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We report the first record of intersexuality in little tunny Euthynnus alletteratus caught in the Mediterranean Sea. The little tunny were sampled in traps from La Azohía (Murcia) south-eastern Spanish Mediterranean coast and Tarifa (Cádiz) between April and June, during 2003 to 2012. We found a low prevalence of intersexuality (two specimens out of a total of 449 little tunny). We show a detailed histological description. 0

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

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 study investigated the somatic growth and energy allocation strategy of two sympatric hake species (Merluccius polli and Merluccius senegalensis), coexisting under the strong influence of the Mauritanian upwelling. The results revealed that ontogeny, bathymetry, geography and reproduction shaped the differences found between the condition dynamics of the two species. Aside from species-specific differences, individuals were observed in better condition in the northernmost area (more influenced by the permanent upwelling) and in the deepest waters, probably the most favourable habitat for Merluccius spp. Both species also displayed contrasting trade-offs in energy allocation probably due to the dissimilarity of their habitats, which favours the existence of divergent adaptive strategies in response to different ontogenic requirements. It was hypothesized that M. polli invests in mass and energy reserves while sacrificing growth, as larger sizes may not provide an ecological advantage in a deeper and more stable environment. Moreover, M. senegalensis capitalizes on a steady growth without major disruptions, enabling earlier spawning at the expense of a lower somatic mass, which is fitting to a less stable shallower environment. This study sheds new light on differences in the biological traits and life strategies of Merluccius spp., which permit their overlap in a complex upwelling system and may contribute to the long-lasting scientific-based management of these species. 2

Background: The bullet tuna (Auxis rochei) is an epipelagic fish with a worldwide distribution that is highly targeted by fisheries. Genetic diversity and population genetics are good indicators of population structure and thus, essential tools for fisheries management. Knowing which factors (biotic and abiotic) might be shaping such structure is crucial for management plans. In the present study, we assessed the population structure of the bullet tuna in the western and central Mediterranean Sea. Methods: We used two types of genetic data: the mitochondrial DNA control region and seven microsatellite loci. The analysis of 431 sequences with a length of 386 bp from the mtDNA CR and the results from 276 individuals were genotyped by seven microsatellite loci. Results: Both types of markers coincided in showing significant genetic differences between an Iberian Peninsula–Strait of Gibraltar stock in comparison with a North African stock. Conclusions: We argue that this differentiation pattern is likely caused by reproductive strategies such as coastal spawning, larval retention, and natal homing behavior. These results should endorse the implementation of management plans for a resource that currently is not being managed. Thus, to ensure sustainability, these new policies should consider the presence of at least two genetically identified stocks., SI

INDITUN

Jellyfish swarms have a direct negative impact on human enterprise, specially on places dependent on the sun and beach economy. The local economy and the health of bathers may be at risk from the emergence of these gelatinous organisms. Economic losses can be mitigated by monitoring the occurrence of jellyfish on the coast. Due to the lack of jellyfish data, environmental citizen science is presented as an alternative for data collection. In this study, fuzzy logic-based models have been used to modelize the knowledge from citizen comments collected by the Infomedusa app. The effect of local climatological factors such as wind speed and direction on the incidence of jellyfish on the coast was studied. The fuzzy logic-based models showed that winds perpendicular to the coast lead to a higher occurrence of jellyfish swarms in central and eastern Malaga, while winds parallel to the coast have a greater influence in the westernmost coasts. Wind speed has a different effect on jellyfish incidence depending on the study area and wind direction. Data extracted from the Infomedusa app can help to address the historical scarcity of scientific data on jellyfish. This app presents an opportunity for future studies to expand the knowledge about the occurrence of these organisms on the coasts and may contribute to the prediction of onshore arrival., Túnidos tropicales del Océano Índico: seguimiento de las pesquerías, asesoramiento e investigación, INDTROP6, SI

15 pages, 8 figures.-- This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, The trophic ecology of European hake (Merluccius merluccius) larvae and early-juveniles from the Iberian shelf off Galicia (NW Spain) are assessed by means of stable isotopes (SIA) and nutritional condition in conjunction with hydrobiological variations observed during the winter and summer season of 2012. Hake early-juveniles (18–47 mm SL) showed higher δ15N than larvae (3–11 mm SL) together with the microzooplankton (55–200 μm) and mesozooplankton (>200 μm) during both seasons. Low δ15N values and high variability in both zooplankton and hake larvae were found during winter coinciding with an unusually strong upwelling event. Inversely, high δ15N content in zooplankton in summer suggests strong nitrogen reutilization. However, hake larvae sampled in summer had a higher RNA:DNA ratio in line with higher Fulton condition factors than those sampled in winter. Higher δ13C values for microzooplankton and mesozooplankton and hake larvae in summer compared to late winter point to prey availability differences. The relationship between nitrogen and carbon stable isotopes versus size or weight suggests an ontogenetic shift in the diet of hake larvae. Early-juveniles had a lower isotopic niche width compared to larvae in both late winter and summer, indicating a trophic specialization related to changes following settlement process from planktonic life to demersal habitat. Higher trophic specialization was observed in summer, which recorded a narrower isotopic niche and higher trophic position estimations, This study was made possible by the financial support of projects CRAMER of the Spanish Ministerio de Economía y Competitividad (CTM2010-21856-C03) and ECOPREGA (10MMA602021PR) of the Galician Government, Xunta de Galicia

