The seafood industry of Saint Pierre and Miquelon (SPM) was severely impacted by the collapse of the Eastern Canadian cod fishery, which led to the 1992 moratorium. This underscored the need for diversification strategies to sustain the local economy. Scallop aquaculture (Placopecten magellanicus) has since been developed on a limited scale, but spatial expansion is required to ensure long-term economic viability. In 2008, a comprehensive research and development programme was launched to address this need. This study focuses on the critical stage of site selection, applying a GIS-based multi-criteria approach to identify suitable areas for on-bottom scallop aquaculture. Acoustic and video surveys, combined with ground-truthing, produced the first large-scale seabed habitat maps of eastern SPM. These maps also provide a geospatial database to support coastal zone management and decision-making in the archipelago. The results identified 8335 ha suitable for aquaculture, subdivided into areas for public stock enhancement and leasing grounds for private operations. Suitable areas are not a limiting factor for expansion, and a 2724-ha zone was identified as the most appropriate for leasing, supporting a potential annual production of ~100 t, based on existing equipment and a current five-year rearing cycle at 4 ind. m–². Habitat characterization also enables optimal matching of dredge types (New Bedford vs toothed crossbar) to seabed conditions, minimizing future benthic impacts. Management recommendations and research priorities are discussed, with particular emphasis on addressing the availability of juveniles for seeding. Large-scale development is constrained by juvenile supply, necessitating optimization of spat collection and/or hatchery production. These findings lay the foundation for a strategic aquaculture growth plan, positioning scallop farming as a key contributor to the long-term economic resilience of the SPM archipelago alongside traditional fisheries.
Tag recoveries from a more than 40-year tagging programme of loggerhead turtles nesting at the three major nesting areas of Greece (Zakynthos, Kyparissia Bay, Rethymno) revealed their post-nesting whereabouts in the Mediterranean. Most tag recoveries, signalling potential foraging areas, occurred in the Central Mediterranean, with major concentrations in the Adriatic Sea and the Tunisian Plateau (both characterized by shallow waters and rich benthic fauna), whereas fewer recoveries were recorded in the Aegean Sea. While turtles from Zakynthos and Kyparissia Bay shared the Adriatic Sea and the Tunisian Plateau, turtles from Rethymno (Crete) preferred the Aegean Sea and the Levantine Sea. Tag recoveries showed a much wider dispersal of post-nesting turtles than the dispersal recorded from satellite telemetry, highlighting the benefits of long-term tagging programmes. More than 60% of the recovered turtles were reported dead, indicating the substantial threats that reproductively active individuals, the most biologically valuable group in the loggerhead population, face in the Mediterranean Sea.
Myliobatis chilensis, commonly known as the Chilean eagle ray, is a benthopelagic species found along the Humboldt Current. Peruvian fisheries target it, but little is known about its life history. This study aimed to gather information on the reproductive biology of M. chilensis from Salaverry. A total of 160 individuals from monthly landings between October 2017 and November 2018 were analysed, with data collected on sex, disc width (DW), clasper calcification, weight, liver and gonads. Sexual maturity was determined by comparing clasper length and clasper calcification in males and by gonadal structure in females. Eighty male individuals (41–153 cm DW) and 80 female individuals (42–221.6 cm DW) were obtained, yielding a sex ratio of 1F:1M. The average ovarian fertility was 32 oocytes, and the median size at sexual maturity was estimated to be 163 cm DW for females and 122 cm DW for males. Histological samples were processed by inclusion in paraplast and stained with haematoxylin and eosin for corroboration. Five stages of ovum development and 11 stages of spermatozoan development were observed. Based on these microstructural observations, a maturity scale with easily distinguishable stages was constructed. The study found that gonads are the sole indicators of maturity in females, while claspers serve as excellent indicators in males. Only mature ovaries were sampled from the second half of each year, and no embryos were found. These reproductive insights are expected to assist in decision-making for sustainable management.
