Contribución INIDEP 2373
Parietti, M.; Giorgini, M.; Orlando, P.; Derisio, C.; Temperoni, B.; Padovani, L.; Marrari, M.; Buratti, C.C. (2025). Beyond the boundaries: poleward range expansion of the Atlantic chub mackerel Scomber colias in SW Atlantic Ocean. Fisheries Oceanography, 34(2). https://onlinelibrary.wiley.com/doi/10.1111/fog.12711

Abstract
Shifts in species distribution have far-reaching implications across ecological, economic, and social dimensions. Pelagic fish, integral to global fisheries, have displayed notable euryhaline and eurythermal characteristics. However, a poleward range expansion trend has emerged in the northern hemisphere for certain Scomber species since the 2010s, attributed to sea surface temperature and food resource dynamics. Scomber colias, a principal pelagic fishery resource in Argentina, stands as an underexploited species with recent landings totaling approximately 14,800 tons. In the North Patagonian shelf waters, where S. colias resides at its southern distribution, there has been documented ocean warming. In this context, this study evaluates potential changes in the distribution and abundance of S. colias from 1991 to 2022 in the Southwestern Atlantic Ocean (SAO). Drawing on two distinct data sources, the analysis reveals a poleward range expansion, extending to 48°5′S, exceeding historical limits by 278 km. This expansion is positively correlated with rising sea surface temperatures, with the most significant displacement observed during summer, when this species has a high feeding activity in the study area. The investigation further explores the relationship between S. colias presence and the abundance of its primary prey species between 2011 and 2022. This is highly possible, yet no significant results were uncovered. This study marks the first documented southward range expansion of S. colias in the SAO, providing essential quantitative insights for biological studies, fisheries management, and the canning manufacturing industry. The latter could benefit from year-round access to fish, potentially generating employment opportunities and fostering economic growth within the local community.

Contribución INIDEP 2374
Mechaly, A.S.; Awruch, C.; Cabrita, E.; Costas, B.; Fernandes, J.M.O.; Gallego, V.; Hirt-Chabbert, J.A.; Konstantinidis, I.; Olivera, C.; Ramos-Júdez, S.; Ramos-Pinto, L.; Fatsini, E. (2025). Cutting-edge methods in teleost and Chondrichthyan reproductive biology. Reviews in Fisheries Science and Aquaculture, 33(1). https://doi.org/10.1080/23308249.2024.2377999

Abstract
Reproduction is a fundamental biological process for producing offspring and ensuring the continuation of the species. With nearly 35,000 fish species worldwide exhibiting a very diverse range of reproductive systems and strategies, the study of fish reproduction is a significant challenge. Research into various fish reproductive models is driven by their use in human biomedical applications, improving the diversification and sustainability of aquaculture species, and developing strategies for biodiversity conservation. These models must be approached from an animal ethics perspective, considering the welfare of the species under study and applying the 3Rs principle (Replacement, Reduction and Refinement). This principle focusses on replacing animals with alternative methods wherever possible, reducing the number of animals used and refining procedures to minimize suffering. While destructive sampling of wild aquatic species should be minimized, the need remains to provide information on reproduction as an important parameter for delineating management and conservation programs. One of the practices that helps reduce and replace the use of animal testing is the scientific study of individuals obtained through bycatch. This is the case for some chondrichthyans, and endangered fish species included in conservation programs. Regarding fish species that are kept under human care (commonly called captivity), studies on reproduction are essential to improve well-being and increase production of farmed species. Research on fish reproduction requires expanding basic knowledge of broodstock management tools, such as gamete quality assessment, reproductive behavior studies, the use of hormone therapies to stimulate reproduction, and the development of non-lethal or less invasive methods using body fluids (e.g., mucus, seminal plasma, blood plasma, or urine) to study reproductive status, as well as novel markers from state-of-the-art omics research. This review describes a multidisciplinary approach that includes the aforementioned reproductive management tools, indicators of welfare, and next-generation sequencing techniques using samples collected by minimally invasive methods.

