The ALBYP has prioritized research on the reproductive biology, to improve knowledge on maturity and fecundity for both North and South Atlantic stocks. Preliminary results have been presented to the northern stock, while for the South Atlantic a significant number of new samples has been collected. Preliminary results suggest different maturity schedules for both stocks. For this reason, it is intended to continue these studies in order to verify, or reject, whether these important biological parameters vary between the two Atlantic stocks. Several electronic tagging surveys targeting large individuals have been conducted off the Canary Islands, where 33 MiniPATs have been implanted. In addition, in the Bay of Biscay tagging has targeted small and medium size albacore, with 2 miniPATs and 155 internal archival tags having already been deployed. To date, data from 47 tracks have been gathered (corresponding to more than 5,000 tracking days), including for the first time more than 1-year tracks for nine specimens. The second round of the northern Atlantic Albacore MSE framework, that is expected to be delivered in 2026 has started. The contractors started the elaboration of a grid of reference OMs, and tested the currently adopted MP on this new reference grid. The New Observation Error Model has been developed and plots were produced aiming to discuss the detection of exceptional circumstances, as requested in Rec. 21-04.

The SMTYP continued collecting biological samples aimed at growth, maturity and stock structure studies on small tunas species. These involve a consortium of 13 institutions (10 CPCs), that continued to: i) fill specific size gaps for estimating the growth and maturity parameters for Little tunny (LTA), Atlantic bonito (BON) and Wahoo (WAH); ii) collection of samples to expand stock structure studies for frigate tuna (FRI) and bullet tuna (BLT) in the Atlantic Ocean and the Mediterranean Sea; iii) advance on the estimation of the growth and reproduction parameters for BON, LTA, and WAH; iv) refine the stock structure analysis for WAH, BON, and LTA and determinate the stock structure analysis for FRI and BLT; and, v) investigate genetic species differentiation between FRI and BLT. Samples were obtained from a broad temporal and spatial range, however, some improvements are still required for specific size ranges to allow the conclusion of the ageing and reproduction studies. ICCAT CPC engagement in sampling and analysis for this program is urgently needed. The ICCAT course on the use of data limited methods for the provision of management advice for these tunas stocks was successfully completed by four scientists, which will enhance the capacity of the SCRS to provide management advice for small tuna that play an important role on small-scale artisanal fisheries for many ICCAT costal Contracting Parties. Other research activities conducted throughout 2024 include: updating the biological meta-database, estimation of length-weight relationships representative at the stocks/regional level, calibration and adopting internationally agreed maturity scales and, further develop capacity building on the use of data limited methods for the provision of management advice for these stocks.

The (EPBR) evaluates adult habitat use and migration in the Eastern Atlantic through e-tagging and studying growth in the North-eastern Atlantic of blue marlin, white marlin and sailfish. In June 2024 a new contract was awarded to the Institut sénégalais de recherches agricoles (ISRA), Centre de Recherches Océanographiques de Dakar/Thiaroye (CRODT, Senegal) to continue the growth studies. Since the last Newsletter 38 additional samples were collected for the three billfish species, however several gaps have been identified in sampling for several size ranges and, therefore, ICCAT CPC engagement in sampling for this program is urgently needed. A contract shall soon be signed with the Instituto Mexicano de Investigación, Centros Regionales de Investigación Acuícola y Pesquera de Veracruz (Mexico), aiming to study blue marlin reproduction in the Gulf of Mexico. A total of two white marlins were tagged with satellite tags, and 29 additional specimens were tagged with conventional tags. There are plans to carry out several additional trips in September and October 2024 devoted to satellite tagging.

Within the SRDCP age readings of new vertebrae samples of southern Atlantic shortfin mako have been taking place, and preliminary growth curves have been presented aiming for the upcoming stock assessment in 2025. Genetic analysis of porbeagle based on mitogenomic analysis continued with the analysis of new samples from the southwestern Atlantic. Results showed that the Northern and Southern Hemisphere porbeagles are two distinct sibling species. While distribution range of the Southern Hemisphere porbeagle is fairly extense throughout the South Atlantic, the Indian, and the South Pacific Oceans, that of the North Atlantic porbeagle is limited to the North Atlantic Ocean. A successfully electronic tagging campaign was carried out along the equatorial Atlantic area. A total of 16 specimens were tagged, including eight silky sharks, three bigeye threshers, two smooth hammerheads and one oceanic whitetip, and one specimen from the secondary shark species, namely one blue shark. Additional e-tagging has been conducted in the northern Atlantic, that allowed tagging five silky sharks, two blue sharks, one smooth hammerhead and one porbeagle, while conventional tagging of blue shark is being opportunistically conducted mostly in the North-eastern Atlantic. The reproductive biology of the North Atlantic shortfin mako continued based in the quantification of reproductive hormones concentrations, with preliminary results suggesting muscle tissue can be used to assess the species reproductive characteristics and critical information regarding important reproductive habitats for the North Atlantic shortfin mako.

Within SWOYP sampling continued for swordfish, from a broad temporal and spatial range in the North and South Atlantic and Mediterranean. Fish were sampled for size, sex, and maturity. Sample processing has continued, particularly for genetic studies aiming determination of stock boundaries, and through bomb radiocarbon dating to advance the age and growth study. Several gaps have been identified in sampling and the next steps require examining sampling representativeness relative to spatial and temporal patterns in recent catch data, but ICCAT CPC engagement in sampling and analysis for this program is urgently needed.

Two very successful electronic tagging campaigns took place in the North-western Atlantic (off Canada) and in the North-eastern Atlantic, with a total of 10 swordfish specimens tagged in each area.

In 2024, the TTRaD has prioritised MSE developments, sample collection for age and growth, and the continuation of funds for tag recovery and maintenance of AOTTP databases. MSE developments have been provided throughout the year at the yellowfin tuna data preparatory and stock assessment meetings and intersessional MSE subgroup meetings. For the western skipjack MSE, updates include development of Candidate Management Procedures (CMPs), incorporation of abundance indices and robustness tests to account for the effects of Climate Change. For the multi-stock MSE, technical work has been undertaken to explore uncertainties, develop conditioned operating models and observation error models, incorporation of Climate Change impacts, and multi-species management procedures (harvest control rule development). To aid in building understanding of the developed MSEs, a workshop is also planned for October 2024 with a focus on building understanding of tropical tuna-specific MSEs. For the age and growth work, relatively limited samples have been collected to date due to closure of fishing in important areas, though further sampling is ongoing with sample collection from the Gulf of Guinea, Central and South Atlantic.

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Staff