The Experts below are selected from a list of 183 Experts worldwide ranked by ideXlab platform
Lorenzo Rojasbracho - One of the best experts on this subject based on the ideXlab platform.
-
decline towards extinction of mexico s vaquita porpoise Phocoena Sinus
Royal Society Open Science, 2019Co-Authors: Armando Jaramillolegorreta, Lorenzo Rojasbracho, Gustavo Cardenashinojosa, Edwyna Nietogarcia, Len Thomas, Jay Ver M Hoef, Jeffrey E Moore, Barbara L Taylor, Jay Barlow, Nicholas TregenzaAbstract:The vaquita (Phocoena Sinus) is a small porpoise endemic to Mexico. It is listed by IUCN as Critically Endangered because of unsustainable levels of bycatch in gillnets. The population has been monitored with passive acoustic detectors every summer from 2011 to 2018; here we report results for 2017 and 2018. We combine the acoustic trends with an independent estimate of population size from 2015, and visual observations of at least seven animals in 2017 and six in 2018. Despite adoption of an emergency gillnet ban in May 2015, the estimated rate of decline remains extremely high: 48% decline in 2017 (95% Bayesian credible interval (CRI) 78% decline to 9% increase) and 47% in 2018 (95% CRI 80% decline to 13% increase). Estimated total population decline since 2011 is 98.6%, with greater than 99% probability the decline is greater than 33% yr-1. We estimate fewer than 19 vaquitas remained as of summer 2018 (posterior mean 9, median 8, 95% CRI 6-19). From March 2016 to March 2019, 10 dead vaquitas killed in gillnets were found. The ongoing presence of illegal gillnets despite the emergency ban continues to drive the vaquita towards extinction. Immediate management action is required if the species is to be saved.
-
a field effort to capture critically endangered vaquitas Phocoena Sinus for protection from entanglement in illegal gillnets
Endangered Species Research, 2019Co-Authors: Lorenzo Rojasbracho, Frances M D Gulland, Cynthia R Smith, Brett M Taylor, Randall S Wells, Peter Thomas, B Bauer, Mads Peter Heidejorgensen, Jonas Teilmann, Rune DietzAbstract:Author(s): Rojas-Bracho, L; Gulland, Frances M.; Smith, Cynthis R.; Taylor, Barbara; Wells, RS; Thomas, PO; Bauer, B; Heide-JA¸rgensen, MP; Teilmann, J; Dietz, R; Balle, JD; Jensen, MV; Sinding, MHS; Jaramillo-Legorreta, A; Abel, G; Read, AJ; Westgate, AJ; Colegrove, K; Gomez, F; Martz, K; Rebolledo, R; Ridgway, Sam H.; Rowles, T; van Elk, CE; Boehm, J; Cardenas-Hinojosa, G; Constandse, R; Nieto-Garcia, E; Phillips, W; Sabio, D; Sanchez, R; Sweeney, J; Townsend, F; Vivanco, J; Vivanco, JC; Walker, S
-
vaquitas and gillnets mexico s ultimate cetacean conservation challenge
Endangered Species Research, 2013Co-Authors: Lorenzo Rojasbracho, Randall R ReevesAbstract:There is a high risk that incidental mortality (bycatch) in gillnets will lead to extinc- tion of the vaquita Phocoena Sinus, a small porpoise endemic to Mexico's northern Gulf of Califor- nia. A zoned Biosphere Reserve established in 1993 proved ineffective at slowing the population's decline, and in 2005, a Vaquita Refuge was declared. The Refuge Program included a ban on gill- netting and trawling in certain areas with relatively high densities of vaquitas. However, it was not until 2008, with the introduction of a Species Conservation Action Plan for Vaquita (PACE- Vaquita), that a comprehensive protection and recovery effort was introduced. Unfortunately, valuable time was lost as officials first needed to bring order to a poorly managed fishery manage- ment system. Also, the voluntary nature of fisherman participation and the chronic deficiency of enforcement have limited PACE's effectiveness. Although efforts to implement the plan probably slowed the vaquita's decline, the goal of eliminating gillnets (and thus most vaquita bycatch) by 2012 was not reached. This example shows the difficulty of achieving conservation when the pro- gram's rationale centers on the preservation of biodiversity with less emphasis on meeting com- munity aspirations. In fact, not only does the vaquita have no economic value, but the measures taken for its conservation have a negative economic impact and hence are met with hostility, or at best indifference, on the part of fishery authorities and fishing communities. On a more positive note, a light trawl has been field-tested and shown to be efficient at capturing shrimp; such 'vaquita-safe' trawls are suitable for replacing gillnets in the shrimp fishery. Similarly suitable alternative gear needs to be developed urgently for use in the finfish fisheries. Unless entangling nets are removed quickly from the vaquita's habitat, it will soon be too late to save the species, which probably already numbers fewer than 200 animals.