Contribución INIDEP 2386
Do Souto, M.; Brown, D.R.; Leonarduzzi, E.; Silva, R.I.; Martínez, A.; Cepeda, G.D.; Macchi, G.J.; Galván, D.E.; Díaz, M.V. (2025). Comfort in stratification and trophic flexibility: argentine anchovy, Engraulis anchoita, larvae life traits in relation to their food sources. Fisheries Research, 281. https://doi.org/10.1016/j.fishres.2024.107215

Abstract
Fish larvae feeding success is crucial for adult recruitment, which affects both fisheries and ecosystem regulation processes. Engraulis anchoita is a species of great ecological and fishing relevance in the South-West Atlantic Ocean, with a wide latitudinal distribution and active spawning throughout the year and strongly associated with frontal areas. E. anchoita larvae have been described as exclusively feeding on small copepods and their early developmental stages. In this study, the diet, nutritional condition, and daily growth of E. anchoita larvae were estimated in different environmental scenarios in the South-West Atlantic Ocean. Carbon and Nitrogen stable isotopes analysis, otolith microstructure analysis, and RNA/DNA index determination were performed. The larval diet, which was evaluated based on the availability of potential prey, varied with respect to the water column stability. It was observed that the larvae tend to feed on microphytoplankton in stratified waters and on calanoid copepods in waters with a homogeneous vertical structure. The growth and nutritional condition indexes responded to ontogeny, presenting higher values at larger larval sizes. Growth indexes also responded positively to the stratified water column structure in comparison to the homogeneous one. The nutritional condition index was only explained by the size of the individuals. This study found that E. anchoita larvae had greater trophic flexibility than previously suspected, as they included microphytoplankton as the main food item under certain oceanographic conditions without negative impacts on their growth or nutritional condition.

Contribución INIDEP 2387
Wöhler, O.C.; Martínez, P.A.; Troccoli, G.H.; Di Marco, E. (2025). Patagonian toothfish (Dissostichus eleginoides) stocks in South American waters and its implications for fishery management. Marine and Fishery Sciences, 38(1), 109-144. https://doi.org/10.47193/mafis.3812025010110

Abstract
Patagonian toothfish (Dissostichus eleginoides) is a highly prized resource in markets due to the quality of its meat. The Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR) implemented controls and regulations in response to the sharp rise in the illegal fishing of D. eleginoides in the 1990s. Today, four fisheries in waters close to the southern tip of South America are managed in accordance with stringent sustainability standards. Even though they are separate management units, both abundance assessments and annual catch allocations are conducted using different criteria regarding stock considerations across the region, leaving one of the fundamental premises of fisheries management unclear. This study examines historical data and recent research to explore the potential differentiation between Patagonian toothfish populations in South American waters, which is crucial for the management of diverse fisheries. Genetic studies, otolith microchemistry, morphometry, parasitic fauna, tagging programs, reproductive characteristics, and the impact of ocean circulation on dispersal and recruitment were analyzed. Tagging studies in the southern hemisphere oceans confirm the species’ affinity to specific habitats, suggesting minimal fish exchange between South American fishing grounds. From a fisheries perspective, this review suggests the existence of distinct stocks of the species structured along the shelf and slope of the southern cone of America based on reproduction areas along the continental shelves and slope, the diverse parasitic fauna, the variability in stable isotopes and trace elements of otoliths, and the little significant exchange of fish between current fishing grounds. All of this could lead to considering the D. eleginoides fishery as independent exploitation units.

Contribución INIDEP 2392
Rodríguez, J.; Alves, N.M.; Fenco Chavesta, H.A.; Macchi, G.J.; Schiariti, A.; Di Mauro, R.; Díaz, M.V. (2025). Exploring nutritional condition of Merluccius hubbsi during early life stages: environmental drivers and possible implications on subsequent recruitment. Fisheries Oceanography. https://doi.org/10.1111/fog.12724

Abstract
The early life stages of fish represent a period of high energy requirements due to profound changes that characterize the passage to adulthood, crucial for fisheries recruitment. This study focuses on the North Patagonian Frontal System (NPFS) that guarantees successful larval development and fulfills the three postulates of Bakun's “fundamental triad” in regards to nutrients, concentration of food, and retention of eggs and larvae inside the favorable area. The objective was to evaluate the nutritional condition of Merluccius hubbsi larvae and juveniles, from the Patagonian stock in January during austral summer (2010–2021). The standardized RNA/DNA index (RDs) was used. Interannual variation in the larval condition was observed in relation to NPFS features. RDs were positively linked to the stratification of the water column in the stratified zone. An opposite trend was observed between larval condition and potential egg production that might indicate the existence of density-dependent mechanisms. On the other hand, the positive relation between larval condition and egg production of older females (≥7 years) supports the idea of a maternal effect on larval survival. There was also a positive relationship between juveniles condition, body size, and recruitment, but no relationship was observed with the stratification of the water column. The high sensitivity of the RDs index links physiological state with survival probability, informing on factors affecting eggs, larvae, and juveniles until their posterior recruitment. This study identified the stratified area of the NPFS as a favorable nursery zone, providing crucial information for managing populations under high fishing pressure.