The swordfish (Xiphias gladius) is an epi- and mesopelagic oceanic species with a wide geographical range within the tropical and temperate waters of all oceans, and is one of the most important target species in surface-longline fisheries. In order to study the vertical habitat-use and migration patterns of swordfish, and to help delimit the stock boundaries and mixing rate of swordfish between the Mediterranean Sea and the North and South Atlantic, satellite telemetry tagging is used. A total of 26 miniPAT tags have been deployed so far in the North (n = 13) and South Atlantic Oceans (n = 9) and the Mediterranean Sea (n = 4). Of the deployed tags, eight individuals suffered post-release mortality; one was fished after one day; three did not transmit; three tags had premature releases with less than 30 days; four had premature releases with more than 30 days; six tags reached full term; and one individuals’ tag is still at large. The data from ten tags were analyzed for horizontal and vertical habitat use. The results presented herein are preliminary, as more tag deployments are planned. The results show that swordfish moved in several directions, travelling considerable distances in both the North and South Atlantic Ocean, while having shorter displacements in the Mediterranean Sea. Regarding vertical habitat use, swordfish spent most of the day-time in deeper waters, and were closer to the surface during the night-time. The deepest dive recorded was 1480 m. Regarding temperature, swordfish inhabited waters with temperatures ranging from 3.9 ◦C to 30.5 ◦C, mostly residing in waters between 10–12 ◦C during the day-time and in waters >20 ◦C during the night-time. The migration of swordfish in this study agrees with the current stock boundaries defined for this species in the Atlantic Ocean, and shows a high vertical overlap with pelagic longline fisheries that are set during the night-time, SI

The use of fish aggregating devices (FADs) in tropical tuna fisheries has increased significantly during recent decades. Concurrently, concern about juvenile tuna mortality, bycatch, and marine debris associated with FAD fisheries increased, and this led to the implementation of FAD management measures and more sustainable designs (e.g., non-entangling or biodegradable FADs, limits on active FADs, etc.). This document reviews data collection and reporting requirements of tuna-Regional Fisheries Management Organizations (t-RFMOs) on drifting FADs and summarizes the work carried out since 2010 under the Spanish FAD management plan to create an adequate standard data collection aimed at improving science-based decision making. The aim of this study is to assist in the strengthening of data collection systems through: (1) a review of the existing data requirements, (2) a review of the status of FAD data collection worldwide and identification of data gaps, and (3) recommendations aimed at improving FAD management through the strengthening of FAD data requirements. Due to the complexities of data collection, we summarize the difficulties faced when processing the data and propose concrete and practical solutions to improve both the data collection system and information quality., INDTROP6, Túnidos tropicales del Océano Índico: seguimiento de las pesquerías, asesoramiento e investigación, SI

Time series of European sardine (Sardina pilchardus) landings from 1962 and environmental variables from 1978 in the northern Alboran Sea are analysed. European sardine spawns in the northern Alboran Sea from mid-autumn to late winter at a temperature range slightly higher than the one observed in the nearby Eastern North Atlantic and the North Western Mediterranean. Individuals hatched during autumn and winter are incorporated to the fishery during the following summer and autumn producing the maximum annual landings. These landings show both a decreasing long-term trend and a strong inter-annual variability. Although further research is needed, the warming trend of sea surface temperature and the decrease in upwelling intensity inferred from empirical orthogonal function (EOF) analyses could have some influence on the negative trends of sardine landings. The inter-annual variability of sardine abundance seems to be related to the wind intensity at a local scale, the second principal component of the chlorophyll concentration and the sardine abundance during the preceding year. If the inter-annual variability is considered, a linear model including these three variables with a one-year time lag allows to explain 79% of the sardine landings variance. If the negative linear trend is also considered, the model explains 86% of the variance. These results indicate that the body condition of spawners, linked to the food availability during the preceding year, is the main factor controlling the recruitment success. The possibility of predicting sardine landings 1 year in advance could have important implications for fishery management., Sí

Climate oscillations affect fish population dynamics, ecological processes and fisheries activities in marine ecosystems. In the western Mediterranean, several atmospheric indices associated with pressure oscillations have been identified as the main drivers of the abundance or availability of certain resources exploited by fisheries. The main aim of this study was to explore the association between the potential effects of the North Atlantic Oscillation (NAO) and the Arctic Oscillation (AO) on the first sale price of fresh fish at the fish market of the most representative commercial species of the fisheries in the Alboran Sea (Mediterranean Sea). We used the Pearson correlation test to investigate correlations between the atmospheric oscillation indices and the fish market price of the selected species. The results suggest that inter- and intra-annual atmospheric oscillations may have an effect on bonito (Sarda sarda), European anchovy (Engraulis encrasicolus) and catsharks (Scyliorhinus spp.) abundance and catchability in the Alboran Sea and, therefore, an impact on their fish market presence and price variability according to the law of supply and demand, Sí

The Gulf of Cadiz (GoC) in the Atlantic Ocean and the northern Alboran Sea (AS) in the Mediterranean Sea are part of an extremely important oceanographic complex in terms of water exchange between the Atlantic and the Mediterranean through the Strait of Gibraltar. Besides its significant role as an ecological transition system, it is unknown whether regional and local envi ronmental drivers affect similarly species inhabiting these two adjacent and connected ecosystems. This study analyses the spatial shifts of representative demersal species and their response to the environmental and demographic drivers in these two regions, using information from two trawl surveys carried out in the GoC and in the AS from 1994 to 2015. Species distribution trends were observed in both basins. However, they were more evident in the GoC, where six out of eleven species presented temporal trends, than in the AS, where only two species displayed significant distribution changes. In both basins, these species showed geographic displacements towards the Strait of Gibraltar. Also, a high percentage of species presented significant differences in mean depth distribution on the two sides of the Strait of Gibraltar. Our study shows a general heterogeneity and independence in the drivers influencing species distributions in the two areas. GoC was highly influenced by both large- and regional-scale climate factors, which affected several species, while in AS the diversity of drivers was greater, with species density being the most common. This study provides a scientific basis for improving ecosystem-based management measures in these important transitional ecosystems., SI

