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Spatio-temporal distribution of small pelagic fish larvae in beaches and mangroves in the Galapagos: Anchoa sp. and Opisthonema sp.
Abstract and Figures
Galapagos presents unique oceanographic and geographic conditions, which allows for the presence of different types of fishes. Among them are small pelagic fishes such as anchovies, herrings and sardines, which are not only part of an important marine trophic level but are used as bait in artisanal fisheries. In Galapagos, few studies had been carried out on the larval stages of the mentioned species, which has not allowed for fisheries management actions. For these reasons, the aim of this study is to understand the spatial / temporal distribution of these fishes. To achieve the objective of the study, light traps were used to collect ichthyoplankton. The traps were placed in sandy beaches next to mangrove forests of three geographically different coastal areas within the central-southeast bioregion: North and South of Santa Cruz Island and Southwest of Floreana Island; and two in the far north bioregion: North of Darwin and southwest of Wolf. Two species were identified morphologically, one genus of anchovies (Anchoa sp., Standard length range, SL: 11-70 mm) and one of herrings (Opisthonema sp., Range of SL: 16-46 mm). Both species were mostly present in the south of Santa Cruz Island, particularly during the first months of the year, which corresponds to the wet season. Future genetic and otolith studies will be carried out to determine the species and estimate age, hatching date and larval growth. This information is vital for the proper management of this resource, which have importance for fisheries and marine ecosystems.
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A survey of Blue-footed Boobies (Sula nebouxii excisa) throughout the taxon's range in Galapagos, Ecuador found similar to 6400 adults, compared to a rough estimate of 20,000 in the 1960s. Few pairs bred in 2011-2013 and almost no birds in juvenile plumage were seen. Long-term data suggest that poor breeding began in 1998. Lack of recruitment over this period would mean that the current population is mostly elderly and experiencing senescent decline in performance. Anthropogenic effects such as introduced predators are unlikely to explain this decline because islands with and without such factors exhibited the same low breeding. The poor reproduction seems to be linked to diet. Previous work indicated that sardine and herring (Clupeidae) supported successful breeding, but these fish were mostly absent from the diet during this study, except in the central part of Galapagos, where most breeding attempts during this study occurred. Elsewhere in the eastern Pacific sardine abundance has decreased dramatically by natural processes in the last 15 years, as part of a well-documented and apparently natural cycle. This cyclic change in abundance provides a possible explanation for the recent demographic changes in Blue-footed Boobies in Galapagos. Whether natural or anthropogenic in origin, the implications of senescent decline in breeding ability and survival are dramatic for this genetically distinct icon of biodiversity and ecotourism.
This study focuses on the comparative analysis of variables related to the trophic niche plasticity in the Galapagos sea lion (Zalophus wollebaeki). There is great concern regarding the future of this species, so study of the diet and the way these animals obtain their food is useful to understand and predict their survival possibilities in the long term. The combined use of scat analysis and stable isotopes helps to determine foraging habits of this species in greater detail. The objective of the study was to assess the feeding habits of Z. wollebaeki and its space-time variation. The scat analysis (n = 200) gave as a result space-time changes in the foraging strategies of this species. The isotopic values (n = 80) showed differences in relation to foraging grounds (delta C-13: P = 0.001), but also suggested an apparent stability in the trophic level of their diet (delta N-15: P = 0.084). These results constitute a relevant finding in the evolutionary behaviour of the species, showing that Z. wollebaeki has developed a high degree of plasticity in its foraging habits that may improve its survival in a highly demanding ecosystem in terms of limited and fluctuating resources.
The diversity of habitats (eg. rocky shore, sandy beaches, mangrove lagoons, coral reefs) harbour an unusual mixture of temperature, subtropical and tropical marine organisms. The major biotopes are described and their communities contrasted with their mainland counterparts. The Ecuadorian Government's policy to ensure protection of nearshore waters is outlined.-from Author
Aim To delineate biogeographical patterns in Galapagos shallow-water reef fauna at regional scales.
Location Galapagos Islands.
Methods Fishes and macro-invertebrates were quantitatively censused using underwater visual techniques along more than 500 transects at defined depth strata across the Galapagos archipelago. Data were analysed using multivariate techniques to define regional patterns and identify species typical of different regions.
Results Subtidal communities of fishes and macro-invertebrates on shallow reefs differed consistently in species composition across the Galapagos archipelago, with three major biogeographical groupings: (1) the ‘far-northern area’ containing the islands of Darwin and Wolf, (2) the ‘central/south-eastern area’, including the east coast of Isabela, and (3) the ‘western area’, encompassing Fernandina and western Isabela. In addition, the northern islands of Pinta, Marchena and Genovesa form a separate region in the central/south-eastern area, and Bahia Elizabeth and Canal Bolivar separate from other parts of the western area. The far-northern bioregion is characterized by high fish species richness overall, including a high proportion of species of Indo-Pacific origin. However, very few endemic fishes or species with distributions extending south from Ecuador (‘Peruvian’ species) are present, and the bioregion also possesses relatively low species richness of mobile macro-invertebrate taxa. By contrast, the ‘western’ bioregion possesses disproportionately high numbers of endemic fish taxa, high numbers of cool-temperate Peruvian fish species, and high invertebrate species richness, but very few species of Indo-Pacific origin. The Bahia Elizabeth/Canal Bolivar bioregion possesses more endemic species and fewer species with Peruvian affinities than coasts within the western bioregion. The northern bioregion of Pinta, Marchena and Genovesa represents an overlap zone with affinities to both the far-northern and south-eastern islands. The south-eastern bioregion includes species from a variety of different sources, particularly ‘Panamic’ species with distributions extending north to Central America.
Main conclusions On the basis of congruent divisions for reef fish and macro-invertebrate communities, the Galapagos archipelago can be separated into three major biogeographical areas, two of which can be further subdivided into two regions. Each of these five bioregions possesses communities characterized by a distinctive mix of species derived from Indo-Pacific, Panamic, Peruvian and endemic source areas. The conservation significance of different regions is not reflected in counts of total species richness. The regions with the lowest overall fish species richness possess a temperate rather than tropical climate and highest levels of endemism.
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Assessment of a bait fishery in the Galapagos marine protected area: implications for sustainable management
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Heel, L. 2012. Assessment of a bait fishery in the Galapagos marine protected area: implications for
sustainable management. Tesis de Pregrado. Leuphana University of Lüneburg, Bremen, Alemania.
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Zonificación e Historia de La Reserva Marina de Galápagos
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Guía de especies de interés pesquero en la Reserva Marina de Galápagos. Ministerio de Agricultura, Pesca y Alimentación, Secretaría General de Pesca Marítima
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Molina, L., Danulat, E., Oviedo, M. & González, J. 2005. Guía de especies de interés pesquero en la
Reserva Marina de Galápagos. Ministerio de Agricultura, Pesca y Alimentación, Secretaría General
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Ecología de la reproducción y potencial reproductivo en las Poblaciones de peces marinos
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peces marinos. Curso Doutoramento do bienio 2004-2006. Universidad de Vigo, España. 71pp.