Contribución INIDEP 2394
Santana, P.E.; Nori, J.; Rojas-Soto, O.; Cortés, F.; Colonello, J.H.; Elisio, M. (2025). Climate change threatens pupping sites of the critically endangered Mustelus schmitti: Insights from Ecological Niche Models for ocean conservation. Estuarine, Coastal and Shelf Science, 314, 109132. https://doi.org/10.1016/j.ecss.2025.109132

Abstract
Climate change is already affecting the oceans, and its impacts on marine threatened biodiversity are expected to worsen, with its effects on marine biodiversity, particularly threatened species, expected to intensify. Understanding these effects is crucial for developing effective mitigation and adaptation strategies. In this study, we applied Ecological Niche Models (ENMs) to assess the impact of climate change on the distribution of breeding areas, critical for the survival of the Critically Endangered narrownose smooth-hound shark (Mustelus schmitti). Using the Wallace package in R, we correlated a detailed geographic database of the pupping sites and five key oceanographic variables under both current and future climate scenarios. Future projections indicate a significant reduction in suitable habitats. Our findings suggest that, under current conditions, the only areas maintaining highly suitable conditions for breeding are the already identified regions of El Rincón and Río de la Plata. Overall, we predicted a severe effect of climate change on the species’ phenology, with stable, high-suitability breeding areas restricted to very small locations meeting minimum and optimal pupping conditions. These findings suggest that climate change may drastically modify the distribution of essential habitats for M. schmitti management, emphasizing the need of integrating these such predictive approaches into conservation and management plans of oceans.

Contribución INIDEP 2401
De Wysiecki, A.M.; Barnett, A.; Sánchez-Carnero, N.; Cortés, Federico; Milessi, A.C.; Trobbiani, G.A.; Jaureguizar, A.J. (2025). Using global occurrence data to predict suitable habitats for widely distributed marine species in data-scarce regions. Biodiversity and Conservation, 34. https://doi.org/10.1007/s10531-025-03030-z

Abstract
This study addresses the challenge of advancing habitat use knowledge of widely distributed marine species populations when regional data is scarce. We use an approach based on ecological niche models (ENMs) calibrated with global presence data to estimate the global niche of species, enabling indirect predictions of suitable habitats and potential distribution in one or more regions of interest. The method leverages a range of global occurrence records, including scientific papers, government data, biodiversity repositories, and citizen science contributions, to overcome regional data scarcity, which are then integrated with environmental variables to predict habitat suitability. As a case study, we apply this method to predict suitable habitats of copper (Carcharhinus brachyurus) and sand tiger (Carcharias taurus) sharks in the Southwest Atlantic, two species of conservation concern in a region with limited data. Suitable habitats for both species were predicted, providing critical information for guiding conservation efforts. Environmental factors (i.e., bottom temperature, distance to the coast, and surface temperature) were key to shaping predicted distribution patterns of these large predatory sharks, aligning with previous knowledge and historical records of their latitudinal ranges. The results have implications for conservation planning and sustainable management of shark populations in the Southwest Atlantic, contributing to broader efforts in marine biodiversity conservation. Additionally, the study highlights the potential of ENMs to identify essential habitats even in the absence of effort data, underscoring their value in marine conservation. This study advances the use of niche modelling in marine systems and demonstrates its applicability for area-based conservation initiatives, particularly in data-poor regions.

Contribución INIDEP 2404
Defeo, O.; Franco, B.C.; Piola, A.R.; Buratti, C.C.; Cardoso, L.G.; Cortés, F.; Gianelli, I.; Giorgini, M.; Jorge-Romero, G.; Lercari, D.; Meerhoff, E.; Ortega, L.; Alvarez Perez, J.A.; Prandoni, N.I.; Sant'Ana, R.. (2025). Facing oceanographic, fisheries, and governance hotspots: Scientific evidence and policy implications from the southwest South Atlantic Ocean. Marine Policy, 173. https://doi.org/10.1016/j.marpol.2024.106584