20 pages, 4 figures, 5 tables, 2 appendixes, [EN] This study analyses the samples collected annually (2012 to 2018) on circalittoral and bathyal soft bottoms (30 to 800 m) by the MEDITS surveys in the northern Alboran Sea (including Alboran Island) and the Gulf of Vera to determine the composition, structure and distribution of decapod crustacean assemblages. A total of 94 decapod crustacean species were identified. Non-metric multidimensional scaling showed depth to be the main factor for distinguishing four main decapod assemblages: the inner shelf (30-100 m depth), outer shelf (101-200 m), upper slope (201-500 m) and middle slope (501-800 m). PERMANOVA analyses revealed further significant depth-related differences between three established geographical sectors of the study area (northern Alboran Sea, Gulf of Vera and Alboran Island). Generalized additive model analyses were used to assess the bathymetrical, geographical and environmental effects on the ecological indices of each assemblage. Results showed that depth and the geographical effect were the main drivers in all cases. Decreases in abundance and increases in species richness, Shannon-Wiener diversity and Pielou’s evenness indices with depth were detected. This study shows the primacy of depth and geographical effect on the distribution of decapod species in the study area, in alignment with findings from other parts of the Mediterranean Sea, [ES] En este estudio se analizan muestras obtenidas anualmente (2012 al 2018) en fondos blandos circalitorales y batiales (30 a 800 m) del norte del mar de Alborán (incluida la Isla de Alborán) y golfo de Vera durante siete campañas de arrastre de fondo, MEDITS, con el fin de determinar la composición, estructura y distribución de las asociaciones de crustáceos decápodos. En total se identificaron 94 especies de decápodos. El escalamiento multidimensional no métrico indicó la profundidad como factor principal en la diferenciación de cuatro asociaciones de decápodos: plataforma interna (30-100 m de profundidad), plataforma externa (101-200 m), talud superior (201-500 m) y talud medio (501-800 m). Los análisis PERMANOVA revelaron diferencias significativas relacionadas con la profundidad entre los tres sectores geográficos establecidos en el área de estudio (norte del mar de Alborán, golfo de Vera e Isla de Alborán). Los modelos aditivos generalizados se utilizaron para evaluar los efectos batimétricos, geográficos y ambientales sobre los índices ecológicos de cada una de las asociaciones encontradas. Los resultados mostraron la profundidad y el efecto geográfico como los principales factores en todos los casos. Se detectó una disminución de la abundancia con la profundidad mientras que la riqueza de especies, el índice de diversidad de Shannon-Wiener y el índice de equidad de Pielou aumentaron. Este estudio muestra la importancia de la profundidad y el efecto geográfico en la distribución de las especies en el área de estudio en consonancia con lo descrito en otras áreas del mar Mediterráneo, This project has been funded by the Spanish Institute of Oceanography and the EU through the European Maritime and Fisheries Fund (EMFF) within the National Programme of collection, management and use of data in the fisheries sector and support for scientific advice regarding the Common Fisheries Policy. We also thank Timothy Dobinson for his revision of the English grammar of the present study. PA acknowledges partial support from the Severo Ochoa Centre of Excellence accreditation (CEX2019-000928-S) to the Institut de Ciències del Mar (ICM-CSIC) and the project CLIFISH CTM2015-66400-C3-3-R, MINECO/FEDER. JLRR acknowledges partial support from the 18-ESMARES2-CIRCA project of the Instituto Español de Oceanografía (IEO-CSIC), under the framework of the tasks comissioned to the IEO by the Ministerio de Transición Ecológica y Reto Demográfico (MITERD) of the Spanish government for the application of the Marine Strategy Framework Directive (MSFD) in Spanish waters

Two distinct contingents of Atlantic bluefin tuna (ABFT), migrants and residents, occur in the Strait of Gibraltar (SoG). Long-term residents are commercially exploited all year round using hook and line gears, whereas migrants are caught by traps in springtime as they pass through the SoG towards Mediterranean spawning grounds. While reproductive features of migrants have been widely studied, the life history of residents remains poorly investigated. The relative contribution of this subpopulation to ABFT eastern stock productivity is therefore un - known. Reproductive traits of resident ABFT were monitored throughout the year, and were com pared with those of migrants crossing the SoG in spring. To assess maturation timing, gonads were classified into maturation stages based on histological features. Our results indicate bio - metric and reproductive differences between SoG residents and migrants. ABFT caught by hook and line gears were smaller on average than those collected from traps. The females sampled from the hook and line fishery in May and early June showed, on average, significantly lower GSI val ues than those caught by trap. In contrast, the GSI values of males sampled in May were not sig nificantly different between gears. Histological analyses showed a more advanced reproductive condition in trap-caught migrants. Delayed maturation schedules of residents in comparison to migrants would result in less egg production and poorer larval survival rates. The present findings encourage further investigation of reproductive schedules in unstudied subpopulations for a better understanding of ABFT dynamics., SI