The spiny lobster, Palinurus elephas (Fabricius 1787) is both a key economic resource and a coastal marine species of conservation concern in the Mediterranean Sea, primarily due to overfishing. To enhance biological understanding and support the integration of fisheries management with conservation efforts, a genetic study was conducted on populations around Corsica (France, Mediterranean Sea). A total of 85 individuals were collected from five sampling sites around the island, in collaboration with local fishermen’s associations. These individuals were genotyped at 21 microsatellite loci. An additional 15 specimens from the Atlantic coast (Brittany, France) were included as an outgroup. Genetic analyses revealed low levels of differentiation among Corsican samples, with no evidence of geographic genetic structuring or isolation by distance around the island. Unexpectedly, the Atlantic population showed no pronounced genetic divergence from the Mediterranean populations. However, a significant overall deviation from panmixia was detected. Variation partitioning of redundancy analyses suggest that this pattern is likely driven by irregular annual recruitment events originating from multiple breeding aggregations, resulting in subtle genetic differentiation among locations and year classes.
This study investigates the reproductive biology and growth of Notacanthus bonaparte based on 158 specimens collected in October 2023 from the Porcupine area, NE Atlantic. The specimens measured between 172 and 495 mm total length. Sagitta otoliths were extracted, photographed, measured and sectioned, revealing age estimates ranging from 4 to 20 years. The growth rate coefficient (k) was calculated as 0.05±0.02 (1 year–1). Gonads were dissected and analysed histologically, confirming that Notacanthus bonaparte in the NE Atlantic is an iteroparous species with group-synchronous oocyte development. Length at maturity (L50) was estimated to be 280 mm of total length for both sexes combined. The parameters of the length-weight equation were a=15.15 and b=3.32, indicating positive allometric growth. This study offers new insights into the life history of Notacanthus bonaparte and provides valuable information on the population dynamics of this deep-sea species.
A wide variety of species use coastal habitats at some or all stages of their life cycle. These habitats are recognized as nurseries for many species. During their early life stages, most commercially exploited species rely on shallow coastal wa-ters, which are heavily affected by anthropogenic influences. This study focuses on characterizing the habitats of juvenile fish of the main commercial species in the Ártabro Gulf (northwest Spain), through the analysis of trawl survey data collected on soft-bottom substrates between 2017 and 2024. We used generalized additive models to quantify the influence of environmental variables (exposure, type of substrate, bottom depth, zone and season) on the abundance of five ecologically and commercially important benthic species in their juvenile stage. Our results identified the Ares-Betanzos zone as the primary nursery ground due to its sheltered conditions, which resulted in the highest juvenile densities. Exposure and depth were found to be the most important determining factors: sheltered areas had densities eight times higher than exposed sites, and maximum abundance was recorded at depths of 30–40 m. Among the species analysed, the spider crab and solenette showed a preference for shallow waters (less than 20 m deep), while the scaldfish preferred muddy sediments. These findings provide a scientific basis for establishing conservation measures, such as seasonal fishing closures or the designation of marine protected areas in shallow waters. This will ensure the sustainability of the region’s fishery resources.
The ispi (Orestias ispi) is one of the species targeted by artisanal fishing in Lake Titicaca. The aim of this study was to understand the most important aspects of ispi biology and fishing, to offer an evaluation of its population situation and degree of exploitation, and to contribute to fisheries management. Information on official fish landings from the Ministry of Production and Puno Regional Production Directorate (1981–2021) and capture, effort and biological data from the Peruvian Sea Institute (2008–2021) were used. Fish landings show an established pattern, with values below 1500 t/year and a biomass of 42336 t for 2021. The size structure was 3.5 a 9.5 cm total length (TL) and the mean size range was 6.1 to 7.1 cm TL, show-ing a non-significant negative trend in relation to the minimum catch size. Growth parameters showed a maximum asymptotic length (Linf) of 9.76 cm TL and a growth rate (K) of 1.01 year-1. The gonadosomatic index showed greater intensity of repro-ductive activity between July and October, and the size at maturity (LM50%) was 5.2 cm TL. Simulations carried out with the method based on catch maximum sustainable yield indicate that the ispi is at the full exploitation level.
