SciCombinator

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Concept: Gulf of California

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Marine mammals are reliable bioindicators of aquatic systems health. Within this group, cetaceans are well known by their high dependence on sound for many of their vital activities such as socialization and mating, prey catching, and navigation. Due to its high dependence on sound, bioacoustic methods become very important for the study of these species. Acoustic monitoring in the field is usually performed using omnidirectional hydrophones to assess the presence of mammals, but for some behavioral studies, it is also important to locate the animals, something which is not possible with that arrangement. Although there are very well known techniques to detect the direction of arrival of the sound, the equipment required is highly specialized and expensive. In this paper, the design and field test of digital and analog versions of a portable linear array of hydrophones capable of locating animal sounds by beamforming, using low cost and easily available equipment is presented. The array was tested in La Paz bay, Mexico, by experts of the Marine Mammals Research Program of the University of Baja California Sur, which were able to locate dolphins (Tursiops truncatus) only by their sound, despite strong sources of noise in the area.

Concepts: Mammal, Acoustics, Dolphin, Sonar, Cetacea, Whale, Baja California Sur, Gulf of California

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The Baja California peninsula is the second longest, most geographically isolated peninsula on Earth. Its physiography and the presence of many surrounding islands has facilitated studies of the underlying patterns and drivers of genetic structuring for a wide spectrum of organisms. Chaetodipus spinatus is endemic to the region and occurs on 12 associated islands, including 10 in the Gulf of California and two in the Pacific Ocean. This distribution makes it a model species for evaluating natural historical barriers. We test hypotheses associated with the relationship between the range of the species, patterns in other species, and its relationship to Pleistocene-Holocene climatic changes. We analyzed sequence data from mtDNA genes encoding cytochrome b (Cytb) and cytochrome c oxidase subunits I (COI) and III (COIII) in 26 populations including all 12 islands. The matrilineal genealogy, statistical parsimony network and Bayesian skyline plot indicated an origin of C. spinatus in the southern part of the peninsula. Our analyses detected several differences from the common pattern of peninsular animals: no mid-peninsula break exists, Isla Carmen hosts the most divergent population, the population on an ancient southern Midriff island does not differ from peninsular populations, and a mtDNA peninsular discordance occurs near Loreto.

Concepts: Biology, Pacific Ocean, Australia, Mexico, Baja California peninsula, Baja California Sur, Gulf of California, Baja California

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Environmental governance is more effective when the scales of ecological processes are well matched with the human institutions charged with managing human-environment interactions. The social-ecological systems (SESs) framework provides guidance on how to assess the social and ecological dimensions that contribute to sustainable resource use and management, but rarely if ever has been operationalized for multiple localities in a spatially explicit, quantitative manner. Here, we use the case of small-scale fisheries in Baja California Sur, Mexico, to identify distinct SES regions and test key aspects of coupled SESs theory. Regions that exhibit greater potential for social-ecological sustainability in one dimension do not necessarily exhibit it in others, highlighting the importance of integrative, coupled system analyses when implementing spatial planning and other ecosystem-based strategies.

Concepts: Scientific method, Dimension, Management, Space, Baja California peninsula, Baja California Sur, Gulf of California, Baja California

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The vaquita (Phocoena sinus) is the world’s most endangered marine mammal with ≈245 individuals remaining in 2008. This species of porpoise is endemic to the northern Gulf of California, Mexico, and has historically suffered population declines from unsustainable bycatch in gillnets. An illegal gillnet fishery for an endangered fish, the totoaba (Totoaba macdonaldi), has recently resurged throughout the vaquita’s range. The secretive but lucrative wildlife trade with China for totoaba swim bladders has probably increased vaquita bycatch mortality, but by an unknown amount. Precise population monitoring by visual surveys is difficult because vaquitas are inherently hard to see and have now become so rare that sighting rates are very low. However, their echolocation clicks can be identified readily on specialized acoustic detectors. Acoustic detections on an array of 46 moored detectors indicate that vaquita acoustic activity declined by 80% between 2011 and 2015 in the central part of the species' range. Statistical models estimate an annual rate of decline of 34% (95% Bayesian Credible Interval -48% to -21%). Based on preliminary acoustic monitoring results from 2011-2014 the Government of Mexico enacted and is enforcing an emergency 2-year ban of gillnets throughout the species' range to prevent extinction, at a cost of $74 million USD to compensate fishers. Developing precise acoustic monitoring methods proved critical to exposing the severity of vaquitas' decline and emphasizes the need for continual monitoring to effectively manage critically endangered species. This article is protected by copyright. All rights reserved.