10 pages, 4 figures, 6 tables, supplementary data https://doi.org/10.1016/j.ecss.2021.107699, Sardine and anchovy have shown important changes in landings, biomass, abundance and body condition with time in the Western Mediterranean Sea. Several hypotheses have been proposed to explain these changes, including the negative interaction with jellyfish blooms. Increases in jellyfish blooms may be one of the reasons for a decline in these fish stocks because several jellyfish species have been shown to feed on fish larvae and juveniles. The main aim of the present study was to test the plausible relationship between jellyfish blooms and stock dynamics (abundance, biomass, and fitness) of anchovy and sardine, and its fisheries within an ecological context of the western Mediterranean Sea. Our main hypothesis was that jellyfish blooms, in combination with other environmental drivers, could have negative effects due to their predation on early stages of small pelagic fish (direct mortality) or due to predation on zooplankton, which is also prey of the small pelagic fish at different ontogenetic stages (direct competition). To test our hypothesis, we developed Bayesian Generalized Linear Mixed Models to compare landings, biomass, abundance, and Kn condition factor of both species with several climatic indices, oceanographic variables, and the occurrences of jellyfish blooms. Our results revealed that the jellyfish bloom occurrence had a high probability of negatively and broadly affecting both species in addition to changes in environmental conditions. This suggests that jellyfish blooms should be added to the likely causes of change when analyzing small pelagic fish change, This study was carried out within the Spanish Research project PELWEB (CTM2017-88939-R) funded by Spanish Ministry of Science, Innovation and Universities, and the Catalonian Government PELCAT projects (CAT 152CAT00013, TAIS ARP059/19/00005). [...] MC acknowledges the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000928-S) to the Institute of Marine Science (ICM-CSIC).

The Western Mediterranean Sea connects the Atlantic Ocean with the rest of the Mediterranean Sea through the Strait of Gibraltar. The Western Mediterranean Sea is important area for cetaceans and it contains highly productive feeding areas, such as the Pelagos Sanctuary and the South Balearic eddy. The main aim of this study was to assess the suitability of a group of Important Marine Mammal Areas (IMMAs) for the conservation of cetaceans inhabiting this area. There were 398 (46.44%) opportunistic sightings (OS) within a number of IMMAs and 459 (53.56%) sightings outside of IMMAs in this area. Trend surface analysis was used to select the OSs (GPOSs hereafter) most likely to be observed within IMMAs as a function of their geographical position. Significant differences were found between the observed GPOS rate and the expected GPOS rate weighted by the surface area of each IMMA. Specifically, there were more sightings than expected in the Alboran Sea IMMA than in the North West Mediterranean Sea, Slope, and Canyon System IMMA. In the latter area, there were fewer sightings than expected, Sí

This paper provides a brief update of the study on habitat use for swordfish, developed within the working plan of the Swordfish Species Group of ICCAT. A total of 9 miniPAT tags have been deployed by observers on Portuguese and Spanish vessels and the Uruguayan research cruise in the North and South Atlantic. Data from eight tags/specimens are available, four specimens suffered from post-release mortality and one individual tag pop-up date has not occurred yet. These preliminary results showed swordfish moved in several directions, travelling considerable distances. Swordfish spent most of the daytime in deeper waters, being closer to the surface during night-time. The main plan for the next phase of the project is to continue the tag deployment during 2020 in several regions of the Atlantic Ocean and Mediterranean Sea, SI

Mature albacore tuna (Thunnus alalunga) are expected to have high energy requirements at the time of breeding. However, there are no descriptions of the diet of albacore in the Mediterranean Sea that can help us to understand if such requirements can be obtained from feeding during reproduction. In this study, we analysed the stomach contents of reproductively active albacore captured from 2010 to 2015 in the oligotrophic waters of the western Mediterranean Sea, one of their main spawning grounds. Estimates of stomach fullness revealed intense feeding activity, and prey composition indicated important consumption of mesopelagic fish, including barracudinas, myctophids and small pelagic crustaceans. Plastic debris occurred in 25%–53% of the stomachs sampled across all years. Prey composition was not different between males and females. However, females fed at higher rates and had higher hepatosomatic index values than males, suggesting that increased feeding could contribute to meet their higher energy demand associated with offspring production. We observed a diet shift from small crustaceans to fish prey along fish size. During the spawning period, albacore showed a specialist feeding behaviour by preying on aggregations of vertically migrating myctophids and small crustaceans, probably when they were near the surface. This study provides information and biological data to support ecosystem modelling and to increase the understanding of albacore ecology., SI

El listado Katsuwonus pelamis es una especie de gran importancia comercial, cuyas capturas representan el 58.1% de las capturas globales de todas las especies de túnidos (FAO, 2019). Aunque el listado es una especie tropical, que principalmente se reproduce en aguas a temperaturas que exceden los 24ºC, las capturas en el mar Mediterráneo son frecuentes, especialmente en las últimas décadas. El Mediterráneo occidental, concretamente el mar Balear, es una zona de puesta para diversas especies de túnidos. El listado es capturado en esta área por la pesquería comercial y deportiva. En este trabajo los individuos muestreados fueron capturados por la pesca deportiva en campeonatos de pesca de altura celebrados en junio y julio en el mar Balear y en agosto y septiembre en el mar de Alborán durante el periodo 2014-2019. El sex ratio (n= 340) de listados (46.5 - 81 cm FL) fue de 1:0.9 (H:M). Se pesaron las gónadas de 329 individuos y su madurez macroscópica asignada, 201 gónadas fueron examinadas histológicamente. El análisis del índice gonadosomático y el examen de las gónadas evidencian que el listado se encuentra reproductivamente activo en el mar Balear (Mediterráneo occidental) coincidiendo en área y época de puesta con el atún blanco Thunnus alalunga. Estos resultados indican que el listado ha ampliado tanto su rango de distribución como sus áreas de puesta. Además, su monitorización es de interés por la su posible impacto sobre otras especies con las que comparte tanto área de distribución como área de puesta en el Mediterráneo occidental.

