Eastern Central Atlantic Research Articles

Reproductive biology of wahoo (Acanthocybium solandri) in the Canary Islands (eastern-central Atlantic)

The reproductive status of wahoo (Acanthocybium solandri) in the eastern-central Atlantic was investigated to better understand their migration and breeding patterns. The waters around the Canary Islands are considered a breeding area for wahoo; and this study documents the first described breeding activity found in the eastern Atlantic. The presence of many mature and spawning capable wahoo reported in this study confirms its spawning activity in this region. Off the Canary Islands, only mature individuals spawn in the region where no immature individuals were observed to date. Most of the specimens captured in Canary Islands waters exceed 100 cm TL (about 2 years old). Values of the gonadosomatic index (GSI) of males were much lower than those estimated for females. Testes showed little changes in size throughout gametogenesis, while ovaries increased significantly (p<0.05). The low values make it inadvisable to use GSI in males to determine spawning activity. In the Canary Islands, wahoo females spawn (fishes with tertiary vitellogenic oocytes, postovulatory follicles or germinal vesicle migration, yolk coalescence, germinal vesicle breakdown and hydrated oocyte) mainly during a 4-month period in summer. Both females of spawning capable outside the main summer breeding period and females in regressing phase during the spawning period have been observed in the Canary Islands. Males were found in the spawning capable phase throughout the year, with greater prevalence between May and October.

The Mechanical Nature of the Lithosphere Beneath the Eastern Central Atlantic Hotspots

AbstractThe Eastern Central Atlantic (ECA) region includes the Azores, Canary, Cape Verde, Great Meteor, and Madeira hotspots. These hotspots exhibit a large variety of characteristics and are rooted in the lithosphere ranging in age from newly created at the Mid Atlantic Ridge to Jurassic at the NW Africa Atlantic margin. Therefore, the ECA region represents an excellent scenario to investigate in an integrated way the effects of hotspots on the mechanical structure of oceanic lithosphere. Here, we calculate the effective elastic thickness (Te) of the lithosphere from an analysis of gravity and topography. Azores hotspot is characterized by a Te &lt; 10 km, whereas the Great Meteor, Cape Verde, and Madeira hotspots have intermediate Te (15–30 km) values. In contrast, the Canary hotspot is characterized by a much higher Te (&gt;50 km), forming the largest and most prominent mechanical feature in the ECA. All the hotspots except Canary show standard elastic thickness values when compared to average values for the same age lithosphere and to other oceanic areas in the world. The high strength of the Canary hotspot may be related to the highly depleted mantle composition in the area. The comparison between the elastic thickness distribution and the upper mantle seismic velocity structure shows no correlation between the Te estimated at the ECA hotspots (with the exception of Azores) and the presence of low shear‐wave velocity anomalies in the underlying mantle. This lack of correlation suggests a negligible effect of upper mantle temperature anomalies on the flexure of the ECA region.

Heavy-metals accumulation in five demersal marine species from Nigerian coastal waters (Eastern Central Atlantic, FAO Area 34)

