Abundance and exploitation of loggerhead turtles nesting in Boa Vista Island, Cape Verde: The only substantial rookery in the eastern Atlantic.

[EN] The main nesting area for loggerhead turtles in the eastern Atlantic is in the Cape Verde Islands, largely restricted to the island of Boa Vista. Extensive monitoring demonstrated a globally significant population for the species despite a sustained high level of anthropogenic take of nesting females for local consumption. Through an extensive stratified monitoring program across the island in the seasons 2007-2009, we estimated a total of 13955, 12028 and 19950 clutches in the 3 years, respectively. These values indicate that the mean number of nesting females averaged 3700. Considering that a female breed, on average, every 2.4 years, we estimate that the overall number of adult females in the population during these three seasons was 8900.

Rate predation on the nesting of Caretta caretta because of Ocypode cursor in Calheta de Pau beach, Boa Vista Island (Cape Verde Rep.)

[EN] Located in the Cape Verde Archipelago is one of the most important nesting population of Caretta caretta, Boa Vista Island being the principal nesting area. This population has been subject of research since 1998.

Preliminary approach to the hatchlings sex-ratio of a population of Caretta caretta of Boavista island, Cape Verde Archipielago (Western Africa).

[EN] A nesting population of loggerhead sea turtles Caretta caretta has recently been described for Boa Vista Island, Cape Verde Archipelago (Western Africa). Since 1998, “Projecto Cabo Verde Natura 2000” has monitored three beaches during the turtle breeding season. The beaches being monitored - Calheta, Errata and Ponta Cosme - are located in the southeast part of Boa Vista Island. This work intends to give a first insight into the Boa Vista Island sea turtle population’s sex ratio using a histological approach, as sexual determination in sea turtles is known to be temperature-dependent (TSD or temperature-dependent sex determination).

Density, nest site characteristics and breeding rates of the osprey (Pandion haliaetus) in the southern limit of its range in the Western Palearctic (Boa Vista, Cape Verde Islands).

[EN] Between 2004 and 2007, we studied density, habitat features and breeding parameters of the osprey (Pandion haliaetus) population in Boa Vista Island (Cape Verde). A total of 79 nest structures were identified, 37 of which were occupied for at least 1 year during the study period. The osprey population ranged between 14 and 18 pairs, and the mean density and distance between neighbouring occupied nests were 2.58 pairs per 100 km2 and 3089 m, respectively. Occupied nests were found to be significantly further from the coastline and roads than unoccupied nests, but the distances from villages were similar.

Injuries observed in nesting females of loggerhead turtles on Boavista island (Cabo Verde Archipelago)

[EN] Different kinds of physical anomalies are frequently observed in any sea turtle breeding population. Nesting beaches are an excellent place to study the injuries and defects that occur in adult females. The archipelago of Cape Verde is situated about 500 km of Senegal, West Africa. Boavista is the eastern most island and may constitute the most important nesting area for the loggerhead turtle in the archipelago. The studies conducted from 1998 to 2004 indicate that Cape Verde might account for one of the most important loggerheads populations in the eastern Atlantic. The nesting females in Boavista were surveyed during the 2004 season, in order to (1) know the health status of the population (2) determine the effects of physical anomalies on nesting behaviour and (3) determine the possible origin of the injuries observed.

Injuries observed in nesting females of loggerhead turtles on Boavista island (Cabo Verde Archipelago)

[EN] Different kinds of physical anomalies are frequently observed in any sea turtle breeding population. Nesting beaches are an excellent place to study the injuries and defects that occur in adult females. The archipelago of Cape Verde is situated about 500 km of Senegal, West Africa. Boavista is the eastern most island and may constitute the most important nesting area for the loggerhead turtle in the archipelago. The studies conducted from 1998 to 2004 indicate that Cape Verde might account for one of the most important loggerheads populations in the eastern Atlantic. The nesting females in Boavista were surveyed during the 2004 season, in order to (1) know the health status of the population (2) determine the effects of physical anomalies on nesting behaviour and (3) determine the possible origin of the injuries observed.