Reproductive biology plays a key role in fish population dynamics and sustainable fisheries management. Howev-er, detailed reproductive data remain particularly scarce for many species of low commercial interest. This study investigates the biology and reproductive strategies of two sole species (Pegusa lascaris and Buglossidium luteum) in the Ártabro Gulf, NW Iberian Peninsula. Sampling was conducted quarterly between 2017 and 2024, and 203 bottom trawl hauls were taken at 13 stations (10–50 m depth). All specimens were measured for length and weight, and sex and maturity stage were recorded macroscopically. Both species showed hyperallometric growth patterns, with females dominating at larger sizes. The spawn-ing period for P. lascaris occurred from May to September, whereas that of B. luteum occurred between March and August. Size at maturity analysis (L50) revealed that P. lascaris matured at 133.6 mm and B. luteum at 80.7 mm. Gonad samples were processed histologically to confirm maturity stages and assess oocyte development. Histological examination confirmed that both species are batch spawners with asynchronous oocyte development. These results will enhance current knowledge of the biology and reproductive strategies of the two species and will significantly improve the input into the stock assessment process, particularly for P. lascaris.
Accurate classification of gonadal maturity stages is essential to ensure reliable estimates of reproductive indicators. In Peruvian anchovy (Engraulis ringens), two gonadal maturity scales have been used: the empirical scale proposed by Einarsson et al. (1966) and the histologically validated scale developed by Buitrón et al. (2015). The adoption of this scale underscores the need to harmonize or retrospectively adjust historical maturity records, which is essential for analysing long-term changes in anchovy reproductive dynamics. In this study, we evaluate the efficacy of the gonadosomatic index (GSI) in predicting stages and groups of gonadal maturity. Data from 115 research surveys conducted between 1984 and 2022 were analysed. Classification models using different algorithms were applied, with the random forest algorithm demonstrating the highest accuracy and robustness, achieving a mean accuracy of >90% and a logarithmic loss of 0.13. GSI and total length were identified as the most influential predictors of gonadal maturity. The classification of historical data (1984–2014) using the M-5 model (which includes GSI, total length, latitude, distance from the coast and condition factor) demonstrated high concordance with the reproductive patterns observed in recent periods (2015-2022), supporting its predictive reliability. The results indicate that the combined use of GSI and machine learning-based classification models is a valuable tool for identifying gonadal maturity stages from historical data and harmonizing them with the current maturity scale, facilitating the interpretation of variations in the reproductive behaviour of the resource over time.
Accurate fish stock evaluation requires proper identification of population structure, for which reproductive ecology studies are essential. This study examines blue whiting (Micromesistius poutassou), a widely distributed mesopelagic gadoid managed as a single stock in the Northeast Atlantic, despite ongoing debate about the existence of distinct spawning components. To investigate potential differentiation, we compared reproductive parameters between two regions: the Porcupine area in southwest Ireland (ICES division 27.7.c,k,h,j) and the Peninsula area off the northern Iberian Peninsula (ICES division 27.8.c-9.a.N). Using biological data from 2018 surveys of the Spanish Institute of Oceanography and commercial vessels, we analysed somatic attributes (length, weight and condition) and assessed the species’ reproductive strategy. We also examined interannual variation in Peninsular females’ somatic features, total and batch fecundity, and geographic variation in fecundity and spawning frequency in February–March. Blue whiting was confirmed as a capital breeder, spawning from February to April. Iberian individuals exhibited smaller sizes and lower condition but higher fecundity (mean potential and batch fecundity: 46.817 vs. 12.223 oocytes, 16.808 vs. 6.112 hydrated oocytes), releasing three batches per season at 11-day intervals, compared with one every ~15 days at Porcupine. These findings suggest a distinct southern component, reinforcing the relevance of reproductive studies for stock assessment and management.