Standardized relative abundance indices of albacore (Thunnus alalunga Bonnaterre, 1788) caught by the Spanish surface longline (LLALB) in the western Mediterranean Sea were estimated for the period 2009-2019. Yearly standardized CPUE were estimated through Generalized Linear Mixed Effects Models (GLMM) under a negative binomial error distribution assumption. The main factors in the standardization analysis were year and season (quarter). The index shows an increasing trend from the beginning of the series (2009) to a maximum in 2011; following a decrease up to 2013, and a relatively stable trend fluctuating around a level three and a half times lower compared to the maximum abundance for the period 2013-2019., SI

Larval abundance indices express retrocalculated abundances of larval densities at hatching time. They provide a proxy for assessing spawning stock biomass and are applied to assess population status of various species in the Gulf of Mexico and in the Balearic Sea. Recently, the methodological approach to calculate the indices was improved to accommodate for non-linear responses of environmental effects on catchability. This improved methodology is routinely applied in the Balearic Sea to assess the bluefin tuna (Thunnus thynnus) spawning stock biomass. Here we apply the same methodology to update the larval index of albacore (Thunnus alalunga) from surveys conducted from 2001 to 2019 in the Balearic Sea, the most relevant spawning ground of this species in the Western Mediterranean. Albacore larval abundances show a decreasing trend and significant lower abundances from 2013 onwards, despite a slight recovery between 2016 and 2017. This larval index, standardized for gears, sampling coverage, salinity, date and sea surface temperature, provides information on the dynamics of the western Mediterranean stock of albacore, which is considered a data poor stock., SI

The heavy exploitation rates of Atlantic bluefin tuna (ABFT) during the nineties propitiated research into the larval ecology of ABFT and its associated species. The transition from a planktivorous to a piscivorous diet is considered a major bottleneck in the survival of ABFT larvae observed in aquaculture experiments. Although larval piscivory was reported in the Gulf of Mexico (GOM), the most important spawning grounds of this species in the W Atlantic, trophic studies have not been able to reveal piscivory in Mediterranean ABFT larvae. This study analyzes the trophic behavior of Mediterranean ABFT larvae by stomach content analysis. The results show that more than 90% of the larvae had at least one prey in their stomachs. The diet shifted from copepods and cladocerans to gastropod larvae in pre-flexion stages and to ABFT larvae in post-flexion stages. This is the first time that cannibalism is reported for wild ABFT larvae from the Mediterranean Sea. Intracohort cannibalistic feeding was observed when the requisite density-dependent processes aligned, namely the spatio/temporal overlap of a wide range of ABFT larval cohorts of different size class. Moreover, stomach contents of ABFT larvae revealed the ingestion of microplastic fibres. Whether these plastic contaminants were passively or actively ingested, they may affect the condition of larvae. The presence of microplastic strands in fish larvae undoubtedly raises concern because its impact on the survival of ABFT larvae still remains uncertain and is open to scientific experimentation., Sí

The northern coasts of the Alboran Sea are known to have thrived from past artisanal fisheries that exploited the early life stages of fishes. This was mainly carried out by a suite of different fishing gears dating back to the eighteenth century to the end of the twentieth century (Sañez-Reguart 1791–1795 reprint 1988; Rodríguez Santamaría 1923). These fishery studies provide detailed descriptions of the fishing gears employed by fishermen exploiting the Iberian Peninsula coasts and a general account of the targeted species and their associated catches. In the Andalusian coasts of the Alboran Sea, beach seines called boliches were among the most common, targeting on sardines, anchovies, and a number of other fish species, as bonitos and tunas that preyed on small pelagic shoals (Fig. 13.1).

Accurately characterizing the biology of a pelagic shark species is critical when assessing its status and resilience to fishing pressure. Natural mortality (M) is well known to be a key parameter determining productivity and resilience, but also one for which estimates are most uncertain. While M can be inferred from life history, validated direct estimates are extremely rare for sharks. Porbeagle (Lamna nasus) and shortfin mako (Isurus oxyrinchus) are presently overfished in the North Atlantic, but there are no directed fisheries and successful live release of bycatch is believed to have increased. Understanding M, post-release mortality (PRM), and variables that affect mortality are necessary for management and effective bycatch mitigation. From 177 deployments of archival satellite tags, we inferred mortality events, characterized physiological recovery periods following release, and applied survival mixture models to assess M and PRM. We also evaluated covariate effects on the duration of any recovery period and PRM to inform mitigation. Although large sample sizes involving extended monitoring periods (>90 days) would be optimal to directly estimate M from survival data, it was possible to constrain estimates and infer probable values for both species. Furthermore, the consistency of M estimates with values derived from longevity information suggests that age determination is relatively accurate for these species. Regarding bycatch mitigation, our analyses suggest that juvenile porbeagle are more susceptible to harm during capture and handling, that keeping lamnid sharks in the water during release is optimal, and that circle hooks are associated with longer recovery periods for shortfin mako., SI