Gonad development and hormone titres in Loggerhead Sea Turtles (Caretta caretta) in the NE Atlantic

The study proposed to describe sexual development in pelagic stage loggerhead sea turtles Caretta caretta and compare this to hatchlings and adults. It is meant as an ontogenic approach, in order to understand reproductive development and population composition and their dynamics in the pelagic environment. The study focused on the pelagic loggerheads that are found in the waters offshore Madeira Island (Portugal) in the North-eastern Atlantic and use it as a developmental habitat. The innovating character of this work relied on the lack of any description regarding the gonad ontogenesis and reproductive development for the pelagic stage in any of the 7 existing sea turtle species, all of them in danger of extinction. Three methods were used to diagnose the sex of each juvenile individual and asses the level of reproductive development: (1) laparoscopy, (2) gonad biopsy and (3) the assessment of two sex steroids circulating levels, namely testosterone and estradiol. In order to cover all life stages and compare data obtained for the juvenile stage, hatchlings and nesting female adults were sampled at the nearest nesting rookery at Boa Vista Island in the Cape Verde Archipelago. Gonads from dead hatchlings were collected for gonad histology and blood was collected from nesting females for sex steroids assessment. Laparoscopies revealed to be a valid sexing method for the juvenile stage, since gonads are morphologically differentiated at these size classes. Moreover, laparoscopy was validated using gonad histology. Gonad histology of juveniles showed that gonads are already completely differentiated into ovaries or testes at the size classes examined, but development seems to be quiescent. Males present already developed seminiferous tubules with spermatogonia lining the interior of the seminiferous tubule. Female gonads present oocytes at different development stages, but only oocytes up to stage III were observed. The maximum oocyte diameter in each individual correlated with body size, suggesting that reproductive development is an on-going process in juvenile females. The circulating levels of both testosterone and estradiol in juveniles of both sexes were very low and consistently lower than the ones observed in the nesting females from Boa Vista Island. No bimodal distribution was found for any of the sex steroids analysed and thus circulating hormone levels were not a reliable tool for sexing juvenile individuals with a non-invasive technique. The ratio testosterone:estradiol did not show a bimodal distribution either. The levels of testosterone correlated with sea surface temperature. The fact that temperatures observed during this study were below 24ºC might have hindered a differential testosterone pattern between juvenile males and females. Sex ratios for this population were generated according to laparoscopy results and compared among years and size classes. An overall sex ratio of 2 females for each male was found, but they varied among size classes but not among years. Possible causes for the sex ratios observed are discussed. This study is a contribution to our knowledge on the pelagic stage of loggerhead turtles, namely on the population structure regarding sex ratio, which is a vital tool for implementing conservation strategies.

Biodiversidad Boa Vista. Conocer y proteger

[ES] El proyecto consiste en crear un libro de fotografías artísticamente atractivo y de calidad divulgativa y científica sobre la isla de Boa Vista para dar a conocer y sensibilizar con imágenes, sobre la cultura, la riqueza y fragilidad de este enclave de biodiversidad en Cabo Verde. La idea para su edición es el crowdfunding a través de la plataforma web VERKAMI

Causes of extreme variability of nest density among close and similar beaches of Boavista island (Cape Verde): From 1 to 2000 annual nests per km.

[EN] The 70 km of white sandy beaches of Boa Vista island in Cape Verde harbours one of the largest rookeries of the endangered loggerhead sea turtle, Caretta caretta. From middle June to early October, approximately 2000 to 4000 females lay up to 20000 nests annually. However, female beach selection, nesting success and nest density strongly varies among beaches and spatial patterns of nest abundance and distribution are relatively constant among seasons. The numbers of nesting activities and nests have been recorded along all beaches of the island during four nesting seasons (2007-2010)

Potential adverse health effects of persistent organic pollutants on sea turtles: Evidences from a cross-sectional study on Cape Verde loggerhead sea turtles

[EN] The Cape Verde nesting population of loggerhead sea turtles (Caretta caretta) is the third largest population of this species in the world. For conservation purposes, it is essential to determine how these reptiles respond to different types of anthropogenic contaminants. We evaluated the presence of organochlorine pesticides (OCPs), polychlorinated biphenyls (PCBs), and polycyclic aromatic hydrocarbons (PAHs) in the plasma of adult nesting loggerheads from Boa Vista Island, Cape Verde, and studied the effects of the contaminants on the health status of the turtles using hematological and biochemical parameters. All turtles had detectable levels of non-dioxin like PCBs, whereas dioxin-like congeners (DL-PCBs) were detected in only 30% of the turtles.

