Bessudo S.,Fundacion Malpelo |
Soler G.A.,Fundacion Malpelo |
Klimley A.P.,University of California at Davis |
Ketchum J.T.,University of California at Davis |
And 3 more authors.
Environmental Biology of Fishes | Year: 2011
Sixty nine hammerhead sharks, Sphyrna lewini, were tagged at Malpelo Island (Colombia) with ultrasonic transmitters during March 2006, 2007 and 2008, as part of a study to understand their residency at the island and their horizontal and vertical movements. Five sharks visited Cocos Island, 627 km distant from Malpelo. One of the sharks that appeared at Cocos Island also visited the Galapagos Islands, 710 km from Cocos, a month later. There is connectivity of Sphyrna lewini between Malpelo, Cocos and the Galapagos Islands, but the frequency of movements between the islands appears to be relatively low (<7% of the tagged sharks). The most common depth at which the sharks swam coincided with the thermocline (rs = 0.72, p < 0.01). The depth of the thermocline varied depending on the time of the year. Nocturnal detections of the sharks were more frequent during the cold season than during the warm season (W = 60, p < 0.01). We also found that hammerheads spent significantly more time on the up-current side of the island (Kruskal-Wallis = 31.1008; p < 0.01). This study contributes to the knowledge of hammerhead sharks not only in Malpelo Island but also at a regional level in the Eastern Tropical Pacific. © 2011 Springer Science+Business Media B.V.
Herron P.,Fundacion Malpelo
Aquatic Conservation: Marine and Freshwater Ecosystems | Year: 2011
Worldwide, there are concerns about the potential impact of a growing tourism industry on the behaviour and ecology of sharks. Several shark species are key attractions in the scuba diving industry in both the Galápagos Marine Reserve (Ecuador) and the Sanctuary of Fauna and Flora Malpelo (Colombia). In this study, the reactions of five species of shark to the behaviour of scuba divers were investigated in the Galápagos and Malpelo. Four discrete categories of shark reaction (evasion, spontaneous approach, alert and no reaction) were identified and analysed against five categories of diver behaviour (direct approach, camera flash, sudden movement, noise and simple presence), two categories of observation strategy (still and movement) and the distance of the focal diver group to the sharks. The type of reaction in the sharks was determined by the behaviour of the divers, their distance to the fish and, especially, by their observation strategy. Shark reactions varied between species and locations and divers acted more intrusively towards those species they were not afraid of, and which they could access more easily due to the conditions of their environment. 5. 'Direct approach', 'sudden movement', the observation strategy 'moving' and distances closer than 4m between divers and sharks elicited stronger behavioural responses by the species targeted. Recommendations are given for the preferred actions divers should employ in order to diminish the effects on the target species analysed in this study. © 2011 John Wiley & Sons, Ltd.
Ketchum J.T.,University of California at Davis |
Hearn A.,University of California at Davis |
Klimley A.P.,University of California at Davis |
Penaherrera C.,University of Tasmania |
And 5 more authors.
Marine Biology | Year: 2014
Marine top predators are common at offshore bathymetric features such as islands, atolls, and seamounts, where most pelagic reef fish reside, while certain sharks perform inter-island movements between these formations. Scalloped hammerhead sharks are known to school in great numbers at small islands and seamounts in the eastern tropical Pacific (ETP) and are very susceptible to fisheries while moving into the open sea. It is, therefore, essential to understand hammerhead inter-island movements and environmental effects to provide baseline information for their conservation and management within and beyond an insular marine protected area. Movements of scalloped hammerheads were analyzed in the Galapagos Marine Reserve (GMR) and ETP, and environmental factors were linked to their movements. Hammerheads were tagged (N = 134) with V16 coded pingers (July 2006 to July 2010) in the northern Galapagos and detected at listening stations around four islands in the GMR and two isolated islands in the ETP, 700 and 1,200 km away. Hammerheads formed daytime schools at specific locations, but dispersed at night. Overall, more daytime than nighttime detections were recorded at all receivers in the northern Galapagos Islands, and more detections in the up-current sides of these islands. Hammerheads remained more days at the northern islands during part of the warm season (December-February) compared to the cool; however, fewer individuals were present in March-June. Movement modes were diel island excursions (24-h cycles) in the northern Galapagos and inter-island in the GMR and ETP at different scales: (1) short back-and-forth (<50 km, SBF), <5 days cycles, (2) medium distance (50-300 km, MDT), 5-20 days, and (3) long distance (>300 km, LDT), 15-52 days. The high degree of inter-island connectivity of hammerheads within the northern GMR is striking compared to the almost nil movement to the central GMR. A seasonal migratory pattern to locations offshore is indicated by (1) fewer hammerheads observed in the northern GMR during part of the warm season (March-June) and (2) evidence of LDT movements from the northern GMR to other islands in the ETP. LDT movements of mature female hammerheads are possibly associated with pupping areas. Our results indicate that currents, season, and individual behavior mainly drive inter-island movements of hammerheads at small (SBF) and medium (MDT) scales. These findings have important implications for the management of a highly mobile and endangered top predator within a marine protected area and beyond. © 2014 Springer-Verlag Berlin Heidelberg.
