ORCID Profile
0000-0002-9662-7320
Current Organisation
James Cook University
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Publisher: Springer Science and Business Media LLC
Date: 22-07-2021
DOI: 10.1038/S41598-021-94126-3
Abstract: Shark fishing, driven by the fin trade, is the primary cause of global shark population declines. Here, we present a case study that exemplifies how industrial fisheries are likely depleting shark populations in the Eastern Tropical Pacific Ocean. In August 2017, the vessel Fu Yuan Yu Leng 999, of Chinese flag, was detained while crossing through the Galápagos Marine Reserve without authorization. This vessel contained 7639 sharks, representing one of the largest seizures recorded to date. Based on a s le of 929 in iduals (12%), we found 12 shark species: 9 considered as Vulnerable or higher risk by the IUCN and 8 listed in CITES. Four species showed a higher proportion of immature than mature in iduals, whereas size-distribution hints that at least some of the fishing ships associated with the operation may have been using purse-seine gear fishing equipment, which, for some species, goes against international conventions. Our data expose the magnitude of the threat that fishing industries and illegal trade represent to sharks in the Eastern Tropical Pacific Ocean.
Publisher: Wildlife Disease Association
Date: 07-2017
DOI: 10.7589/2016-05-092
Abstract: The Galapagos sea lion ( Zalophus wollebaeki ), an endangered species, experiences high pup mortality (up to 100%) in years when El Niño events reduce food supply in the Galapagos Islands. Mortality of pups in non-El Niño years is estimated to be 5% in undisturbed colonies. From 2009 to 2012 we observed high pup mortality (up to 67%) in colonies close to the Galapagos capital, Puerto Baquerizo Moreno, where contact with humans, domestic animals, and rats is frequent. Gross postmortem findings from 54 pups included hemorrhagic lesions in liver and congestion in lungs histopathology suggested a possible association with infectious diseases. Evidence of Leptospira infection was found in five out of seven s les collected in 2010. Canine distemper viral (CDV) RNA was detected in tissues from six sea lions (in 2011-12), four of which were confirmed by nucleotide sequencing. The absence of CDV antibodies in 109 juvenile animals tested in 2014 at urban and remote colonies could indicate that the CDV infection observed in 2011 was likely confined to a few animals. Our results indicated that Galapagos sea lions have been exposed at least to two pathogens, Leptospira and CDV however, the impact of these infections on the sea lions is unclear.
Publisher: Oxford University Press (OUP)
Date: 2017
Publisher: Wildlife Disease Association
Date: 2016
DOI: 10.7589/2015-04-084
Abstract: The Galápagos sea lion, Zalophus wollebaeki, is an endemic and endangered species subject to population decline associated with environmental variability, such as El Niño events, constant feeding stress, and exposure to diseases through contact with introduced species. Reference blood parameter intervals have been published for some pinniped species, but baseline biochemical and blood gas values are lacking from Z. wollebaeki. We analyzed blood s les from 30 juvenile Galápagos sea lions (19 females, 11 males) captured in two rookeries on San Cristóbal Island. A portable blood analyzer (iSTAT) was used to obtain near-immediate field results for pH, partial pressure of O2, partial pressure of CO2, bicarbonate (HCO3(-)), hematocrit (Hct), hemoglobin, Na, K, ionized Ca, and glucose, and blood lactate was measured using a portable Lactate Plus(TM) analyzer. Average heart rate, biochemistry, and hematology parameters were comparable with healthy in iduals of other pinniped species. Hemoglobin was significantly correlated with body condition of juvenile Galápagos sea lions. When compared with available blood values of clinically healthy California sea lions, Galápagos sea lions had higher total protein and Hct and lower Ca and K levels. Our results provide baseline data that may be useful in comparisons among populations and in detecting changes in health status among Galápagos sea lions.
Publisher: Elsevier BV
Date: 11-2015
Publisher: Oxford University Press (OUP)
Date: 2015
Publisher: Frontiers Media SA
Date: 13-02-2018
Publisher: Wiley
Date: 07-09-2021
DOI: 10.1111/GEB.13379
Abstract: The interplay of animal dispersal and environmental heterogeneity is fundamental for the distribution of bio ersity on earth. In the ocean, the interaction of physical barriers and dispersal has primarily been examined for organisms with planktonic larvae. Animals that lack a planktonic life stage and depend on active dispersal are however likely to produce distinctive patterns. We used available literature on population genetics and phylogeography of elasmobranchs (sharks, rays and skates) to examine how marine barriers and dispersal ecology shape genetic connectivity in animals with active dispersal. We provide a global geographical overview of barriers extracted from the literature and synthesize the geographical and hydrological factors, spatial and temporal scales to characterize different types of barriers. The three most studied barriers were used to analyse the effect of elasmobranch dispersal potential and barrier type on genetic connectivity. We characterized nine broad types of marine barriers, with the three most common barriers being related to ocean bathymetry. The maximum depth of occurrence , maximum body size and habitat of each species were used as proxies for dispersal potential, and were important predictors of genetic connectivity with varying effect depending on barrier type. Environmental tolerance and reproductive behaviour may also play a crucial role in population connectivity in animals with active dispersal. However, we find that studies commonly lack appropriate study designs based on a priori hypotheses to test the effect of physical barriers while accounting for animal behaviour. Our synthesis highlights the relative contribution of different barrier types in shaping elasmobranch populations. We provide a new perspective on how barriers and dispersal ecology interact to rearrange genetic variation of marine animals with active dispersal. We illustrate methodological sources that can bias the detection of barriers and provide potential solutions for future research in the field.
Publisher: Public Library of Science (PLoS)
Date: 13-05-2014
Publisher: Springer Science and Business Media LLC
Date: 03-07-2023
DOI: 10.1038/S41437-023-00635-4
Abstract: Oceanic islands play a central role in the study of evolution and island biogeography. The Galapagos Islands are one of the most studied oceanic archipelagos but research has almost exclusively focused on terrestrial organisms compared to marine species. Here we used the Galapagos bullhead shark ( Heterodontus quoyi ) and single nucleotide polymorphisms (SNPs) to examine evolutionary processes and their consequences for genetic ergence and island biogeography in a shallow-water marine species without larval dispersal. The sequential separation of in idual islands from a central island cluster gradually established different ocean depths between islands that pose barriers to dispersal in H. quoyi . Isolation by resistance analysis suggested that ocean bathymetry and historical sea level fluctuations modified genetic connectivity. These processes resulted in at least three genetic clusters that exhibit low genetic ersity and effective population sizes that scale with island size and the level of geographic isolation. Our results exemplify that island formation and climatic cycles shape genetic ergence and biogeography of coastal marine organisms with limited dispersal comparable to terrestrial taxa. Because similar scenarios exist in oceanic islands around the globe our research provides a new perspective on marine evolution and biogeography with implications for the conservation of island bio ersity.
No related grants have been discovered for Maximilian Hirschfeld.