The study was conducted on heavy-metals accumulation in five demersal marine species from the Nigerian coastal water (FAO, Area 34) to ascertain the bio-integrity and safety of the Sea foods for export. Five hundred and six (506) specimens (Parapenaeopsis atlantica, Penaeus monodon, Penaeus notialis, Portunus validus and Cynoglossus browni). were sampled from 32 fishing trawlers owned by a reputable private company and assessed fresh for biological (morphometric data) and heavy metals analysis (In-vivo) using 210 Atomic Absorption Spectrophotometer (AAS). Study revealed the Mean weight (Mean±SD) of P. atlantica, P. monodon, P. notialis, P. validus and C. browni were: 9.42 ±0.26, 96.79 ± 2.38, 26.82 ± 1.34, 284.09 ± 7.34 and 411.09 ± 15.27g respectively. Heavy-metal accumulated in the muscles (mg/kg) showed Lead (Pb): 0.15 ± 0.05 for P. atlantica; 0.12 ± 0.06 for P. monodon; 0.15 ± 0.02 for P. notialis; 0.14 ± 0.07 for C. browni; and 0.14 ± 0.08 for P. validus. Iron (Fe) revealed: 2.7 ±0.07, 2.26 ± 0.06, 2.32 ± 0.08, 2.43 ± 0.12, and 2.42 ± 0.09 respectively. Zinc (Zn) also showed: 8.68 ± 0.12, 8.97 ± 0.14, 9.13 ± 0.12, 8.99 ± 0.11 and 8.86 ± 0.08 respectively. Zn and Fe value for P. atlantica were above acceptable limit by FAO/WHO standard. The decreasing order of mean concentrations was Zn&gt;Fe&gt;Pb. Arsenic (As) and Cadmium (Cd) had values of &lt;0.01 for all the species. This report concludes that Mercury (Hg) was not detected throughout the study for all the species. But the detection of lead, iron and zinc in the muscles of species under study cast grey light on the integrity and safety of the fish species and thus relevant agencies are required to respond to reduce this trend for the safety of humans.

Using Cumulative Impact Mapping to Prioritize Marine Conservation Efforts in Equatorial Guinea

Marine biodiversity is under extreme pressure from anthropogenic activity globally, leading to calls to protect at least 10% of the world’s oceans within marine protected areas (MPAs) and other effective area-based conservation measures by 2020. Fulfilling such commitments, however, requires a detailed understanding of the distribution of potentially detrimental human activities, and their predicted impacts. One such approach that is being increasingly used to strengthen our understanding of human impacts is cumulative impact mapping; as it can help identify economic sectors with the greatest potential impact on species and ecosystems in order to prioritise conservation management strategies, providing clear direction for intervention. In this paper, we present the first local cumulative utilisation impact mapping exercise for the Bioko-Corisco-Continental area of Equatorial Guinea’s Exclusive Economic Zone – situated in the Gulf of Guinea one of the most important and least studied marine regions in the Eastern Central Atlantic. This study examines the potential impact of ten direct anthropogenic activities on a suite of key marine megafauna species and reveals that the most suitable habitats for these species, located on the continental shelf, are subject to the highest threat scores. However, in some coastal areas, the persistence of highly suitable habitat subject to lower threat scores suggests that there are still several strategic areas that are less impacted by human activity that may be suitable sites for protected area expansion. Highlighting both the areas with potentially the highest impact, and those with lower impact levels, as well as particularly damaging activities can inform the direction of future conservation initiatives in the region.

More than fifteen years of collaboration on the assessment of small pelagic fish off Northwest Africa: Lessons learned and future perspectives

Ensuring the sustainable use of the small pelagic fish stocks and the sustainable management of the fisheries exploiting them is a significant challenge faced by countries in Northwest Africa. Small pelagic fish constitute the bulk of the landings in this region, with annual catches of the main species ranging from approximately 1.7 to 2.5 million tonnes over the last few decades. Many of the main pelagic stocks are distributed across the 200 nautical-mile boundaries of the sub-region, and are shared bilaterally or sub-regionally among countries of Western Africa. These resources, which migrate along the Northwest African coast, are exploited by local fleets of both the artisanal and industrial sectors, as well as distant water fishing vessels from Europe, Asia, and Central America. The transboundary nature of these fish stocks calls for joint action with respect to their monitoring and management. In 2001, the Food and Agriculture Organization of the United Nations created a permanent working group on the assessment of small pelagic fish off Northwest Africa, which today reports to the Fishery Committee for the Eastern Central Atlantic. As a result of this Working Group's efforts, more consistent series of catch and effort and annual abundance indices of the main small pelagic fish species are now available, and significant improvements in sampling intensity have been achieved. Furthermore, consolidated annual advice is provided at a regional scale on the state of these resources that complements the national assessment and management advice systems. This paper provides some reflections on the contributions of the Working Group to science-based fisheries management and possible future actions that could further strengthen the collaborative momentum gained through this type of regional collaboration.

