Status, Ecology, and Conservation of Sea Turtles in Guinea-Bissau

Chelonian Conservation and Biology, 2009, 8(2): 150–160 g 2009 Chelonian Research Foundation Status, Ecology, and Conservation of Sea Turtles in Guinea-Bissau 1 2 3 4 5 PAULO CATRY ,CASTRO BARBOSA ,BRUNO PARIS ,BUCAR INDJAI ,AMADEU ALMEIDA , 6 2 2 BENOIT LIMOGES ,CRISTINA SILVA , AND HONO´ RIO PEREIRA 1Eco-Ethology Research Unit & Centro de Biocieˆncias, Instituto Superior de Psicologia Aplicada, Rua Jardim do Tabaco 34, 1149-041 Lisboa, Portugal [[email protected]]; 2Instituto da Biodiversidade e das A´reas Protegidas, Bissau. Guinea-Bissau [[email protected]; [email protected]]; 3Department of the Environment, Canada [[email protected]]; 4Instituto Nacional de Estudos e Pesquisas, Bissau [[email protected]]; 5Centro de Investigaçaõ Pesqueira Aplicada, Bissau; 6Ministe`re du De´veloppement durable, de l’Environnement et des parcs du Que´bec [[email protected]] ABSTRACT. – This paper provides the first overview of sea turtles in Guinea-Bissau, presents data on their ecology, and analyzes threats and conservation initiatives. The green turtle (Chelonia mydas) is by far the most widespread and abundant of the 5 species that nest in Guinea-Bissau. Between ca. 7000 and 29,000 green turtle nests are laid per year at the globally important site of Poilaõ Island, with a few hundred more on surrounding islands. There is a marked interspecific variability in nesting seasonality, with green and hawksbill (Eretmochelys imbricata) turtles nesting mostly during the rainy season and olive ridley (Lepidochelys olivacea) and leatherback turtles (Dermochelys coriacea) during the dry season. Informal interviews all over the coastal zone suggest that sea turtle populations have markedly declined within living memory. Main threats are poaching of eggs and of nesting females and the incidental capture in fishing gear. Amongst the major achievements of sea turtle conservation efforts are that all species are protected by law, the most important nesting beaches have been included in the protected area network, and significant progress has been made in removing the presence of settlements of foreign fishermen from the areas near the turtle concentrations where accidental captures used to occur. On the down side, it should be pointed out that protection in the national parks is insufficient. The main problem seems to be the weak enforcement of park and national rules by park authorities, which creates a feeling of relative impunity in park residents and visiting fishermen. KEY WORDS. – Reptilia; Testudines; Cheloniidae; Chelonia mydas; Lepidochelys olivacea; Eretmochelys imbricata; Dermochelys coriacea; green turtle; olive ridley; hawksbill; leatherback; Poilaõ; West Africa Marine turtles have suffered catastrophic declines of sea turtles in this country. Most information gathered over the past few centuries and in many regions and all so far, however, has remained unpublished. The few evidence points to the fact that only a tiny fraction of the published reports with a wider diffusion (Barbosa et al. original numbers remains (e.g., King 1995; Jackson et al. 1998; Fortes et al. 1998; Fretey 2001; Catry et al. 2002; 2001). In many regions, such decline continues or is Formia et al. 2006) do suggest that national turtle accelerating, even though data are often sparse. In most populations may be of regional and even global recent decades, many research and conservation projects significance. Five species have been confirmed to occur have been developed, with large improvements in in the country, namely green (Chelonia mydas), hawksbill knowledge and some successful conservation stories (Eretmochelys imbricata), olive ridley (Lepidochelys (e.g., Hays 2004; Chaloupka et al. 2008). Still, particu- olivacea), loggerhead (Caretta caretta), and leatherback larly in developing nations, there are many countries and turtle (Dermochelys coriacea) (Limoges 1989; Barbosa et regions from where it is difficult to find published al. 1998). Green turtle nesting numbers are particularly information on marine turtles and where conservation relevant in an international context (Catry et al. 2002). efforts are limited. This is particularly true in parts of From the early 1990s, several Guinea-Bissau biolo- Africa, where some of the most important nesting and gists, forest and park guards, local collaborators, and other foraging grounds are known or suspected to be located technicians received training on sea turtle monitoring, (Fretey 2001). supervised by expatriate researchers. Over the past 20 Guinea-Bissau is a West African country with a years, many expeditions and small research projects relatively large coastal archipelago (the Bijago´s). There (under the umbrella of various institutions) were carried have been several efforts to improve the conservation out, often resulting in short internal reports (many of status and the knowledge of the ecology and distribution which with little or no quantitative data) or simply in an CATRY ET AL. — Sea Turtles in Guinea-Bissau 151 Figure 1. The coastal area of