DOI: 10.5061/dryad.cfxpnvxdq
title: Green and hawksbill sea turtle nesting in the Gulf of Guinea: A 9-year survey

description: Sea turtles are critical components of marine ecosystems, and their
 conservation is important for Ocean Governance and Global Planet Health.
 However, there is limited knowledge of their ecology in the Gulf of
 Guinea. To fill this knowledge gap, this study presents the first
 integrative assessment of green and hawksbill turtles in the region,
 combining nesting area surveys over 9 years, and telemetry data, to offer
 insights into these population dynamics, and behaviours including nesting
 preferences, morphological and reproductive parameters, diving patterns
 and inter-nesting core-use areas. Green turtles are likely making a
 recovery in São Tomé, potentially driven by sustained conservation
 efforts. In contrast, the status of the hawksbill turtle remains less
 clear. There are preliminary indications of recovery, but we interpret
 this cautiously. Coupled with satellite tracking, this study estimated
 that 482 to 736 green turtles, and 135 to 217 hawksbills, nest on the
 beaches of São Tomé. Their movements overlap significantly with a proposed
 Marine Protected Area (MPA), which suggests they may be well placed for
 conservation if managed appropriately. However, the presence of artisanal
 fisheries and emerging threats, such as sand mining and unregulated
 tourism, highlight the urgent need for robust management strategies that
 align global conservation objectives with local socioeconomic realities.
 This study significantly enhances our understanding of the ecology and
 conservation needs of the green and hawksbill turtles in the Gulf of
 Guinea. The insights gleaned here can contribute to the development of
 tailored conservation strategies that benefit these populations and the
 ecosystem services upon which they depend.
description: <em>Nesting </em><em>Data Collection and
 Analysis: </em>We recorded nest parameters, whenever possible,
 including clutch size, nest depth, and emergence success. Females were
 tagged during nesting with Inconel tags (Style 681, National Band and Tag
 Company) in both front flippers and their curved carapace length (CCL) was
 measured. To analyse changes in length between nesting seasons, we used a
 Kruskal-Wallis test. For the CCL analyses, we considered only the first
 recorded data from each female per season to avoid potential bias
 introduced by repeat records of high-frequency nesters, ensuring that each
 turtle contributed only once to the data set within a nesting season. For
 other reproductive parameters such as clutch size, nest depth, emergence
 success, and incubation period, we conducted a descriptive statistical
 analysis using all available data from each female throughout the season.
 This involved calculating the mean, minimum, maximum, and standard
 deviation for each parameter to provide a comprehensive understanding of
 their distribution and variability across the nesting season. We
 calculated emergence success as the proportion of eggs that produced live
 hatchlings that reached the surface of the sand and included the failed
 nests (with 0% emergence success). The incubation period was determined as
 the number of days between the day of oviposition and the emergence of the
 first hatchling.
description: # Green and hawksbill sea turtle nesting in the Gulf of Guinea: A 9-year
 survey The dataset is structured with the following variables: * RecCode:
 This is a unique automated code generated to link related datasets across
 multiple databases for tracking and analysis purposes. * Season: Indicates
 the nesting season, spanning from July of one year to May of the following
 year, to accommodate the annual nesting cycle of the species. * NewDate:
 Indicates the date of the nesting or false crawl event. * Area: Indicates
 the area where the event occurred. Not the specific nesting beach but the
 area. * Specie: Specifies the species of the turtle. CM stands for
 Chelonia mydas (Green Turtle) and EI stands for Eretmochelys imbricata
 (Hawksbill Turtle). * LeftTag and RighhTag: Each turtle has one or two
 tags, in the left or right flippers. * NewRecap: Designates whether the
 turtle is a new individual to the study (1 for New Turtle) or a recaptured
 individual that has been previously tagged or identified (2 for Recapture
 Turtle). * CCL: Curved Carapace Length measured in centimeters (cm), from
 the nuchal notch to the tip of the supracaudal scute. * CCW: Curved
 Carapace Width measured in centimeters (cm), across the carapace at its
 widest point. * Nest: Binary indicator of nesting activity, where 1
 denotes a successful nesting event (Nest) and 0 denotes an unsuccessful
 attempt or false crawl. * Type of Nest: Categorizes the nest based on its
 condition or management as follows - 1 for nests left in situ, 2 for nests
 transferred to a different location on the beach, and 3 for nests moved to
 a hatchery. * NestDepth and NestWidth: Transferred nests to a different
 location on the beachor to a hatchery were record the depth (cm) and width
 (cm). * Shells: Counts the total number of eggshells found within a nest,
 indicating the number of eggs that were laid. * Dead Hatch: The count of
 dead hatchlings discovered inside the nest post-emergence. * Total Eggs:
 The total count of eggs laid in a single nesting event. * Live Hatch: The
 number of live hatchlings that emerged from the nest. * EmergeRate: The
 hatchling emergence rate, is calculated as the proportion of live
 hatchlings to the total number of eggs. * EmergeDate: The date on which
 hatchlings emerged from the nest. * IncubPer: The incubation period,
 recorded as the number of days between the laying of eggs and the
 emergence of hatchlings. Empty cells in our dataset indicate
 'null' or 'n/a,' for unavailable or inapplicable
 information. If you have any questions regarding this dataset or require
 additional information, please contact the corresponding authors.