-
vaquita Phocoena Sinus
Encyclopedia of Marine Mammals (Second Edition), 2009Co-Authors: Lorenzo Rojasbracho, Armando M JaramillolegorettaAbstract:Summary The vaquita is endemic to the Upper Gulf of California, Mexico and is the most critically endangered cetacean species in the world, due to incidental mortality in gillnets. A recent 64-day survey in December 2015 estimated the population size in around 60 animals. Previous estimates of abundance were 567 in 1997 and 245 in 2008. The acoustic monitoring program, from 2011 to 2015, estimated a population decline of 80% along this period. The accelerated rate of decline observed during the last years, can primarily be attributed to bycatch in the explosive resurgence of the illegal gillnet fishing for totoaba, which satisfies the lucrative Chinese black-market for their swim bladder. Without effective conservation actions vaquita will soon be gone. The Mexican Government implemented an emergency 2-year ban of gillnets, combined with interagency enforcement and a fishermen compensation program. However, the demand for totoaba swim bladder has the clock ticking for the survival of vaquita.
-
genetic drift vs natural selection in a long term small isolated population major histocompatibility complex class ii variation in the gulf of california endemic porpoise Phocoena Sinus
Molecular Ecology, 2007Co-Authors: Adrian Munguiavega, Lorenzo Rojasbracho, Yareli Esquergarrigos, Ricardo Vazquezjuarez, Aines Castroprieto, Sergio FloresramirezAbstract:Although many studies confirm long-term small isolated populations (e.g. island endemics) commonly sustain low neutral genetic variation as a result of genetic drift, it is less clear how selection on adaptive or detrimental genes interplay with random forces. We investigated sequence variation at two major histocompatibility complex (Mhc) class II loci on a porpoise endemic to the upper Gulf of California, Mexico (Phocoena Sinus, or vaquita). Its unique declining population is estimated around 500 individuals. Single-strand conformation polymorphism analysis revealed one putative functional allele fixed at the locus DQB (n = 25). At the DRB locus, we found two presumed functional alleles (n = 29), differing by a single nonsynonymous nucleotide substitution that could increase the stability at the dimer interface of alphabeta-heterodimers on heterozygous individuals. Identical trans-specific DQB1 and DRB1 alleles were identified between P. Sinus and its closest relative, the Burmeister's porpoise (Phocoena spinipinnis). Comparison with studies on four island endemic mammals suggests fixation of one allele, due to genetic drift, commonly occurs at the DQA or DQB loci (effectively neutral). Similarly, deleterious alleles of small effect are also effectively neutral and can become fixed; a high frequency of anatomical malformations on vaquita gave empirical support to this prediction. In contrast, retention of low but functional polymorphism at the DRB locus was consistent with higher selection intensity. These observations indicated natural selection could maintain (and likely also purge) some crucial alleles even in the face of strong and prolonged genetic drift and inbreeding, suggesting long-term small populations should display low inbreeding depression. Low levels of Mhc variation warn about a high susceptibility to novel pathogens and diseases in vaquita.
Barbara L. Taylor - One of the best experts on this subject based on the ideXlab platform.