Características sedimentológicas de la Playa de Calheta de PAU (Isla de Boa Vista, República de Cabo Verde): implicaciones en la anidación de Caretta caretta (Linnaeus, 1758)

Programa de doctorado en Oceanografía

Incidental Capture of Loggerhead Turtles (Caretta caretta) on Boa Vista (Cape Verde Islands)

[EN] The sea is one of the major natural resources of the Cape Verde Islands, a small archipelago located 500 kilometers off the coast of Senegal (West Africa). This country consists of ten main islands and several islets, and possesses an Exclusive Economical Zone (EEZ) of about 734 square kilometers and a coastal perimeter of nearly 2000 kilometers. The marine shelf, whose limit is the 200 m isobath, is particularly extensive on the island of Boa Vista (Figure 1). lt is likely that most of the loggerhead turtles (Caretta caretta) that breed in this archipelago are concentrated on this island (López-Jurado et al., 1999).

Hidroquímica e qualidade das águas subterrâneas da Ilha de Santiago - Cabo Verde

A ilha de Santiago, Cabo Verde é uma ilha de origem vulcânica, constituída basicamente por lavas e piroclastos, localizada no Oceano Atlântico ao lado da costa ocidental de África. A ilha é caracterizada por três unidades hidrogeológicas, sendo estas a Formação de Base (semi-confinada), a Formação Intermédia (freática) e a Formação Recente (freática), que apresentam características geológicas e comportamentos hidráulicos que as diferenciam, recebendo recarga directa e/ ou diferida por infiltração das águas de chuva e descarregam ao mar, na rede hidrográfica ou, ainda, em outros níveis aquíferos subjacentes, desde que induzidos por gradientes hidráulicos favoráveis. O clima de Santiago é árido a semi-árido, com precipitações muito escassas e irregulares, condicionadas na sua distribuição pela altitude, ventos e orientação das vertentes, dando por vezes origem a períodos de seca prolongados. Em anos de ‘boa’ chuva, as precipitações propiciam a existência temporária de recursos hídricos superficiais e a recarga dos recursos de água subterrânea. Foi realizado um estudo hidrogeoquímico detalhado da ilha que incluiu a recolha de amostras em 133 pontos de água, entre furos, poços e nascentes. A composição química das águas analisadas na ilha de Santiago apresenta significativas variações em função da geologia e do tempo de residência. Na ausência de episódios de contaminação, as águas subterrâneas têm uma composição do tipo bicarbonatada-sódica (HCO3-Na) nas zonas mais altas da ilha, onde afloram as formações da Unidade Aquífera Intermédia. Nas zonas mais próximas da costa ocorrem águas de composição cloretada-magnesiana (Cl-Mg) ou cloretada-sódica (Cl-Na). Estas últimas predominam nas partes terminais das ribeiras, onde afloram materiais de elevada permeabilidade, e o excesso de bombagem para irrigação tem conduzido a um avanço da cunha de intrusão marinha. A ocorrência da fácies Cl-Na é neste caso o resultado de processos de intercâmbio catiónico que ocorrem durante o processo de intrusão e é concordante com os elevados teores de cloretos e de condutividade eléctrica observados. Os resultados das análises de isótopos estáveis de oxigénio-18 e deutério, realizadas em amostras recolhidas a distintas altitudes, revelam um gradiente negativo com a altitude, que já tinha sido verificado em outras ilhas com declives acentuados, permitindo assim determinar altitudes de recarga de água subterrânea. Os estudos hidrogeoquímicos até agora realizados permitiram caracterizar os principais níveis aquíferos da ilha de Santiago, colocando em evidência a limitada recarga do aquífero e o risco de gradual degradação dos recursos de água subterrânea por fenómenos de intrusão salina e contaminação agrícola. Estes resultados revelam a importância da gestão integrada da qualidade e quantidade dos parcos recursos de água subterrânea na ilha de Santiago.