Edgar G.J.,Wildlife Conservation Society |
Edgar G.J.,Charles Darwin Foundation |
Edgar G.J.,University of Tasmania |
Banks S.A.,Charles Darwin Foundation |
And 9 more authors.
Global Ecology and Biogeography | Year: 2011
Aim To quantify general differences in reef community structure between well-enforced and poorly enforced marine protected areas (MPAs) and fished sites across the Eastern Tropical Pacific (ETP) regional seascape Location The Pacific continental margin and oceanic islands of Costa Rica, Panama, Colombia and Ecuador, including World Heritage sites at Galapagos, Coiba, Cocos and Malpelo Methods Densities of reef fishes, mobile and sessile invertebrates, and macroalgae were quantified using underwater visual surveys at 136 'no-take' and 54 openly fished sites associated with seven large MPAs that encompassed a range of management strategies. Spatial variation in multivariate and univariate community metrics was related to three levels of fishing pressure (high-protection MPAs, limited-protection MPAs, fishing zones) for both continental and oceanic reefs. Results High-protection MPAs possessed a much greater biomass of higher carnivorous fishes, lower densities of asteroids and Eucidaris spp. urchins, and higher coral cover than limited-protection MPAs and fished zones. These results were generally consistent with the hypothesis that overfishing of predatory fishes within the ETP has led to increased densities of habitat-modifying macroinvertebrates, which has contributed to regional declines in coral cover. Major differences in ecological patterns were also evident between continental and oceanic biogeographic provinces. Main conclusions Fishing down the food web, with associated trophic cascades, has occurred to a greater extent along the continental coast than off oceanic islands. Poorly enforced MPAs generate food webs more similar to those present in fished areas than in well-protected MPAs. © 2011 Blackwell Publishing Ltd.
Palacios D.M.,University of Hawaii at Manoa |
Palacios D.M.,Pacific Research Fisheries Center |
Herrera J.C.,Aereo |
Gerrodette T.,Southwest Fisheries Science Center |
And 8 more authors.
Journal of Cetacean Research and Management | Year: 2012
Cetacean sighting data collected under various programmes in Colombian Pacific waters were collated with the goal of assessing the distribution and abundance patterns of all species occurring in the exclusive economic zone (EEZ). Distribution maps are presented for 19 species and one genus based on 603 sightings collected between 1986 and 2008. Ordered by sighting frequency, these species were: humpback whale (Megaptera novaeangliae); striped dolphin (Stenella coeruleoalba); common bottlenose dolphin (Tursiops truncatus); pantropical spotted dolphin (Stenella attenuata); common dolphin (Delphinus delphis); Risso's dolphin (Grampus griseus); sperm whale (Physeter macrocephalus); rough-toothed dolphin (Steno bredanensis); short-finned pilot whale (Globicephala macrorhynchus); mesoplodont whales (Mesoplodon spp.); Cuvier's beaked whale (Ziphius cavirostris); melon-headed whale (Peponocephala electro); false killer whale (Pseudorca crassidens); killer whale (Orcinus orca); spinner dolphin (Stenella longirostris); dwarf sperm whale (Kogia sima); Bryde's whale (Balaenoptera edeni); pygmy killer whale (Feresa attenuata); minke whale (Balaenoptera acutorostrata) and fin whale (Balaenoptera physalus). Concentrations of sightings were observed in three geographic areas: (1) the continental shelf (depths <200m) and the contiguous continental slope (200-2,000m); (2) over the Malpelo Ridge, an offshore bathymétrie feature and (3) the northeast corner of the EEZ between Golfo de Cupica and the border with Panamá, although we do not rule out that these patterns could be an artefact of non-random effort. In inshore waters, the most frequently seen species were pantropical spotted dolphin, common bottlenose dolphin and humpback whale. For several of the data sets we provide encounter rates as indices of relative abundance, but urge caution in their interpretation because of methodological limitations and because several factors that affect sightability could not be accounted for in these estimates. Our results provide useful information for ongoing regional research and conservation initiatives aimed at determining occurrence, population status and connectivity within adjacent EEZs in the eastern tropical Pacific. Suggested research priorities include conducting dedicated surveys designed for estimating abundance and monitoring trends throughout the EEZ and focused studies in areas of special interest like the continental shelf, the Malpelo Ridge and the vicinity of Cupica and Cabo Marzo. More research is also needed in terms of quantifying the sources and impact of anthropogenic mortality on population size. Studies characterising genetic diversity and stock discreteness in coastal species (pantropical spotted dolphin and common bottlenose dolphin) would help inform local management strategies.