Analysis of Main Arsenic Species in Canned Fish Marketed in the Czech Republic and Austria

Total arsenic and water-soluble arsenic species were determined in canned fish bought in Graz (n = 6) and Prague (n = 8) with inductively-coupled plasma mass spectrometry and anion-exchange liquid chromatography. A difference in total arsenic content between samples from Prague (mean 3.4; standard deviation (s.d.) 1.2 mg kg–1) and Graz (mean 2.5; s.d. 0.7 mg kg–1) was not significant, however Prague samples differed in abundance of arsenobetaine (mean 83% of extractable arsenic; s.d. 16%) vs. Graz samples (mean 66%; s.d. 10%). No differences in total arsenic were caused by fish species (mackerel, sardine, herring, tuna) and origin (Northeast and Eastern-central Atlantic).

Особенности использования индексов пополнения в прогнозировании динамики запаса скумбрии Центрально-Восточной Атлантики

Особенности использования индексов пополнения в прогнозировании динамики запаса скумбрии Центрально-Восточной Атлантики

Taxonomic and morphological revision of butterfly rays of the Gymnura micrura (Bloch & Schneider 1801) species complex, with the description of two new species (Myliobatiformes: Gymnuridae).

An extensive taxonomic revision of Gymnura micrura based on external and internal morphology, and considering specimens from its entire geographical distribution in the Atlantic Ocean, is presented. Gymnura micrura is redescribed and a neotype is designated; its distributional range is limited to the Southwestern Atlantic. Two new species of butterfly rays are described: Gymnura lessae, sp. nov., occurring in the North and Central Western Atlantic, and Gymnura sereti, sp. nov., found in the Eastern Central Atlantic. The three species are morphologically very similar (with G. micrura most similar to G. lessae, sp. nov.) and cannot be distinguished based on the primary diagnostic characters typically utilized for butterfly rays. The dorsal color, smaller size and eventual presence of a dorsal fin in some males may be helpful to distinguish G. micrura, whereas the size and morphology of the clasper are the main external characters separating G. sereti, sp. nov., from the other two species, although the shape of disc (especially among adult males) and contour of the lower lip are also helpful. Despite the skeleton being conservative among the species, we found consistent variations that support the validity of the new species described. Due to similarity in external morphology these internal characters were fundamental to discriminate the new species. The scapulocoracoid was an important diagnostic skeletal structure, exhibiting a series of variations that separated the three species. Variations in the synarcual, outline of the dorsal cranial fontanelle, number and shape of mesopterygia, and small differences in the mandibular arches and pelvic girdle were useful to diagnose G. sereti, sp. nov. The contour of the hyomandibula was an important diagnostic character distinguishing G. lessae, sp. nov., from the other two species. Meristic data were also useful, with G. sereti, sp. nov., presenting a lower number of radials in the second element of the mesopterygium and a higher number of diplospondylous vertebrae. In contrast, G. lessae, sp. nov., presented a higher number of pectoral-fin radials. Subtle, but consistent differences, were also found in the design of the ventral lateral-line system. A Canonical Discriminant Analysis provides strong statistical support for the validity of the new species, significantly distinguishing the three species groupings (p < 0.00001). External morphology, ventral lateral-line system and skeleton are described and illustrated for all three valid species.

The status of marine biodiversity in the Eastern Central Atlantic (West and Central Africa)