-
A combined visual and acoustic estimate of 2008 abundance, and change in abundance since 1997, for the vaquita, Phocoena Sinus
Marine Mammal Science, 2010Co-Authors: Tim Gerrodette, Barbara L. Taylor, René Swift, Shannon Rankin, Armando Jaramillo-legorreta, Lorenzo Rojas-brachoAbstract:A line-transect survey for the critically endangered vaquita, Phocoena Sinus, was carried out in October–November 2008, in the northern Gulf of California, Mexico. Areas with deeper water were sampled visually from a large research vessel, while shallow water areas were covered by a sailboat towing an acoustic array. Total vaquita abundance in 2008 was estimated to be 245 animals (CV = 73%, 95% CI 68–884). The 2008 estimate was 57% lower than the 1997 estimate, an average rate of decline of 7.6%/yr. Bayesian analyses found an 89% probability of decline in total population size during the 11 yr period, and a 100% probability of decline in the central part of the range. Acoustic detections were assumed to represent porpoises with an average group size of 1.9, the same as visual sightings. Based on simultaneous visual and acoustic data in a calibration area, the probability of detecting vaquitas acoustically on the trackline was estimated to be 0.41 (CV = 108%). The Refuge Area for the Protection of the Vaquita, where gill net fishing is currently banned, contained approximately 50% of the population. While animals move in and out of the Refuge Area, on average half of the population remains exposed to bycatch in artisanal gill nets.
-
risk factors affecting the vaquita Phocoena Sinus 1
Marine Mammal Science, 1999Co-Authors: Lorenzo Rojasbracho, Barbara L. TaylorAbstract:Despite the vaquita being commonly cited as one of the most endangered marine mammals in the world, there is still disagreement over which factors put the species at greatest risk of extinction. This lack of agreement hinders management decisions needed to reduce the risk to the species. To expedite decision-making we consider four major risk factors. Habitat alteration from reduced flow of the Colorado River does not currently appear to be a risk factor because productivity remains high in vaquita habitat. Pollutant loads are low and pose low to no risk. Reduced fitness from inbreeding depression and loss of genetic variability are unlikely to pose high risk currently, though risk will increase if vaquitas remain at low abundance over long periods of time. Mortality resulting from fisheries bycatch poses high risk. Thus, short term management should not be hindered by uncertainty in estimating the risk of these factors, and primary conservation efforts should be directed to wards immediate elimination of incidental fishery mortality.
-
examining the risk of inbreeding depression in a naturally rare cetacean the vaquita Phocoena Sinus 1
Marine Mammal Science, 1999Co-Authors: Barbara L. Taylor, Lorenzo RojasbrachoAbstract:Uncertainty about the magnitude of various risks facing endangered species can paralyze conservation action. The vaquita is a naturally rare porpoise that has declined to the low hundreds of individuals because of gillnet mortality over the past 57 years. No variability in mitochondrial DNA (mtDNA) was found in vaquitas (n= 43). Because reducing gillnet mortality will require strong conservation action, the question was raised whether vaquitas are doomed because of inbreeding depression and whether, therefore, mitigation efforts would be futile. We use simulations to investigate the “doom hypothesis” by first asking whether the current level of genetic variability results from the recent decline or from historical factors. If fixation was historical then deleterious alleles could have been selected out of vaquitas over thousands of years, reducing concerns about inbreeding depression. Simulations showed that fixation most likely resulted from historical rather than recent loss. Of 1,000 simulations done at plausible abundances and mutation rates, 247 (84.3%) fixed before and 46 (15.7%) fixed during the recent decline. Fixation correlates with historical abundance, making it more likely that because vaquitas are fixed, they are also a naturally rate species. However, because studies on purging deleterious alleles have not shown purging to be universally beneficial we also examine the doom hypothesis using data on the response to inbreeding of a wide variety of captive animals. Responses are so variable that the doom hypothesis cannot be affirmed. We further explore whether more data from vaquitas would lead to conclusive results and found that the data required, such as the adult survival rate, will be impossible to obtain. We conclude that because the doom hypothesis cannot be affirmed this risk factor should not delay conservation actions.