ECOlogía trófica comparativa de LArvas de aTUN rojo atlántico (Thunnus thynnus) de las áreas de puesta del Medterraneo-NO y el Golfo de México., ECOLATUN

Catch and effort data from the Spanish recreational fishery in the Balearic Sea (Western Mediterranean) were analysed to estimate an index of relative abundance for albacore for the years 2005-2019. Standardized catch per unit effort (CPUE) in number were estimated through a General Linear Mixed Modeling (GLMM) approach under a negative binomial (NB) error distribution assumption. Nominal catch rates and a standardized abundance index are presented along with estimates of 95% confidence limits of the predicted means. These indices show an upward trend from the start of the series 2005 peaking in 2013; followed by a decrease until 2015. For the latest four-year period (2016-2019), the index shows a relatively stable trend fluctuating around a level two times lower than the maximum abundance recorded in the time series., SI

Atlantic bluefin tuna (ABT) (Thunnus thynnus) travel long distances to spawn in oligotrophic regions of the Gulf of Mexico (GoM) which suggests these regions offer some unique benefit to offspring survival. To better understand how larval survival varies within the GoM a spatially explicit, Lagrangian, individual-based model was developed that simulates dispersal and mortality of ABT early life stages within realistic predator and prey fields during the spawning periods from 1993 to 2012. The model estimates that starvation is the largest cumulative source of mortality associated with an early critical period. However, elevated predation on older larvae is identified as the main factor limiting survival to late postflexion. As a result, first-feeding larvae have higher survival on the shelf where food is abundant, whereas older larvae have higher survival in the open ocean with fewer predators, making the shelf break an optimal spawning area. The modeling framework developed in this study explicitly simulates both physical and biological factors that impact larval survival and hence could be used to support ecosystem based management efforts for ABT under current and future climate conditions., ECOlogía trófica comparativa de LArvas de aTUN rojo atlántico (Thunnus thynnus) de las áreas de puesta del Medterraneo-NO y el Golfo de México., ECOLATUN, SI

Este estudio tiene como objetivo analizar el efecto de la interacción trófica entre la melva (BT), Auxis rochei (Risso, 1810) y el atún rojo del Atlántico (ABFT), Thunnus thynnus (Linnaeus, 1758) sobre el crecimiento larvario. ABFT es una especie migratoria de gran tamaño y depredadora oceánica superior que entre los meses de junio y agosto cruza el Estrecho de Gibraltar desde zonas de alimentación en el Atlántico hasta alcanzar su principal área de reproducción en el archipiélago Balear. BT presenta una amplia distribución mundial, siendo el más abundante de los pequeños túnidos frente a las costas mediterráneas española. Durante la campaña oceanográfica MEDIAS 2011, llevada a cabo en la costa del levante español (suroeste del Mediterráneo), se muestrearon un total de 193 larvas, de las cuales 107 eran de ABFT y 86 de ellas eran de BT, en un total de 23 estaciones. En el presente TFM examinamos la influencia del comportamiento de alimentación en el crecimiento larvario considerando variables ambientales, variables somáticas, biometría de otolitos, análisis de isótopos estables y trofodinámicos. Las variables ambientales no mostraron diferencias entre estaciones de muestreo entre ambas especies, por lo que se planteó la hipótesis de que el crecimiento estuviera influenciado principalmente por el comportamiento trófico. Nuestros datos se compararon primero entre especies y, a continuación, considerando cuando la BT estaba sola o coexistía con ABFT en la misma estación. En todos los casos, BT mostró mayor crecimiento en talla y peso, mayor posición trófica (TP) y mayor ancho de nicho isotópico que ABFT, lo que sugiere que BT muestra una mayor plasticidad trófica. No se detectó superposición isotópica entre sus nichos, lo que indica que se produce una segregación trófica entre BT y ABFT. Esta segregación de nichos tróficos puede influir en el crecimiento diario., Instituto Español de Oceanografía. La presente Tesis Final de Máster se ha desarrollado en el marco del proyecto ECOLATUN CTM2015-68473-R (MINECO/FEDER) financiado por el Ministerio de Economía y Competitividad al Instituto Español de Oceanografía., Un total de 16470 palabras, 60 páginas.

ECOlogía trófica comparativa de LArvas de aTUN rojo atlántico (Thunnus thynnus) de las áreas de puesta del Medterraneo-NO y el Golfo de México., ECOLATUN

We investigated aminoacyl-tRNA synthetases (AARS) activity and individual growth rate (IGR) as individual-based in situ indicators of growth in adult krill, Euphausia pacifica. AARS enzymes catalyze the first step in protein synthesis while the IGR method is based on changes in body length during molting. Growth rates of field-collected krill were measured via the IGR method and individuals were subsequently preserved for AARS analysis to yield paired measurements. Our results show that conditions during the IGR incubation period influenced AARS activity in these individuals precluding a direct comparison but revealing the different timescales across which these two measures integrate. Importantly, they show that AARS activity provides a snap-shot image of an organism's metabolism, while IGR of krill is thought to integrate their environmental experience over several days. Each method would require repeated measurements to estimate population growth rates integrated over seasonal or generational time scales. As part of this project, we investigated how specific the AARS assay is to protein synthesis by testing a modified protocol that includes an additional blank and found evidence that the current assay may be measuring other cellular processes in addition to its intended signal. Our results suggest that a new NADH Blank might be optimized to improve the specificity of the assay., SI