Abstract The status of marine biodiversity in the Eastern Central Atlantic (ECA), especially of coastal and pelagic fishes, is of concern owing to a number of threats including overharvesting, habitat loss, pollution, and climate change combined with inadequate policy responses, legislation, and enforcement. This study provides the first comprehensive documentation of the presence, status, and level of extinction risk, based on IUCN Red List assessment methodology, for more than 1800 marine species, including all taxonomically described marine vertebrates (marine mammals, sea turtles, seabirds, fishes); complete clades of selected marine invertebrates (sea cucumbers, cone snails, cephalopods, lobsters, reef‐building corals); and marine plants (mangroves, seagrasses). Approximately 8% of all marine species assessed in the ECA are in threatened categories, while 4% are listed as Near Threatened, 73% are Least Concern, and 15% are Data Deficient. Fisheries and overharvesting are the biggest threats to living marine resources in the ECA, with 87% of threatened species across all taxonomic groups affected by both large‐ and small‐scale targeted fisheries, excessive capture as by‐catch, or unsustainable harvest. The results of this study will transform the current state of knowledge and increase capacity for regional stakeholders to identify and enact marine conservation and research priorities, as a number of species are identified as having high conservation and/or research priorities in the region. Through the process of marine species data collection and risk assessments conducted over the past 5 years, several key conservation actions and research needs are identified to enable more effective conservation of marine biodiversity in the ECA, including increased governance, multilateral collaboration, taxonomic training, and improved reporting of fisheries catch and effort.

Deep-sea fishes from Senghor Seamount and the adjacent abyssal plain (Eastern Central Atlantic)

Senghor Seamount is an important fishing ground around the Cape Verde archipelago in the Eastern Central Atlantic. On an experimental field survey in October 2009 and December 2011, a total of 115 deep-sea fishes of 26 species belonging to 18 families were caught on the seamount summit, along the slopes and on the adjacent abyssal plane, using longlines, fish traps, beam trawl and otter trawl. Here we report seven new records for the Cape Verde deep-sea fish fauna. Most species are known from other areas of the Atlantic Ocean, but our findings are an important contribution to our understanding of the distribution of deep-water fish species. The co-occurrence of northern and southern Atlantic ichthyofauna components at Senghor Seamount, and the Cape Verde area in general, can be attributed to the large-scale hydrographic regime with two water masses merging at the Cape Verde Frontal Zone, the North Atlantic Central Water and the South Atlantic Central Water.

Human exposure in Italy to lead, cadmium and mercury through fish and seafood product consumption from Eastern Central Atlantic Fishing Area

The presence of cadmium (Cd), lead (Pb) and mercury (Hg) was investigated in fish and seafood products collected from the FAO Major Fishing Area 34, Eastern Central Atlantic. Samples were purchased from different retail outlets in Italy. Samples were selected so as to assess human exposure through diet. Metals were detected by Q-ICP-MS and Hg-AAS. All the metal concentrations detected were largely below the maximum levels (MLs) established by the European Union. The exposure assessment was undertaken by matching the concentration of Cd, Pb and total Hg in fish and other seafood products selected purposed according to Italian consumption data. The estimated weekly intakes (EWIs) for the evaluated elements related to the consumption of fish and other seafood products by the median of the Italian total population accounted for 14%, 2% and 14% of the standard tolerable weekly intake (TWI) for Cd and Hg as well as the provisional tolerable weekly intake (PTWI) for Pb, respectively.

Octopus lipid and vitamin E composition: interspecies, interorigin, and nutritional variability.

Octopus vulgaris, Octopus maya, and Eledone cirrhosa from distinct marine environments [Northeast Atlantic (NEA), Northwest Atlantic (NWA), Eastern Central Atlantic, Western Central Atlantic (WCA), Pacific Ocean, and Mediterranean Sea] were characterized regarding their lipid and vitamin E composition. These species are those commercially more relevant worldwide. Significant interspecies and interorigin differences were observed. Unsaturated fatty acids account for more than 65% of total fatty acids, mostly ω-3 PUFA due to docosahexaenoic (18.4-29.3%) and eicosapentanoic acid (11.4-23.9%) contributions. The highest ω-3 PUFA amounts and ω-3/ω-6 ratios were quantified in the heaviest specimens, O. vulgaris from NWA, with high market price, and simultaneously in the lowest graded samples, E. cirrhosa from NEA, of reduced dimensions. Although having the highest cholesterol contents, E. cirrhosa from NEA and O. maya from WCA have also higher protective fatty acid indexes. Chemometric discrimination allowed clustering the selected species and several origins based on lipid and vitamin E profiles.