-
the uses of statistical power in conservation biology the vaquita and northern spotted owl
Conservation Biology, 1993Co-Authors: Barbara L. Taylor, Tim GerrodetteAbstract:The consequences of accepting a false null hypothesis can be acute in conservation biology because endangered populations leave little margin for recovery from incorrect management decisions. The concept of statistical power provides a method of estimating the probability of accepting a false null hypothesis. We illustrate how to calculate and interpret statistical power in a conservation context with two examples based on the vaquita (Phocoena Sinus), an endangered porpoise, and the Northern Spotted Owl (Strix occidentalis caurina). The vaquita example shows how to estimate power to detect negative trends in abundance. Power to detect a decline in abundance decreases as populations become smaller, and, for the vaquita, is unacceptably low witin the range of estimated population sizes. Consequently, detection of a decline should not be a necessary criterion for enacting conservation measures for rare species. For the Northern Spotted Owl, estimates of power allow a reinterpretation of results of a previous demographic analysis that concluded the population was stable. We find that even if the owl population had been declining at 4% per year, the probability of detecting the decline was at most 0.64, and probably closer to 0.13; hence, concluding that the population was stable was not justified. Finally, we show how calculations of power can be used to compare different methods of monitoring changes in the size of small populations. The optimal method of monitoring Northern Spotted Owl populations may depend both on the size of the study area in relation to the effort expended and on the density of animals. At low densities, a demographic approach can be more powerful than direct estimation of population size through surveys. At higher densities the demographic approach may be more powerful for small populations, but surveys are more powerful for populations larger than about 100 owls. The tradeoff point depends on density but apparently not on rate of decline. Power decreases at low population sizes for both methods because of demographic stochasticity. En conservacion biologica, las consecuencias de aceptar hipotesis nulas falsas pueden ser muy severas puesto que las poblaciones en peligro de extincion dejan poco margen para revertir el efecto de decisiones incorrectas de manejo. El concepto de poder estadistico provee un metodo para estimar la probabilidad de aceptar hipotesis nulas falsas. Nosotros ilustramos como calcular e interpretar el poder estadistico en un contexto de conservacion con dos ejemplos basados en la vaquita (Phocoena Sinus), una marsopa en peligro de extincion, y el buho moteado del Norte (Strix occidentalis caurina). El ejemplo de la vaquita muestra como estimar el poder para detectar tendencias negativas en abundancia. El poder para detectar una disminucion en la abundancia decrece a medida que las poblaciones se hacen mas pequenas, y en el caso de la vaquita, es inaceptablemente bajo para el rango de tamanos poblacionales estimados. Por consiguiente, la deteccion de una declinacion en el tamano poblacional no debe ser un criterio necesario para decretar medidas de conservacion en especies raras. En el caso del buho moteado del Norte, la estimacion del poder permite la reinterpretacion de resultados de analisis demograficos previos que concluyeron que la poblacion era estable. Nosotros encontramos que aun si la poblacion del buho moteado a estado declinando un 4% por ano, la probabilidad de detectar esta declinacion fue de a lo sumo 0.64%, y probablemente mas cercana al 0.13%. Por consiguiente, no se justificaba concluir que la poblacion era estable. Finalmente, demostramos como los calculos de poder pueden ser usados para comparar distintos metodos de monitoreo de cambios en el tamano de poblaciones pequenas. El metodo optimo de monitoreo de las poblaciones del buho moteado del Norte depende quizas tanto del tamano del area de estudio en relacion con el esfuerzo realizado como de la densidad de los aminales. A bajas densidades, la aproximacion demografica puede ser mas poderosa que la estimacion directa del tamano poblacional a partir de evaluaciones. A mayores densidades la aproximacion demografica puede ser mas poderosa para poblaciones pequenas, pero las evaluaciones son mas poderosas para poblaciones de mas de 100 buhos. El punto de relacion (tradeoff) depende de la densidad pero aparantemente no depende de la tasa de declinacion. Para tamanos poblacionales bajos, el poder decrece para ambos metodos debido a la estocasticidad demografica.
Alfredo Ortegarubio - One of the best experts on this subject based on the ideXlab platform.