The red pandora (Pagellus bellottii) is a coastal demersal species of great social and economic importance in West African fisheries. Increasing fishing pressure and environmental variability threaten the sustainability of its exploitation, highlighting the need for updated biological and reproductive data to inform management strategies. This paper examines weight-related and reproductive parameters of P. bellottii in Côte d’Ivoire and Ghana from 2745 individuals sampled monthly between October 2019 and March 2021 (10–32.5 cm total length). The length-weight relationship, condition factor (K), sex ratio (M:F), gonadosomatic index (GSI), reproduction period and length at first maturity of females (L50) were determined. Males predominated in both countries (1:0.6 in Côte d’Ivoire, 1:0.8 in Ghana). The presence of mature females most of the year suggests continuous reproduction. However, monthly variations in GSI and in the proportion of mature females revealed two reproductive peaks: a main one between May and August/September, and a secondary one between December and February, likely associated with coastal upwelling. An inverse pattern between K and GSI was observed, reflecting energy allocation to gonadal development. The estimated female L50 in both countries was 17.8 cm. These findings, ideally complemented by longer study periods, provide essential data for science-based fisheries management and stock assessment.
Southern right whales migrate seasonally between breeding and feeding grounds, and the southern coast of Brazil is one of their key breeding areas in the Atlantic Ocean. Recent observations suggest a notable decline in whale occurrences in this region since 2015. Since 2015, the occurrence and abundance patterns of right whales in Brazil have changed. To better understand past habitat use and establish a baseline for comparing future distribution trends, we modelled whale distribution using data from aerial surveys conducted between 2003 and 2012, covering the area from Palhoça, Santa Caterina to Torres, Rio Grande do Sul, Brazil. Generalized additive models were employed to assess the influence of environmental and spatio-temporal variables on whale distribution. Our results revealed that whale abundance follows a four-year cycle, which differs from the established three-year reproductive cycle. Higher whale numbers were observed in shallow areas (<10 metres deep) with gentle slopes and near river mouths. The Ribanceira/Ibiraquera region exhibits the highest concentration of whales. These findings provide critical insights into historical habitat preferences and serve as a valuable reference point for evaluating ongoing and future changes in the species’ spatial distribution along the Brazilian coast, thereby supporting the development of targeted conservation strategies and more effective management plans for southern right whales in the region.
The global climate has undergone substantial palaeoclimatic changes, such as the rhythmicity between glacial and interglacial periods, during the last three million years. These changes imply the existence of major variations in the latitudinal distribution of heat, with a changing Atlantic meridional overturning circulation (AMOC) likely playing a major role in the Earth’s shift between different climatic states. The anthropogenic-driven warming and melting of the subpolar North Atlantic is now turning its surface waters more buoyant, opening the possibility of an AMOC breakdown that could drive the Earth towards a new state. The debate remains open: available instrumental data tell us that the AMOC has remained fairly stable during the last two decades, while global coupled climate models predict a moderate weakening during this century. Additionally, complex-theory statistics of some regional ocean indexes, assumed to be fingerprints of the AMOC’s intensity, suggest that the AMOC may be approaching a tipping point leading to collapse in the coming decades. Furthermore, the Earth’s growing radiative energy imbalance, caused primarily by the increase in atmospheric greenhouse gases, causes a huge amount of energy to be stored in the ocean, which will be distributed and released in yet unknown manners that will likely affect the AMOC. Though the available in situ data are robust, the diversity of analyses warns us that transitions may take place faster than projected by numerical models, emphasizing the urgent need to reduce pressures that risk undermining the climate system and the well-being of future generations.