Description of Alpheus cedrici sp. n., a strikingly coloured snapping shrimp (Crustacea, Decapoda, Alpheidae) from Ascension Island, central Atlantic Ocean

Alpheus cedrici sp. n. is described based on two specimens collected under rocks while scuba diving off the coast of Ascension Island, central Atlantic Ocean. The new species belongs to the Alpheus macrocheles (Hailstone, 1835) species complex and appears to be most closely related to the eastern–central Atlantic Alpheus macrocheles, the western Atlantic Alpheus amblyonyx Chace, 1972, and the eastern Pacific Alpheus bellimanus Lockington, 1877 and Alpheus rectus Kim & Abele, 1988. However, it differs from all these species by a combination of morphological characters and by a diagnostic and striking colour pattern.

Validation of age determination methods and growth studies of the sand sole Pegusa lascaris (Soleidae) from the eastern-central Atlantic

The age and growth of the sand sole Pegusa lascaris from the Canarian Archipelago were studied from 2107 fish collected between January 2005 and December 2007. To find an appropriate method for age determination, sagittal otoliths were observed by surface-reading and frontal section and the results were compared. The two methods did not differ significantly in estimated age but the surface-reading method is superior in terms of cost and time efficiency. The sand sole has a moderate life span, with ages up to 10 years recorded. Individuals grow quickly in their first two years, attaining approximately 48% of their maximum standard length; after the second year, their growth rate drops rapidly as energy is diverted to reproduction. Males and females show dimorphism in growth, with females reaching a slightly greater length and age than males. Von Bertalanffy, seasonalized von Bertalanfy, Gompertz, and Schnute growth models were fitted to length-at-age data. Akaike weights for the seasonalized von Bertalanffy growth model indicated that the probability of choosing the correct model from the group of models used was &gt;0.999 for males and females. The seasonalized von Bertalanffy growth parameters estimated were: L∞ = 309 mm standard length, k = 0.166 yr–1, t0 = –1.88 yr, C = 0.347, and ts = 0.578 for males; and L∞ = 318 mm standard length, k = 0.164 yr–1, t0 = –1.653 yr, C = 0.820, and ts = 0.691 for females. Fish standard length and otolith radius are closely correlated (R2 = 0.902). The relation between standard length and otolith radius is described by a power function (α = 85.11, v = 0.906).

Reproductive characteristics of the sand sole Pegusa lascaris (Soleidae), from the eastern-central Atlantic

The reproductive biology of 1318 sand sole, Pegusa lascaris, was investigated. This species is a gonochoristic species with no evidence of sexual dimorphism. The overall sex-ratio was 1 male to 0.92 females. Females predominate in the larger size intervals, with a significant difference in mean standard length and range between sexes. Size at first maturity for males and females is attained at 17.2 and 17.7 cm standard length, respectively. Vitellogenesis does not begin synchronously for all females, as a consequence the spawning season appears to be continuous. In each female spawning takes place in two batches which are spawned mainly in spring and autumn, indicating that fish are serial synchronous spawners.

Life history of Plesionika edwardsi (Crustacea, Decapoda, Pandalidae) around the Canary Islands, Eastern Central Atlantic

The life history of Plesionika edwardsi (Brandt, 1851) around the Canary Islands in the Eastern Central Atlantic was investigated, based on a total of 11 434 shrimps ranging in length between 8 and 40 mm carapace length (CL). The species carries out seasonal migrations; they concentrate in deep water during winter, move shallower in summer and return to deep water again in autumn. Ovigerous females occur throughout the year, but a spawning peak was determined between April and September. The size at maturity for females was approximately 26 mm CL. Shrimp size generally increased with increasing water depth. The growth parameters for males were L ∞ = 25.75 mm CL and K = 0.55 year−1, and L ∞ = 28.28 mm CL and K = 0.66·year−1 for females. The species displays the typical reproductive pattern of tropical pandalids and is dioecious.