-
lessons for sustainable development marine mammal conservation policies and its social and economic effects
Sustainability, 2018Co-Authors: Nahieli Manjarrezbringas, Eugenio Alberto Aragonnoriega, Luis Felipe Beltranmorales, Michael Victor Cordobamatson, Alfredo OrtegarubioAbstract:The objective of this research is to assess the main social and economic effects on local fishermen in El Golfo de Santa Clara, as a result of the severe fishing restrictions enforced to protect the marine mammal “vaquita” ( Phocoena Sinus ). Sustainable development includes natural resources conservation and the improvement of the social and economic conditions of local inhabitants. In Mexico, the vaquita is in imminent danger of extinction. It is a marine cetacean endemic to the Upper Gulf of California. Conservation measures to save this species, such as gear-switching and transformation subsidies from fishing activities to tourist services, have caused severe social and economic impacts on the local fishermen of this region. Presently, it is estimated that there are only 30 vaquita individuals left in the wild, and none are in captivity. In this study, we conduct surveys of the human local population involved in the incidental bycatch fishing of the vaquita, and also use secondary sources to come up with recommendations, based on taking into account stakeholder needs. For this fishing community the economic and social problems have worsened because currently there are limited economic activity options in the area for the human population, and the vaquita population continues to decline. Recommendations are offered to contribute to the ecological sustainability of this species, and for economic and social sustainability of local fishermen.
-
managing a protected marine area for the conservation of critically endangered vaquita Phocoena Sinus norris 1958 in the upper gulf of california
International Journal of Sustainable Development and World Ecology, 2010Co-Authors: Eugenio Alberto Aragonnoriega, Miguel A Cisnerosmata, G Rodriguezquiroz, Alfredo OrtegarubioAbstract:We analysed fisheries trends in the northern region of the Gulf of California, within the Biosphere Reserve of the Upper Gulf of California and Colorado Delta River and the Vaquita Refuge Area, and suggest measures to protect the vaquita, Phocoena Sinus. We compiled and analysed catch reports of artisanal fishermen in the three fishing communities of the Upper Gulf of California (San Felipe in the State of Baja California, and Golfo de Santa Clara and Puerto Penasco in the State of Sonora) from 1995 to 2007. This information was categorised with respect to geographic information systems, and all fishing sites within two marine protected areas in the region were identified. In addition, from a survey based on direct interviews with artisanal fishermen in each of the three ports, we identified that 23% of fishermen will continue fishing despite on-going fishing buy-out programmes in the region. We suggest several specific courses of action to decrease the fishing impact on this critically endangered cetacea...
Armando Jaramillolegorreta - One of the best experts on this subject based on the ideXlab platform.
-
decline towards extinction of mexico s vaquita porpoise Phocoena Sinus
Royal Society Open Science, 2019Co-Authors: Armando Jaramillolegorreta, Lorenzo Rojasbracho, Gustavo Cardenashinojosa, Edwyna Nietogarcia, Len Thomas, Jay Ver M Hoef, Jeffrey E Moore, Barbara L Taylor, Jay Barlow, Nicholas TregenzaAbstract:The vaquita (Phocoena Sinus) is a small porpoise endemic to Mexico. It is listed by IUCN as Critically Endangered because of unsustainable levels of bycatch in gillnets. The population has been monitored with passive acoustic detectors every summer from 2011 to 2018; here we report results for 2017 and 2018. We combine the acoustic trends with an independent estimate of population size from 2015, and visual observations of at least seven animals in 2017 and six in 2018. Despite adoption of an emergency gillnet ban in May 2015, the estimated rate of decline remains extremely high: 48% decline in 2017 (95% Bayesian credible interval (CRI) 78% decline to 9% increase) and 47% in 2018 (95% CRI 80% decline to 13% increase). Estimated total population decline since 2011 is 98.6%, with greater than 99% probability the decline is greater than 33% yr-1. We estimate fewer than 19 vaquitas remained as of summer 2018 (posterior mean 9, median 8, 95% CRI 6-19). From March 2016 to March 2019, 10 dead vaquitas killed in gillnets were found. The ongoing presence of illegal gillnets despite the emergency ban continues to drive the vaquita towards extinction. Immediate management action is required if the species is to be saved.