Abstract
The southwest South Atlantic Ocean (SWAO) is a highly dynamic region where subtropical and subantarctic waters converge, making it one of the world's most productive marine areas. The SWAO is also one of the world’s most intense marine hotspots, with rising sea surface temperatures and climate-induced shifts in species distribution posing significant challenges. This paper investigates long-term trends in key fishery resources exploited by Brazil, Uruguay, and Argentina over the past 70 years, focusing on the transboundary and straddling stocks that dominate the region's catch statistics. Key strengths identified include the use of diverse stock assessment methods, the implementation of effective management measures, and the establishment of collaborative governance systems, all of which have contributed to fostering sustainable fisheries. However, the study highlights the need for adaptive management strategies due to the impacts of climate change, including the tropicalization of species and shifts in fish abundance. Governance challenges are exacerbated by weak coordination among countries and the absence of robust and inclusive international agreements, particularly for managing straddling stocks in international waters. The paper emphasizes the need for an international governance framework aligned with ecological, social, and institutional scales aiming to ensure sustainable fisheries amid climate-induced changes. Recommendations include the development of dynamic and adaptive management approaches, enhanced monitoring systems, and stronger regional cooperation to address the shared challenges in the SWAO. The interplay between climate, biodiversity, and fisheries management and governance is essential for establishing resilient social-ecological systems in this region.

Contribución INIDEP 2405
Novillo, M.; Moreira, E.; Elisio, M.; Macchi, G.J.; Barrera-Oro, E.; La Mesa, M. (2025). A comprehensive study of the life history traits of Trematomus newnesi (Pisces, Notothenioidei) off the South Shetland Islands. Estuarine, Coastal and Shelf Science, 312. https://doi.org/10.1016/j.ecss.2024.109040

Abstract
Understanding the life history traits of Antarctic fish species is crucial for effective management and conservation purposes. This study provides a comprehensive evaluation of the reproductive dynamics, age and growth characteristics in Trematomus newnesi, a common nototheniid species in the High-Antarctic zone. Field observations conducted in Potter Cove, South Shetland Islands, revealed significant variations in photoperiod and water temperature from November to March, with water temperatures reaching a peak in mid-December. The gonadosomatic index, as a proxy of gonad development, increased exponentially in both sexes from November to March. Sex steroid plasma levels, particularly testosterone (T) and estradiol (E2), showed significant temporal variations, with a significant increase in the period when late vitellogenesis was evident, suggesting the proximity of final maturation and spawning. Age estimation through otolith readings provided a range of ages up to five years for both sexes. Comparison with previous studies on T. newnesi from other Antarctic areas highlighted similarities in reproductive patterns and differences in growth parameters. Photoperiod and an increase in temperature resulted to be trigger factors promoting vitellogenesis in T. newnesi, ending in an early austral autumn spawning event. The environmental cues and reproductive data recorded at Potter Cove suggest that this area serves as a spawning ground for T. newnesi. Likewise, larval hatching was estimated to occur from early to mid-August, after an egg incubation period of four months. Overall, this study provides insights into the life history traits of T. newnesi, as a valuable contribution for appropriate management and conservation of Antarctic fish populations.

Contribución INIDEP 2421
Do Souto, M.; Capitanio, F.L.; Galván, D.E.; Macchi, G.J.; Díaz, M.V. (2025). Trophic position and feeding sources of Engraulis anchoita larvae from the Buenos Aires stock, southwest Atlantic Ocean. Marine and Fishery Sciences, 38(2), 295-310. https://doi.org/10.47193/mafis.3822025010114

Abstract
The existing literature has classified Engraulis anchoita larvae as exclusively zooplanktophagous, with copepod eggs and nauplii larvae as their main prey. However, there is evidence that other plankton components that have not been identified by intestinal content analysis may be a part of their diet. The objective of this work was to explore trophic positions and main food sources of E. anchoita larvae by analyzing stable nitrogen and carbon isotopes (δ15N and δ13C) with respect to other plankton components (particulate organic material, calanoid copepods, and chaetognaths) at a fixed sampling station close to the coast of the Province of Buenos Aires, Argentina, southwest Atlantic. Samples were collected at different times of the year between the end of 2016 and the beginning of 2018. By averaging δ15N and δ13C values of all surveys, it was found that the anchovy larvae in their three development stages coincided with the same trophic position as chaetognaths, suggesting that their diets overlap. When surveys carried out in autumn were analyzed separately, trophic levels of anchovy larvae differed in a staggered manner among their stages, being situated between the positions of copepods and chaetognaths. Compared to other stages of development, anchovy larvae in the preflexion stage consumed a higher proportion of particulate organic material rather than small copepods. These findings suggest that anchovy larvae may consume a variety of food items and shift their trophic position in response to environmental conditions.