Many shark species face serious threats that have generally led to a collapse in their numbers at a global scale. The blue shark (Prionace glauca) is one of the most by-caught large shark species in the Mediterranean Sea, where it has been classified as critically endangered. Despite the status of the species in this sea, little is known about its breeding areas. Here, we provide evidence that the Cape of Creus marine canyon and its surrounding areas are a blue shark mating, birthing and nursery area. We carried out a total of 170 chumming pelagic surveys from April to October in 2022, 2023 and 2024, with a total sampling effort of 933 h. In those surveys, we carried out 213 blue shark observations, including young of the year (n=10), some of them newborns, and adults (n=25), one of them a pregnant female. The encounter rate of blue sharks during periods of high adult and newborn presence was estimated at 0.42 individuals per hour, showing a significant seasonal concentration in this area. The peak presence of adults occurred between June and July, while that of newborns was observed in late June, overlapping with the peak of adults. We also registered two young of the year near the head of the Begur/La Fonera submarine canyon. A significant number of juveniles were also found in the study area, showing that this zone is also crucial for them. We conclude that the Cape of Creus, Lacaze-Duthiers and Begur/La Fonera submarine canyons are important areas for conservation of the blue shark in the western Mediterranean Sea and therefore emphasize the need for effective management and conservation strategies.
Marine ecosystems can undergo abrupt changes due to the interaction between human activities and environmental drivers. These changes can result in a non-linear response, causing the system to shift to a different state, known as a regime shift. Such shifts imply changes in the structure, dynamics and functioning of ecosystems, ultimately impacting on the services they provide to humans. Additionally, such abrupt changes can have serious implications for the effectiveness of management measures, hindering the sustainable exploitation of marine resources and affecting their overall well-being. In our study, we adopted a multi-method approach to test for abrupt changes in Adriatic Sea fishery landings over five decades (1970–2020) and their potential connection with climate change. The ensemble of statistical changepoint analyses applied here identified that the fish community experienced an instability period during the 1990s under the influence of a changing climate, as indicated by significant correlations between fish landings and climate indices. Our study reveals important insights into the development of Adriatic Sea fishery landings under climate change and provides important knowledge for decision-making, sustainable fishery management and preserving the biodiversity and economic viability of the fishery.
The large-scaled gurnard, Lepidotrigla cavillone, is one of the most abundant Triglidae fish in the Mediterranean Sea. We studied its main life-history traits in the Balearic Islands. Samples were obtained monthly from the bottom trawl fleet and from oceanographic surveys delivered in spring-summer. Overall, 833 specimens were sampled, ranging from 4.3 to 15.3 cm total length, and a female-male ratio of 1:0.81. Length-weight relationships showed no differences between sexes and a positive allometric growth, using both total and eviscerated weight. The estimated age of the individuals ranged from 0 to 4 years. Females mature at a smaller length (L50=9.1 cm) than males (L50=10.2 cm). The spawning season runs from April to August, with annual realized fecundity of 16000-47000 oocytes per female. The seasonal variation of condition indices showed that food intake supported liver reserves during vitellogenesis, whereas muscle reserves were depleted during spawning, indicating a mixed income-capital breeder strategy. Diet analysis indicated generalist feeding habits, based on epi-and suprabenthic small-sized crustaceans, resulting in a trophic level of 3.35. In the Balearic Islands, the large-scaled gurnard inhabits up to 250 m depth, showing its highest abundances on sandy-muddy bottoms between 120 and 180 m.
This study examined the reproductive biology of Acanthurus chirurgus through monthly collections from May 2016 to May 2018. A total of 505 specimens (317 males, 188 females) were analysed, with males having a larger total length than females (32.0 cm vs. 30.8 cm). The highest frequency of individuals was in the 23–25 cm size range. Reproduction occurred from January to July, with peak spawning in February, March and June. The first (L50) and maximum (L99) maturation sizes were 18.0 and 22.1 cm, respectively. Spawning was synchronous, occurring in batches and following an indeterminate fecundity pattern. Spawning frequency was estimated at every 4.2 days (hydrated oocytes) and 3.5 days (post-ovulatory follicles). Batch fecundity ranged from 15403.9 to 48030.9 oocytes, and relative batch fecundity from 2710628.5 to 16842518.6 oocytes. Due to the long reproductive period, recommendations include catch quotas, a closed season (February, March and June) and an 18 cm minimum size.