-
conservation of the vaquita Phocoena Sinus
Mammal Review, 2006Co-Authors: Lorenzo Rojasbracho, Randall R Reeves, Armando JaramillolegorretaAbstract:The vaquita Phocoena Sinus is a small porpoise that is endemic to the northern Gulf of California, Mexico. It is the most critically endangered marine small cetacean in the world. The most precise estimate of global abundance based on a 1997 survey is 567 (95% CI 177- 1073). 2. Vaquitas mainly live north of 30 ° 45 ' N and west of 114 ° 20 ' W. Their 'core area' consists of about 2235 km 2 centred around Rocas Consag, 40 km east of San Felipe, Baja California. Genetic analyses and population simulations suggest that the vaquita has always been rare, and that its extreme loss of genomic variability occurred over evolutionary time rather than being caused by human activities. 3. Gill nets for fish and shrimp cause very high rates of by-catch (entanglement) of vaquitas. Estimates of bycatch rates are from 1993-94 and refer to one of three main fishing ports: 84 per year (95% CI 14-155) using only data collected by observers and 39 per year (95% CI 14-93) using combined data from observers and interviews with fishermen. Boats from other ports may experience similar rates, and the total is probably well above what would be
Randall R Reeves - One of the best experts on this subject based on the ideXlab platform.
-
vaquitas and gillnets mexico s ultimate cetacean conservation challenge
Endangered Species Research, 2013Co-Authors: Lorenzo Rojasbracho, Randall R ReevesAbstract:There is a high risk that incidental mortality (bycatch) in gillnets will lead to extinc- tion of the vaquita Phocoena Sinus, a small porpoise endemic to Mexico's northern Gulf of Califor- nia. A zoned Biosphere Reserve established in 1993 proved ineffective at slowing the population's decline, and in 2005, a Vaquita Refuge was declared. The Refuge Program included a ban on gill- netting and trawling in certain areas with relatively high densities of vaquitas. However, it was not until 2008, with the introduction of a Species Conservation Action Plan for Vaquita (PACE- Vaquita), that a comprehensive protection and recovery effort was introduced. Unfortunately, valuable time was lost as officials first needed to bring order to a poorly managed fishery manage- ment system. Also, the voluntary nature of fisherman participation and the chronic deficiency of enforcement have limited PACE's effectiveness. Although efforts to implement the plan probably slowed the vaquita's decline, the goal of eliminating gillnets (and thus most vaquita bycatch) by 2012 was not reached. This example shows the difficulty of achieving conservation when the pro- gram's rationale centers on the preservation of biodiversity with less emphasis on meeting com- munity aspirations. In fact, not only does the vaquita have no economic value, but the measures taken for its conservation have a negative economic impact and hence are met with hostility, or at best indifference, on the part of fishery authorities and fishing communities. On a more positive note, a light trawl has been field-tested and shown to be efficient at capturing shrimp; such 'vaquita-safe' trawls are suitable for replacing gillnets in the shrimp fishery. Similarly suitable alternative gear needs to be developed urgently for use in the finfish fisheries. Unless entangling nets are removed quickly from the vaquita's habitat, it will soon be too late to save the species, which probably already numbers fewer than 200 animals.
-
conservation of the vaquita Phocoena Sinus
Mammal Review, 2006Co-Authors: Lorenzo Rojasbracho, Randall R Reeves, Armando JaramillolegorretaAbstract:The vaquita Phocoena Sinus is a small porpoise that is endemic to the northern Gulf of California, Mexico. It is the most critically endangered marine small cetacean in the world. The most precise estimate of global abundance based on a 1997 survey is 567 (95% CI 177- 1073). 2. Vaquitas mainly live north of 30 ° 45 ' N and west of 114 ° 20 ' W. Their 'core area' consists of about 2235 km 2 centred around Rocas Consag, 40 km east of San Felipe, Baja California. Genetic analyses and population simulations suggest that the vaquita has always been rare, and that its extreme loss of genomic variability occurred over evolutionary time rather than being caused by human activities. 3. Gill nets for fish and shrimp cause very high rates of by-catch (entanglement) of vaquitas. Estimates of bycatch rates are from 1993-94 and refer to one of three main fishing ports: 84 per year (95% CI 14-155) using only data collected by observers and 39 per year (95% CI 14-93) using combined data from observers and interviews with fishermen. Boats from other ports may experience similar rates, and the total is probably well above what would be
-
Conservation of the vaquita
2006Co-Authors: Armando Jaramillo-legorreta, Lorenzo Rojas-bracho, Phocoena Sinus, Randall R ReevesAbstract:1. The vaquita Phocoena Sinus is a small porpoise that is endemic to the northern Gulf o