The overall aim of the workshop is to advance in the identification of candidate ecologically meaningful regions that can serve as a basis to produce a more integrated ecosystem-based advice, and thereby support the implementation and operationalization of ecosystem-based fisheries management (EBFM) in the International Commission for the Conservation of Atlantic Tunas (ICCAT) convention area. The candidate regions should have boundaries that make ecological sense, and are practical in informing fisheries management. The workshop will gather CPC national scientists and external experts from different scientific disciplines (e.g. biogeography, oceanography, ecology, fisheries and fisheries management in the ICCAT area) to develop a “proof of concept” for broad-scale regionalization of the ICCAT convention area., L'objectif général de l'atelier est de progresser dans l'identification de possibles régions écologiquement significatives qui peuvent servir de base pour produire un avis écosystémique plus intégré, et ainsi soutenir la mise en œuvre et la mise en marche de la gestion des pêcheries basée sur les écosystèmes (EBFM) dans la zone de la Convention de la Commission internationale pour la conservation des thonidés de l'Atlantique (ICCAT). Les régions candidates doivent avoir des limites qui ont un sens écologique, et qui sont pratiques pour renseigner la gestion des pêcheries. L'atelier réunira des scientifiques nationaux des CPC et des experts externes de différentes disciplines scientifiques (par exemple, la biogéographie, l'océanographie, l'écologie, la pêche et la gestion des pêcheries dans la zone de l'ICCAT) afin de développer une preuve conceptuelle pour une régionalisation à grande échelle de la zone de la Convention ICCAT, El objetivo global del taller es avanzar en la identificación de posibles regiones ecológicamente significativas que puedan servir como base para formular un asesoramiento basado en el ecosistema más integrado, apoyando la implementación y puesta en marcha de la ordenación pesquera basada en el ecosistema (EBFM) en la zona del Convenio de la Comisión Internacional para la Conservación del Atún Atlántico (ICCAT). Las regiones candidatas deberían tener límites que tengan sentido ecológico y que sean prácticas para aportar información a la ordenación pesquera. El taller reunirá a científicos nacionales de las CPC y a expertos externos de diversas disciplinas (por ejemplo, biogeografía, oceanografía, ecología, pesca y ordenación pesquera en la zona de ICCAT) para desarrollar una demostración conceptual para una regionalización a gran escala de la zona del Convenio de ICCAT., SI

Resumen del trabajo presentado en el XIII Congreso de la Asociación Ibérica de Endocrinología Comparada - AIEC, celebrado online los días 16 y 17 de septiembre de 2021, Atlantic bluefin tuna (ABFT), Thunnus thynnus (Linnaeus, 1758), is a large migratory oceanic top predator, considered as an important worldwide fishery source and a key species in pelagic ecosystems. Survival during the early life stages is crucial for future recruitment success, with larval growth being a determining process. Fish growth and development are mainly controlled by the GH/IGF axis, being involved in skeletal and soft tissue growth, as well as in immune function, appetite control, behavior (including foraging, aggression, and predator avoidance). To characterize the ontogenetic development profile of the GH/IGF axis at the level of gene expression, an ABFT larval rearing experiment (under controlled feeding conditions) was performed in the aquaculture facilities of the Spanish Institute of Oceanography (IEO), in Mazarrón during June 2019. Eggs and larvae from 3 replicates were collected regularly every 2-3 days from 0 until 30 days post-hatching (dph). In a total of 14 sampling points (n = 6-12 larvae) along the ontogeny, growth hormone (gh) and two forms of insulin growth factor (igf1 and igf2) were analyzed by real-time RT-PCR. A sigmoidal gh expression profile was observed, with higher values at 5 and 23 (maximum) dph, and lower values at 0 (minimum), 12 and 30 dph. Nevertheless, igf1 and igf2 showed a gradual increase from early days, also with lower values at 0 and 12 dph, but with maximum levels at 30 dph. Results are discussed considering growing rates and transition from larvae to juvenile, underlining the importance of gh/ igf axis during the ABFT early development and growth, Research funded by ECOLATUN CTM2015-68473-R (MINECO/FEDER). The authors wish to thank the technicians from the culture facilities of the Aquaculture Experimental plant in Mazarrón, Murcia (IEO-CSIC).

Since 2001, ichthyoplankton and hydrographic surveys directed to tuna species have been conducted in the Balearic Islands, a main tuna spawning ground in the Mediterranean. These campaigns provide today key information about the interannual changes on larval abundances for Bluefin tuna and albacore, also allowing the investigation of the early-life ecology of various species. The Balearic Islands have been identified as a prominent oceanographic retention area within the western Mediterranean as well as the main spawning area for tuna species. Hence, the regular ichthyoplankton surveys become an opportunity to increase the knowledge of those species whose pelagic early-life stages are encountered during the summer in this area. This is the case of swordfish (Xiphias gladius). Here we analyse the possibility of applying those surveys to investigate the early life ecology of the Mediterranean swordfish, exploring the interannual changes on larval abundances and the hydrographic preferences of larval habitats, SI

Marine megafauna typically include large pelagic sharks, sea turtles, seabirds, and marine mammals. These megafauna are mainly associated with pelagic ecosystems through which they undertake long-distance migration. The Alboran Sea connects the Atlantic Ocean and Mediterranean Sea and is thus a relevant hotspot for marine megafauna. In this area, the overlap between various human activities—such as marine traffic or fisheries on the north and south coasts—and pollution entails the capture or mortality of marine megafauna. We review the main research and findings on marine megafauna in the Alboran Sea and discuss research approaches that could provide suggestions for the effective management of large marine ecosystems.