Guinea-Bissau with names of places mentioned in the text (see also other figures). The small black dots scattered along the coast show confirmed nesting sites of green turtles. ONP 5 Orango National Park; JV/PMNP 5 Joaõ Vieira–Poilaõ Marine National Park. accumulation of knowledge by the people involved. well beyond the coast and the numerous islands. Most of Countless formal and informal interviews with local the mainland coast is characterized by wide intertidal people were carried out all over the coastal area. areas with mudflats and sandbanks and extensive Deficiencies in planning and implementation of monitor- mangrove areas. Only in the extreme north and south ing schemes (due to insufficient funding and training, can one find sandy beaches facing the open ocean. The logistical difficulties, etc.), plus the fact that many Bijago´s archipelago is made of 88 islands and islets, of original data files have been lost (particularly during the which only 21 are permanently or temporarily inhabited. 1998 war) mean that although there is a very large Sandy beaches with deep water approaches are uncom- accumulated experience among the people involved, data mon, being mostly found on the outer face of the outer are often scant or need to be handled with care. Still, islands. Most of the Bijago´s are sparsely populated, with a much valuable information can be presented in a total population of ca. 25,000 people in a land area of qualitative way. Furthermore, some major surveys were 90,000 ha (Cuq 2001). Besides resident populations, carried out in a more systematic fashion. which live mostly on subsistence agriculture, there are This paper has 3 objectives. First, by analyzing old increasing numbers of seasonal immigrants (mostly from and recent unpublished data on the marine turtles of Senegal) who fish from large open pirogues, mostly Guinea-Bissau, we intend to bring to light the valuable targeting sharks, rays, barracudas, snappers, and other information that is in the ever-present danger of falling large predatory fish. There is no industrial fishing within into oblivion. Second, we present the first comprehensive the archipelago or near the mainland shore. The climate is review of the available biological data on sea turtles in tropical, hot, and humid. Rainfall is highly seasonal, with this country. Finally, we provide an overview of a monsoonal type rainy season from May to November conservation efforts developed so far, discuss their that, in coastal areas, averages around 2000 mm per year. successes and weaknesses, and provide suggestions for future priorities. Field Surveys METHODS Most of our detailed knowledge on the sea turtles of Guinea-Bissau results from a number of field surveys that Study Area are described below in some detail. Surveys for green and hawksbill turtles generally occurred during peak nesting Guinea-Bissau is a small West African country with a activity in August–October, whereas those for olive ridley generally flat coast indented by numerous flooded valleys turtles occurred during the peak nesting period in and estuaries (Fig. 1). A large continental shelf extends January–February. 152 CHELONIAN CONSERVATION AND BIOLOGY, Volume 8, Number 2 – 2009 Figure 2. Main nesting beaches in the Orango National Park that were object of detailed surveys in 1992–1994 and less intense monitoring in subsequent years. Broad Bijago´s Survey. — After gathering preliminary curved carapace length and width were measured with a information of the location of important potential nesting tape. Eggs were counted as deposited. Results from daily beaches, a survey was conducted from 11 to 27 August counts of tracks and nesting turtles have been lost. 1990, during the peak green turtle nesting season. This Poilaõ Green Turtle Tagging. — From 1994 until survey included 23 islands and islets and a total of 2007 (in 9 different years), at least 5453 green turtles 118 km of beach. Many beaches were surveyed on foot were double-tagged on Poilaõ with metal flipper-tags. A and all of them were inspected from a Zodiac traveling small number (ca. 10) of hawksbill turtles were also parallel to the shore at low speed. Tracks were identified marked. Local recaptures were noted during tagging by their imprinted characteristics and width (see Limoges sessions. Daily tagging from July till December, in 2000 and Robillard 1991b, 1991c for more details). and 2007, allowed the calculation of internesting Orango National Park Survey. — Between December intervals. When 2 records for an individual female were 1992 and November 1994, frequent surveys of the 6 most separated by an interval greater than 18 days (Broderick et important beaches of the Orango group of islands, more al. 2003), we considered that it represented more than one recently classified as the Orango National Park, were nesting interval. Each female contributed one (randomly carried out (Fig. 2). Beaches were walked in the early chosen) single value for the internesting interval statistics. morning, up to 5 times per month, with an overall full Unhocomo Green Turtle Surveys.

Load more