The analysis of the genetic variability of the sequence of mitochondrial control regions depicts a clear heterogeneity among locations. The shared genetic pool that comprises the locations within the Mediterranean (Spain and Tunis), including also a sample from the northeast Atlantic (Portugal), is clearly different from the African locations (Senegal and Côte d’Ivoire). Moreover, these two African locations are also genetically differentiated between them. Morocco and Mauritania locations seems to be located in an intermediate situation between these two groups of locations. These results can be used to infer a management policy by ICCAT on the fisheries of this species

This document is the final report of the second year of the short-term contract of the Small Tuna Year Program by ICCAT. In 2018, the Small Tuna Species Group decided to prioritize Little tunny (LTA) (Euthynnus alletteratus) Atlantic bonito (BON) (Sarda sarda) and Wahoo (WAH) (Acanthocybium solandri), based on their economic importance and the deficiency of knowledge of their biology. The objectives of the contract for three species were: i) Collect biological samples for estimating growth parameters, assessing the maturity and stock structure analysis (populations genetics), and ii) Conclude the analysis of the stock structure for at least one of the three species and provide preliminary results for the remaining. The obtained samples for growth, maturity and stock structure analysis was almost completed for Little tunny and Atlantic bonito, whereas for Wahoo the samples are scarce. The analysis of stock structure for Little tunny and Atlantic bonito revealed that the observed diff