1. Sexual segregation in foraging strategies has been little studied in marine species with slight sexual size dimorphism (SSD), particularly regarding the role of environmental conditions and fishery activities. Sexual differences in fishery attendance are of particular concern because uneven mortality associated with bycatch may exacerbate impacts in wildlife populations. 2. Using a seabird species with slight SSD, the Scopoli's shearwater Calonectris diomedea, we assessed sexual differences in foraging strategies and evaluated whether annual environmental conditions and fishery activity shaped such differences. 3. We used a 4-year dataset combining bird GPS tracking, stable isotope analysis, the North Atlantic Oscillation index (NAO, as main proxy of the annual environmental conditions), and fishing vessel positioning data (Vessel Monitoring System, VMS) from the North Western Mediterranean, a region under intense fishery pressure. 4. From 2012 to 2015, we tracked 635 foraging trips from 78 individuals. Females showed a greater foraging effort, a lower fishery attendance, a lower trophic level, and a narrower isotopic niche width than males. Moreover, in years with unfavourable environmental conditions, both sexes showed a lower fishery attendance and increased foraging effort compared to the year with most favourable conditions. 5. Our results revealed that environmental conditions influence space use, feeding resources and fishery attendance differently in males and females, overall suggesting competitive exclusion of females by males from main foraging areas and feeding resources, particularly in unfavourable environmental conditions. We highlight the importance of evaluating sexual segregation under disparate environmental conditions, particularly in species with slight SSD, since segregation may pass otherwise unnoticed if only years with similar environmental conditions are considered. The higher fishery attendance of males likely explains the malebiased bycatch ratio for this species. Thus, inter-sexual differences in foraging strategies can lead to an unbalanced exposure to relevant threats and have implications for the conservation of long-lived species., Sí

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La llampuga Coryphaena hippurus (Linnaeus, 1758) también conocida como dorado o lirio es una especie epipelágica migratoria ampliamente distribuida en aguas tropicales y subtropicales. Esta especie es de gran interés tanto para las pesquerías comerciales como para las deportivas en múltiples países a nivel mundial. Las llampugas son reproductores parciales con periodos de puesta que se extienden durante varios meses en aguas cálidas preferentemente de 21-30ºC. En este trabajo se emplearon ejemplares capturados por la pesca deportiva en campeonatos de pesca de altura celebrados en aguas del Mediterráneo, concretamente en el mar de Alborán, durante nueve años (2011-2019) en los meses de agosto y septiembre. El análisis del sex ratio de 70 individuos (57 – 114 cm) mostró una mayor proporción de hembras que de machos (2:1). Un total de 45 ovarios fueron clasificados macroscópicamente, de los cuales 30 fueron examinados histológicamente. Las estimas de la fecundidad por tandas de 10 hembras (58 – 101 cm) varío entre 104179 y 1231207 ovocitos hidratados con una media de 686495 ± 409088 ovocitos hidratados. El análisis del índice gonadosomático y el examen de las gónadas (macroscópico y microscópico) ponen de manifiesto que el mar de Alborán es una zona de puesta para la llampuga.

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., SI

The North Atlantic Oscillation (NAO) is the most important large-scale climatic oscillation affecting the North Atlantic region. The variability introduced by the NAO affects many meteorological parameters, including wind speed and direction, and differences in air temperature and rainfall, particularly during the boreal winter. The NAO is also known to affect the ocean by changing heat content, sea surface temperature, gyre circulation, mixed layer depth, salinity, high-latitude deep water formation, and sea ice cover. Consequently, the NAO has been widely used to analyze the variability of marine ecosystems. Several researchers found that fishery resources were teleconnected with the NAO variability, resulting in a significant relationship between this climatic oscillation and fishery yields. More precisely, the NAO affects the target species abundance, recruitment, catchability, and body condition. These effects can be cumulative over time and act synergistically. In this study, the available information about this topic is reviewed, and the importance of the NAO as a large-scale climatic oscillation in fisheries management is discussed using an ecosystem approach. We also discuss the possible effects of climate change on Atlantic and Mediterranean fisheries if this change were to affect the NAO pattern., SI

ECOlogía trófica comparativa de LArvas de aTUN rojo atlántico (Thunnus thynnus) de las áreas de puesta del Medterraneo-NO y el Golfo de México., ECOLATUN

The objective of this study was to determine how preservation methods affect the standard length (SL, mm) of European hake larvae. We used five fixative methods: (i) freezing in seawater at −20°C; (ii) RNAlater at −80°C; (iii) 4% borax-buffered formalin; (iv) freezing with liquid nitrogen and (v) 95% ethanol. Standard length hake larvae were initially measured and individually fixed in each of the five fixatives. To evaluate the effect of the time preserved in each one, we obtained the SL of larvae for a second time after three different preservation periods: 15, 44 and 91 days. To assess the effect of initial size on final shrinkage, we analysed two groups of larvae born in captivity, 15 and 24 days post hatching respectively. Most shrinkage occurred within the first period of preservation in all fixatives, the preservation time having no effect on the percentage of shrinkage for any preservative. However, initial SL affects the percentage of shrinkage depending on the fixative used. We suggest five correlation equations to convert an initial SL into a final contracted size of hake larvae for each fixative., CRAMER, Ecología del reclutamiento de la merluza: implicaciones sobre la gestión del recurso, ECOPREGA, Ecología del reclutamiento y primeros estadios de vida de la merluza en Galicia, SI