Contribución INIDEP 2423
Parietti, Manuela; Giorgini, Micaela; Menna, Bruno V.; Orlando, Paula; Buratti, Claudio C. (2025). Seasonal patterns in the distribution of Engraulis anchoita in the North Patagonian Continental Shelf of Southwestern Atlantic Ocean. Marine Ecology Progress Series, 756. https://doi.org/10.3354/meps14810

Abstract
The Patagonian stock of the anchovy Engraulis anchoita is distributed between 41° and 47°30’S over the Argentinian Shelf. This is an underexploited species that plays a key role in the North Patagonian ecosystem (Southwestern Atlantic Ocean) since it constitutes the food of numerous species of fish, birds, and marine mammals. Knowing the spatial and seasonal dynamics of the abundance of this species is a valuable source of information for understanding how it could affect the functioning of this ecosystem. To this end, the effect of oceanographical variables on the presence/absence and relative abundance of the Patagonian anchovy were analyzed in 2 seasons over a 10 yr period. A mixed effect of the oceanographic variables and the relative abundance in warm and cold seasons was found, as well as differences in abundance and presence of this species when comparing consecutive seasons. The spatial evolution of the distribution of the Patagonian anchovy shows a contraction/expansion pattern. It contracts towards the northern area and towards lower latitudes during cold seasons (up to 45°30’S) and then disperses to occupy the entire studied area during warm seasons, reaching 47°30’S. Knowing the spatial and seasonal dynamics of small pelagic fish is valuable for achieving sustainable management of different resources within the framework of an ecosystem approach.

Contribución INIDEP 2426
Berrueta, M.M.; López, A.V.; Radonic, M.; Aristizábal, E.O.; Gorriti, B. (2025). In vivo determination of sex and reproductive status of Octopus tehuelchus (Cephalopoda: Octopodidae) by ultrasound techniques. Marine and Fishery Sciences, 38(3). https://doi.org/10.47193/mafis.3832025010702

Abstract
In recent years, studies on the cultivation of various species of cephalopods have grown with the aim of diversifying the supply of aquaculture products in the world market. Ultrasound images constitute a non-invasive method that has been utilized to determine sex and maturity stages in fish, being a useful tool for the management of captive broodstocks. The objective of this work was to evaluate the effectiveness of ultrasound techniques for the identification of sex and reproductive status of the small Patagonian octopus Octopus tehuelchus. Observations were carried out with a portable ultrasound machine (Sono Site Ultrasound System) and a transducer (10-5 Mhz) in eight anesthetized individuals. In ventral view, the testis had a spherical, homogeneous and compact appearance, while the spermatophore complex appeared as a hyperechoic structure with respect to the testis, highlighting the presence of spermatophores in mature individuals. In females, the dorsal view allowed to identify a granular-appearance ovary with anechogenic areas, indicating a maturing ovary. Ultrasounds allowed unequivocal sexing. In this way, the ultrasound technique was a practical and non-invasive method for determining sexes and gonadal maturation in live specimens of O. tehuelchus.

Contribución INIDEP 2427
Brown, D.R.; Leonarduzzi, E.; Buratti, C.C.; Carvalho, F.; Hernández, D.R. (2025). Age and daily growth of juveniles Engraulis anchoita from southern Brazil. Marine and Fishery Sciences, 38(3). https://doi.org/10.47193/mafis.3832025010701

Abstract
The daily growth of 73 juvenile Argentine anchovies (Engraulis anchoita) with total lengths ranging from 37 to 86 mm collected in the southern Brazilian shelf during four research cruises in 2010 and 2011 was studied by counting and measuring daily increments in their sagittal otoliths. The mean somatic growth rate in length ranged from 0.20 mm day-1 to 0.57 mm day-1. Back-calculated lengths at age in days were best fitted by the power model L(t) = 1.89 t0.70 (R2 = 0.96). The growth showed a close relationship with metamorphosis, as observed in other species of the Genus Engraulis. When comparing growth results with other individuals of the same species from the Argentine shelf, some differences in growth pattern were noticed, which could be attributed to seasonality or the fact that they may constitute different stocks. All specimens hatched between February and August, mainly in June and July, coinciding with a period of high chlorophyll-a concentration in the study area. By applying a mixed general linear model, a slightly higher growth was detected during the first days of life in individuals hatched in April (0.51 mm day-1 ± 0.013) than in those born in July (0.48 mm day-1 ± 0.012), which could probably be attributable to thermal influence. The specimens of E. anchoita in this study would not have benefited from a rapid growth during the larval stages to ensure survival to the juvenile stage.