Concepts: Biodiversity, Critical thinking, Endangered species, Albatross, Cetacea, Gulf of California, Vaquita, Porpoise

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Minimizing fishery bycatch threats might involve trade-offs between maintaining viable populations and economic benefits. Understanding these trade-offs can help managers reconcile conflicting goals. An example is a set of bycatch reduction measures for the Critically Endangered vaquita porpoise (Phocoena sinus), in the Northern Gulf of California, Mexico. The vaquita is an endemic species threatened with extinction by artisanal net bycatch within its limited range; in this area fisheries are the chief source of economic productivity.

Concepts: Biodiversity, Endangered species, Cetacea, Gulf of California, Porpoises, Vaquita, Porpoise, Bycatch

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Small-scale fisheries are an important source of food and livelihoods to coastal communities around the world. Understanding the seasonality of fisheries catch and composition is crucial to fisheries management, particularly in the context of changing environmental and socioeconomic conditions. While seasonal variability directly impacts the lives of fishers, most fisheries studies focus on longer-term change. Here we examine seasonal variability in the small-scale fisheries of Baja California Sur, Mexico based on 13 years of government fisheries data. We investigate how four fisheries indicators with direct relevance to ecological resilience-magnitude and variance of landed fish biomass, taxon richness and the proportion of top-trophic-level taxa in total catch-vary within and among years and at multiple spatial scales. We find that these resilience indicators vary both seasonally and spatially. These results highlight the value of finer-scale monitoring and management, particularly for data-poor fisheries.

Concepts: California, Pacific Ocean, Baja California peninsula, Baja California Sur, Gulf of California, Baja California, Municipalities of Mexico, La Paz, Baja California Sur

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Large [moment magnitude (M(w)) ≥ 7] continental earthquakes often generate complex, multifault ruptures linked by enigmatic zones of distributed deformation. Here, we report the collection and results of a high-resolution (≥nine returns per square meter) airborne light detection and ranging (LIDAR) topographic survey of the 2010 M(w) 7.2 El Mayor-Cucapah earthquake that produced a 120-kilometer-long multifault rupture through northernmost Baja California, Mexico. This differential LIDAR survey completely captures an earthquake surface rupture in a sparsely vegetated region with pre-earthquake lower-resolution (5-meter-pixel) LIDAR data. The postevent survey reveals numerous surface ruptures, including previously undocumented blind faults within thick sediments of the Colorado River delta. Differential elevation changes show distributed, kilometer-scale bending strains as large as ~10(3) microstrains in response to slip along discontinuous faults cutting crystalline bedrock of the Sierra Cucapah.

Concepts: California, River delta, Earthquake, Arizona, Gulf of California, Baja California, Colorado River, Colorado River Delta

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The 16SrXIII group from phytoplasma bacteria were identified in salivary glands from Homalodisca liturata, which were collected in El Comitán on the Baja California peninsula in Mexico. We were able to positively identify 15 16S rRNA gene sequences with the corresponding signature sequence of ‘CandidatusPhytoplasma’ (CAAGAYBATKATGTKTAGCYGGDCT) and in silico restriction fragment length polymorphism (RFLP) profiles (F value estimations) coupled with a phylogenetic analysis to confirm their relatedness to ‘CandidatusPhytoplasma hispanicum’, which in turn belongs to the 16SrXIII group. A restriction analysis was carried out with AluI and EcoRI to confirm that the five sequences belongs to subgroup D. The rest of the sequences did not exhibit any known RFLP profile related to a subgroup reported in the 16SrXIII group.

Concepts: Ribosomal RNA, 16S ribosomal RNA, Mexico, Restriction fragment length polymorphism, Baja California peninsula, Baja California Sur, Gulf of California, Baja California

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Smoking methamphetamine is associated with increased risk of HIV among female sex workers (FSW). The structural context of substance use is an important shaper of individual behaviour; however, structural determinants of methamphetamine use among FSWs are largely unknown. We identified individual, structural and neighbourhood factors associated with smoking methamphetamine among FSWs in the border city of Tijuana, Baja California, Mexico.

Concepts: California, Mexico, San Diego, Baja California peninsula, Gulf of California, Baja California, Mexicali, Tijuana